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■iMuimAECL-11567 CA9700302

A Description of 60Co Gamma Irradiation Facilities in the Radiation Biology and Health Physics Branch

Description des installations d irradiation gamma an 60Co de Radiobiologie et Radioprotection

B.P. Smith, RE. Lee

June 1996 juin

VOL 286 19

AECL

A DESCRIPTION OF 60Co GAMMA IRRADIATION FACILITIES IN THE RADIATION BIOLOGY AND HEALTH PHYSICS BRANCH

by

B.P. Smith and P E. Lee

Radiation Biology and Health Physics Branch Chalk River Laboratories

Chalk River, Ontario KOI 110 1996 June

AECL-11567

EACL

DESCRIPTION DES INSTALLATIONS DTRRADIATION GAMMA AU “CO DE RADIOBIOLOGIE ET RADIOPROTECTION

par

B P Smith et P E Lee

RESUME

Le service Radiobiologie et Radioprotection assure la gestion de trois installations d’irradiation au “Co (Gammabeam 150C, Gammacell 200 et Gammacell 220). Ces installations conviennent a des applications diverses en raison de la vaste plage de doses d’irradiation possibles. Le present rapport decrit les caracteristiques des installations, les mesures dosimetriques et les procedures d’exploitation.

Radiobiologie et Radioprotection Laboratoires de Chalk River

Chalk River (Ontario) KOI 1 JO 1996 Juin

AECL-11567

AECL

A DESCRIPTION OF 60Co GAMMA IRRADIATION FACILITIES IN THE RADIATION BIOLOGY AND HEALTH PHYSICS BRANCH

by

B P Smith and P E Lee

ABSTRACT

The Radiation Biology and Health Physics Branch manages three 60Co irradiation facilities, to (Gammabeam 150C, Gammacell 200 and Gammacell 220) provide a range of dose rates suitable for a variety of applications. This report describes the physical characteristics of the facilities, a description of the dosimetry and operating procedures.

Radiation Biology and Health Physics Branch Chalk River Laboratories

Chalk River, Ontario KOJ 1 JO 1996 June

AECL-11567

CONTENTS

Page

1 INTRODUCTION 1

2. BASIC FACILITIES 1

2.1 Physical Layout 12.2 Radiation Sources 1

2.2.1 Gammabeam 150C 12.2.2 Gammacell 200 22.2.3 Gammacell 220 2

2.3 Dosimetry 22.3.1 Historical 22.3.2 Keithley Therapy Dosimeter 32.3.3 Ionization Chambers 32.3.4 Gammabeam 150C Dosimetry 3

2.3.4.1 Dose Rate Summary (for 1994 September 12) 42.3.5 Gammabeam Dose/Distance Calculation 42.3.6 Gammacell 200/220 Dosimetry 4

2.4 Cobalt-60 Gamma Decay Calculations 52.4.1 Gammabeam 15 0C 52.4.2 Gammacell “Dead-Time” Dose Calculations 5

3. RADIATION DOSE CONVERSIONS 6

4. REFERENCES 7

ACKNOWLEDGMENTS 7

APPENDIX A Operating Procedures 22

APPENDIX B Decay Charts 30

continued....

II

CONTENTS (concluded)Page

LIST OF FIGURES

1. Gammabeam 150C 8

2. Gammacell 200 9

3. Gammacell 220 10

4. Gammacell 150C Radiation Field (50 cm) 11

5. Gammacell 150C Radiation Field Cross Section (50 cm) 12

6. Gammabeam 150C Radiation Field (392 cm) 13

7. Gammabeam 150C Radiation Field Cross Section (392 cm) 14

8. Gammabeam 150C Radiation Field (989.5 cm) 15

9. Gammabeam 150C Radiation Field Cross Section (989.5 cm) 16

9a. Gammacell 200 Isodose Curves 17

9b. Gammacell 220 Radiation Field 18

10a. Gammacell 220 Isodose Curves 19

10b. Gammacell 220 Isodose Curves 20

A1 Gammabeam 150C Control Panel 25

LIST OF TABLES

1. Cobalt-60 Decay Table 21

B1. Cobalt-60 Decay Chart for Gammabeam 150c 31

B2. Cobalt-60 Decay Chart for Gammacell 200 32

B3. Cobalt-60 Decay Chart for Gammacell 220 33

1. INTRODUCTION

The 60Co gamma irradiation facilities, managed by the Radiation Biology and Health Physics Branch at the Chalk River Laboratories (CRL), include a Gammabeam 150C, Gammacell 200 and a Gammacell 220. These facilities, which were all manufactured by Atomic Energy of Canada Limited, Commercial Products (now Nordion), provide a range of dose rates suitable for a variety of applications. Increasing internal and external demands for use of the facilities has prompted the acquisition of a dosimeter for routine dose rate calibrations. This document provides a physical description of these facilities and the dosimetry and operational procedures used in these facilities. The Radiation Biology and Health Physics Branch has additional irradiation facilities including x-ray, neutron and 137CS sources are described elsewhere (Freedman et al. 1994).

2. BASIC FACILITIES

These facilities, in combination with experienced personnel, offer the opportunity to do a wide variety of radiation exposure applications. The Gammabeam 150C is currently located in building 404B, with a planned move to the new Biological Research Facility (BRF). An addendum to this report will be attached describing the new facilities in the BRF after they become operational. The Gammacell 200 and 220 units are located in Building 513 A, Room 2 at CRL. Access to all irradiation facilities is restricted to trained personnel who must book the facility in advance, obtain a key from the current owner (Blake Smith) and return the key on sign-out.

2.1 Physical Layout

The Gammabeam 150C is housed in a shielded room and provides a beam of 60Co radiation (Figure 1) offering the advantage of a variable dose rate and target size. The Gammacells 200 and 220 are self-contained irradiation sources (see Figures 2 and 3). The 60Co radiation sources are shielded by a lead castle and are accessed by a movable irradiation chamber in the Gammacells.

2.2 Radiation Sources

2.2.1 Gammabeam 15 0C

The Gammabeam 150C is a 60Co irradiation facility designed for use in a shielded room (AECL 1979). See Appendix A, Section 1 for an operating procedure. It is a basic panoramic unit equipped with a beam port head (Figure 3) emitting a radiation beam (5.08 cm. by 2.85 cm) at the cylindrical surface of the source. The beam is confined to 15° above, below and to either side of the beam. This unit was charged with 179 TBq (4.82 kCi) of 60Co in 1968 May. The source in the down position is shielded, whereas when the drawer is raised the source becomes fully exposed in the beam port. Source exposure time is controlled by an electronic timer designed at CRL. The Gammabeam room has a solenoid operated door interlock as a safety measure. This facility offers a variable dose rate dependent on the distance from the source (Table Bl).

2

2.2.2 Gammacell 200

The Gammacell 200 is a 60Co irradiation facility designed for use in an unshielded room (AECL 1970). The unit consists of an annular-shaped source, a lead shield around the source, and a long cylindrical drawer, free to move vertically through the centre of the source. The unit was charged with 17.8 TBq (480 Ci) of 60Co in 1975 May. The drawer carries samples to be irradiated from outside the shield to inside the source. Irradiation of samples up to 8.9 cm in diameter and 13.9 cm in height can be undertaken with relative safety for operating personnel (< 5 mrad/hr on contact).An access tube in the drawer top allows liquid, gas, electrical or mechanical connections to the sample chamber. A CRL-designed digital electronic timer allows control from 0 to 999 in periods of seconds, minutes or hours. (See Appendix A, Section 2 for the Operating Procedures). The dose rate for 1996 June was 1.45 R/s (1 R = 2.58 x 1CT4 C/kg)(Table B2).

2.2.3 Gammacell 220

The Gammacell 220 is also a 60Co irradiation facility designed for use in an unshielded room (AECL 1978). The 220 unit is essentially identical in operation to the 200 (see above) but has greater shielding to accommodate 897 TBq (24.25 kCi) of 60Co, charged in 1980 January. The cylindrical sample chamber is 20.5 cm high and has a diameter of 15 cm with external access during irradiation via a one-inch channel through the top of the drawer. A CRL-designed electronic timer allows control of exposure time from 0 to 999 in periods of seconds, minutes or hours (See Appendix A, Section 3 for the Operating Procedures.). The dose rate for 1996 June was 4.091 kR/min. (Table B3).

2.3 Dosimetry

Dosimetry is presently performed using ionization chambers of varying volumes connected to a Keithley Therapy Dosimeter. The instrument and ionization chambers are calibrated by the Instrument Calibration Section of the Radiation Biology and Health Physics Branch, against National Research Council of Canada standards.

2.3.1 Historical

Prior to 1994, dosimetry of the facilities was based on calibrations using the Fricke method (Spinks and Wood 1964). This is a chemical method that involves the oxidation of an acid solution of ferrous sulfate to the ferric salt, in the presence of oxygen and under the influence of radiation. This is performed under meticulously “clean” conditions and solutions are read on a spectrophotometer, comparing absorbance of irradiated and non-irradiated samples at 304 nm (the maximum absorbance of the ferric ion). Calibration curves of dose versus time are constructed. This method was designed to measure higher doses (>40 Gy) but can be tailored for lower doses. In practice, the error is approximately 10%.

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2.3.2 Keithley Therapy Dosimeter

All dose measurements reported in this document were made using a Keithley Model 35040 Therapy Dosimeter. This instrument provides automatic correction for air density (temperature and barometric pressure) and ionization chamber volume. The instrument provides a bias voltage for the chamber through the connecting cable, which also returns the signal. See Appendix, Section 4, for an operating procedure. This is a reference grade instrument and is extremely stable, linear and maintains zero drift. The instrument uses calibrated ion chambers to simultaneously measure and display dose and dose rate in user-specified radiological units. Roentgens per minute, (R/min.) are used for most measurements. It also supplies a stable, user-programmable, electronic bias voltage for ion chambers, which is continuously monitored. Calibration factors for ion chambers, pressure measurement units and bias voltage are input from an IBM PC compatible computer and downloaded to the electrometer’s EPROM where the values are stored. Additional factors such as daily temperature and barometric pressures are entered at the front panel of the instrument.

2.3.3 Ionization Chambers

Exposures are measured using ionization chambers of varying volumes, depending on the required dose range. The Farmer-type 0.6 cm3 chamber consists of a thin-walled, high-purity graphite thimble and a pure aluminum electrode, supported by a thin-walled aluminum stem. This is connected to the meter by a length of low noise triaxial cable with a Bendix TNC triaxial plug. An electrical bias of 300 Vdc is normally applied. The probe tip is protected by a 0.3 MV to 2 MV, vented, built-up cap. A Keithley Model 35040 Therapy Dosimeter with a New England Technologies 15 cm3 flat,

graphite ion chamber with a 5-mm Perspex window was used to measure intermediate doses. The calibration factor for the detector was 2.094 roentgens per nanocoulomb (R/nc), as established against a 35 cm3 ion chamber previously calibrated against a National Research Council of Canada standard. Ionization chambers for lower ranges are also available.

2.3.4 Gammabeam 150C Dosimetry

The Gammabeam 150C fields were mapped at three distances corresponding to low, intermediate and high dose rates. See Figures 4 to 8 for details. In addition, cross sections at each distance were measured until a significant decrease dose energy was found at each side of an arbitrary midpoint.For the 50-cm measurement, a reading above and below the centre point was taken to give a vertical profile of the beam. The resulting dose measurements were then plotted using a spreadsheet program and the respective graphs were plotted. Note that the dose will decrease as a function of distance from the midpoint. All exposures therefore should be calculated and performed at the centre of the beam. See Appendix B for monthly dose decay charts from 1996 January to 1999 December for the three radiation sources.

4

2.3.4.1 Dose Rate Summary (for 1994 September 12):

50 cm - 9.38 R/min.392 cm - 0.148 R/min.989.5 cm - 0.027 R/min

2.3.5 Gammabeam Dose/Distance Calculation

When using the Gammabeam 150C, the option of using a given dose rate is available by selecting an appropriate exposure distance. Dose rates may also be calculated by using the inverse square law (e g., when the distance from the source is doubled, the dose rate is reduced to one quarter).

Example: A dose rate of 9.38 R/min. measured at 50 cm from the source becomes(9.38/4) or 2.345 R/min. at 100 cm.

Example: To calculate the distance for a given dose rate, - for example. 2 R/min. proceed asfollows:

Dose rate is proportional to factor K/distance2

At 50 cm the dose rate is 9.38 R/min (measured), factor K is calculated to be

9.38 R/min = K/502

Therefore K = 23450

To deliver 2 R/min, the distance from source is calculated as

2 R/min = 23450 / distance2

distance = V23450/2 R/min = 108.3 cm

Therefore, the distance from source to deliver a dose rate of 2 R/min is 108.3 cm.

2.3.6 Gammacell 200/220 Dosimetry

The Gammacell 200 and 220 radiation fields were measured using a previously calibrated 0.6 cm3 graphite pencil-type ion chamber. The calibration factor for this detector was 5.024 roentgen per nanocoulomb. The gammacell measurements were made at three different heights (bottom, middle and top) of each chamber (Figures 9a and 10a). At each height, five measurements were made to give a cross section. See Appendix B for monthly dose decay charts for the three radiation sources.

Note that the fields within the irradiation chamber of the Gammacells follow isometric dose curves. (See Figures 9b and 10b) There is an increase in dose from the midpoint to any of the vertical walls and a decrease in dose as you approach the top and bottom of the chamber. This is to due to the

5

geometry of the chamber in relation to the position of the sources. Again provision should be taken to use the midpoint, whenever possible.

2.4 Cobalt-60 Gamma Decay Calculations

Cobalt-60 decays with a half life of 5.27 years (63.24 months). Therefore each month the dose rate is reduced by 1.096% resulting in the necessity of calculating the dose rate on a monthly basis. See Appendix B for monthly dose decay charts for the three radiation sources. This is done routinely using a decay rate table (Table 1). To calculate a current dose rate, the measured dose rate for a given date (starting time) is multiplied by the decay factor for the current date, as read from the decay table. These values are calculated from the equation:

where

Activitylim.=Activity{^e{^"~)where

ti/2 = half-life of 60Co (63.24 months)tnow - present time minus starting time (in months)

2.4.1 Gammabeam 150C

A measured dose rate for a starting time of 1994 September of 9.38 R/min. for the Gammabeam 150C has decayed in 18 months (1996 March) by a factor of 0.8209, as read from the decay table (Table 1). Therefore, the 1996 March dose rate is (9.38 x 0.8209) or 7.700 R/min.

2.4.2 Gammacell “Dead-Time” Dose Calculations

For the two 60Co gammacells (the 200 and 220), the pencil sources are fixed. The irradiation chamber, containing sample materials, is lowered into the gamma field by a mechanical elevator system. As the chamber moves down towards the exposed pencils at the “rest” position, the material in the chamber gradually sees an increasing field. Therefore, the sample is being irradiated as it is being lowered into position. To account for this, the required exposure time must include the deadtime dose. (i.e. dose = dead-time dose + exposure dose for time ‘t’) Both dead-time dose and exposure dose must be corrected for decay of the source. These values are given for the dates between 1996 January and 1999 December in tables B2 and B3.

Using the 1994 September Keithley data from Figures 4, 9 and 10, the dose rates for the next 5 years have been calculated. See Appendix B, (Bl, B2, B3).

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3. RADIATION DOSE CONVERSIONS

The dosimetry provided by the Keithley Therapy Dosimeter is read in roentgens. However, some applications require dose rates in water or tissue, expressed in rads or grays. Roentgens are defined as the exposure that generates one electrostatic unit of charge per 1 cm3 of air (Johns and Cunningham 1969). One rad is 100 ergs of energy absorbed from any type of radiation per gram of the absorber.

1 roentgen = 1 R = 2.58 x 10'4 coulombs/kg exposure

1 rad = 100 ergs

100 rads = 1 Gy = 1 J/kg

Therefore, an absorbed dose in air corresponding to a gamma-ray exposure of 1 roentgen, or coulomb/kg amounts to 33.8 J/kg or 33.8 Gy or 3380 rads

Therefore, (for gamma-rays): 1 roentgen (R) = (3380 x 2.58 x 10-4) = 0.87 rads in air.

1 rem is defined as the unit of dose equivalent and is the product of the absorbed dose (D) rads and a quality factor (Q) or radiation weighing factor (Wr).

The quality factor (Q) = 1 for gamma-rays and X-rays

Therefore: 1 rem (dose equivalent) is numerically equal to 1 rad ~ 1.149 roentgens

100 rem = 100 rads = 1 Gy = 1 Sv (sievert)

To obtain the absorbed dose in tissue, Dussue (rads) from the exposure measured in air, E lir, (roentgens) the ‘roentgens-to-rads’ conversion factor, f tissue is used:5

Dtissue f tissue * E air

wherefassue =0.869(p/ p) tissue {p ! p)air

and p/p = mass energy absorption coefficients (m2/kg)

For 60Co gamma rays: /tissue = 0.96

DOSE CONVERSION IN AIR: 1 ROENTGEN = 0.87 RAD (1 RAD = 1.149 R)

DOSE CONVERSION IN TISSUE: 1 ROENTGEN = 0.96 RAD (1 RAD = 1.042R)

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4. REFERENCES

1. Freedman, NO, Aikens, M.S. and Szornel, K. The Radiation Biology and Health Physics Branch Irradiation Facility Uprgrade, AECL (Atomic Energy of Canada Limited), Chalk River, 1994 December.

2. AECL (Atomic Energy of Canada Limited), Instruction Manual Gammabeam 150 f°Co irradiation unit), Commercial Products, Edition No. 5, 1979 November.

3. AECL (Atomic Energy of Canada Limited), Instruction Manual for Gammacell 200 f°Co irradiation unit), Commercial Products, Edition No. 7, 1970 March.

4. AECL (Atomic Energy of Canada Limited), Operator’s Manual for Gammacell 220 I60Co irradiation unit), Commercial Products, Edition No. 7, 1978 March.

5. Spinks, J.W.T. and Woods, R.J. An Introduction to Radiation Chemistry, John Whiley & Sons Inc., Publ., New York (1964).

6. Johns, HE. and Cunningham, J.R. The Physics of Radiology, Charles C. Thomas, Publisher, Springfield, Illinois (1969).

ACKNOWLEDGMENTS

The authors are grateful to N O. Freedman for consultation during preparation of the report, to K.L. Gale for Gammacell/beam protocol preparation advice and support in the writing, and to K. Szornel, C.L. Greenstock, A.J. Waker, R.B. Richardson and P.A. Rochefort for assistance with definitions and revisions.

8

(CAM CONDITION INDICATOR ROD

SHIELDING RLU6

SOURCE APERTURE

• CAM PORT HEAD

DRIVE ENCLOSURE

Figure 1: Gammabeam 150C

9

INTERLOCK PLUG AND SOCKET (PG. ) SK.1)

CONTROL PANEL

RUBBER KICK STRIP

SHIELD PLUG

DRAWER TOP

SAMPLE CHAMBER DOOR

SAMPLE CHAMBER

'MICROFLEX'TIMER

MASTER KEY SWITCH (S.l)

FUSE (F.l)

DRAWER CONTROL ROCKER SWITCH (5.2)

MANUAL CRANK ACCESS PLUG BUTTON

FRONT STEP

Figure 2: Gammacell 200

10

TOP PLUGINTERLOCK MICROSWITCH

TOP SHIELDING PLUG

DRAWER TOP

COLLAR INTERLOCK MICROSWITCHES

COLLAR HANDLES COLLAR

HEAD

DOOR INTERLOCK ASSEMBLY

SAMPLE CHAMBER DOOR

CONTROL PANEL

DRIVE MECHANISM ACCESS PANEL

PLATFORM

Figure 3: Gammacell 220

11

GAMMABEAM 150C RADIATION FIELD (All measurements at 133 cm height)

September 12, 1994

Source (po 60, gamma)

50 cm Measurements

50 cm

7 cm8.578 R/min

7 cm9.251 R/min 9.376 R/min

230 cm

3.5 cm3.5 cm9.471 9.397R/min R/min

Figure 4. Gammabeam 150C Radiation Field (50 cm)

Wel

l

Expo

sure

(R/m

in)

12

Gammabeam 150C Cross Section at 50 cm from Source

9.3 -

9.2 --

9.1 --

8.8 -

8.7 -

8.6 -

Distance from Right wall (facing source)

Figure 5: Gammabeam 150C Radiation Field Cross Section (50 cm)

13

GAMMABEAM 150C RADIATION FIELD

(All measurements made at 133 cm height)1994 September 12

Soiree(Cobalt 60, gamma)

392 cm Measurements

392 cm

0.004 0.023 0.11$ 0.138 0.147 0.140 0.148 0.136 0.108

'Allxhti Mn 30.5an«part.

222 cm

Figure 6: Gammabeam 150C Radiation Field (392 cm)

Wal

l

Expo

sure

(R/m

in)

14

Gammabeam 150C Cross Section at 392 cm

450

Figure 7: Gammabeam 150C Radiation Field Cross Section (392 cm)

15

GAMMABEAM 150C RADIATION FIELD

(All measurments at 133 cm height) 1994 September 12

Sdurc# (Co SO. qimma)

2 nd Measurement PosiSan

989.5 on (from source)

ISO oa237 era 187 era 137 era (tom Id pt) 6.022 R/rah 0.025 R/nin 0.026 7Vm*i 0JZZ7 Wain 0.027 R/nA

Figure 8. Gammabeam 150C Radiation Field (989.5 cm)

Expo

sure

(R/m

in)

16

0.028

Gammabeam 150C Cross Section at 989.5 cm from Source

0.027

0.026

0.025

0.024

0.023

0.022

0.021

0.020 100 200 300 400 500 600

Distance from Right Wall (facing source)

Figure 9: Gammabeam 150C Radiation Field Cross Section (989.5 cm)

17

THE GAMMACELL 200 (Measurement Locations Within Sample Chamber)

The circled numbers indicate the relative dose as a percentage of the dose at the centre of the chamber (109.8 R/min - 1994 September 12).

Position 3

Position 2

Position 1

Figure 9a: Gammacell 200 Isodose Curves

18

ISODOSE CURVES GAMMACELL 200 STANDARD LOADING

|«—VERTICAL AXIS OF CHAMBER

8.9 cm INSIDE DIAMETER OF CHAMBER

The isodose distribution in the irradiation chamber of the Gammacell 200 unit with standard loading should agree within +5% with the relative values shown.

The numbers indicate the relative dose expressed as a percentage of the dose at the centre of the chamber. (♦Reproduced from Atomic Energy of Canada Ltd, Commercial Products (now NORDION), 1975 May)

Figure 9b: Gammacell 220 Radiation Field

20.6

cm

19

THE GAMMACELL 220(Measurement Locations Within Sample Chamber)

The circled numbers indicate the relative dose as a percentage of the dose at the centre of the chamber. (5.15 kR/min - 1994 September 12)

Position 3

Position 2

Position 1

Figure 10a: Gammacell 220 Isodose Curves

20

ISODOSE CURVES GAMMACELL 220 STANDARD LOADING

VERTICAL AXIS OF CHAMBER

15.2 cm INSIDE DIAMETER OF CHAMBER

The isodose distribution in the irradiation chamber of the Gammacell 220 unit with standard loading should agree within +5% with the relative values shown.

The numbers indicate the relative dose expressed as a percentage of the dose at the centre of the chamber. (*Reproduced from Atomic Energy of Canada Ltd, Commercial Products (now NORDION), 1980 January)

Figure 10b: Gammacell 220 Isodose Curves

X factor (1 month) = 0.01096 T 1/2 = 5.27 years

Months 0 1 2 3 4 5 6 7 8 9

0 0.9891 0.9783 0.9676 0.9571 0.9467 0.9363 0.9262 0.9160 0.906110 0.8962 0.8864 0.8768 0.8673 0.8578 0.8484 0 8391 0.8300 0.8209 0.812020 0.8032 0.7944 0.7858 0.7772 0.7687 0.7603 0.7520 0.7439 0.7357 0.727730 0.7198 0.7120 0.7042 0.6965 0.6889 0.6814 0.6739 0.6666 0.6594 0.652140 0.6451 0.6380 0.6311 0.6242 0.6174 0.6107 0.6040 0.5974 0.5909 0.5844

50 0.5781 0.5718 0.5655 0.5594 0.5533 0.5473 0.5413 0.5354 0 5296 0.523860 0.5181 0.5124 0.5068 0.5013 0.4958 0.4905 0.4851 0.4798 0.4746 0.469470 0.4643 0.4592 0.4540 0.4493 0.4444 0.4396 0.4347 0.4300 0.4253 0.420780 0.4161 0.4116 0.4071 0.4026 0.3982 0.3939 0.3896 0.3854 0.3812 0.377090 0.3729 0.3688 0.3648 0.3608 0 3569 0.3530 0.3492 0.3453 0.3416 0.3379

100 0.3342 0.3305 0.3269 0.3234 0.3199 0.3164 0.3129 0.3095 0.3061 0.3026110 0.2995 0.2962 0.2930 0.2898 0.2866 0.2835 0.2804 0.2774 0.2743 0.2714120 0.2684 0.2655 0.2626 0.2597 0.2569 0.2541 0.2513 0.2486 0.2459 0.2432130 0.2405 0.2379 0.2353 0.2327 0.2302 0.2277 0.2252 0.2228 0.2203 0.2179140 0.2156 0.2132 0.2109 0.2086 0.2063 0.2041 0.2018 0.1996 0.1974 0.1953

Table 1: Cobalt-60 Decay Table

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APPENDIX A

Protocols

1. GAMMABEAM 150 OPERATING PROCEDURE

1.1 GENERAL INFORMATION

1. Only authorized personnel may operate this unit, as determined by the owner.

2. Before use, the operator will fill in the sign-out book located next to the door in Room 10, Bldg. 513 A. The information required is the operator's name, the anticipated length of time for exposure and setup of equipment, if necessary.

3. After use, the key is returned to Room 10, Bldg. 513 A next to the signout book.

4. The complete manual for this instrument (as supplied by Nordion International) can be found in Room 10, Bldg. 513 (please see the owner).

5. The sequence of operating instructions must be followed exactly, or the cobalt source cannot be raised out of the lead castle.

6. For the unit to function, the back shipping door, located inside the irradiation room behind and to the left of the irradiator, must be tightly closed as this ensures proper functioning of one of the interlock systems.

7. The large door leading into the irradiation room must also be tightly closed, to activate a second interlock system. If this door is not tightly closed, the source cannot be raised.

8. A radiation detector is located inside the irradiation room and can be seen through the window to the left of the operating panel for this unit. It is pointed towards the source and the monitor is located outside the beam room, to the left of the viewing window. The detector/monitor system act to operate the red flashing lights located inside the irradiation room as well as outside over the interlock door in the control room. The flashing lights indicate that a radiation field exists inside the beam room when the source is raised; however, the lights in the control room serve ONLY AS A VISUAL INDICATOR that the source is in fact in the raised position.

9. If the source should become stuck in the raised position the emergency cable used to manually lower the source is located in the storage room, to the left of the control room. To lower the source in this manner, firmly grasp the emergency cable by the counter weight and pull down. This will cause the source to be lowered into the lead castle.

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10. This facility has been monitored by Radiation Protection Branch (RPB) personnel. All exterior walls and adjacent areas to this facility have been evaluated for radiation levels and all have been found to be at background values. The control room area has also been monitored and found to have background radiation levels, when the source is raised.

11. Radiation Protection Branch personnel monitor this facility, in particular the irradiator, for radiation levels when the source is lowered, and these levels are recorded on a small chalkboard located on the front of the irradiator.

12. When work is being done on the roof (ceiling) of the beam room, the interlock key that activates the interlock on the door from the control room into the beam room will be removed and held by building supervisor. This is a safety precaution that prevents the beam from being raised while work is being done on the roof of the facility.

13. Extensive dosimetry information for this facility is available in Room 10, Bldg. 513A, above the signout book.

1.2 OPERATING INSTRUCTIONS

1. The control panel for the Gammabeam 150C (see Figure A1 in Appendix A, Section 1) is located in Bldg. 404B. Place the Gammabeam key (stored in Room 10, Bldg. 513 A) into slot A and turn to the right or left. The "power on" and "power trip" orange lights should now be on.

2. Ensure that the timer B is in the "D" mode and select the desired exposure time (this is a "countdown" timer). Also, check that the "safe/source down" toggle G is in the "safe to expose" direction. Reset the elapse timer to keep track of the exposure time (this is a "count up" timer).

3. Enter the facility through the large door, taking the door interlock key C with you. Note that a green light is on above this door.

NOTE: If the interlock door is closed, remove the interlock key C and while pushing on the red button H, slide the door to the left. To open this door, power must be supplied to the control panel (it will not open if the key A is not activating the control panel).

4. Place samples at the desired distance from the irradiator. A trolley designed for this purpose is available.

5. Before leaving the beam room, depress the red button located on the right front comer of the green bottom housing of the irradiator (you now have only 1 min to leave the room and activate the unit or the timer must be reset).

6. Leave the room, close the door GENTLY and position the base of the door firmly against the angle iron "foot rest" on the floor.

24

7. Replace the door interlock key C and turn it 1/4 turn clockwise.

8. On the control panel, press the power reset button D, the timer reset button E and finally the start exposure button F. You will now hear the source go up (you can check this by looking through the window, to the left of the control panel).

9. Once the source is fully in the "up" position the detector will give an auditory signal, the red lights will be flashing inside the control and gamma beam rooms, and the source can be seen fully extended through the window. A red light will now be on above the interlock door.

10. At the end of the elapsed time, the source will drop down into the safe position automatically, and the green light will come back on above the interlock door.

11. If you want to stop the exposure before the elapsed time, switch the toggle G to the right (stop exposure). To restart the exposure, the above steps have to be repeated (you might have to recalculate your exposure time and make adjustments at the time).

25

POWER ON SOURCE EXPOSEDPOWER TRIP

POWER RESET PRESS TO EXPOSESOURCE

% TIME

SOURCE SAFEELAPSED TIME

SAFE TO SOURCEEXPOSE DOWN

TIMER SET

•eor interlock

H

Figure Al: Gammabeam 150C Control Panel

26

2. GAMMACELL 200 OPERATING PROCEDURES

The Gammacell 200 has been designed to enable operating personnel to load the sample chamber and operate the unit with a minimum exposure to radiation. To ensure protection, the following sequence of operation is recommended.

1. With the drawer in the load (up) position, remove the sample chamber door by squeezing the clips at the top of the door.

2. The sample or accessory apparatus may now be placed in the sample chamber (see note 1).

3. Replace the sample door by inserting the lower edge into the register provided and pushing the top edge forward until the door is properly seated.

4. Insert the Gammacell 200 key (stored in Room 10, Bldg. 513 A) into the control panel. With the toggle switch in manual control, the drawer can be raised or lowered by pressing the up or down switches. For auto control, set the required irradiation time by first dialing in the time and selecting seconds, minutes or hours with the appropriate decimal place. Push the reset button to activate the timer and confirm the time set. Set the toggle switch to the auto position. To lower the chamber push the down button. The drawer will lower the sample into the irradiating position, activate the timer and remain there until the preset time interval has elapsed when it will automatically return to the start position (see note 2)

5. To remove the sample, repeat steps 1 to 3.

NOTE 1: Material likely to change state during irradiation should be kept in suitable containers. Liquids expected to expand or boil should be provided with secondary containers for overflow or vented to the access tubes. Any accessory equipment should now be inserted into the access hole by lifting the top plug and taking care not to crimp cables etc when replacing the plug. Note that the interlock will prevent usage, unless it is properly seated.

NOTE 2: On completion of a timed operation, the timer can be reset to the same operation time by depressing the reset knob.

2.1 POWER FAILURE

In the event of a power failure the timer will stop, and it will be necessary to raise the drawer manually once the power has been restored.

3. GAMMACELL 220 OPERATING PROCEDURES

The Gammacell 220 has been designed to enable operation with minimum exposure of the operator to radiation. To ensure protection, operators should adhere to the following procedures.

27

3.1 AUTOMATIC OPERATION

1. Insert the Gammacell 220 key (stored in Room 10, Bldg. 513 A) into the control panel.

2. To open the collar doors, press and hold in the button on the top of the door interlock, grasp the right-hand door handle, pull back the latch lever, release the button and pull the doors open.

3. Slide the sample chamber locking ring to the right, remove the door by lifting it up and outwards.

4. Place the sample in the chamber (see note 3). The access tube in the drawer top accommodates accessory tubes and electrical leads, which should be fitted in accordance with the instructions provided in the Gammacell 220 Accessories Manual (available from the owner).

5. Replace the sample chamber door with a forward and downward motion. Move the locking ring to the left, until it snaps into position. If difficulties are experienced, check that the door is correctly positioned in the port.

6. To close the collar doors, press and hold in the button on the top of the door interlock.Grasp the right-hand door handle, pull back the latch lever, release the button and push the doors closed.

7. Set the required irradiation time by first dialing in the time and selecting seconds, minutes or hours with the appropriate decimal place. Push the reset button to activate the timer and confirm the time set. Set the toggle switch to the auto position. To lower the chamber push, the down button. The drawer will lower the sample into the irradiating position, activate the timer and remain there until the preset time interval has elapsed when it will automatically return to the start position. For manual operation, read the preceding steps 2 to 6, then select manual on the control panel. Press the down switch. The drawer will lower and remain there indefinitely until the up switch is operated (see note 4).

NOTE 3: Materials expected to change state during irradiation should be placed in suitable containers. Liquids expected to expand or boil should be provided with secondary containers for overflow, or vented to one of the access tubes. The sample chamber and source cage will not withstand repeated spills or corrosive materials.

8. To remove the sample, repeat steps 2 and 3. Press the down switch. The drawer will lower and remain there indefinitely, until the up switch is operated.

NOTE 4: On completion of a timed operation, the timer can be reset to the same operation time by depressing the reset knob.

28

3.2 POWER FAILURE

In the event of a power failure the timer will stop, and it will be necessary to raise the drawer manually once the power has been restored.

29

4. KEITHLEY THERAPY DOSIMETER - OPERATING PROCEDURES

1. Select appropriate volume ion chamber for the desired working range. Connect to dosimeter.

2. Turn on dosimeter and allow it to warm up for 20 min. Check that the correct type of ion chamber is selected. Press “Detector Select” then the “up” or “down” arrow to step through the choices.

3. Press “Air Density” and use the arrow keys to step through selections for temperature (°C). Press “Air Density” again to select barometric pressure reading and adjust to correct pressure using the arrow keys.

4. Press “Units Select” for readout in the correct range of interest. Use arrow keys to step through choices.

5. Press “Bias Select” and make sure that -300 Vdc (100%) is selected. Note: Do not disconnect detector lead when bias voltage or system power is on.

6. Press “Reset/Measure” twice to zero the instrument and get ready to start measurement.

4.1 NOTES:

Expose the detector for a short time (-100 s) before zeroing when using it for the first time that day. Leave power on if you are taking several readings over the day. Adjust the temperature and pressure if large fluctuations occur during a day.

30

APPENDIX B

Decay Charts

31

(based on measurements made on 1994 September 12 - starting doses at centre of beam)

Table Bl. COBALT - 60 DECAY CHART FOR GAMMABEAM 150C fto 1999 DECEMBER)

Date Decav Factor No. of Months Dose Rate at 50 cm Dose Rate at 392 cm Dose Rate at 989.5cm(R/hr) (R/min) (R/hr) (R/min.) (R/hr) (R/min)

Jan-96 0.8391 0 472.0 7.867 7.44 0.124 1.38 0.023Feb-96 0.8300 1 466.9 7.781 7.36 0.123 1.36 0.023Mar-96 0.8209 2 461.8 7.696 7.28 0.121 1.35 0.023Apr-96 0.8120 3 456.8 7.613 7.20 0.120 1.34 0.022May-96 0.8031 4 451.8 7.530 7.12 0.119 1.32 0.022Jun-96 0.7944 5 446.8 7.447 7.04 0.117 1.31 0.022Jul-96 0.7857 6 442.0 7.366 6 97 0.116 1.29 0.022

Aug-96 0.7771 7 437.2 7.286 689 0.115 1.28 0.021Sep-96 0.7687 8 432.4 7.207 6.82 0.114 1.26 0.021Oct-96 0.7603 9 427.7 7.128 6.74 0.112 1.25 0.021Nov-96 0.7520 10 423.0 7.050 6.67 0.111 1.24 0.021Dec-96 0.7438 11 418.4 6.973 6.59 0.110 1.22 0.020Jan-97 0.7357 12 413.8 6.897 6.52 0.109 1.21 0.020Feb-97 0.7277 13 409.3 6.822 6.45 0.108 1.20 0.020Mar-97 0.7197 14 404.9 6.748 6.38 0.106 1.18 0.020Apr-97 0.7119 15 400.5 6.674 6.31 0.105 1.17 0.020May-97 0.7041 16 396.1 6.602 6.24 0.104 1.16 0.019Jun-97 0.6965 17 391.8 6.530 6.18 0.103 1.15 0.019Jul-97 0.6889 18 387.5 6.458 6.11 0.102 1.13 0.019

Aug-97 0.6814 19 383.3 6.388 6.04 0.101 1.12 0.019Sep-97 0.6739 20 379.1 6.318 5.98 0.100 111 0.018Oct-97 0.6666 21 375.0 6.250 5.91 0.099 1.10 0.018Nov-97 0.6593 22 370.9 6.181 5.85 0.097 1.08 0.018Dec-97 0.6521 23 366.8 6.114 5.78 0.096 1.07 0.018Jan-98 0.6450 24 362.8 6.047 5.72 0.095 1.06 0.018Feb-98 0.6380 25 358.9 5.981 566 0.094 1.05 0.017Mar-98 0.6310 26 355.0 5.916 5.60 0.093 1.04 0.017Apr-98 0.6242 27 351.1 5.852 5.53 0.092 1.03 0.017May-98 0.6173 28 347.3 5.788 5.47 0.091 1.02 0.017Jun-98 0.6106 29 343.5 5.725 5.41 0.090 1.00 0.017Jul-98 0.6040 30 339.7 5.662 5.36 0.089 0.99 0.017

Aug-98 0.5974 31 336.0 5.601 5.30 0.088 0.98 0.016Sep-98 0.5909 32 332.4 5.540 5.24 0.087 0.97 0.016Oct-98 0.5844 33 328.8 5.479 5.18 0.086 0.96 0.016Nov-98 0.5781 34 325.2 5.420 5.13 0.085 0.95 0.016Dec-98 0.5718 35 321.6 5.360 5.07 0.084 0.94 0.016Jan-99 0.5655 36 318.1 5.302 5.01 0.084 0.93 0.016Feb-99 0.5594 37 314.7 5.244 4.96 0.083 0.92 0.015Mar-99 0.5533 38 311.2 5.187 4.91 0.082 0.91 0.015Apr-99 0.5472 39 307.8 5.131 4.85 0.081 0.90 0.015May-99 0.5413 40 304.5 5.075 4.80 0.080 0.89 0.015Jun-99 0.5354 41 301.2 5.019 4.75 0.079 0.88 0.015Jul-99 0.5295 42 297.9 4.965 4.70 0.078 0.87 0.015

Aug-99 0.5238 43 294.6 4.910 4.64 0.077 0.86 0.014Sep-99 0.5180 44 291.4 4.857 4.59 0.077 0.85 0.014Oct-99 0.5124 45 288.2 4.804 4.54 0.076 0.84 0.014Nov-99 0.5068 46 285.1 4.752 4.49 0.075 0.83 0.014Dec-99 0.5013 47 282.0 4.700 4.44 0.074 0.82 0.014

Dose is proportional to l/(distance squared) Dose = K/d2

32

(based on measurements made 1994 September 12 - centre of chamber =109.8 R/min)1 R (roentgen) = 87 Gy (gray) (in air) or 96 Gy (in tissue)

Time of Dose Required = (dose - deadtime dose) dose rate

Table B2. COBALT-60 DECAY CHART FOR GAMMACELL 200 fTO 1999 DECEMBER')

Date Decay Factor No. of Months Dead-time Dose Dose Rate Dead-Time Dose Dose Rate(roentgens) (R/s) (cGy in tissue) (cGy/s in tissue)

Jan-96 0.8391 0 7.55 1.54 7.25 1.47Feb-96 0.8300 1 7.47 1.52 7.17 1.46Mar-96 0.8209 2 7.39 1.50 7.09 1.44Apr-96 0.8120 3 7.31 1.49 7.01 1.43May-96 0.8031 4 7.23 1.47 6.94 1.41Jun-96 0.7944 5 7.15 1.45 6.86 1.40Jul-96 0.7857 6 7.07 1.44 6.79 1.38

Aug-96 0.7771 7 6.99 1.42 6.71 1.37Sep-96 0.7687 8 6.92 1.41 6.64 1.35Oct-96 0.7603 9 6.84 1.39 6.57 1.34Nov-96 0.7520 10 6.77 1.38 6.50 1.32Dec-96 0.7438 11 6.69 1.36 6.42 1.31Jan-97 0.7357 12 6.62 1.35 6.35 1.29Feb-97 0.7277 13 6.55 1.33 6.29 1.28Mar-97 0.7197 14 6.48 1.32 6.22 1.26Apr-97 0.7119 15 6.41 1.30 6.15 1.25May-97 0.7041 16 6.34 1.29 6.08 1.24Jun-97 0.6965 17 6.27 1.27 6.02 1.22Jul-97 0.6889 18 6.20 1.26 5.95 1.21

Aug-97 0.6814 19 6.13 1.25 5.89 1.20Sep-97 0.6739 20 6.06 1.23 5.82 1.18Oct-97 0.6666 21 6.00 1.22 5.76 1.17Nov-97 0.6593 22 5.93 1.21 5.70 1.16Dec-97 0.6521 23 5.87 1.19 5.63 1.15Jan-98 0.6450 24 5.80 1.18 5.57 1.13Feb-98 0.6380 25 5.74 1.17 5.51 1.12Mar-98 0.6310 26 5.68 1.16 5.45 111Apr-98 0.6242 27 5.62 1.14 5.39 1.10May-98 0.6173 28 5.55 1.13 5.33 1.08Jun-98 0.6106 29 5.49 1.12 5.27 1.07Jul-98 0.6040 30 5.43 1.11 5.22 1.06


Aug-99 0.5238 43 4.71 0.96 4.52 0.92Sep-99 0.5180 44 4.66 0.95 4.47 0.91Oct-99 0.5124 45 4.61 0.94 4.43 0.90Nov-99 0.5068 46 4.56 0.93 4.38 0.89Dec-99 0.5013 47 4.51 0.92 4.33 0.88

33

(based on measurements made on 1994 September 12 - central point of chamber = 5.15 kR/min)1 R (roentgen) = 87 Gy (gray) (in air) or 96 Gy (in tissue)

Time of Dose Required = (dose - deadtime dose) dose rate

Table B3. COBALT-60 DECAY CHART FOR GAMMACELL 220 (TO 1999 DECEMBER!

Date Decay Factor No. of Months Dead-Time Dose(kR)

Dose Rate(kR/min)

Dead-Time Dose(Grays in tissue)

Dose Rate(Gy/min in tissue)

Jan-96 0.8391 0 0.3496 4.321 3.3562 41.48Feb-96 0.8300 1 0.3458 4.274 3.3196 41.03Mar-96 0.8209 2 0.3420 4.227 3.2834 40.58Apr-96 0.8120 3 0.3383 4.181 3.2476 40.14May-96 0.8031 4 0.3346 4.136 3.2122 39.70Jun-96 0.7944 5 0.3310 4.091 3.1772 39.27Jul-96 0.7857 6 0.3273 4.046 3.1425 38.84




Aug-99 0.5238 43 0.2182 2.697 2.0949 25.89Sep-99 0.5180 44 0.2158 2.668 2.0720 25.61Oct-99 0.5124 45 0.2135 2.639 2.0494 25.33Nov-99 0.5068 46 0.2112 2.610 2.0271 25.05Dec-99 0.5013 47 0.2089 2.581 2.0050 24.78

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