Sources of RadiationSources of Radiation

• Natural background radiation is everywhere• There are terrestrial and cosmic sources as

well as those all over our planet.• The level is variable by location.• The largest single source is radon. Radon is

a radioactive gas that can accumulate in homes and in the workplace. The levels vary by location but the national average is 200 mrem/year.

Typical natural background levels are Typical natural background levels are 60 mrem in NE, E, W, and Central 60 mrem in NE, E, W, and Central

United States.United States.45 mrem in Atlantic and Gulf Coastal 45 mrem in Atlantic and Gulf Coastal states and 120 mrem in the Colorado states and 120 mrem in the Colorado

Plateau. Plateau. The amount of radiation the typical The amount of radiation the typical

radiation worker is exposed to is about radiation worker is exposed to is about the same order of magnitude as an the same order of magnitude as an average abdominal radiograph or a average abdominal radiograph or a

year’s background exposure.year’s background exposure.

Units of Activity in U.S.Units of Activity in U.S.

• In the United States, exposure is commonly measured in units of mrem, or 1/1000 of a Rem. In other countries the unit of measure is typically the “millisievert”. This is defined later.

• In this exercise we are only concerned with ionizing radiation because it contains sufficient energy to break chemical bonds by removing an electron from an atom or molecular substance.

• Breaking of bonds in biological systems can cause the system to malfunction.

Kinds of Radiation at Union Kinds of Radiation at Union CollegeCollege

• At Union College the radiation sources are sources of Alpha particle, Beta particle, gamma radiation, X-rays, and in some instances neutrons.

• Alpha particles lose their energy in short distances, as within 2 inches of air or the surface of skin thus generally it is not dangerous. Its danger is if it enters the body internally where its lifetime and energy can be very harmful.

• i.e., Alpha emitters mostly come from long lived isotopes like uranium so emit for a long time.

Most Common Radiation at Most Common Radiation at Union CollegeUnion College

• Beta emitters are the most common isotopes dealt with at Union College.

• They can typically penetrate into the skin one/half inch, through a few feet of air but might be blocked by a plastic shield. A problem with a shield made from dense material is that the Beta particle can generate other radiation which is detected beyond the expected penetration depth. Often this radiation is gamma.

• Beta emitting isotopes life times vary over a large range.

Non-particulate RadiationNon-particulate Radiation

• Gamma radiation is not a particle like first two. It penetrates many shields and normally requires several inches of lead to stop it. Its source might be from isotopes undergoing decay and can come from beta particles striking certain materials. Their energy levels vary considerably and so exposure to them is not recommended. They find use in medical imaging.

The Third ParticleThe Third Particle

• Neutrons are particles and being neutral in charge typically penetrate most materials without interaction. Their danger depends on the energy of the neutron. Typically Union College’s only “connection” with them is their use for activating materials for analysis by the Geologists via neutron activation done at Oregon State University.

Quantity of Radiation Quantity of Radiation TerminologyTerminology

• Dose: This is a generic term for the quantity of absorbed radiation per unit mass. “Dose equivalent” is the term for quantity of absorbed dose in tissue modified by certain risk factors dependent upon the type of radiation to which one is exposed.

• Dose rate: Is the absorbed dose delivered per unit of time

More Radiation TerminologyMore Radiation Terminology

• Rad: Is the “absorbed radiation dose”, the unit of dose (or energy absorbed) per unit mass in materials, including tissue. The international unit is the Gray ( 1 Gy = 100 rad)

What is a Roentgen?What is a Roentgen?

• It is the unit to measure ionization in air as a result of exposure to X-Rays or gamma-radiation; there is no international equivalent term.

• Curie: A unit of activity of radioactive substances (decaying at the rate of 3.7 E10 disintegrations per second per curie); The international unit for activity is the becquerel ( 1 disintegration per second). It is abbreviated “Bq”. 3.7E10 Bq is one curie

Even More Radiation Even More Radiation TerminologyTerminology

• Rem: This is most commonly the term used by the Radiation Safety Officer. It is “the Roentgen Equivalent in Man” versus air, i.e., it is unit of effective dose that corrects absorbed dose for the risk for high energy particle radiation which do more damage to tissue than an equivalent absorbed dose of X- or Gamma-rays. International unit is sievert (1 Sv = 100 rem)

An Important term relating the An Important term relating the strength of your samplestrength of your sample

• Curie: The unit of activity of radioactive substances (decaying at the rate of 3.3 E10 disintegrations per second is a curie. The number comes from the activity of uranium. At Union College we deal mostly with mCi or uCi. The international unit of activity is the becqueral (1 disintegration per second) abbreviated Bq.

How do we describe or discuss How do we describe or discuss the life or stability of an isotope?the life or stability of an isotope?• This is measured by a term called “half-life”. The

larger this number the more stable and longer lived is that isotope. It represents the amount of time for half of the quantity of the isotope to undergo decay, i.e., changed into a different isotope or isotopes.

• The t1/2 for tritium is small compared to that of uranium; U-238 is about 4E9 years while tritium is about 12 years. Any given quantity of H3 disappears in about 120 years, about ten half-lives.

Less commonly used termLess commonly used term

• Sometimes we are concerned with the radiation near the surface.

• The Half Value Layer is the thickness of a given substance required to cut exposure from a beam of radiation in half. Such a layer might be 20 to 80 percent of total radiation being emitted.

• Leak Test: Is a test of the surface of a sealed source to determine whether the seal is still in tact.

Man-made sources of exposureMan-made sources of exposure

• Typically an individual might encounter sources of radiation in

• diagnostic radiology

• Nuclear medicine

• Radiation therapy

• During medical X-ray analysis

• In a Laboratory

Most Common SourcesMost Common Sources

• But the most common sources of radiation are in water (even bottled water), soil, and the air. Radiation received from the sun and natural radioactive material (ores) are often a greater source of radiation exposure than the radiation found in the workplace. In the United States, Colorado has about the highest level in soil.

What are the undesirable effects What are the undesirable effects from higher exposuresfrom higher exposures

• Although low when adhering to safe radiation standards undesirable effects from higher exposures are

• Cancer

• Genetic mutations

• Effects on an embryo/fetus

Effects from various exposure Effects from various exposure levelslevels

• Even though radiation can be of great benefit, too much exposure, like from the sun can be dangerous. Two types of effects are

• 1. Effects that will occur when given a certain minimum exposure (or threshold effects)

• 2. Effects that have a higher chance of occurring with higher levels of exposure.

Effects from Threshold Levels of Effects from Threshold Levels of radiation exposureradiation exposure

• Cataracts in the eyes

• Skin erythema (skin reddening)

• Hair loss

• Precancerous skin conditions

Given these effects what are Given these effects what are normal levels of radiation in a normal levels of radiation in a

procedure?procedure?

• Radiation Oncology 5K rad (tumor treatment)

• CT of Pelvis 1 rad. or CT of Head 3 rad

• Chest X-ray 15 mrad

• Dental exam 300 mrad

• Mammogram 150 mrad glandular dose

Chances of Getting CancerChances of Getting Cancer

• However, the reality is that risks from natural and most medical levels of radiation are quite low. The chance of getting cancer from 10 mrem of radiation is equivalent to the change of winning the lottery when you bought only one lottery ticket

What are the Occupational Dose What are the Occupational Dose Limits?Limits?

• Effective dose: 2E3 mRem per year

• To the lens of the eye: 15E3 mRem

• To the skin: 50E3 mRem

• To the hands, feet, knees, elbows: 50E3 mRem

• Those expected to receive 10% of the limit level must wear dosimeters.

How do we minimize exposure?How do we minimize exposure?What are Safe PracticesWhat are Safe Practices

• The ALARA (as low as reasonably achievable) philosophy and its guidelines are what help to keep the risk or radiation down. The ALARA guidelines are limits established to ensure that safety is maintained. We know the lower doses carry lower risk, and this concept helps to maintain cost effective safety.

ALARAALARA

• Time: Less exposure time means lower exposure level

• Distance: The radiation level falls off at a rate of inverse square of the distance. So stay as far from the sample as possible

• Shielding: As indicated earlier, various shields can diminish or block the radiation

Key Safety TipsKey Safety Tips

• Be able to recognize radiation signage and which packages might contain radioactive materials. Apply the ALARA practice to them.

• Do not consume anything or put items like cosmetics on your face where there are radioactive material or might have been from contamination. Wear gloves, wash hands.

• If radioactive materials are spilled, restrict access to the area and contact the Radiation Safety Officer

Who should be specially Who should be specially cautions?cautions?

• Individuals close to their exposure limits• Females who are pregnant or might become

pregnant• Young children or infants• Old frail individuals• Those who have cancer or similar diseases• Women might want to declare they are pregnant

because exposure limits are lower for them thus protecting the fetus.

So what do you do in a Radiation So what do you do in a Radiation Emergency?Emergency?

• Follow the letters in the word RACE

• R rescue or evacuate anyone in the area of a spill or condition of high exposure

• A alarm, sound one if appropriate

C call the Radiation Safety Officer (RSO)

E exit the area but be close enough to communicate with the RSO information

Contact NumbersContact Numbers

• Campus Safety 388-6911 This is a good first number as they can contact the RSO via radio or by using one of several phone numbers

• RSO 388-6911 (office number) or (518) 788-1181 (cell phone which is normally carried at all times by the RSO)

• Please complete the following Quiz and submit to the RSO

QUIZQUIZ• Quiz questions for Radiation Program• Where besides a laboratory with radioactive materials might you find ionizing radiation? Give three examples• Which state in the United States has the highest natural background levels of radiation?• What ionizing radiation material are you using or will be using in your research?• Which ionizing radiation particle could be most harmful to you but also has a short distance of travel in air?• What is one potential problem with assuming that beta particle radiation can be stopped with a high density

material and there would be no other radiation in the area.• Which generic term applies to the quantity of absorbed radiation per unit mass?• What is described as a unit of activity of radioactive substance whose international unit is the becquerel?• REM ?• What term might be used to describe the stability of an isotope?• Name a two potentially undesirable effects of high exposures to radiation.• What is ALARA a mnemonic of ?• What are the three terms most associated with the philosophy ALARA?• Is it reasonable to put anything in your mouth which might have been exposed to radioactive material?• In case of a spill, who always must be contacted (not necessarily the first person though)?• Why are young children more susceptible to radiation damage than very old people?• When an emergency arises, what do the letters “RACE” stand for?• Should a spill of radioactive material or some other emergency related to radiation, what is the most sure fire

phone number to call?