1. RADIATION SAFETY

2. Definitions Roentgen RAD REM 2.58 x104 coulombs/kg air
Radiation Absorbed Dose- Density dependant (to convert roentgens to rads you must include a density factor)
REM
Roentgen Equivalent Man
The roentgen is a measure of charge/kg air. The unit of absorbed dose is the rad. The rad is the absorbed energy/gram tissue (100 ergs/gram. The Gray is the new unit of absorbed dose and is 1 joule/kg. One gray is equil to 100 rad. The rem is a unit to account for different biological effects due to the same absorbed dose causing different biological effects. The rem is only used when dealing with chronic or long term biological effects such as cancer. The rem = rad * Q factor where the Q factor is a factor developed for each specific type of ionizing radiation. Beta particles, x-rays and gamma rays have a Q factor of 1. Alpha particles have a Q factor of 20.
The sievert is the new international unit representing relative biological effect and is equal to 100 rem.

3. REM RAD * Q factor = REM GRAY * Q factor = Sievert
The Q factor is an estimate of how damaging a specific absorbed dose is depending on the type of ionizing radiation that causes the absorbed dose. Absorbed doses are given as either the RAD (radiation absorbed dose which is equil to 100 ergs of energy deposited per gram of tissue) or the Gray which is equil to one joule per kilogram of tissue. One Gray is equivalent to 100 RAD’s.
The Q factor for beta particles, gamma rays or x-rays is 1. Hence for this type of radiation one rad = 1 rem.
The Q factor for alpha particles is 20. Thus one rad exposure will result in a dose of 20 rem.
The REM or Sievert are only applicable to chronic long term damage, principally cancer.

4. Definitions
Gray = 100 RAD
Sievert = 100 REM

5. Definitions Curie = 3.7 * 1010 dps Becquerel = 1 dps cps vs dps
Obviously it takes 3.7 * 1010 Becquerels to make one Curie.
One Count per second is the measured quantity using an instrument. One disintegration per second is the actual number of disintegrating atomic nuclei. The difference is the efficiency of the counting instrument. Thus a 100 dps source measured with an instrument with 50% efficiency will result in 50 counts per second. The geometry of the detector will have a major influence on the count. A detector with a single flat detector surface can only detect 50% of the emissions from a point source. This is called 2 pi geometry. The term 2 pi comes from the formula for the surface area of a sphere which is 4 π r2. A device that can measure the emissions from half of a sphere is said to have 2 pi gemoetry. In assessing a measurement using a flat detector such as a pancake Geiger Mueller tube, if the efficiency of the instrument has a 2 pi efficiency of 10% then it will only detect 5% of the total emissions. It will detect one in ten of the beta particles that actually impinge on the counting window.

6. Definitions Linear Energy Transfer (LET) Specific Ionization (SI)
Energy given up per unit distance traveled
Specific Ionization (SI)
Ion pairs formed per distance traveled
Note a high LET or SI gives greater radiotoxicity
LET and SI are very similar concepts. Since you can calculate the average energy required to ionize one electron, the linear energy transfer (how much energy is deposited by an ionizing particle per unit distance traveled) can be easily estimated from the specific ionization (the number of ion pairs formed by an ionizing particle per unit distance traveled)
Radiootoxicity is how damaging an isotope is if it is inhaled or ingested. In general the higher the SI or LET the higher the radiotoxicity.

7. LET or SI + + + _
If the straight path of the ionizing particle is one micron (from left to right) the specific ionization would be 6/micron. _ + _ + + _ _ _

8. Definitions Background Radiation Erythema Dose LD50 1-2 msieverts/year
1 gray to the skin
LD50
5 gray whole body exposure
Natural background ionizing radiation exposures.
Cosmic radiation
The sun showers the earth with high speed particles and photons. These smash into our atmosphere resulting in a cascade of charged particles, x-rays and gamma rays. At the surface of the earth we are shielded from the charged particles and partially shielded from the photons (gamma rays and x-rays). The amount of shielding is dependant on the total mass of the atmosphere between a person and the sun. The atmosphere is thicker at sea level than in Utah. A person in Provo Utah will therefore receive more cosmic radiation than a person living on the beach in California.
Tritium and Carbon14 are formed in the atmosphere by cosmic radiation. Any time you eat or drink materials with hydrogen or carbon you are exposed to radioactive isotopes. Potassium 40 is a primordial nuclide (created when the material of the earth was created). Potassium intake is essential for life. Exposure due to potassium 40 is an unavoidable element of natural background radiation.
Uranium and thorium are also primordial nuclides. The decay of Uranium results in the release of radon which is a significant part of our natural background exposure.
The erythema dose is the amount of energy deposited in the dermal layer of tissue by ionizing radiation sufficient to cause the skin to get red.
LD50 the amount of radiation exposure that will result in the death of 50 percent of the population exposed. The most critical tissue for the LD50 is the bone marrow. Rapidly growing or rapidly metabolizing cells are more susceptible to ionizing radiation than metabolically dormant cells. The blast cells in the bone marrow are very sensitive. If those cells are all destroyed, the person will die without a bone marrow transplant. Other tissues that are quite sensitive include cells lining the gastrointestinal tract, hair follicles, and secretory cells such as the salivary glands.

9. Definitions ALARA As Low As Is Reasonably Achievable Because we don’t
know
At BYU we will always keep our exposures to ionizing radiation as low as we reasonable can. Even though we do not know of any short or long term harm due to doses less than 1 rem/ year, there is not enough data to say for certain that that level of exposure may not cause some level of increased risk of cancer.
The term used for this conservative approach to radiation exposure is ALARA. You will be expected to understand this term for the examination.

10. ALARA Continued
While the regulatory limit is 50 msievert per year (about 12.5 msievert/quarter) At BYU I will investigate any quarterly dose above 100 mrem (1 msievert)

11. Definitions Gamma ray Origin Nucleus Low mass, charge Low LET
Gamma rays are photons just like visible light, but with much higher energy. Gamma rays come from the rearrangement of an unstable atomic nucleus. A 30 thousand electron volt gamma ray is exactly the same as a 30 thousand electron volt x-ray (x-rays are produced when electrons undergo negative acceleration traveling through mass.

12. Definitions X-ray just like gamma but origin is an electron
Beta Particles
Mass and charge = electron
high LET
KERMA = kenitic energy released per unit mass
Beta particles can be either positively charged (positrons) or negatively charged (electrons). A negative beta particle has the same mass and charge as an electron but it comes from a decaying nucleus. With negative beta decay a neutron in the nucleus is converted to a proton and the negative charge plus mass is thrown out of the nucleus as a beta particle. Thus Carbon 14 (atomic number 6) decays to Nitrogen 14 (atomic number 7).
Air kerma is the energy released by innizing radiation per unit mass of air.

13. Definitions Electron capture Beta Decay Alpha Decay
Electron capture is essentially the reverse of negative beta decay. An unstable nucleus with too many protons decays by capturing an electron ( from the k shell). The electron is combined with a proton to produce a neutron. The atomic number drops by one. The only emission from a nucleus undergoing electron capture is gamma radiation. However the empty orbital will be filled by a higher energy electron resulting in either a characteristic x-ray emission or an auger electron (auger electrons occur when a vacancy in the orbital shell is filled by a higher energy orbital electron with the excess energy transferred to another electron which is ejected becoming a free electron) Thus even though electron capture only results in the release of gamma rays from the nucleus, free electrons (just like beta particles) are also created.
Alpha decay occurs when an element is too heavy to be stable. There are no stable elements above atomic number 83. Bismuth 209 is the heaviest stable isotope. Alpha emissions consist of two neutrons and two protons (a helium nucleus without any electrons). Alpha particles have high energy (typically over 4 million electron volts) ahd the highest LET of all radioactive emissions. The quality factor for alpha particles is 20.

14. Definitions Total Effective Dose Equivalent
Cumulative Committed Effective Dose Equivalent
Deep Dose Equivalent
The total effective dose equivalent is the sum of the internal and external doses. The cumulative committed effective dose equivalent is the dose due to internalized radioactive materials while the deep dose equivalent is the dose from external sources.

15. Biological Effects Acute Chronic
Acute toxicity for radioactive exposure is damage visible within a few weeks. Chronic damage is typically only demonstrated after years. The most common chronic type of damage is cancer. Note chronic damage is a random (stochastic) variable. You cannot predict that a specific individual will get cancer from a given radiation exposure. Only that the person has an increased cancer risk. Chronic effects are typically studied over thousands of exposed people and for extended periods of time.
Acute effects are much more predictable. An absorbed dose of one gray to the dermal layer of tissue will result in redness (erythema) of the skin. A dose of 20 grays to the esophagus, stomach, and intestines will result in destruction of the Gi tract with resultant death (this is not a probability it is a certainty). Acute effects are deterministic rather than stochastic.

16. Biological Effects
Direct chemical damage due to ionization of important biological molecules
Most damage is done by radical formation – the most common is the hydroxyl radical
H2O + radiation > H+ + OH (unpaired electron)
Radicals are atoms or molecules with unpaired electrons. The radical most frequently formed by ionizing radiation is the hydroxyl radical due to the fact that water is the dominant molecule in cells. Most of the cellular damage caused by ionizing radiation is actually the result of chemical rearrangements due to hydroxyl radicals.

17. Biological Effects
Acute

18. Biological Effects Erythema (skin gets red) 1 gray
Bone Marrow and white blood cells destroyed (about 5 gray or 500 RAD) this is the LD50. Ionizing radiation is a “metabolic poison” it preferentially damages rapidly metabolizing cells.
Gi tract -10 to 20 gray whole body (death certain)
CNS is destroyed at 50 gray and above
The LD50 is the level of radiation that will completely destroy the blast cells in the bone marrow for 50% of an irradiated population. For humans the LD50 is between 350 and 500 rads or from 3.5 to 5 grays. The erythema dose is the absorbed dose (rad or gray) that will cause enough damage to the dermal layer of the skin resulting in redness.
An acute dose of 20 gray will destroy the cells lining the GI tract resulting, this is always a fatal dose.
An acute does of 50 to 100 gray will destroy the central nervous system resulting in coma within a few minutes and death within a few days.

19. Biological Effects
Chronic

20. Biological Effects Cancer Mutations Teratogens
Cancer is the most likely chronic effect caused by ionizing radiation. For a single short exposure resulting in a dose of 25 rem or more (.25 sieverts) there is very good data indicating that the risk of cancer is increased and that the increased risk is a linear function of the dose received. If the dose doubles the risk of cancer doubles. There is less data on mutations and damage to the fetus (teratogen). One would expect the fetus to be more sensitive to damage caused by ionizing radiation due to the fact that the fetal cells are growing and dividing much more rapidly than adult cells.

21. Biological Effects DNA Damage RNA Damage Enzyme Damage
NOTE: Damage to DNA is amplified through transcription and replication
Cellular damage is caused by chemical rearrangements caused either directly by ionizing events or by the action of radicals causing chemical changes. Since damage to DNA results in a cascade of damaged mRNA then synthesized proteins, this is typically the most critical sub- cellular element damaged. Note, as mentioned before those cells rapidly copying DNA into other DNA or mRNA are very susceptible to damage due to ionizing radiation.

22. As mentioned the dose response for cancer caused by ionizing radiation is linear above a level of 25 rem whole body dose. (note 25 rem to the little finger does not carry a high risk of cancer to the organism).
From a regulatory standpoint we assume that the dose response curve is linear and further that it extends down to the origin. That is any small dose of ionizing radiation will cause a commensurate increase in the lifetime risk of cancer. There is no good data for exposures below 10 rem that there is any increased risk of cancer. It is possible that below a certain threshold there is no increased risk of cancer. We do not have the data to prove either hypothesis. So for now we assume that the dose response curve is linear with no threshold.

23. Biological Effects
Linear No Threshold Theory states that if the dose is doubled the risk of toxic effects (due to ionizing radiation) is doubled
Not definitively demonstrated at low doses
Not applicable to acute dose, applicable to stochastic or random events like cancer
Always RBE (rem or sievert)
When creating a dose response curve for excess cancers, the unit of dose used is always in terms of relative biological effect, that is, either rems or sieverts.

24. Biological Effects Internal vs External Hazard (epithelial barrier)
Some nuclides can only hurt you if they get inside you. Examples low energy beta emitters such as 35S, 3H, 14C and alpha emitters
Radiotoxicity
LET, Target Organ, Effective Half Life
An alpha particle is very damaging if it is in direct contact with viable tissue. The epidermal layer protects people from the detrimental effects of alpha particles and low energy beta particles such as those emitted by 14C, 3H, and 35S. These would all be considered only internal health threats. Whereas 32P and 125I emit radiation that can penetrate the epidermal layer causing damage from outside the organism.
Radio toxicity is the measure of damage to an organism from internalized isotopes. The factors that make an isotope more radiotoxic are LET, effective half-life, and target organ, and energy. The higher the LET the higher the toxicity, the more specific the target organ the higher the toxicity. For example iodine is rapidly taken up by the thyroid gland. This constitutes a small tissue mass with high avidity for any iodine isotope. This makes radioactive iodine highly radiotoxic. The longer the material stays in the body the higher the damage.

25. Interactions (Photons)
Compton scattering
Photoelectric effect
Pair Production
Half Value Layer
Compton scattering results when a photon (gamma ray or x-ray) interacts with an electron ionizing the electron with a resultant change in energy and direction of the photon.
Photoelectric effect occurs when a photon interacts with an electron giving all of it’s energy to the electron. The photon is completely absorbed.
Photoelectric effect and Compton scattering are two competing routes for photon interaction with matter. Increasing energy of the photon increases the likelihood of Compton scattering while increasing atomic number of the absorbing material increases the likelihood of photoelectric effect.

26. Interactions (Beta Particles)
Bremsstraahlung
Ionization
Range
Beta particles can emit x-rays when they undergo negative acceleration. This is not a desirable outcome if you are attempting to limit exposure to ionizing radiation. It is relatively simple to shield someone from even a high energy beta particle, but it requires much more mass to effectively shield even low energy photons
Beta particles have much higher LET than photons
Range for 32P is about 0.8 cm

27. Interactions (Beta Particles)
Bremsstraahlung (x-rays)
Increased by high atomic number materials
Increased by high energy electrons
Bremsstraahlung occurs when beta particles interact with matter. The higher the atomic number of the material an electron is traversing the more rapid the kinetic energy drop. This energy goes into ionization of electrons, heat, and it will also be transferred to photons. Bremsstraahlung is also termed breaking radiation or electromagnetic radiation caused by the negative acceleration of a charged particle. For 32P it is best to slow the high energy down more gradually resulting in fewer and less energetic photons. It is quite possible to produce x-ray level energy photons from 32P beta particles. We do not use lead as a shielding material for 32P since the higher the atomic number of the absorbing medium the more energy emitted as x-rays. Shielding for 32P is usually plastic or wood. Both have large percentages of hydrogen, and carbon which tend to slow the energetic beta particles more gradually releasing fewer and less energetic x-rays.

28. Nuclide Characteristics
Tritium 3H
Very Low energy –Beta emitter
Cannot be detected with Geiger Counter
LSC and Gas proportional counters
12 year half-life
6 keV
Yu should be familiar with the general energy range, half life, type of emission, and likely range of each of the nuclides typically used at BYU. These nuclides include tritium, 32P, 33P, 35S, 14C, 125I.

29. Nuclide Characteristics
35S and 14C
Low Energy Beta
10 percent 2pi efficiency
87 day half-life
50 keV, range in air 22 cm

30. Nuclide Characteristics
32P
High energy – bremsstraahlung
GM detector gives high efficiency
14.29 days half life
700 keV energy, range in air 6 meters
LET is inversely proportional to energy

31. Nuclide Characteristics
Gamma emitter low energy (electron capture)
Target organ – thyroid
60 day half-life
Solid scintillation is best detection method

32. Nuclide Characteristics
33P Low energy beta emitter 27 day half life
14C low energy beta emitter 5000 year half life

33. Waste Disposal Decay Sewer Ship Chemicals
Management (characterization)
These are the only three ways that we are permitted to dispose of radioactive waste.

34. Waste Disposal Decay Half life less than 90 days Remove all labels
The University is allowed to dispose of radioactive isotopes with a half-life of less than 90 days by storing the material for ten half-lives and then checking the material and throwing it away as standard trash. Decay in storage must be done by the Environmental Management Group. The time the nuclide spends in the laboratory does not count toward the duration of decay in storage. Only the Environmental Management Group may discard decayed isotopes.

35. Waste Disposal Sewer 100 microcuries of tritium 100 microcuries of 35S
100 microcuries of 14 C
100 microcuries of 32P
No Iodine
It is legal to dispose of radioactive isotopes to the sewer so long as less htan 100 microcopies per day are discarded by each laboratory and the material is readily dispersable in water. The exception is 125I which may not be discarded to the sanitary sewer. Note; all sewer disposals must be recorded in the radiation safety manual and there is good evidence that the chemical form of the isotope is readily soluble in water.

36. Waste Disposal Remove all labels List Nuclide Note quantity
Before you place tubes, plates or other containers in the radioactive trash, always remove or deface all radioactive labels. Then when you are ready for the trash to be picked up make sure the bag is securely closed, labeled with the laboratory number, date, nuclide, and quantity of material in the bag. You should use clear plastic bags, which allow the Environmental Management employees to visually check the contents of the bag without opening the waste. It is preferable to use plastic liquid scintillation vials rather than glass scintillation vials.

37. Waste Disposal Liquids must be in Plastic leak proof containers
Solids should be in a closed plastic bag
List laboratory

38. Waste Disposal
Never mix hazardous chemical wastes with radioactive wastes without RSO Approval
Never mix short half life nuclides with long half life nuclides without RSO approval
Get approval from the RSO before using radioactive isotopes in animals

39. Dosimetry TLD badges for external hazard materials
Significant Quantities
Over 2 millicuries in one package
Over 3 millicuries in one month
If your laboratory receives more than two millicuries of 32P in one package or more than 3 millicures of 32P in one month the people working with 32P in the laboratory will be required to wear both a finger badge and a lapel badge to estimate exposures. If your laboratory receives more than 30 microcuries in one month you will be required to have a dosimetry badge. You should wear the ring badge with the active element (the thin crystal
For 35S, 14C, 3H, or 33P you will not be required to get a badge.
TLD stands for thermoluminescent dosimetry. The actual detector is a crystalline wafer that can trap energy absorbed from ionizing radiation in the crystalline structure of the wafer. At three month intervals the TLD badge is sent to the manufacturer and ‘read’ by heating until the the electrons in the crystal drop back to their ground state releasing photons of visible or near visible light. The light flashes are counted with photomultiplier tubes. Please be aware that if you leave your TLD badge in an area like the back window of a car, the heat can ‘reset’ the badge to 0. Also leaving the badge in an area of high radiation while you are not wearing the badge will give a false high estimate of your exposure.
The whole body badge should be worn at the lapel, the finger badge should be on the finger with the TLD crystal on the working side of your hand (dorsal surface) if you are using 32P. A 32P beta can traverse 0.8 cm of unit density (soft) tissue. It is unlikely that you will have any 32P betas traversing your hand. If you have a ring badge for photon exposures it does not matter which direction the chip is facing.

40. Dosimetry Thermoluminescent Dosimetry
Heat
Wear the badge on or near your lapel
Wear ring badge with TLD crystal to the inside (exposed) portion of your hand
Wear fetal badge near stomach

41. Iodinations
E 238 BNSN
Perform thyroid assay before, following and 24 hrs later
Use RSO’s survey meter
Keep results in your book and send them to the RSO
The only facility at BYU authorized for iodinations is room E238 BNSN. If you do an iodination you will make three thyroid assays. The first is a background assay prior to handling radioactive iodine. The second is done immediately following the iodination, and the third is done 24 hours after the iodination. If any evidence of thyroid contamination is detected following the iodination, it will still be possible to have a physician prescribe potassium iodide to block the thyroid and limit the uptake of radioactive iodine. Of course if you do not do the bioassay or If you fail to report the bioassay, the MD cannot intervene.
Always keep records of the bioassays in your radiation safety manual and sent the results to the RSO You will always use the RSO’s low energy gamma scintillator for the bioassay (do not use your own instrument it is not as sensitive and it has not been checked for proper response to a thyroid dose).

42. Bioassay If you handle 5 mCi or more you will do bioassays
Bioassays required for all iodinations
Solid Scintillator
Urine (early morning – 1 ml count one minute)
If you ever work with 5 millicuries or more of a loose isotope, you are required to do a bioassay the morning following your potential exposure. This bioassay is completed by placing 1 ml urine (first void in the morning) in liquid scintillation counting cocktail and counting on a LSC counter.

43. Leak Check All new material should be leak checked prior to use
Call the RSO if a leak is detected
Always open the isotope in a functioning hood. Always wear gloves, a laboratory coat and goggles when opening radioactive isotopes.
For isotopes other than tritium, rub the surface of the vial containing the radioactive isotope with a chemwipe or paper towel. Then place the swipe on a clean bench (at least two meters from the vial) and count using a Geiger counter. Report any count above the background to the RSO. For tritium wipe with a 2 to 3 cm square or round piece of chemwipe. Place the chemwipe in liquid scintillation coctail and count for one minute with the window setting from 2 to 17 kev.
Record your leak checks of new material on the inventory sheet.

44. Protection Time, Distance, Shielding and Quantity
Use Personal Protective Equipment
Gloves, goggles, lab coat
You can manipulate the following variables to keep your exposure to ionizing radiation as low as reasonably achievable.
Time – Your exposure is directly proportional to the time you are exposed.
Distance – your exposure is inversely proportional to the square of the distance you are from the source.
Shielding can be used to decrease your exposure
Your exposure is directly proportional to the quantity of the material you are working with.

45. Eating and Drinking
Never eat, drink or apply makeup in a laboratory authorized for use of radioactive isotopes

46. Regulations R313-15 and R313-18, 10 CFR 20, License
Allowable Exposure 5 Rem/Year
Pregnancy mrem/pregnancy
You are required to read R313-15, R and guide 8-29.
The permissible occupational exposure (whole body dose or total effective dose equivalent) must be less than 5 rems per year or 0.05 sieverts
The fetus may not receive more than 50 millirems (0.5 sieverts) in one month nor more than 500 millirems (5 millisieverts) in the total duration of the pregnancy. A woman is not required to declare her pregnancy, but if the pregnancy is declared, the University has an obligation to see that the fetus does not exceed the above limits. A formal declaration is made in writing to the RSO.

47. Regulations
The University has an obligation to the pregnant woman and her unborne baby. But this obligation begins with a formal (written) declaration of the pregnancy.
The University does not have the right to compel a woman to reveal her pregnancy status. However, if you want the legal protection afforded under the law, you will need to send a letter or note (signed) to the Radiation Safety Officer (Edwin Jackson 103 TOMH) declaring your pregnancy.

48. Regulations Security Locked Up –double locks
Under personal supervision of an authorized individual
All radioactive isotopes used at the University must be secured at all times. That means that they are either under the direct physical control (within the view of) of a person authorized to have radioactive isotopes or they are secured with a lock. In fact, for all concentrated isotopes, the isotopes should be secured with a double lock system when not under the physical control of an authorized user. That typically means tht they are in a locked laboratory and inside a locked refrigerator, freezer, cabinet or other lockable device. For radioactive waste the only requirement is to be in a locked room or laboratory.
There are no other options.

49. Regulations Required Notice DRC04 must be posted
Dosimetry Report annually.
Every laboratory using ionizing radiation should have a DRC-04 form posted in the laboratory
Every individual who is issued a dosimetry badge will receive an report once per year listing the person’s annual exposure to ionizing radiation. This report is for your records and should not be sent back to the RSO. I do request that each department keep a log of everyone who was given or sent a dosimetry report. That log certifying that everyone in the department received their report should be sent back to the RSO.

50. Instrumentation Ionization Chamber Gas proportional counter
Geiger Mueller counter
At BYU instruments used for the detection of ionizing radiation can be classified based on the detection medium. We have:
Gas filled detectors
Liquid detectors
Solid detectors
The three types of instrument based on a gas detection medium used at BYU include: ionization chambers, gas proportional counters and gieger muller counters.

51. Laboratory Surveys
Survey your laboratory each day that isotopes are in use
Log the survey values
Identify the survey meter and person

52. Instrumentation + _ + _ _ + Gas Filled Chamber Electronics
+ _ + _ _ +
All of the gas filled detectors work in the same basic manner. Ionizing radiation radiation enters the counting chamber and ionizes molecules of the gas detection medium. The positively charged ions flow to the negatively charged pole and the electrons flow to the positively charged pole. The resultant current is measured. This current flow is what is actually measured. In the case of an ionization chamber the counting medium (gas) is air and the voltage inside the chamber is relatively low. For each ionizing event a single count is recorded. With gas proportional chambers the voltage is ste higher and each ion pair will cause additional ionizations as they move to the cathode or anode. The measured response is proportional to the energy on the original ionizing radiation (the higher the initial energy the larger the cascade of ions). Gas proportional counters typically use P-10 counting gas (10% methane and 90 % argon) flowed into an open window. Due to the fact that the window is open the gas proportional counter can detect very low energy beta emitters such as tritium and alpha particles. The Geiger Mueller tube has the highest voltage and when a single event occures the cascade of secondary ion pairs essentially involves all of the detector medium. The detector medium is a defined mixture of organic gas, noble gas and quenching chemicals. If you put a hole in a Geiger Mueller tube the tube will no longer work properly. A GM tube based instrument with a very thin mylar window can be expected to get approximately 10% 2 pi efficiency for carbon14 (or sulfur 35).
Gas Filled Chamber
Electronics

53. Instrumentation Solid Scintillator Liquid Scintillation
Most sensitive for photons (required if you use 125I)
Liquid Scintillation
4 π geometry
Tritium detection
Gamma rays and x-rays have very low likelihood of interacting in a small gas filled chamber. The way to increase the chance of detecting photons is to increase the density of the detector medium. The most efficient photon detectors are based on solid crystals that trap the energy from ionizing radiation in the crystalline structure. Typically these crystals are doped with material that will emit flashes of visible light when exposed to energy. The crystal is surrounded by photomultiplier tubes that convert visible light into an electrical signal. The detector based on this principle is called a solid scintillation detector. The most common crystal used is sodium iodide.
The same type of system can be created using a liquid system that traps energy in the resonance structure of an organic molecule. Typically these are based on molecules based on the benzene ring (such as poly linear alkyl benzene). Again flours are addded to the energy trap that will emit visible or near visible light which is converted by photomultiplier tubes to electrical energy and counted. This system is called Liquid Scintillation Counting. Liquid Scintillation Counters have 4 pi geometry (the full spherical surface of particles emitted in three dimensions will be counted). Liquid scintillation can detect tritium with over 50% efficiency and most other nuclides with over 95% efficiency.

54. Instrumentation Efficiency Geometry - surface area of a sphere =4π r2
Coincidence
Window
Note, a flat detector can not detect more than one half of the emitted particles from a point source. This type of detector has what is termed two pi geometry. Its total efficiency can never be better than 50% due to the geometry factor. In addition for many high LET emissions such as low energy beta particles and alpha particles the window thickness will be the main factor determining efficiency of the instrument. Coincidence losses occur when two separate ionizing events occur so close together in time that only a single count is detected. Coincidence can become a problem with very high count rates.

55. Instrumentation Calibration must be completed at least annually.
Photon detectors must be sent out
Beta survey instruments may be calibrated by Risk Management
Every instrument used at BYU must be calibrated once per year. The Radiation Safety Office will check all beta survey instruments. Those instruments used to detect photons (x-rays and gamma rays) must be sent by the laboratory to an outside vendor for calibration.

56. Laboratory Surveys
Check hands, telephone, bench, floor in front of bench, soles of shoes, computer keyboard, centrifuges, door handle
Survey at the end of each day that rad material is used.
Be prepared to calculate surface contamination
Laboratory surveys must be completed in a laboratory following the use of radioactive isotopes. This need only be done once per day. Always record the laboratory survey in the Radiation Safety Manual. The following information is required: serial number of the survey instrument, a battery check, a check source count, the results of the survey, and the initials of the person doing the survey.
Surveys should always include the bench where work was completed, the floor directly in front of the bench, hands, equipment used, telephone, sink, door handle, computer keyboards, and the bottom of the shoes. As long as you know the efficiency of your survey instrument for the nuclide that you are using it is simple to calculate a particular amount of radioactive contaminant. Always remember that a GM tube gives only 2 pi efficiency.

57. Laboratory Surveys Documentation Date Instrument SN Battery check
Check Source count
ID of person completing the survey
Survey result
Anything above background is positive

58. Laboratory Surveys Important variables Nuclide energy
Distance from the surface
Speed of detector movement
Audible is more sensitive than instrument reading
Remember the faster you move the detector the more likely you are to miss a contaminated area. Distance from the surface being checked is a critical factor in detecting most nuclides but it is especially important for low energy beta emitters. You will typically hear an elevated count before you will see a noticeable increase on the meter.

59. Documentation Receipt logs Disposal logs Survey logs
You are required to have receipt logs disposal logs and survey logs in the laboratory. The Receipt log and disposal log may be the same physical inventory form. All documentation should be in the Radiation Safety Manual so the they can be easily found and checked by the RSO.

60. Documentation Certification User Authorization Facility Authorization
Training list
Each person authorized to work with ionizing radiation must sign a Certification sheet. The certification sheets should be kept in the Radiation Safety Users Manual. In addition there should be a User Authorization form for the PI and a Facility Authorization for the laboratory in the Radiation Safety Manual.
You should keep a sheet with a list of people who are authorized to use radioactive isotopes in the front part of your Radiation Safety Manual.

61. Emergencies Call 2-2222 if no risk of life or health
Call 911 if risk of life or health
In an emergency involving radioactive materials call 911 or from any campus telephone.
For contained spills (spills on soaker paper or in a drip pan or other spill control device. Clean up the spill and discard the waste.
For an uncontrolled spill of less than 10 microcuries, carefully absorb the liquid material with an absorbent towel or pad. Discard the towel into the radioactive waste. Wipe the spill area with a damp paper towel from the outside of the spill area to the inside. Remember you do not want to spread the spill. Check the area with an appropriate detector. If there is still contamination, use a strong detergent such as Micro-90, RadOff, or Isoterge (or any other good detergent). Wipe down the area and discard the towel. Always remember that your gloves may be contaminated. If necessary change gloves after each operation to avoid spreading contamination.
If the spill involves more than ten microcuries of material or if you do not feel comfortable cleaning up the spill call and ask for assistance from the RSO.

62. Emergency Procedures Get Help - Emergencies call 911 on a campus phone
If help is needed immediately call
Radiation Safety Officer
In the case of a spill or other emergency with radioactive materials call for immediate assistance. If the matter is considered urgent call 911 from any on campus telephone. Both of the calls will go to the University Police dispatcher. A 911 call has precedence. Let dispatch know who you are, where you are and the nature of the incident or emergency. Let them know that you need the assistance of the Radiation Safety Officer. For spills always attempt to keep others from being exposed and limit the spread of the spill.

63. Emergency Procedures First priority Human life and safety
Second priority limit the spread (consistent with first priority)
Clean the spill up
Block off the area
Survey for contamination on yourself and the ‘clean areas around you’ pay particular attention to your shoes.
Always remember to limit t he spread of the spilled radioactive isotope. It is much easier to clean up a two square inch area than a twenty foot square inch area. The following are guidelines for spill cleanup.
For any spill on soaker paper you may simply discard the soaker paper into the radioactive trash. This is considered a contained spill and you do not need to call the RSO.
For a spill involving less than 10 microcuries of material you should clean up the spill using normal PPE by first absorbing all of the free liquid with absorbent towels, pads, or other absorbent material that will not tend to spread the spill. Once there is no free liquid survey the area and define the area of the spill. You can typically use a marker (staying an inch or so outside the contaminated zone) to show where the spill is. Finally clean up the spill wiping from the least contaminated area to the most contaminated to minimize spreading any surface contamination. If necessary use a detergent such as radoff, isoterge, or micro-90 to help remove residual contamination. If you cannot remove all of the contamination, mark the area with radioactive labeling tape and notify the RSO.
For uncontrolled spills larger than 10 microcuries call and request the RSO.
Please note the redundancy is intentional. I really really want you to know what to do in an emergency. Once you have read the slides twice and commented on how dumb that was, I expect you to remember what to do in an emergency.