Radiation Safety Test Questions
The objective of the Radiation Safety Exam is to insure that those people using
radioactive isotopes are very familiar with:
1.
2.
3.
4.
5.
6.
7.
8.
9.
Biological hazards associated with ionizing radiation
Definitions and terms associated with ionizing radiation
Nature and types of ionizing radiation
Ionizing radiation detectors
Calculations including
a. Dilution problems
b. Half life calculations
c. Exposure rate calculations
Rules, regulations and license stipulations
Contamination surveys, and leak checks
Required paperwork and documentation
Emergency procedures
Section 1 Biological Hazards
What is a radical or free radical and what role does it play in biological damage
due to ionizing radiation?
Describe the liner no threshold dose response hypothesis.
What is the role of specific ionization, biological half-life, and target organ in
radiotoxicity?
What is the normal background ionizing radiation dose?
Which cells or tissues are most susceptible to damage by ionizing radiation?
What is the erythema dose?
What is the LD50?
Which subcellular elements magnify the biological effects of damage due to
ionizing radiation?
What is a metabolic poison?
Do people at different ages have different resistance or susceptibility to ionizing
radiation?
At what level will ionizing radiation affect the bone marrow, skin, GI tract, CNS?
How deeply will different types and energies of ionizing radiation penetrate in
tissue?
Section 2 Definitions and Terms
Be familiar with the following
Becquerel
Curie
Roentgen
REM
RAD
Gray
Sievert
Specific Ionization
LET (linear energy transfer
Committed Effective Dose
Deep Dose Equivalent
Total Effective Dose Equivalent
Ion
ALARA
Section 3: Nature and types of ionizing radiation
Be familiar with range, mode of production, Q factor energy etc for the following
ionizing radiation;
1.
2.
3.
4.
Gamma and X-radiation
Beta particles
Alpha particles
32P, 33P, 35S, 14C, 125I, 3H
Be familiar with the following terms or concepts
5. Compton scattering
6. Photoelectric effect
7. Bremsstraahlung
8. half-value layer
9. best shielding for high energy beta particles
10. best shielding for high energy gamma rays
Section 4: Radiation Detection Equipment
Know the advantages, disadvantages, and detection capabilities of the following
instruments:
1. Geiger Mueller tube type detector
2. Ionization Chamber
3. Gas proportional detector
4. solid scintillator
5. Liquid Scintillation
6. Be able to explain efficiency of an instrument and the parameters that alter
efficiency
7. Understand the difference between counts per minute and disintegrations per
minute.
8. be familiar with TLD dosimetry and the proper positioning of a dosimetry
badge
9. Be familiar with the requirements for bioassays at BYU, including when, and
how to do them.
Section 5: Be able to complete the following calculations
1. Calculate the activity of radioactive material which must be added to a growing
cell culture to obtain a specific activity in the test sample (usually an aliquot of
the original) This involves instrument efficiency, labeling efficiency, and
dilution.
2. Calculate the absorbed dose if told the ionizing radiation flux and given the
linear energy transfer (for example, calculate the dose due to a skin exposure to
P32 given that 32P beta’s deposit approximately 200,000 electron volts in the
first 0.1 cm traveled through soft tissue) or given a point source activity calculate
the flux.
3. Calculate the half-life of a material
4. Calculate dilutions factors or concentrations given the appropriate information.
5. Calculate the actual contamination in becquerels per square centimerter of a
small area of contamination given a survey meter reading.
6. Given a point source of x becqureels and the exposure rate per becquerel,
calculate the exposure at 10 cm.
Section 6: Rules and Regulations
1. Be familiar with bioassays and when they must be done
2. Know how to properly dispose of radioactive material
3. Understand the requirements for proper security
4. Be familiar with the state rules governing ionizing radiation
5. Understand the allowable occupational dose for an adult and a fetus
6. Know how to declare a pregnancy
7. Calculate the actual contamination level in Bq or Ci on a surface given an
instrument count and the efficiency of the instrument.
Section 7 Surveys
1. know how to properly leak check a package
2. know how often your survey meter must be calibrated and where to get the
calibrating done
3. know where to conduct surveys
4. know how to do a contamination survey
5. know how to properly document a survey
Section 8 Paperwork and Documentation
1. Know the required paperwork in the laboratory including
a. user Authorization (know who authorizes the PI)
b. facility authorization
c. receipt documentation
d. waste documentation
e. certification
f. training list
Section 9 Emergency Procedures
1. Understand that the most important objective in any incident involving
radioactive material is human safety.
2. Consistent with the primary objective, you should limit the spread of
radioactive material by reporting, isolation, evacuation, and removal. If a nuclide is
splashed or spilled onto a person, it should be washed off as soon as possible.
Remember that exposure is directly proportional to the time of the exposure.
3. Get help by dialing 911 for an emergency or 2-2222 if the matter is not an
emergency. University Police will notify the RSO night or day.
Radiation Safety Examination study outline. You should read the following:
1 Radiation Safety Program
2. DRC 313-15 and DRC 313-18
3. NRC Guide 8-29
In addition be familiar with the following concepts and terms
1. Tissue Damage and Biological Effects of ionizing radiation
1.1.
1.2.
1.3.
1.4.
DNA may be chemically altered
Protein bonds may be altered or broken
Free Radicals alter the structure of biomolecules
Acute Exposures
1.4.1. Erythema may result above an absorbed dose of 100 rad to the
skin.
1.4.2. The LD50 for humans is about 400 rad (4 gray) whole body dose.
Death at this exposure is typically due to bone marrow destruction.
1.5. Chronic Effects
1.5.1. Mutagen
1.5.2. Teratogen
1.5.3. Carcinogen
1.6. Dose Response Curve. Understand that regulations are based on a linear
no threshold dose response curve. Below doses allowed by regulations we have no
unambiguous experimental data that defines the risk of chronic effects. We assume
that such effects exist (there is no lower threshold) and that they are a linear function of
dose.
1.7 Normal background doses vary from one geographic location to another. All
people receive ionizing radiation from radon, potassium 40, carbon 14 and tritium.
These are all naturally occurring nuclides that are in the environment. In addition
cosmic radiation and radiation from building materials contaminated with naturally
occurring nuclides give us a constant exposure to high energy photons. A total natural
background exposure is in the range of 200 to 400 mrem/year.
1.8 External and internal hazards. Generally all alpha emitters, and beta
emitters with energy less than 50 KEV will not penetrate the dead layers of skin to
cause direct physiological damage from outside the body. The radiation can do
damage if in direct contact with living tissue. High energy beta particles and photons do
present a hazard from outside the body.
2. Ionizing Radiation and its interaction with matter.
2.1. Compton scattering: photons interact with electrons producing a free
electron and a scattered photon with less energy.
2.2. Bremsstraahlung: Energetic electrons interact with mater, undergo change
in momentum and photons are produced. High atomic number absorbing materials
increase the number and energy of bremsstraahlung photons.
2.3. Specific Ionization and LET: the measure of ion pairs formed per unit
distance traveled is called specific ionization (SI). The energy deposited per unit
distance traveled is called linear energy transfer or LET.
2.4. Pair Production: high energy photons (above 1.02 MEV) may produce a pair
of electron like particles (electron and positron).
2.5. Photoelectric effect: A photon reacts with an electron resulting in an
energetic electron with no remaining photon. This competes with Compton scattering
as a means of dissipating photon energy. High atomic number materials shift the
balance in favor of photoelectric effect. High energy photons tend to shift the balance
in favor of Compton scattering.
2.6. Shielding: It is better to shield a high energy beta with low atomic number
materials than with high atomic number materials to reduce bremsstraahlung.
3. Types of Ionizing Radiation.
3.1. ß origin and characteristics: Origin of a negative beta particle is the nucleus.
The beta has low mass but a high charge. Quality factor usually =1.
3.1.1. Note range and half layer values
3.1.2. P32 range about 0.8 cm in unit density material such as water or
soft tissue.
3.2. α origin and characteristics: Origin in the nucleus, usually very high energy,
and very short range due to charge and mass. Hence high LET. Will not penetrate the
keratinized epidermal layer. Quality factor assigned is typically 20.
3.3. γ origin and characteristics: origin in the nucleus, no mass, no charge, very
penetrating. External hazard. Quality factor 1 for isotope related energies (up to a few
MeV).
3.4. X-ray: Origin orbital electrons or energetic electrons. Properties same as
gamma rays. (Both are termed photons) quality factor 1 for normal energies associated
with tracers.
3.5.
Neutrons: high mass, no charge penetrate well can be very
damaging to tissue, may have a quality factor above 10
3.6.
Neutrinos and anti-neutrinos – don’t sweat the small stuff
4. Waste Disposal
4.1. Decay in Storage: only allowed for nuclides with half live less than 90 days.
4.2. Discharge: We may discharge water soluble radioactive materials in certain
quantities. We must be able to demonstrate that the materials are freely soluble. The
following daily limits are set:
4.2.1. 3H
100 microcuries
14
4.2.2. C
100 microcuries
4.2.3. 35S
100 microcuries
32
4.2.4. P
100 microcuries
4.3. Ship: All materials that cannot be decayed or discharged must be shipped to
a low level radioactive waste repository.
4.4. Preparation for Disposal
4.4.1. Packaging
4.4.1.1. Plastic containers not glass
4.4.1.2. Seal the Containers
4.4.1.3. Label Nuclide, date, laboratory and quantity.
4.4.2. Do not mix any short half life material with long (greater than 90
day) half life material. Ever! I mean really ever. Unless you have explicit permission
from the RSO don’t do it. I will charge a flat 100 dollar fee for any such waste unless it
has been specifically cleared through my office.
4.4.3. Scintillation Cocktail; all old varieties containing toluene or xylene
will be surcharged.
4.4.4. Mixed waste: Do not create a mixed waste without explicit
permission from the RSO. A mixed waste is a waste that is both a hazardous chemical
waste and a radioactive waste. These are almost impossible to dispose of. Almost any
organic solvent, including methyl alcohol, would be considered a hazardous chemical
waste. Ethyl alcohol is considered hazardous waste above 24% concentration in
aqueous solution.
4.4.5. Make sure that your disposal logs accurately reflect the disposal of
radioactive materials.
5. Personal Protection.
5.1. Dosimetry. We require dosimetry devices for anyone using significant
quantities of nuclides that are external health hazards. These include 125I and 32P.
Significant quantities means more than 3 millicuries of 32P received by one laboratory
in one month or more than 2 millicuries of 32P in one shipment. For 125I, bound
iodine in kits less than 30 microcuries does not require dosimetry.
5.2 Bioassays Anyone receiving and manipulating more than 5 millicuries of any
isotope will check with the RSO to complete appropriate bioassays. All iodinations will
require an appropriate bioassay. Bioassays will also be required if there is reason to
believe that you have ingested or inhaled a radioactive material.
5.3 Personal Protective Equipment
Standard Equipment includes: lab coat, gloves, and goggles
5.4. Laboratory Surveys: Should be performed at the end of each working day
when isotopes are used. These surveys should be logged in your manual. Areas
surveyed should include hands, bottom of shoes, floor near work area, telephone,
computer, sink, anywhere your hands frequent and lab bench where work was
completed.
5.2. Leak checking new material: The RSO leak checks all materials except
tritiated compounds at the outer surface of the box and the outer surface of the inner
packaging. Once you remove a vial you should check the vial before using the material
and record the leak check results on the inventory form.
5.3. Shielding, distance, time, quantity. Are manipulable parameters for
maintaining exposures ALARA.
5.4. Accident response.
5.4.5. Protect life and health
5.4.6. Safely limit the spread (may include cleaning the material up)
5.4.7. Call RSO
5.5. Eating and drinking are forbidden in an area cleared for the use of
radioactive isotopes.
6. Regulations.
6.1. Pregnancy.
6.1.1. Allowable exposure to fetus = 50 mrem/month or 500 mrem/
pregnancy
6.1.2 The University has an obligation to the mother and fetus if the
mother decides to declare her pregnancy.
6.2. 10 CFR 20 is the federal regulation covering general worker safety.
6.3. R-313-15 Utah regulation covering worker safety and R-313-18 covers
notices to workers.
6.4. Security: All radioactive materials including radioactive waste must be under
the personal supervision of a qualified user or locked up at all times. Period.
6.5. Reporting. Report spills, leaks, or other occurrences to the RSO (2-5779) If
you have an emergency, that is imminent or immediate threat to life or health call 911,
or 2-2222.
7. Radio toxicity variables.
7.1. Biological half life - In general the longer the half life the more toxic the
nuclide.
7.2. Target Organ – if a nuclide concentrates in an organ it is typically more
radiotoxic than one which does not have a target organ.
7.3. Specific Ionization - the higher the SI or LET the higher the toxicity
8. Units Of Measurement.
8.1. roentgen (measure of exposure in air 2.58 * 10-4 Coulomb/kg air)
8.2. RAD (radiation(or roentgen) absorbed dose) 100 ergs/gram of tissue = 1 rad
8.3. REM (roentgen equivalent man) RAD X Quality factor
8.4. Gray = 1 joule;kg one Gray = 100 RAD;
8.5. Sievert = 100 REM Gray times Q factor = 100 REM
8.6. Becquerel = 1 dps
8.7. Coulombs/kg (C/kg) (measure of exposure in air)
8.8. Curie = 3.7 x 1010 dps
9. Instrumentation
9.1. Liquid Scintillation: no losses due to geometry. Material in direct contact
with counting medium. Can count tritium.
9.2. Solid Scintillation: Can have high mass detectors for efficiency in counting
photons. May detect differences in energy, hence spectrometry possible. Required for
work with 125I. Expensive.
9.3. Geiger-Muller Counter. Gas filled chamber, relatively inexpensive, normal
instruments cannot detect tritium, about 10 % 2 pi efficiency for Carbon14.
9.4. Ionization Chamber. Very good for defining exposure (roentgens) generally
somewhat expensive,
9.5. Gas Proportional Counter. Can be used for spectrometry, often open
window hence can be used for tritium. Low efficiency for photons. Generally
expensive.
10.
Calculations
10.1. Decay Nt = Noe-0.693t/T where t is the time elapsed and T is the half life.
10.2. 1 mrad = 62,400 MeV per gram Rule of thumb: 100 beta particles per cm
per second = 10 mrad/hr exposure with high energy betas.
Problem calculate the exposure if a thin window gm tube detector gives 30,000 counts
per minute the counter has 5 cm2 surface area and 100% counting efficiency (assume
even distribution of beta flux over the window surface).
We can say that the 30,000 counts are picked up in a 5 square cm area or we have
6,000 counts per minute through each square centimeter. This is equal to 100 counts
per cm per second or about 10 mrad/hr. If you had been given the precise energy of
the beta particle then it is a simple matter to convert electron volts/gram to rad and
come up with a precise answer. For example 100 beta's per second from 32P with an
average energy of 0.7 Mev/beta and a range of 0.8 cm will deposit all of their energy in
the first cm of tissue. Thus 100 X 0.7 = 70MeV of energy is deposited in one gram
(1cm3 soft tissue is about one gram and one erg = 6.24*105 MeV). The rest is a simple
conversion problem. An interesting problem would be to give the amount of energy
deposited in the first tenth of a cm and that deposited in the second tenth of a cm and
allow you to find the different dose rates to the various layers of tissue.
10.3. Dilution Problems. Activity * dilution factor = Activity after dilution
Be prepared to complete dilution problems
Dilution factor = volume added/(volume added + volume present)
11. Required Documentation in the laboratory.
11.1. Receipt logs
11.2. Disposal logs
11.3. Survey logs
11.4. Required paperwork for authorization;
11.4.1. Certification (All authorized users)
11.4.2. User Authorization Form (PI only)
11.4.3. Facility Authorization Form (PI only)
11.5 Training record