QUESTION BANK ON RADIATION PROTECTION

1. Define - AtomAtom is the smallest unit of an element exhibiting the properties of that element.

2. Define - Atomic mass numberThe number of protons and number of neutrons in the nucleus of the atom gives the mass number (A) of the atom

3. Define - Atomic number,Number of protons present in the atom gives the atomic number (Z) of the atom.

4. Define - IsotopesAtoms with same number of protons but different number of neutrons are called isotopes. Isotopes may be stable / unstable.

5. Define - Isobars nuclides

ISOBARS are the nuclei with the same mass number ‘A’ but different atomic number Z are called Isobars. The nuclei 8O

16 and 7N16 are having same mass

number (A=16) but different atomic number ( Z = 8 & Z =7 ). The isobars are atoms of different elements and have different chemical and physical properties.

6. Define - Isotones

ISOTONES are the nuclei with same number of neutrons and with different number of protons (Z). Some example of the nuclei are 6C

14, 7N15 & 8O

16 each nuclei have 8 neutrons in its nucleus.

7. Define - IsomersISOMERS are the nuclei of atom with same Z and A, but they differ from one another in their energy states and exhibit difference in their internal structure. These nuclei are distinguished by their transformation timings.

28Ni60m28Ni60

8. Define - Radioactivity.It is the process in which an unstable radionuclide spontaneously changes to another nuclide by emitting particles or energy. The unstable nuclide is said to be radioactive. The particles/energy emitted is called nuclear radiation.88Ra226

86Rn222 + α (alpha)27Co60

28Ni60 + β (Beta) + γ (Gamma)9. Define - Decay law.

The number of radioactive nuclides present goes on decreasing with time and also the disintegration rate. The rate of disintegration is proportional to the number of radionuclides present at that time. - dN/dt α N : - dN/dt = λN : N=N0e

-

t : λ is called decay constant.

10. Define - Decay constantIn the decay equation - dN/dt = λN, λ is decay or transformation constant in units of reciprocal seconds. It is the probability of transformation taking place in unit time.

11. What does N represent?The quantity N represent the decay rate dN/dt.

12. Define half life, short lived and long lived radionuclides.Some radionuclides decay very fast and some very slow. The time in which the number of radionuclides reduces to half of its original value is called HALF- LIFE.In case of air borne activity at KAPS, The radionuclides having half life of less than 30 minutes are termed as short lived activity.

13. What is radioactive decay equilibrium?If the daughter product is also radioactive, it will decay into another daughter product resulting in a chain. The daughter product will be in equilibrium with parent.

i) Secular equilibrium T1 1/2 >> T2 1/2 or 1 << 2

ii) Transient equilibrium. T1 1/2 > T2 1/2 or 1 < 2

iii) No equilibrium.

14. What is the unit of radioactivity?Bequerrel is that quantity of radioactive material in which one atom is transformed per second.

Curie is that quantity of radioactive material in which 3.7 x 1010 transformation per second takes place.

15. Define specific activity. What is the relation between mass and activity?Activity per unit mass is called specific activity. Specific Activity =Act/mass=N/NM/Av= Av/M

16. What is artificial and natural radioactivity?Natural radioactivity is the one existing in the nature like K40, C14, Uranium and Thorium series.Artificial radioactivity is man made radioactivity like Co60, I131, Fission products etc.

17. What are the various sources of natural radiation?

Source Annual Exposure in µSvNatural SourcesCosmic rays 450Soil 150Water, food 250Uranium series 1340Thorium series 340Manmade sources

Medical X Rays 200Nuclear Installation 10 - 20Total 2000 – 2400

18. What is the dose delivered by these sources?On the average 2 mSv/year dose is delivered by natural sources.

19. What are the different factors on which the dose due to natural radiation depends?Dose due to natural radiation depends on altitude, latitude of the location and radioactivity present in the earth crust.

20. What is fission product? Name some fission productRadionuclides produced after fission reaction are called fission product. e. g. I131,

Cs137

, Sr90

21. What are the different types of radiation?Energy emitted by unstable nuclides is called nuclear radiation.Nuclear radiation is of four typesi) Alpha Radiation (α)ii) Beta Radiation (β)iii) Gamma Radiation (γ)iv) Neutron Radiation (n)

22. What is particle? Explain alpha decay.Alpha disintegration occurs mainly in heavy nuclei. (A >200) An alpha particle consisting of two protons and two neutrons (Helium nucleus) is ejected. After emission of alpha particle the daughter nucleus will be left with Z-2 protons (atomic number) and atomic mass of A-4. After emission of alpha particle the nucleus is still in excited state. This excess energy is emitted in form of electromagnetic radiation known as Gamma rays.

23. What is particle? Explain decay.During the process of disintegration one of the neutron within the nucleus

changes into a proton and a negative electron which is ejected as a - particle. In such a transformation the mass number of the daughter product will remain the same but the atomic number increases by 1 since there is now one more proton in the nucleus.

24. What are rays? Explain decay.Usually after an alpha decay or beta decay processes, the newly formed daughter nucleus is left in the excited state. This daughter nucleus thus emits electromagnetic radiation known as gamma rays to come to the ground state i.e. stable state. The energy of the gamma radiation is equal to the energy level difference of the excited state and the ground state of the daughter nucleus.

25. What is the unit used for expressing the energy of radiation?Electron volt (eV). It is the energy acquired by an electron when it is accelerated through a potential difference of 1 volt. 1 eV = 1.6 x 10-12 erg.

26. How radiation interacts with matter?Charged particle interacts with matter directly by causing excitation or ionization of the atoms in the medium.Uncharged particle (neutrons) interact indirectly with the atoms of the medium. Electromagnetic radiation interacts with medium causing Photoelectric effect (bound), Compton scattering (free), Pair production (E-1.02).

27. How the Gamma radiation interacts with matter?

i) Photoelectric effectIn this process inner bound electron is involved. Ejected electron is known as photoelectron.Probability Z5 / E4 where Z= Atomic Number

ii) Compton scatteringIn this process outer free electron is involved Probability Z / E

iii) Pair productionThis process takes place in the vicinity of the nucleus Probability Z2 * ( E-1.02)

28. How does a charged particle interact with matter? What is excitation? Charged particle interacts with matter directly by causing excitation or ionization of the atoms in the medium. Excitation is raising the orbital electrons to its higher energy level.

29. What is ionization? What is specific ionization? Which radiation can cause ionization?While passing through the medium a fast moving charged particle, on approaching close to an atom removes an electron from the atom. This is called ionization.The rate of energy loss per unit path is called specific ionization. It also represents the number of ion pairs produced per unit path. Mathematically the energy loss per unit path is represented bydE/dx = 4πNZz2e4l/mev

2

It is seen that the energy loss depends directly on Z of medium and inversely on energy of the particle.

30. Explain attenuation of gamma rays in matter? Explain each term?While passing through the medium, gamma photons are removed so the intensity falls off in exponential manner.For absorber of thickness 'x' the attenuation of a narrow collimated beam of gamma photon, transmitted intensity is given by

I=I0 e-x

31. What is relaxation length?Relaxation length or Mean free path () = 1/. It is the distance a gamma photon travels through the medium without undergoing any interaction.

32. What are tenth and half valve layers?Half Value Layer (HVL) is the thickness of the absorber (material) required to reduce the radiation intensity to half of its initial value.

Tenth-Value Layer (TVL) is the thickness of the absorber (material) required to reduce the radiation intensity to one tenth of its initial value.

33. What is the relation between TVL/ HVL?I=I0 e

-x : I0/10=I0 e-TVL : e-TVL=1/10 : eTVL=10 : TVL=loge 10= TVL :

TVL=2.303/The ratio of TVL/ HVL is given asTVL/ HVL = 2.303// 0.693/ = 3.3

34. How neutrons are produced?A radioactive source which emits neutrons is not available easily. Hence neutrons sources are made by utilising nuclear reactions producing neutrons.

i) FISSION

a) U235 , U233, Pu239

U235 + 0n1 F.P. + 0n

1 ( 2 or 3 ) + Energy (~ 200 MeV)b) SPONTANEOUS FISSION of Cf252 ( T1/2 = 2.65 Years

ii) ACCELERATORDD Reaction: 1H

2 + 1H2

2He3 + 0n1 + 3.26 MeV.

DT Reaction: 1H2 + 1H

32He4 + 0n

1 + 17.6 MeV.

1Li3 + 1H1

4Be7 + 0n1 + Energy

iii) PHOTO NEUTRON SOURCES ray emitter used are Ra226, Sb124, Ga72, La140, Na24 . Mono energic neutrons are produced depending on the gamma energy.4Be9 + 4Be8 + 0n

1 - 1.66 MeV. (Q)Drawback : High field associated with neutron sources.Note : Source used in KAPS reactor is Antimony-Beryllium source. Sb123

gets activated to Sb124, which is γ (1.66MeV) emitter. The γ interact with Beryllium giving out photo neutron.iv) ALPHA NEUTRON SOURCESAlpha emitting radionuclides like Ra226, Pu239, Po210 are used with beryllium to produce neutrons.

4Be9 + 2He46C

12 + 0n1 + Energy

35. How neutrons are classified?

Neutrons are classified according to its energyTYPE ENERGY

Thermal NeutronsEnergy below 0.5

eV ( mostly 0.025 eV)Intermediate Energy 0.5 eV - 100 KeV

Fast Neutrons 100 KeV - 20 MeV

High Energy ABOVE 20 MeV

36. What are the different interactions of neutrons with matter?1. Elastic Scattering2. Inelastic Scattering3. Non-Elastic Scattering Or Nuclear Reactions4. Neutron Capture5. Fission and Spallation

37. What is nuclear fission? What is fissile and fertile material? NUCLEAR FISSIONThis is a capture phenomenon in which the incident neutron is capable of breaking the interacting nucleus into two non-equal fragments with lot of energy. For example,U235 is fissionable with thermal neutrons with a cross-section of 535 barns and about 200 MeV energy per fission is liberated. Fission has i t sImportance as it can be used as a continuous source of energy by maintaining a chain reaction.eg. 92U

235 + 0n1

38Sr94 + 54Xe140 + 2 0n1 +

38. How much energy is released in fission reaction?200 MeV (~0.2 amu)Distribution of fission energyi) Kinetic energy of fission fragments 168 MeVii) Fission neutron energy 5 "iii) Prompt gamma rays 5 "iv) Total 200 “

39. What is cross section? What is its unit?The probability of a particular nuclear reaction per unit area is represented by cross section. It is an imaginary area offered by a nucleus to the neutron to cause particular reaction. barn=10-24 cm2 is the unit of cross section.

40. Explain radiological significance of ,, and neutron radiation.Alpha radiation is least penetrating radiation. Hence it does not cause any harm externally. External monitoring of alpha radiation is not required. The specific ionisation of radiation is very high. Hence it is most harmful internally. Internal contamination / organ dose due to radio nuclides emitting alpha radiation (e.g.Pu239) is monitored by bio assay technique. Lung monitor is also used forMonitoring activity in the lungs.

Beta radiation is more penetrating than radiation. It can penetrate the skin resulting skin dose. TLD is used for monitoring beta dose. Internal contamination/ Dose due to radionuclides emitting beta radiation (e.g. Sr90) is monitored by bio- assay technique.

Gamma radiation is most penetrating radiation. It penetrates through human body resulting whole body dose. TLD is used for monitoring gamma dose.Internal contamination / dose due to radionuclides emitting gamma radiation (e.g. Co60) is monitored by Whole body monitors.

Neutron radiation is penetrating radiation like gamma radiation. The harm/dose delivered to human body depends on its energy. The radiation weighting factor varies from 5 to 20 for various energy. The dose is monitored by neutron badges (CR39)

41. What are the different materials used for shielding ,, and radiation?

Radiation Shielding material No Shielding required, paper Aluminium Lead, concrete, water, depleted

Uranium Hydrogenous material, concrete

42. Define dose.Dose meaning absorbed dose, is the energy absorbed from ionising radiation per unit mass of the material at the point of interest.Unit of absorbed dose is Gray (Joule per kg) : Old unit is RAD (100 ergs/gm)

43. Define Radiation weighting factorThe probability of stochastic effects is found to depend on the absorbed dose and also on type and energy of the radiation causing the dose. WR Depends on type and energy of radiation. Relative biological effectiveness of the radiation in causing the particular effect is represented by Radiation Weighting Factor.

Type And Energy Range WR

Photon of all energies 1Electrons, muons of all energies 1Neutrons <10 kev 5

10 kev to 100 kev 10100 kev to 2 Mev 20

2 Mev to 20 Mev 10>20 Mev 5

Protons >20 Mev 5α- particles, fission fragments 20

44. Equivalent doseDifferent types of radiation may result in different amount of biological damage. Equivalent Dose takes into account the absorbed dose and its biological effectiveness in causing the damage.HT = ΣRWR.DR

Unit of equivalent dose is Sievert (Joule per kg).

45. Tissue weighting factorIt is a ratio of the detriment of each tissue specific cancer or hereditary disease relative to the total aggregated detriment to the whole body.

Tissue or organ Tissue weighting factor (WT)Gonads 0.2

Red Bone marrow 0.12Colon 0.12Lung 0.12Stomach 0.12Bladder 0.05Breast 0.05Liver 0.05Oesophagus 0.05Thyroid 0.05Skin 0.01Bone surface 0.01Remainder 0.05

Remainder includes the adrenals, brain, small intestine, upper large intestine, kidney, muscle, pancreas, spleen, thymus and uterus.

46. Effective doseRadiation dose may be delivered uniformly to whole body or to certain organs or tissues. In order to find out the risk to the whole body due to the damage suffered by exposed organs, an effective dose to the whole boy is computed.HE = ΣTWT.HT

Its unit is Sievert

47. Committed equivalent dose (H50,T)Committed Equivalent dose to a given organ or tissue from a single intake of radioactive material into the body is the dose equivalent that will be accumulated over 50 years, representing the working life. It is the time integral of the dose equivalent rate following an intake of radionuclide.

t+50

H50 = ∫ H(t) dt

48. Committed effective dose (HE,50)Committed effective Dose Equivalent is the time integral of the effective dose equivalent rate following an intake of a radionuclide.HE50 = Σt H50(t) WT(t)

49. What is collective dose?Collective dose is the sum of the individual doses received by the members in a population group and is expressed in units of person-Sv or man-rem.

50. How does radiation interact with cell?Radiation induces damage in cells either by directly ionising the DNA molecule or indirectly by producing chemically reactive species namely the radiolytic products of water. Since the cells contain 80% water, radiolytic products like radicals Ho, OHo, HO2

o, molecular product H2O2 and O2- are formed. Indirecteffects brought by these chemical species account for more than 70% of all the damage induced by low LET radiations.

51. What is stochastic effect?Stochastic Effects result from radiation induced non lethal cell modification. These are late effects whose occurrence probability is proportional to the dose. No threshold dose exists for these types of effects. The probability or the risk of expression of these effects starts from very low dose and goes on increasing with dose. Radiation carcinogenesis and genetic effects come under this category. These effects can occur at low dose also. Other environmental agents also cause these effects.

52. What is deterministic effect?Deterministic (Non stochastic) effects are caused as a result of accidental exposure to large doses of radiation. Large number of cells may have to be killed for the induction of such damage. The examples of such effects are radiation sickness, death and damage to individual organs such as skin, bone marrow, gonads, intestines, eye lens etc. Deterministic effects do not occur below the threshold doses or following chronic exposures as encountered in occupational radiation workers.

53. What is radiation sickness?Radiation sickness refers to early response to acute whole body radiation exposures in excess of 1 Sv. The syndrome is characterised by nausea, vomiting, diarrhea, lack of appetite, fever, headache, dizziness etc. Almost all the exposed individuals show radiation sickness if the dose is approximately 3 Sv. Time course of onset of the syndrome and its persistence is dose dependent. At higher doses (4-6 Sv) the sickness ensues within an hour after exposure, for doses of 1-2 Sv the sickness may appear after 3 hours.

54. Explain acute and chronic effectsAcute Effects:Effect observed after acute exposure (high dose rate in short period of time) is termed as Acute effects.Chronic Effects:Effect observed after Chronic exposure (low dose rate for longer duration of time) is termed as chronic effects.

55. What is the aim of radiation protection?The primary aim of radiological protection is to protect man from radiation while deriving benefits from nuclear activities.

56. What is the objective of radiation protection?The above aim will be achieved with following objectives.

i) To prevent deterministic effects, andii) To limit the occurrence of stochastic effects in the exposed persons and

their progenies.

57. What is intervention?Any human activity, which reduces radiation exposure, is termed as intervention. Counter measures adopted during radiological emergencies comers under this category.

58. What are the dose limits for occupational radiation workers?i) The cumulative effective dose constraint for five year block is 100 mSv

for individual radiation workers.ii) The annual effective dose to individual workers in any calendar year

during the five year block shall not exceed the limit of 30 mSv.iii) The cumulative life-time occupational effective dose limit is 1 Sv (100

rem)iv) When the cumulative occupational effective dose reaches 0.5 Sv (50

rem) further exposure of such individual shall be reviewed by medical authorities.

59. What are the annual dose limits for skin, lenses of the eyes?The annual dose limits for skin, lenses of the eyes are 500 , 150 mSv respectively.

60. What are the dose limits for temporary workers?The dose limits for temporary workers are 10 mSv in a month and 15 mSv in a year.

61. What is planned exposure and how much it is more than monthly dose limit? Exposures above monthly investigation level of 10 mSv are planned during excegencies of work in consultation/ information to head HPD,BARC. Maximum planned exposure is 15 mSv in a month.

62. What is emergency exposure?1) For occupational worker:

- 250 mSv2) For member of public:

- 100 mSv

63. What do you understand by over exposure?Exposures exceeding the investigation level and authorised limit are termed over exposure.

64. What is the procedure followed for handling exposure exceeding investigation level cases?Over exposure committee handles such cases and gives necessary recommendation?

65. Who are the members of the exposure investigation committee?The committee is having following members.i) Chief Superintendent - Convenorii) Health Physicist - Member Secretaryiii) Section Head of the worker - Memberiv) Medical Superintendent - Member (In case exposure exceeding

authorised limit)

66. Who investigates the exposure cases exceeding 2 rem (in a year)?

Apex committee constituted by SARCOP

67. Who investigates the exposure cases exceeding 10 rem (in 5 years)?Special committee constituted by AERB in which Head, HPD is one of the members.

68. What is the difference between contamination and radiation?Radiation is emitted by radioactive substance. Contamination is presence of radioactive substance where it is not expected or desirable. Radiation will be always present wherever contamination is there. But presence of radioactive substance does not necessarily imply that contamination is present.

69. What are external and internal exposures?Exposures resulting from radioactive substance present outside the body are called external exposure. Exposures resulting from radioactive substance present inside the body are called internal exposure.

70. What are the different ways by which internal contamination is caused?Internal contamination is caused by -i) Inhalationii) Ingestion.iii) Injectioniv) Absorption through skin.

71. What are the different methods used for controlling internal contamination? How the internal contamination is measured?Whole body counting for gamma emitters, bioassay, urine samples for beta, alpha emitters.The different methods used for controlling internal contamination -i) By using respirator in areas having air borne activity.ii) By preventing eating and drinking in controlled area.iii) By using proper protective clothing.iv) By covering the injuries or preventing entries of persons to

contaminated areas of persons having injuries.

72. What is ALI?It is the amount of that radio nuclide in an year which would result in a committed effective dose equal to annual effective dose limit 20 mSv.

73. What is DAC?It is the concentration of the radionuclide in air, which if breathed for a working year of 2000 hours (breathing rate 1.2 m3/hr) will result in intake of 1 ALI.DAC =ALI(Bq)/2400m31 DAC-hr will give CED of 1 mR (10 µSv)

74. What are the methods of external exposure control?Methods used for external exposure control are –i) Timeii) Distanceiii) Shielding

75. How is exposure control implemented in KAPS?RWPs are cleared by HP taking into consideration all the three methods of exposure control. Station ALARA committee reviews jobs expected to result in collective dose of 5 Person-mSv and recommendation based on these three methods are given for reducing the radiation level and collective dose.

76. What is the function of station level ALARA committee and sectional level ALARA committee?Station level ALARA committee Prepares, review budget, suggest methods for dose-reduction. It also coordinates activities between different sections.Sectional level ALARA committee prepares and reviews budget for the section. It also conduct ALARA meetings for jobs expected to consume 5 Person-mSv.

77. Who are the members of the committee?The members of the station level ALARA committee are CS,OS,MS,TSS,ALL SMEs, and HP.The members of the sectional level ALARA committee are Section head, concerned supervisor/engineer and HP representative.

78. Name the radionuclides seen in reactor water.Important fission product nuclides observed in Reactor water

Radio Nuclide HALF LIFE Radiation/Energy in MeV

Beta Gamma

I131 8.05 days 0.608 0.364

I133 21hrs 1.3 0.53

I132 2.2 hrs 1.22 0.773

I134 52 mins 2.43 0.85

I135 6.7 hrs 1.0 1.14

Cs137 30 yrs 0.514 0.662

Cs134 2.3yrs 0.662 0.6&0.8

Tc99m 6.0 hrs 0.14

Np239 2.33 days 0.437 0.106Important Activation product nuclides observed in Reactor water

Radio Nuclide

Mode offormation

Half Life Radiation emitted and energy in MeV

Co60 Co59(n,) Co60 5.3 yrs 0.314 1.17&1.33

Co58 Ni58(n,p) Co58 72 days 0.47 0.81

Cr51 Cr50(n,) Cr51 27.8 days 0.32

Mn54 Mn53(n,)Mn54 300 days 0.835Fe59 Fe58(n,)Fe59 45.1 days 0.475 1.095

Cu54 Cu63(n,)Cu64 0.53 days 0.571

79. What are the radionuclides observed in FPNG?26 radio nuclides of FPNG are produced during fission reaction. Out of these 22 radionuclides reach off gas system. 17 radio nuclides gets released to environment through stack. All other gets decayed. Following six radio nuclides are analysed and extrapolated to 17 radio nuclides released through stack.Xe 133 (5.3 d), Xe 135(9.2 h), Xe 138(18 m), Kr 85m( 4.4 h), Kr 87(78 m), Kr 88(2.8 h)

.

80. What are the radionuclides observed in Particulate and Iodine?Important radio nuclides observed are La140, Ba140, Cs137, Sr89, Sr90, Co60 etc. in particulate form and iodine radio nuclides observed are I131and I133.

81. What is the technical specification for liquid effluent releases? What is the basis?Annual average concentration of 5.55 Bq/l at MOF corresponding to 5 mrem/yr to critical group.

82. What are the AERB authorised limits for radio active waste disposal? Solid waste:

Category Radiation level R/h AERB Authorised limitVolume m3 Activity MBq

I D<=0.2 400 44 E04II 0.2<D<=2 80 20 E06III 2<D 60 56 E06

83. What is the dose limit for member of public?The dose limit for member of public is 1 mSv/yr(100 mrem/yr) .

84. What are the principles of radiation detection?The radiation is detected by the following processes.Ionisation, scintillation, fluorescence, el-hole pair in semiconductors, formation of recoil protons tracks

85. How many types of radiation detectors you know and on what principle do they operate?Ionisation chamber, inorganic & organic scintillators, GM tubes, solid state HP- Ge.

86. Name radiation monitoring instruments used in KAPS. Indicate the type of detector used and radiation monitored by them.

Instrument Type of detector Radiation monitored

TLD Thermo luminescent βγDirect reading dosimeter Ionisation chamber γDigital dosimeter Semi-conductor γNeutron dosimeter CR39- Recoil proton

trackn

Portal monitor GM βγHand |& Shoe monitor GM βγContamination monitor GM βγTeletector GM βγGun monitor Ionisation chamber βγGM survey meter GM βγNeutron monitor BF3 Counter n

87. What is the function of Area radiation monitor?Function of Area radiation monitor is to monitor ambient area radiation level and to notify the increase in radiation level by alarm.

88. How areas are classified on the basis of contamination? What is the contamination level permitted in these areas? What are protective clothing requirement for working in these areas?The areas are classified as zones as follows.

Zone Permitted contamination level

Clothing Requirement Areas in the station

1 Nil (clean area) Personal clothing. Area up to HP counter.2 0.1 0.1 DWL

(DWL=37 kBq/m2)

Personal clothing + plant shoes

1. Change room.2. Passage to RW3. Service bldg 118’ corridor

3. 0.5 DWL Lab coat, cap, cotton shoe cover & gloves

All areas in RB, TB, RWB

4. >0.5 DWL Type II / III clothing. All step off pad area

89. What is radioactive waste? How many types of solid radioactive wastes are generated at our plant? What are the methods of their disposal?Solid waste- low active in earthen trenches, high active in concrete trenches, alpha bearing and resins in tile holes, SPERT (temporary storage for active resins)

90. What are the three techniques used for waste management?The three techniques used for waste disposal are

i) Dilute and disperse.ii) Delay and decay.iii) Concentrate and confine.

91. How many types of liquid wastes are generated at our plant and what are the methods of their treatment and disposal? What is the limit for storage of liquid waste in outside tank? What is the basis?DRW/CRW based on conductivity.

a. CC (conc. / containment)b. DD (delay, dilution) philosophy

0.93TBq(25 Ci) (yearly discharge limit not to be exceeded).

92. How the solid waste is categorised? Is there any restriction / limitation on volume / activity of solid waste generated? Explain?AERB guidelines (SW classification)Category Dose rate Volume Act. limit / yrI <=2 mGy/hr 400 m3 44* 104 MBqII <=20 mGy/hr 80 20* 106

III > 20 mGy/hr 60 56* 106

IV Alpha Nil

93. What is radiation emergency?Un-intended event which may have potential to result in exposure above stipulated dose limit.

94. How many types of emergencies are there?There are 5 types of emergencies.i) Emergency Alertii) Personnel Emergencyiii) Plant Emergency,iv) Site Emergency andv) Off-Site Emergency

95. What is exclusion zone, Sterilised zone and EPZ? Exclusion zone ( 0 – 1.6 km )The exclusion zone extends up to a distance of 1.6 km around the plant where no public habitation is permitted. This zone is physically isolated from outside areas by plant fencing and is under the control of NPP.Sterilised zone ( 1.6 – 5 km )Sterilised zone is an area where no new growth of population is permitted. Natural growth is however allowed in this zone. This area extends up to a radius of 5 km from the plant.

Primary Zone: (1.6 – 8 km)Primary Zone covers between 1.6 km and 8 km radius around the center of KAPS Nuclear Facility.Secondary Zone: (1.6 – 16 km)Secondary Zone covers between 1.6 km and 16 km radius around the center of KAPS Nuclear Facility.EPZ - Emergency planning zoneEmergency planning zone defined around the plant up to 16 km radius, provides a basic geographic frame work for decision making on implementing measures as part of a graded response in the event of an emergency.

96. What are projected dose and averted dose?Dose likely to be received during emergency if countermeasures are not implemented is projected dose.Averted dose is the dose reduced due to implementation of countermeasures

97. How emergency is declared at KAPS?SCE on duty makes the assessment of the situation. He informs OS/CS/SD. He declares emergency after consulting these authorities.

98. What are the immediate counter measures taken during emergency?At Plant / sitei) Assemblyii) Administration of prophylactics /evacuation.

At Off sitei) Administration of prophylacticsii) Shelteringiii) Evacuation.iv) Control of foodstuff.

99. How site and off-site emergency declared?Site emergency is declared by site director after consulting the SEC members. Siren is blown in all the plants in the site.Siren 5 s on 5 s off for 2 minutes.Off site emergency is declared by Off site director in consultation with SE director. Announcement is made on PA system in the affected areas.

100. How plant and off-site emergency terminated?Continuous siren for 2 minutes

101. What is prophylaxis?Administration of stable iodine to prevent uptake due to 131I.

.102. When is prophylactic distribution and administration done during radiation

emergency?As early as possible

103. How effective is prophylactic administration?Time of administration of stable iodine is important for thyroid dose reduction. The reduction factors are given below

Time of Stable Iodine Administration Dose Reduction%Before exposure 1001 hr after exposure 806hrs after exposure 501 Day after exposure Negligible

104. What do you understand by sheltering, when is it undertaken?i) Sheltering means 'stay in-doors' and refrain from going outside until further

advice.ii) Sheltering is normally assumed for a period of 12 to 24 hours and may

precede evacuation.

105. What is difference between evacuation and relocation?Evacuation - Movement of population from affected zone to radio logically safe zone.Relocation - Resettling of evacuated population.

106. When is evacuation implemented?If the DIL have exceeded in the affected area, the evacuation is implemented as a last resort considering psychological impact to avoid high exposure.

1. What is dose?

A measure of the radiation received or absorbed by a target.

2. What is dose rate?

Dose rate is amount of Energy absorbed per unit mass of the body per unit time (Gy/hr). The effect of radiation depends on dose and dose rate of the radiation. As the time of exposure increases, the amount of dose received increases.

3. What is absorbed dose?

The amount of radiation energy absorbed per unit mass of the material is called absorbed dose.

DTR

Where D TR

==

D/MAbsorbed dose in tissue T due to radiation R

D = Energy absorbedM = Mass of the organ

4. What is equivalent dose?

Equivalent dose is defined as

HT

When DTR

=

=

WR DTR

Absorbed dose

WR = Radiation weighting factor

WR (radiation weighing factor) depends on the linear energy transfer (LET) of the radiation which in turn is related to specific ionization of the radiation. The unit of equivalent dose is Sievert (Sv) (1 Sv = 100 rem).

WR for different radiation types

Radiation Type Radiation weighting factor

Gamma rays 1Alpha particles 20Bet particles and muons (all energies) 1Protons other than recoil protons (all energies) 1Neutrons with e nergy < 10 keV 510 keV to 100 keV 20100 keV to 2 MeV 102 MeV to 20 MeV> 20 MeVFission fragments (all energies)

51020

Heavy nuclei (all energies) 20

5. What is effective dose and committed effective dose?

The equivalent dose when multiplied by the tissue-weighting factor (WT) for the tissue or organ T receiving the dose is called effective dose, ‘E’.E = WT WR DTR

T R

Where D TR means absorbed dose in tissue or organ T delivered by radiation R. WR = radiation weighting factor

The effective dose calculation is important, as the effect of radiation is different for different tissue or organs.WT = maximum for Gonads = 0.30WT = 1 for whole body

When a radionuclide is taken inside the body, it continuously keeps irradiating our body and we continue receiving the radiation dose till the radionuclide resides inside our body or in other words we commit ourselves to this particular amount of dose. This is called as committed dose and when the tissue weighting factor for the particular organ or tissue which is getting irradiated and also the radiation type being emitted by the radio -nuclide (radiation weighting factor) is taken into account it is called committed effective dose .

6. What are Stochastic and deterministic effects of radia tion?

Stochastic effects Deterministic effects1. The probability of occurring the

effects in proportional to the dose and

2. The probability of occurrence increases with the dose.

3. Occurs in exposed individual and future generations

4. Delayed effects

1. These effects occur above a threshold and

2. The severity increases with theDose

3. Occurs in exposed individuals only

4. Early effects

Example: Cancer, Genetic effects Examples: Skin erythema

7. Dose limit for occupational workers, contract workers trainees etc.?

Summary of Annual Dose Limits and Constraint

Category Radiation Workers

Apprentices trainee

Temporary worker

Member of public

Life time E (Sv)

1.0 **

Annual dose 30 6 15 1(mSv)Equivalentdose limit(mSv)Lens of eye 150 50 75 15(mSv)Skin mSv) 500 150 250 50Extremities (mSv)

500 150 250 -

Intake 1 ALI 30%

* E = Effective Dose

** = Medical review after 0.5 Sv

8. Explain Annual Limit of Intake (ALI) & DAC? On what factors does the ALI value of a radionuclide depends? How DAC calculation for tritium (HTO) is different than that for I- 131

Annual limit of intake (ALI) is that quantity of a radionuclide taken inside the body which could lead to an effective committed dose (1 50 year dose commitment) not exceeding 20 mSv and an annual equivalent dose to any single organ or tissue not exceeding 500 mSv.

The ICRP has recommended ALI values for a number of radionuclides:

ALI for 1H³ (HTO form) = 1 X 109

Bq

The quantity (Bq) which defines 1ALI varies widely for diffe rent radionuclides. TheALI for a radionuclide depends on each of the following.

(i) Type of radiation emitted (W R)(ii) Energy of radiation emitted.(iii) Selective deposition in the body.(iv) Presence of radioactive daughters

Derived air concentration (DAC)

It is the concentration of any radionuclide in air to which is a person is exposed for 2000 hours (40 hours a week, 50 weeks a year).

DAC = ALI . Annual breathing rate

The annual breathing rate for a “Reference man” is 2.4 x 10³ m³.

Derived Air Concentration (DAC) for Tritium (HTO)In in the case of HTO, the DAC value has to be obtained by multiplying the above value by 2/3 for accounting 66% uptake through inhalation route. Hence for this particular radio-nuclide of tritium DAC is calculated as below:

ALI (Bq) DAC = 2/3 x -----------------

2400 m³

9. How is tritium produced in our Reactor and why is it hazardous?

Heavy water is used as Moderator and also as primary coolant in PHT system

Tritium production is as per the reaction

1H² + 0n1 - 1H³ + r

In the physical for tritium is present in the form of TDO (Tritiated Heavy Water). The behavior of tritium will be same as that of water or water vapour. Whenever water is exposed to air, some of the heavy water and its contained tritium will evaporate and so we will have an air born tritium hazard.

10. Tritium is hazardous due to the following reasons:

Tritium is not an external hazard duct to the following r e a s o n s .

(i) Tritium emits beta particles but no rays.

(ii) Emax () = 18 Kev

(iii) Living cells are covered with a outer dead layer of skin (at least 0.007 mm thick).

(iv) Tritium beta can penetrate only 0.05 mm.

(v) Particles require at least 70 kv to penetrate the outer layer of skin.

Hence, tritium is not an external hazard. Tritium is a serious internal hazards as

a) The cells inside the body are not protected by a dead layer.

b) When tritium is inside the body is in direct contact with live cells and even diffuses right inside them.

c) In spite of their extremely low penetrating lever, tritium beta particles can damage the cells.

Hence to minimize the amount of damage, the amount of tritium allowed in the body is to be limited.

11. How is protection factor defined? What i s the p r o t e c t i o n factor for different clothings?

Protection factor (PF) = Uptake without protection Uptake with protection

PF for plastic suit = 30 (against 1H³) PF for an air respirator = 2 (a gainst 1H³)

12. What are three principles of radiation protection?The main features of the system of dose limitation shall be the following:

Justification:

No practice shall be adopted unless its introduction produces a sufficient benefitto the exposed individual or to the society to offset the radiation harm that it might cause.

Optimization:

All exposures shall be kept As Low As Reasonably Achievable (ALARA) economic and social factors being taken into consideration.

Dose limitation:

The normal exposures of individuals resulting from all relevant practices should be subjected to dose limits to ensure that no individual is exposed to a risk that is judged to be unacceptable.

13. What are the basic fundamental methods to protect against external exposures?

The basic principles adopted to control external exposures are:

a) Time: Time spent in radioactive work area should be optimized.b) Distance: Keep distance from the sourcec) Shielding: Shielding the source will reduce radiation intensity.d) Decay: allow the short lived radio nuclides to decay before entry.

14. What are the basic fundamental methods to protect against internal exposures?

The basic principles used to protect against internal exposures are:

a) Inhalation route: use suitable respiratory protectionb) Ingestion route: Eatables should not be taken to radioactive areas.c) Ingestion through open wound: Not allow to work in radioactive aread) Through skin absorption: Use ventilated respiratory protection

15. Why is the nuclear plant divided in four zones? What are the four zones in a typical plant? What is the change room and what are the three fold purposes of designing a change room?

A Nuclear plant-operating island is divided into four zones called Zone – 1, Zone– 2, Zone – 3 and Zone – 4 to prevent from spread of contamination.

Zone – 1 : Clean Zone. No contamination existsZone – 2 : As such no contamination exists. Area may get contaminated due

to personnel movement.Zone – 3 : Contamination exists but contained Zone – 4 : Source of contamination

Change Room:

Change Room is the place where personnel clothings are removed and plant clothes are worn by plant personnel proceeding to work in radioactive areas (Zone – 3 & 4 ).

Objectives:

1. To separate plant and personnel clothes to avoid cross contamination2. To avoid spread of contamination to Zone – 1 areas3. To avoid individuals getting contaminated during radioactive job.

16. What is the procedure for entering to shutdown accessible area during reactor operation?

Entry procedure for shutdown accessible areas like pump room, moderator room, DNM room during Unit operation. Any entry to Shutdown Accessible Area during Unit operation in called on power entry. The following procedures shall be followed:

Step -1: On power entry should be justified, ON power entry should be made only for inspection purposes.

Take approval for on power entry in on power entry form (filled in duplicate) from CS/SD.

Step -2: Conduct ALARA meeting for the entry with man-hours, manrem required & persons entering the shutdown accessible area.All individuals should be briefed about the job. Follow three-way communication.

Step -3: Collect all protective clothings, (Ventilated plastic suits), protective wear and respiratory protection prior to the entry. The dosimeters to be collected include high range DRD, Alarming dosimeter, Neutron Badge in addition to TLD and DRD.

Step -4: Time spent in pump room shall be as minimum as possible and shall work in batches.

Step -5: Once the job is completed, assess the doses received by each i n d i v i d u a l & fill up the ALARA planning sheet and conduct post job review.

17. While the reactor is operating, the reactor building exhaust duct shows “very high” activity alarm. List out various causes for this alarm and the actions (manual as well as auto) to be taken after this alarm as far as radioactivity is concerned.

The causes for very high activity in Reactor Building exhaust duct may be due to the following:

1. High FPNG release2. High argon release3. High Iodine – 131 release4. LOCA condition

Check area radiations field of RB on RADAS.Manual actions taken during very high activity alarm: The sample cell, which is sealed at ventilation exhaust room is removed for analysis of various radionuclides present in the sample by gamma spectroscopy analysis. This will help in identifying the source of radiation and origin of the source/system. Depending on the source system, action will be taken suitably.

Auto actions:

When RB exhaust duct show very high activity alarm, the sample cell and RB will be boxed up automatically as per logic by triplicated Ventilation Duct Radiation Monitors. After the situation is assessed and controlled, the logic will be reset.

18. What the current doses limits are as applied to radiation workers and members of public?

Dose Limits recommended by AERB

Application Dose Limit

Occupational Public

Effective D o s e 30 mSv per year and 100 mSv whenAveraged over defined period of 5 years.

1 mSv in year and 500 averaged over5 years.

Annual equivalent dose for:

Lens of the eye 150 mSv 15 mSv

Skin 500 mSv 50 mSv

Hands and feet 500 mSv --

19. Name five fission products and five activation products observed in your plant and also indicate the systems in which these are found.

Fission Products: Activation ProductsI-131Cs-137

Co-60Zr-95

PHT & ModPHT

Cs-134 Sr-90 PHT

Nb-95 Ar-41

PHTAGMS, Mod & PHT Cover gas

Xe-133 Xe-135

Fe -59 H-3Sb-124

ModMod & PHT PHT

20. Outline the methods of contamination control in respect of surface contamination.

- Spread polythene sheets before taking up maintenance activities in the working area.

- Avoid keeping contaminated equipment on floors. Wrap all contaminated equipment with polythene sheet

- Decontaminate the floors as soon as identified as contamination is detected.- Proper rubber area / rubber change area.- Follow rubber change procedures.

21. Outl ine the methods of contamination control in respect of body contamination.

- Use protective clothings- Use respiratory protective equipment- Follow strictly radiation protection procedures, which include rubber station

procedures, which include Rubber Station procedures etc.- Avoid touching contaminated wall / equipment if not required.

22. What are the limits for contamination in body, personal c l o t h e s a n d personal shoes?

Derived working levels for radioactive contamination

Derived Working Levels (DWLs) for radioactive contamination

Surfaces Beta Emitters (Bq/cm2) Alpha Emitters (Bq/cm

2)

Skin 1.5 1.0Hands 350* 250*

Clothes:Plant 6 2

Personnel 2 0.5Shoes:Plant 37 3.7

Personnel 0.37 0.037Floor/Equipment 3.7

0.37

* Total contamination on either side.* No loose contamination is permitted on hands and skin.

23. What is natural background radiation? On what factors does it depend? Name the isotopes causing natural background radiation.

The radiation due to presence of naturally occurring radionuclides in atmosphere, earth crust, etc. gives to natural background radiation. The sources of natural background radiation include Radon (Uranium series), Thoron (Thorium series), K-40, Cs-137 (Nuclear fallout), cosmic rays, etc. The natural back background radiation in a place depends on

a. Intensity of cosmic radiationb. K-40c. Nuclear fall outd. Presence of Uranium or Thorium materials in the earth cruste. The elevation of a place with reference to sea level

24. A failed fuel bundle was being transported from your station to Bombay. On the way it met an accident what actions you will undertake as the leader of the convoy?

Actions to be taken by CIC during level 3 emergencies are:

a. Attend to the injured and if necessary arrange for medical aidb. Monitor the cask for radiation and contamination l e v e l s . Also monitor the

wagon/conveyance and adjoining areas for possible contamination. Monitor the radiation levels around the cask.

c. Inform the local / concerned railway/police/district authorities and seek their assistance.

d. In case of fire, get assistance of local fire brigade. Firefighting personnel should make use of the standard respiratory protective equipment

e. Cordon off the area as specified in the TREMCARD.f. Inform the consignor and the CMG, DAE about the emergency situation in the

prescribed format and seek any assistance that may require.g. Keep a watch over the controlled area until the Emergency Response team (ERT)

arrives.h. Assist in the efforts of the emergency response personnel sent by the railways,

Police or local fire brigade.i. Assist the Emergency Response Team (ERT)j. Decontaminate the affected area, if any, and arrange for improvised shielding, tie

-down, etc, for the cask, if require as recommended by the Emergency Response Team (ERT)

k. Inform the consignor and the CMG, DAE upon completion of the emergency response work.

l. Resume the shipment in accordance with the advice of the ERT.

25. What are the different categories of radioactive s h i p m e n t s ? Give their dose limits

Categories of the Radioactive Shipments

All shipments shall be in any one of the following four categories:

CategoryConditions

Maximum radiation level at any point on external surface

Transport Index (TI)

1- White

2- - Yellow

Not more than 0.005 mSv/h (0.5 mR/h)

More than 0.005 mSv/h (0.5 mR/h ) but not more than 0.5 mSv/h (50 mR/h )

0

More than 0 but not more than 1

3 - Yellow More than 0.5 mSv/h (50 mR/h) but not more than 2 mSv/h (200 mR/h)

More than 1 but not more than 10

3 - Yellow (for exclusive

use)

More than 2 mSv/h (200 mR/h ) but not more than 10 mSv/h (1000 mR/h )

More than 10

26. A Heat transport pump is to be transported to Bombay. The radiation f i e l d on contact of the package is 150 mrem/h. Write down its category and the documents required to be filled up and required to accompany?

Radiation field on contact of the package in 1.5 mSv/h. Since on contact radiation field is less than 2 mSv/h, the radioactive shipment comes under category III yellow.

Documents required for category III yellow package:

1. Radioactive shipment advice (for the consignee and station records)2. Normal Release Permit (for station security)3. Instructions to vehicle drivers ( for emergency conditions)4. Tremcard5. Tremdata

The above documents shall be filled up and accompany the consignment.

27. What is plant emergency? Give a few examples. Who is Plant Emergency Director?

This involves excessive release of radioactive materials or high radiation fields in a section of the plant requiring immediate operator action and /or automatic operation of safety systems. Although positive isolations or restrictions on occupancy of the affected areas might be enforced, evacuation of personnel might be required if it is suspected that the doses to personnel are likely to exceed the intervention levels

1. Actual or suspected occurrences of loss of core cooling both during operation and shutdown.

2. Closure of RB isolation damper on high activity release or high pressure in reactor building or emergency core cooling system.

3. Major fire in Reactor Building.

4. Earthquake measuring more than 6.0 Richter's scale or major damage observed due to earthquake.

5. Failure of a structure inside reactor building which may incapacitate the core cooling or reactor protection system or regulating system.

Plant Emergency Director: Station D i r e c t o r

28. Give a sketch for possible escape routes for radioactive materials from fuel to the environment. What are the likely isotopes to escape?

Fuel Fuel claddingFuel cladding Primary Heat Transport System Primary Containment Secondary Containment Secondary containment Environment

Isotopes likely to escape from fuel: I-131, Xe -133, Xe-135 etc.

29. What is an emergency? What are different types of emergency? Explain with one example each. What and where is he various counter measures to be taken in each type of emergency?

Emergency:

Emergency is an incident in a nuclear power plant, which may lead to release of radioactivity into the environment above the technical specifications in an uncontrolled manner.

There are three types of emergencies encountered at Nuclear Power Plants:

Plant Emergency:

This involves excessive release of radioactive materials or high radiation fields in a section of the plant requiring immediate operator action and /or automatic operation of s a f e t y s y s t e m s . Although positive isolations or r e s t r i c t i o n s on occupancy of the affected areas might be enforced, evacuation of personnel might be required if it is suspected that the doses to personnel are likely to exceed the intervention levels.

Counter measures implemented:

a) Assembly of personnel in Assembly areas for mutual counting.b) Shelteringc) Access control

Examples:

1. Actual or suspected occurrences of loss of core cooling both during operation and shutdown.

2. Closure of RB isolation damper on high activity release or high pressure in reactor building or emergency core cooling system.

3. Major fire in Reactor Building.

4. Earthquake measuring more than 6.0 Richter's scale or major damage observed due to earthquake.

5. Failure of a structure inside reactor building which may incapacitate the core cooling or reactor protection system or regulating system.

Site Emergency:

This class of emergency arises due to situation, which seriously affects plant operations involving high radiation fields in accessible areas and release of radioactive materials extending beyond the plant up to the site environment. The protective measures such as incorporation of stable Iodine, sheltering and evacuation of personnel from plant areas other than control room to areas designated to be habitable under the site emergency conditions and evacuation of non-essential persons from the site may be considered.

Counter measures implemented:

a) Access controlb) Shelteringc) Evacuation

Examples:

1. Known loss of coolant greater than make up pump capacity.2. Actual or suspected core melting.3. Fire affecting safety systems.4. Primary steam line breaks outside containment without isolat ion.5. Severe natural phenomena being experienced or projected with plant not in cold

shutdown condition.

Off-site Emergency:

An Off-site emergency situation results when the release of radioactive materials from the plant is of a magnitude necessitating protective action to be taken for members of the public in the neighborhood of the plant.

Counter measure implemented:

a) Access controlb) Administration of stable Iodinec) Shelteringd) Evacuatione) Control on food stuff

Examples:

1. Known loss of coolant greater than make up pump capacity.2. Actual or suspected core melting.3. Fire affecting safety systems.4. Primary steam line breaks outside containment without isolation.5. Severe natural phenomena being experienced or projected with plant not in cold

shutdown condition.

30. How area around a nuclear power plant is is divided? What is the significance of each zone?

Emergency planning zone, defined around the plant up to 16 KM radius, provides a basic geographic framework for decision making on implementing measures as part of a graded response in the event of an emergency. The area around the RAPS site is divided into the following zones up to 16 KM radius.

Exclusion Zone:

The exclusion zone extends up to a distance of 1.6 KM around the central plant zone of 0.7 KM where no public habitation is permitted. This zone is physically isolated from outside areas by plant fencing and is under the control of RAPS.

Sterilized Zone:

Sterilized zone is an area where no new growth of population is permitted. Natural growth is however allowed in this zone. This area extends up to a radius of 5 Kms from the central plant zone. This zone is defined to restrict the population to an easily transportable number in case of an Emergency.

Primary Zone:

The primary zone extends up to 8 Kms from central plant zone where protective measures like evacuation and sheltering are required against possible plume exposures during an Emergency.

Secondary Zone:

The secondary zone extends up to 16 Kms from Central Plant Zone protective measures like sheltering control on foodstuff are required against possible exposures from ingestion of radioactivity.

Sectional Division of EPZ:

The Emergency-planning zone around the RAPS-3&4 is further divided into 16 sectors radially (designated by letter codes 'A' to 'P' marked clockwise) to implement protective measures to areas actually affected during an emergency. Each sector covers 22.5 and the centerlines of sector 'A', 'E', 'I' and 'M' coincide with the North, East, South and West directions respectively.

31. With unit operating at full power “Stack Iodine Activityhigh” annunciates. What could be the causes and what actions

will you take?

Stack iodine activity high annunciates when unit is operating at full power

The reasons for above can be

a) Discharge of failed fuel bundles to SFSBb) Loss of coolant accident in RB

Actions to be taken:

a) Put into service the Iodine filter beds in spent fuel storage bay area for removal ofiodine during failed fuel discharge.

b) Put into service, the primary containment filtration & pump back system, and secondary containment of iodine during LOCA condition.

32. What are the radionuclides that are significant at later stage in the event of accident? How do they affect the population?

The radionuclides likely to be released to the environment during an offsite emergency are Cuss-137, I-131, Xe-133, Xe-135, Sr-90, Co-60 etc. Different radionuclides will be absorbed in different ranges of the body.

Example Cs-137 I-131

Muscle Thyroid

Sr-90 Bones

33. In a hypothetical radiation accident in the plant, automatic closure of R/B dampers isolates the Reactor Building. Explain the basic principles or bases or methods for:

a) How would an assessment of the activity released be madeb) Declaring Plant and Off-site emergencyc) Deciding on evacuation and sheltering measuresd) Treatment of contamination injuries

The Reactor Building gets boxed up by automatic closure of Reactor Building dampers in a hypothetical accident

a) The assessment of activity released through the stack is estimated by counting the 5-liter sample cell kept at Ventilation Duct Radiation Monitoring room. The radionuclides present and quantitative estimation of releases is e s t ima ted .

b) Declaring Plant and Off-site emergency

Plant Emergency is declared based on the following conditions:

Whole body dose: 5 mSvor committed equivalent dose to thyroid : 50 mSv to many persons in the plant.

Off-site Emergency:

When the radiation level at 1 m above the ground level is more than 0.01 mSv/h or food samples containing activity more than allowed limits for c o n s u m p t i o n .

c) Deciding on evacuation and sheltering measures

Sheltering:

The radiation level is more than 0.01 mSv/h in domain 2 and more than 0.1 mSv/h in domain 1 and persistent for 10 hours, sheltering of the public shall be done to avoid inhalation dose and plume dose.

Evacuation:

Evacuation is implemented, if the radiation level is more than 1.0 mSv/h and persistent for 4 hours in domain 1, within 12 hours.

d) Treatment of contamination injuries

Treatment of contaminated injuries: The contaminated injuries are treated at Radiation Emergency Medical Center (REMC) prior to decontamination of injured persons, first aid and medical treatment will be given to save the life. Later, decontamination of the injured person will be carried out at Radiation Emergency Medical Center.

34. Which are the samples to be collected from an affected area? What will be the follow up actions, if required?

The following samples are collected during a radiation emergency in an affected area:

a) Air samples for estimation air borne radioactivity present in the affected area.These samples include for particulate and iodine

b) To estimate the contamination level in food materials, the following food samples are collected for analysis:(i) Water samples(ii) Paddy rice(iii) Milk(iv) Milk products(v) Goat’s thyroid(vi) Soil samples etc.,

Follow up actions required during emergency:

The frequency of sample collection shall be increased if the radioactivity levels are in increasing trend in all food samples as mentioned above. If the activity levels are more than the allowed limits, the countermeasure of control on foodstuff shall be implemented. Sheltering and Administration of stable Iodine shall be done based on radiation levels at 1m above the ground level in the affected area/village.

35. Classify the off-site emergency on space domain basis; specify the dose limits for counter-measures in the domain.

Time space domains are defined to appraise the implementation of countermeasures.

Concepts DomainDomain – 3 Domain - 2 Domain - 1

Radiation level (mSv/h)

<0.01 0.01-0.1 >0.1

Objective To reduce collective dose and thus to minimize the overall incidence of stochastic effects

To limit the stochastic risk to individual members of the public

To avoid individual doses so as to avoid serious deterministic effects (0.5 Gy & 5 Gy)

Exposure pathways

Ingestion route predominant

Ingestion route (major) a. Inhalation routeof exposure to thyroid

b. External gamma dose from plume

c. External gamma dose from ground deposition

Counter measures

Control of food stuff

a. Administration of stable iodine

b. Sheltering andc. Control of food stuff

a. Administration of stable iodine

b. Sheltering and / orc. Evacuation

36. What are intervention levels for various counter measures in off-site emergency?

Intervention levels for various counter measures in different domains during an Off-site emergency are given below:

Intervention levels for implementation of countermeasures

Domain Countermeasure Intervention level (mSv)Whole body Thyroid

Lower Upper Lower UpperDomain –1 Administration of -- -- 500 2500

stable iodine

Sheltering 20 100 -- --

Evacuation 100 500 -- --

Domain – 2 Administration of -- -- 50 500stable iodine

Sheltering 5 20 -- --

Control on food stuff 5 20 50 500

Domain – 3 Control on food stuff 1 5 Not anticipated

Note: The Ils for Doma ins 1 and 2 are CED / CEED from intakes during the first year following the accident

37. What are the different protective measures suggested in the off-site emergency? When and how will these be implemented?

The protective measures implemented during an Off-site Emergency are:

a) Administration of Stable Iodine: KIO3 Tablets are administered at the earliest by district medical authorities

b) Sheltering: Sheltering of all public in the affected village is implemented within 24 hours if the radiation level at 1 m above the ground level is more than 0.1 mSv/h by police personnel.

c) Evacuation: Evacuation of all public in the affected village is done within 12 hours of the radiation level at 1 m above the ground level is more than 1.0 mSv/h by police personnel.

d) Access Control: Entry and Exit of vehicles from affected villages are diverted and traffic in controlled by police p e r s o n n e l .

e) Control on foodstuff: Consumption of contaminated food is restricted by district authorities.

38. What are the different design features provided at your station to handle emergency in order to ensure releases are within technical specifications?

The design features provided to handle emergency in order to ensure releases are within technical specifications are as f o l l o w s :

a) Pressure Suppression System:

The suppression pool system is designed to remove undissolved gases and reduce the pressure of primary contaminant by dissolving certain gases in a water column of 2.1 meters. Most of the soluble radioactivity may also be contained in the system.

b) Primary Containment Filtration and pump back system:

This system is designed to remove iodine released during emergency conditions.

c) Secondary Containment recirculation and purge system:

This system is derived to remove iodine & particulate activities of any leakage from primary containment and to avoid ground releases.

e) Primary Containment Control Discharge:

This system is designed to discharge the gaseous effluents in a controlled manner during post-accident situation based on suitable meteorological conditions.

f) Double containment:

The secondary containment avoids the ground releases if any leakage & from primary containment by keeping at negative pressure and starting of secondary containment recirculation and purge system.

39. a. What is the source term? Mention the inventory of I-131 and Noble gases in PHWRs.

b) Outline the s y s t e m of measuring radioactivity discharge from NPP under building box up conditions during accidents.

a) Source Term

Source Term denotes “information about the actual or potential release of radioactive material from a given source, which may include a specification of the amount, the composition, the rate and the mode of release.

The following characteristics of the source term have an important bearing on the accident consequences:

(i) The rate and the total amount of radioactive material released:

This is determined by the reactor inventory (which in turn depends on the design and operating power of the reactor), and by the nature and severity of the accident.

(ii) The relative mixture of radio -nuclides released:

This may be different from the composition existing in the core before the accident. It is determined by the chemical, physical and radiological properties of the nuclides concerned.

(iii) The relative mixture of gases, volatiles and particulates released:

The physical form of the activity released determines primarily its escape potential from the plant.

(iv) The environment of release and the accompanying energy:

Atmospheric releases at high level, accompanied by high energy, ensure a wide dispersal of radioactivity.

Inventory of I-131 and Noble gases at RAPS-3&4

For LOCA:

I-131: 1.06 106

curiesNoble gases: 1.56 10

6 curies

For LOCA+ ECCS failure:

I-131: 22.6 106

curiesNoble gases: 201.7 10

6 curies

b. Sample Cells are used to analyze air activity of Reactor Building (RB) quantitatively and qualitatively during accidental conditions when reactor gets boxed up. Sample cell is located at Ventilation Duct Radiation Monitoring (VDRM) room at 106m.El. Of Service building. The air from RB continuously flows through ugh the cells. When the reactor is boxed up, the cell will be sealed and the air gets trapped in the cell. The sample is removed and analyzed on MCA for various radionuclides.

- The sample cell is connected with quick disconnect couplings.- Shift Charge Engineer will inform Shift Health Physicist about reactor box-up.- Immediately after Reactor box up, disconnect the sample cell.- Note the time of removal of sample cell.- Analyze the cell on Multi Channel Analyzer system as per standard procedure.- Note the activity of each radionuclide.- Inform the values to control room and Station Health Physicist.- Connect the sample cell back in the system.- Reset the flow through the sample cell.

40. Give the bases, on which the limits of releases of radioactive effluents are stipulated. Give the limits of, releases of the following radionuclides in your reactor

a) Tritium in air routeb) Iodine in air routec) Gross beta activity in water route

The limits on release of radioactive effluents are derived based on the following factors:

a) Site dispersion factorb) Critical path of exposure

c) Critical group for a given path of exposured) Food habits & consumption ratee) Transfer coefficientsf) Relative humidityg) Atmospheric stability classh) Deposition velocity of Radionuclide

Release limits for RAPS-3&4 (annual average rate of d i s c h a r g e )

a) Tritium in air route (as oxide)

7.4 TBq/d (200 Ci/d). Ten times maximum discharge from both the units in a single day can be the average daily discharge limit provided annual average is not exceeded.

b. Iodine in air route

0.74 GBq/d (20 Ci/d). Ten times in a day provided annual average is not exceeded.

c) Gross beta activity in water route

Total release not to exceed 1.48 GBq/d for R-1 to 4 (total 40 mCi/d, 20 mCi/d,Each for RAPS-1&2 & RAPS-3&4) and concentration in water shall not exceed 7.4 x 10

-4 MBq/ml. Ten times in a day provided annual average is not exceeded.

41. What are the factors that determine the radioactive releases to the environment? What are specifications of these releases for your station? Your answer should include both air and water routes?

The factors that determine the radioactive releases to the environment are:

a) Site dispersion factorb) Critical path of exposurec) Critical group for a given path of exposured) Food habits & consumption ratee) Atmospheric stabilityf) Radio nuclides releasedg) Deposition velocity of radio nuclides h) Transfer coefficient of radioactivity from Grass to Animals etc.,i) Relative humidity of atmosphere

Liquid Effluents

Tritium Gross Beta-gamma activity

Release limit 35 Ci/d (for RAPS-3&4) 20 mCi/d (for RAPS-3&4)

Concentration in water

30 PCi/ml 2.0 x 10-8

µCi/ml

Gaseous Effluents

Radionuclide Release limit

Tritium (as oxide) 7.4 TBq/d (200 Ci/d)

FPNG 23.68 TBq (640 Ci/d)

Ar-41 2.96 TBq (80 Ci/d)

I-131 0.74 TBq/d (20 mCi/d)

Particulate 0.56 TBq/d (15 mCi/d)

The releases can be ten times in a day provided the annual average is not exceeded.

42. What do you mean by target dose, manrem budgeting and manpower control?

a) Target Dose:

Target dose in the limit of collective dose approved by SARCOP derived from source control techniques at design, construction and operation of nuclear power plants a n d e x p e r i e n c e .This dose limit should not be crossed by adopting appropriate ALARA practices.

Manrem Budgeting:

A manrem budget is a plan expressed in quantitative terms of dose for a particular group/job. It includes;

a) Quantification of tasks to be performed

b) Quantification of manpower required and

c) Scheduling the works in active areas

The manrem budget provides a set of guidelines for use in controlling the operation and maintenance activities in the organization.

Manpower control:

Manpower control means the availability of manpower and man-hours for executing the planned jobs during the years. The employment of temporary workers may increase the collective dose due to less efficiency while working in radioactive areas.

43. How can source control technique help in reducing the total manrem consumption?

The above can be achieved by reducing the inventory or eliminating the following.

Activation products

The major activation products observed in PHT and moderator system are Co-60 and Fe -59. The selection of components shall be such that the impurities of these will be minimum so that source control can be achieved.

Examples: Selection of colomony for adjuster rod ball bearings.

System inventories of radionuclides

The major radionuclides observed in PHT and Moderator system are: Zr-95, Zr- 97, Mn -56, Co -60, Cu-64, Fe-59 and Mn -65.

The equilibrium system activity of various radionuclides is available in design manual on shielding for RAPS-3&4. These inventories can be minimized by increasing the current time and reducing the corrosion rate by maintaining good system chemistry.

44. Which are the important factors, important role in the achieving of low annual occupational exposure at NPP’s?

The important factors to achieve low annual occupational exposures at NPPs are:

a) Manrem Budgeting

A manrem budget is a plan expressed in quantitative terms of dose for a particular lar group/job. It includes;

- Quantification of tasks to be performed- Quantification of manpower required and- Scheduling the works in active areas

The manrem budget provides a set of guidelines for use in controlling the operation and maintenance activities in the o r g a n i z a t i o n .

b) Monitoring of working conditions

RP group monitors the radiological conditions in the work area routinely and/or before carrying out any special jobs. A database of radiological conditions is created by HPU in specific areas to study any increase/change in such conditions and necessary action will be taken by the management to reduce the dose- rates/contamination levels in the work environment. The radiological survey in general includes:

- Assessment of radiation levels- Identification of hot spots- Assessment of air borne contamination levels- Assessment of surface contamination levels

c) Work process steering and control

Work process steering and control can be achieved by adopting the following procedures:

- Radiological work permit for all radioactive jobs for dose accounting.- Work area supervision by a Green qualified person- Dose follow -up and review for jobs with radiation exposure- Job co -ordination by supervisors and Engineers in the work area to avoid r ework .

d) Training on “ALARA Principles and practices”:

Education and Training are one of the pre-requisites for worker's involvement to achieve ALARA exposures. To implement and follow an ALARA approach, all personnel shall be trained and ALARA principles & practices. An Operating Manual is prepared on "ALARA Principles and Practices" to train all personnel and it is necessary to write examination on this topic to be Green qualified. The training programme will be repeated as a refresher course before outages to inform workers of the important aspects of radiation protection and special aspects of dose reduction in work.

45. Proper dose management system helps to take correct actions and enforce radiation protection standards

a) What is the dose management system followed at your station?b) Give five important examples of administrative factor achieve ALARA doses.

a. Individual and collective dose control is a requirement in nuclear power plants. Atomic Energy Regulatory Board in tune with the recommendations of International Commission on Radiological Protection stipulates individual dose limits. Several inputs such as Training of personnel in radiation safety aspects, work-planning methodology, assessment of radiological conditions in plant areas and techniques to achieve ALARA measures form part of overall dose management in the power station.

i) Organization on Radiation Safetyii) Training on Radiation Safetyiii) ALARA Committeeiv) Job planning and ALARA Techniques

a) Manrem Budgetb) Manhours of working conditionsc) Work process status and controld) Training on ALARA principles and practices

v) Use of computers in Dose Management

a) Computerization of dose recordsb) On-line dosimeter issuec) Display of radiation levels in charts

vi) Quality circle

b) Administrative factors to achieve ALARA doses are:

- Access Gates to shutdown Accessible areas- No entry to Zone-2 onwards without TLD- No exit to Zone-1 without monitoring at Exit Portal Monitor- No work is allowed in radioactive area without Radiological work permit- No entry to radioactive areas without Direct Reading Dosimeter.

46. What is ALARA? Why no numerical value is given for ALARA?

ALARA is an abbreviation for As Low as Reasonably Achievable. This principle is used for optimization of radiation protection and is defined as follows:

"In relation to any particular source within a practice, the magnitude of individual doses, the number of people exposed, and the likelihood of incurring exposures where these are not certain to be received should all be kept as low as reasonably achievable (ALARA), economic and social factors being taken into account. This procedure should be constrained by restrictions on the dose s to individuals (Dose Constraints) or the risks to individuals in the case of potential exposures (Risk Constraints), so as to limit the inequity likely to result from the inherent economic and social judgments (The optimization of Protection)".

No nume rical value is given for ALARA, as it is a qualitative term used to indicate the reduction in dose by various optimization processes.

47. What are the different characteristics of the stack release needed for evaluation of dose due to gaseous discharge from NPPs?

Four general elements necessary for performing dose assessments a re :

Characterization of the radionuclide or the radiation source – including the chemical form and the type of radiation emitted.

Determination of radionuclide distributions in cluding where and how the radionuclides are being released (e.g. stacks, water discharges, etc.)

Determination of radiation incident on the population and / or its radionuclide accumulation.

Determination of the subsequent radiation dose to the populat ion .

48. a. What are the data Meteorological Laboratory attached to NPP are collecting?

b. What is X/Q? On what does it depend?c. How does X/Q value influence release limit for a given apportioned dose

at fence post? Is a lower or higher value of X/Q desirable?

a. The data collected by meteorological laboratory and the application of data is given below:

Description of data Application1. Wind direction To know the affected section2. Wind speed To know the extent up to which the sector is

affected3. Rain f a l l To take into accent wash down factors etc.4. Atmospheric stability class To make decision for release of gaseous effluents

During accidental conditions

5. Horizontal and vertical dispersion coefficients

To identify suitable atmospheric conditions for effluent releases during accidental conditions.

b. X/Q is the ratio of ground concentration to the release rate of gaseous effluents through the stack. It is called Site dispersion factor. The site dispersion factor depends on atmo spheric stability class, terrain and height of the stack, etc.,

c. For a given apportioned dose at fence post, the release limit decreases with increase in X/Q value. The lower X/Q is desirable to increase release l imi ts .

49. What are the basic meteorological parameters needed in evaluation of the dose due to gaseous releases?

The basic meteorological parameters needed for evaluation of the dose due to gaseous releases are:

- Wind direction- Wind speed- Affected sector- Stability class- Site dispersion faction- Maximum temperature- Relative Humidity- Rainfall etc.,

50. Explain the following terms:

a) Inversionb) Fumigationc) wake effectd) deposition velocitye) critical pathwayf) Fanningg) Loftingh) Coningi) Looping

Inversion:

The reversal of the usual variation of an atmospheric property(Temperature) with height is called Inversion and the layer through which the reversal takes place is called Inversion layer.

Fumigation:

The transport to the ground of radioactive effluent plume when there is an adiabatic lapse rate in the lower layer topped by an inversion. Downward mixing goes on readily but the inversion limits the upward mixing. This configuration arises when there is an inversion at the ground at sunrise, which arises above the stack plume level due to heating from solar radiation. After this level is reached, the effluents mix downward rapidly fumigating the ground, which has until this time been protected from the plume by the inversion. This process may result in an abrupt increase of the effluent concentration at the ground to a high l e v e l .

Wake effect:

Radioactive materials released through leaks in the buildings or from short stacks will be mixed in the turbulent wake created by the ambient air flow around these buildings. This effect creates a volume source, called Wake effect.

Deposition velocity:

Deposition velocity is a parameter used to apply correction for impaction or adsorption on surfaces along the Plume downwind direction. The Deposition velocity is defined as:

Vg ( m sec -1 ) =Rate of deposition (Bq cm-² sec

-1)

Concentration near the surface (Bq cm -3

)

For Iodine -131, Vg = For Particulate, Vg =

Critical pathway:

Radionuclides released into the environment can irradiate the population through many pathways. But some pathway may result in substantially higher dose to public than others. Such pathways which cause maximum dose to public for a given release / concentration are called critical pathways. For e g . I-131 released into the environment, the air-grass-cow-milk pathway is the critical pathway of exposure.

T

h

Fanning:

When the radioactive effluents are emitted into an inversion layer, the stability prevents diffusion up and down, so that the only spreading of the effluents is sideways. Since the plume is thin in the vertical and is V -shaped in the horizontal, the phenomena are fanning.

Lofting:

The spreading in upward arcs of a radioactive plume emitted into air with an inversion below the stack exit and an unstable lapse rate at and above it. The radioactive effluents are emitted at the top of an inversion layer, where it is kept from mixing downward but spreads upward. This tendency to be carried aloft but to the ground has been termed as lofting.

Coning:

The radioactive effluents released from a stack into a deep adiabatic layer allow spreading of plume uniformly in all cross wind directions. viz., lateral & vertical) The turbulent motions that are induced by irregularities of the ground and shearing of the wind are not amplified by instability. The vertical spreading and lateral spreading are about equal and the effluent plume resembles a cone

Looping:

When there is a super adiabatic lapse rate through a deep layer the radioactive effluents are carried up -and -down by convection currents forming a looping pattern and are rapidly diluted by the intense vertical mixing.

51. Explain the following terms:

a) Lapse rateb) Adiabatic Lapse ratec) Sub Adiabatic Lapse rated) Super Adiabatic Lapse ratee) Stable conditio nf) Unstable conditiong) Neutral condition

Lapse rate:

The rate of decrease of temperature with height is known as lapse rate. Adiabatic Lapse rate

A process in which no heat exchange between an air parcel and its surroundings occur is called adiabatic process. The motions of the air are approximately adiabatic near the ground.

The rate of decrease of temperature with height as one goes upward in air column is different from the adiabatic rate of cooling.

- = observed

T

h- =

Adiabatic process

If the lapse rate in an air column ( ) is equal to the rate of adiabatic cooling , the air column is said to have an adiabatic lapse rate.

Sub Adiabatic Lapse rate:

If the lapse rate in an air column () is less than the rate of adiabatic cooling , the air column is said to have super adiabatic lapse rate.

Super Adiabatic Lapse rate:

If the lapse rate in an air column ( ) is greater than the rate of adiabatic cooling, the air column is said to have super adiabatic lapse rate.

Stable condition:

If the displacement of the object gives rise to forces that tend to bring it back to its original equilibrium position is said to be stable.

The lapse rate (sub adiabatic) is less than the adiabatic rate of cooling , the system is said to be under stable equilibrium.

Unstable condition:

If the displacement of the object leads to forces that tend to increase the displacement from the equilibrium position, the equilibrium is called Unstable.

The lapse rate (super adiabatic lapse rate) is greater than the adiabatic rate of cooling . The system is said to be under unstable equilibrium

Neutral condition:

If no forces arise from the displacement of the object, the equilibrium is neutral. The lapse rate is equal to the adiabatic rate of cooling . The system is said to be under Neutral equilibrium

52. Explain the classification of Pasquill atmospheric stability.

Classification of Pasquill atmospheric stability:

Class A - Strongly unstableClass B - Moderately unstable Class C - Slightly unstable Class D - NeutralClass E - Slightly stable Class F- - Moderately stable

The above classification depends on wind speed, horizontal and vertical dispersion coefficients in the atmosphere.

53. What do you understand by:

(a) Windrose

Wind rose is the graphical display of wind speed and wind direction by magnitude. Wind rose indicates the predominant wind direction and magnitudes of wind direction in percentage at different elevations.

54. What are the limits in the following cases:

a) Monthly dose to a radiation workerb) Annual dose to a casual radiation workerc) Annual dose to skind) Annual dose to eye lense) Emergency planned dose

- Monthly dose to a radiation worker : 10 mSv- Annual dose to casual radiation worker : 15 mSv- Annual dose to skin : 500 mSv- Annual dose to eye lens : 150 mSv- Emergency planned dose : 250 mSv

55. Why are the ALI values of different radioisotopes different?

The committed effective dose due to unit uptake of a radionuclide is different for different radionuclides. ALI is derived from annual effective dose of 20 mSv. Hence, ALI values are different for different radionuclides.

56. What is the maximum unplanned dose for one month? What action is required if it is planned to exceed this limit?

The maximum unplanned monthly dose limit is 5 mSv for department persons and 2.5 mSv for contractor persons.

Notification of planned exposure (NOPE) is required for the persons who planned to exceed the l i m i t s . NOPE shall be authorized by section Head in case of department personnel and CS in case of contractors.

57. Outline the procedure for disposal of the following types of radioactive wastes

- Ion exchange Resin (field is less than 10 R/h)- Wet filter cartridge (field: 50 R/h)- Organic liquid wastes

a. Ion exchange Resin (field is less than 10 R/h)

Ion-exchange resin ejected from SS hopper of PHT/Mod system at Waste Management Centralized Facility (WMCF) into MS hoppers for disposal purposes. If the field is less than 50 R/h, these MS hoppers are disposed into RCC trenches or RCC vaults.

b. Wet filter cartridge (field: 50 R/h)

The wet filter cartridges removed from various systems are shielded after removal and transported to Waste Management Centralized Facility for treatment and disposal. The systems, which generate wet filters as a waste, are PHT Gland Filters, SFSB, Filters, PHT Filters, Resin transfer system filters, liquid effluent treatment process filters etc.

The wet filters are fixed with cement and vermiculate soil in a 200 l drum and allowed for curing.

The wet filter fixed in a drum will be disposed of at Solid Waste Management Facility (SWMF) based on the radiation l e v e l s .

c. Organic liquid wastes

Procedure for disposal of organic liquid waste: The organic liquid waste is collected in carboys at the source mainly from tritium counting laboratory and chemical control laboratories. Then, the organic waste is transferred to Waste Management Centralized Facility (WMCF) for treatment and disposal purpose. At WMCF, the organic waste is transferred to a 200 l drum and vermiculate powder is sprinkled to soak in organic waste. The solidified organic waste is disposed of into RCC trenches in respective of radiation levels.

58. What are the basic principles of waste management? How are high active liquid wastes disposed of?

Basic principles of waste management:

- Dilute and Disperse (Low active Liquid effluents)- Concentration and contain (High active liquid effluents)- Delay and Decay (Short live radio nuclides)

Disposal of high active Liquid wastes:

High active liquid waste is fixed in vermiculate glass matrix. The disposal of conditional high active liquid waste is depends on the nature of radionuclides and disposed into suitable various engineered safety disposal facility based on the radiation levels.

What is over-exposure? How can it be avoided? How and why it is investigated?

Over exposure: Dose limits are specified for occupational and temporary workers for a block period of 5 years. In house limits are provided by the station, to ensure that these dose limits are not exceeded. These limits are specified for monthly, quarterly, yearly and internal uptake of tritium & iodine. Any person exceeding these in house limits are said to be received over exposure.

Over exposure shall be investigated to know the genuineness of the dose received by an individual.

Over exposure cases shall be investigated within 72 hours of the report of the exposure, if the quarterly or annual limits are exceeded. In other cases, investigation shall be carried out within 15 days of the report. Investigation

Report shall be issued with 48 hours of investigation. A copy of the report shall be sent to SARCOP.

Over exposure can be avoided by following radiation protection procedures, ALARA practices during normal operation of the plant and by following radiation emergency procedures during emergency conditions. These procedures mainly includes the following:

- Adhering to Radiation protection procedures.- Use of Alarming dosimeters- Monitoring individual doses during the job

What are the objectives of stack monitoring (sampling)? What are the technical specifications for releases through stack at your station?

- To estimate the amount of radionuclides released through the stalk to the environment

- To ensure that the effluents released to the environment are within technical specifications of the station approved by Atomic Energy Regulatory Board

- To control the consequences which lead to release of effluents in excess ofTechnical specifications.

Technical Specifications for Gaseous e f f l u e n t s :

H-3 (as oxide) 7.4 TBq/d 200Ci/dAr-41 2.96 TBq/d 80Ci/d

FPNG 23.68 TBq/d 640 Ci/dRadioactive Particulate 0.56 GBq/d 15 m Ci/d

Iodine-131 0.74 GBq/d 20 mCi/d

ALI values are different for different radioisotopes

ALI values are different for different radioisotopes. The committed effective dose due to each radionuclide is different. This is due to type of radiations emitted from a radionuclide, its energies and fields are different. Hence, the dose received by one Bq of different radionuclides is different and thus ALI values are different.

Tritium : 3 × 109

BqIodine -131: 1× 10

6 Bq

Tritiated water is more hazardous than tritium

Tritiated water is more hazardous than tritium. Human body consists of water 60% weight. Hence, tritiated water is easily miscible with body water and thus gives exposure to whole body. Whereas tritium can only replace hydrogen atoms present in body water and gives dose locally. Hence tritiated water is more hazardous than tritium.

What hazards do neutrons and X-ray present to the eye?Neutron possess high Linear Energy Transfer (LET) per a given distance traveled. Hence, exposure of neutrons to eye may cause cataract of the lens. Similarly, X- rays are monoenergetic in nature, may lead to cataract of the e y e .

Name two changes that occur to atom / molecule when radiation passes through matter

The radiation effects the atom/molecule in two different ways:

- Excitation- Ionization

In excitation, the irradiated atom/ molecule goes to high energy level and comes to ground level by emitting excess release in the form of energy. For this process, the atom/molecules rearranges its e l e c t r o n s .

In Ionization, the irradiated atom/molecules divided into positive and negative and which further react with other biological chemical molecules thus changing the chemistry of the body.

How internal exposure of your plant is is measured and how it can be minimized?

Internal Exposure: The internal exposure of plant personnel is estimated by urine analysis. All plant personnel are advised to submit urine samples two hours after completion of the job. The frequency of submission of urine samples shall be once in a week or as and when tritium uptake is suspected.

The internal dose is estimated using the formula:

D (mSv) = 0.0583 Q T (for weekly sample submission)= 0.5 Q (Committed dose assuming Tb= 6 d)

Where Q=(Q1+Q2)/2 - average tritium uptake in the body in MBq/l.Q1 - tritium uptake on date t1 in MBq/lQ2 - tritium uptake on date t2 in MBq/lT - The time period between two sample submission in days.

Control of internal dose: Internal exposure due to tritium can be minimized by the following methods:

a) Use of appropriate respiratory protectionb) Avoiding skin wettingc) Providing local ventilation in high tritiated atmospheres.d) Use of remotely operating vacuum mopping systems for recovery of heavy water.

Tritium dose contributes a significant % of the collective dose. Give a comprehensive recommendation and an action p l a n for minimizing tritium exposure in the operating units.

Tritium dose contributes to about 20% of the collective dose in Pressurized Heavy Water Reactors (PHWRs). The tritium dose can be minimized in PHWRs by the following:

a) Minimizing leaks from PHT System in all areas of reactor building

b) Ensuring the availability of all dryers for heavy water collection and with high efficiency.

c) Ensure proper ventilation balance in all reactor-building areas.

d) Provide remotely operable vacuum mopping systems like vacuum for heavy water recovery.

e) Use of appropriate respiratory protection

f) Avoiding Skin wetting during heavy water recovery

g) Proper isolation of the system, which has high potential for heavy water spillage prior to taking up the maintenance jobs.

59. What is the importance of Radiation Work Permit (RWP)? How is it issued?

RWP issue procedures:

- RWP Shall be applied by a Green qualified person for all radioactive jobs- Person applying RWP shall fill up all the columns like Reactor Status, Job details, Job

code; persons involved in the job with TLD Nos. and planned doses.- The Shift Health Physicist shall fill up the current month, annual dose details,

Uptake details and category details in the permit- He also mention the radiological conditions- He also shall recommend appropriate protective wear and respiratory protective

equipment depending on the radiological conditions.- He also should mention any special precautions to be taken in the work area.- The permit shall be signed by Shift Health Physicist and permit holder

The Radiological Work Permit is valid for a shift, a day depending on the nature of the job

60. Name three dosimetry devices and explain when they are used to maximum advantage.

a) Thermo luminescent dosimeter (TLD):

Used for assessment of gamma and beta dose of station personnel on monthly basis. It is mandatory to use this dosimeter regularly and treated as official dosimeter.

b) Direct Reading Dosimeter (DRD):

Used for assessment of gamma dose on day to day basis for accounting of dose to ensure that monthly, quarterly or yearly doses are not exceeded. It is mandatory to use this dosimeter regularly along with TLD during worker in a radioactive area.

c) Fast Neutron Foils (Cr-39)

Used for assessment of fast neutron dose during on power entry to moderator room or pump room where neutron fields exist fast. It is mandatory to use this dosimeter during on power entry for neutron dose assessment.

State the factors on which the tritium concentration in PHT & Moderator System depends?

The tritium concentration in PHT and Moderator System depends on the following factors:

? Average thermal neutron flux in the system? Activate cross section of deuteron.? Disintegrate constant/half-life of tritium? Total circuit time? Core transit or influx time? Total time of reactor operation (full power days)

What are the isotopes monitored during whole body counting. What is the type of detector?

The isotopes monitored during while body counting are I131

, Co 60

, Cs137.

Gamma detector is used for measuring the activity due to the above isotopes during the whole body counting.