1962
RADIATION PROBLEMS ON AN AIR FORCE BASE
Captain Carl .J. Weinberg
Headquarters Air Force Logistic~ Command
INTRODUCTION’..
1. The theme of the program this afternoon is “Radiation Problems on an Air Force Base,” and was chosen to correspond to your requests. You may remember that I sent out a letter early this year asking for suggestions on what you would like to hear at a health physics symposium. The overwhelming m3jority asked for answers on what to look for in three broad topic areas:
a. What radioisotopes to look for on an Air Force Base.
b. How to conduct a radar unit survey.
c. How to conduct an x-ray protection survey.
2. I will start off with what isotopes to look for on a typical base. Captain Kendig from the Regional Environmental Health Laboratory at. Kelly AFB will discuss the x-ray surveys, and Captain Kennebeck from the Regional Environmental Laboratory at McClellan AYE will discuss the radar survey. We have kept the presentations shorter than the allotted, time deliberately to allow questions. There will be a short question period at the end of each presentation and a general question period when all presentations have been completed. I want to re-emphasize the importance of asking questions. It is only in this way that we can discuss and help you with your specific problems.
3. We have deliberately steered away from some topics as they will be presented by other speakers. You will notice on your program that tomorrow morning is also heavy on the health physics aspects of your job. So, this afternoon, we will not discuss in detail the film badge program, exposure limits, aircraft contamination, or standard radiac instruments, as these subjects will be covered by the speakers tomorrow.
4. Since this is to be a symposium, I would like this afternoon at least to have the spirit of the symposium prevail in the old Greek tradition. In ancient Greece a symposium was a drinking together, usually following the banquet proper, with music, singing, and conversation; hence, a social gathering at which there is a free interchange of ideas. Lunch wasn’t quite a banquet--and the music, singing, and drinking won’t start until tonight, but I do hope that this afternoon will bring at least free interchange of ideas!
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WHAT ISOTOPES TO LOOK FOR ON AN AIR FORCE BASE
1. One of the primary potentials for exposure on any Air Force base outside of the hospital is in the Precision Maintenance Equipment Laboratory (PME Laboratory). These laboratories are now authorized to calibrate all radiac instruments on any Air Force Base and to do this job they are provided with radioactive calibration sources. The present authorized Co-60 sources are being replaced by Cs-l37 calibration sources. This replacement is now taking place. The new Cs-137 sources are described in TO. llH4-8 -5-i, Utilization and Maintenance of Cs -137 Test Samples. The sample contains about 100-120 mc of Cs-137, with a half-life of 26.6 years and emits gamma radiation. of 0. 66 mev. It has some beta emission but the source is doubly encapsulated and all beta emission is absorbed. In addition, the PME Laboratories are authorized a Plutonium-239 calibration test. set for calibration of alpha measuring instruments.
2. Actually, these sources represent a good example of a typical hazard and I would like to use it to illustrate some of the requirements of a radiation protection program. Also, since these sources are licensed by the AEC, (that is the AEC authorized the USAF Radioisotope Committee to distribute and control the sources within the Air Force) their use must conform both to AEC and AF regulations. The basic requirement for the AEC are contained in 1OCFR2O, Standards for Protection Against Radiation (of which you have a copy), and for the Air Force in TO. 00-llON-3. If you read any documents, read these two. Actually,TO. 00-11ON-3 has been revised to conform to 1OCFR2O in most cases.
3. So let us take a “for instance.” A PME Laboratory has just been organized on your base and is applying for calibration sources, CS-137 and Pu-239. In order to get the sources from SAAMA, you must have an Air Force Radioisotope Committee Permit. This permit has been revised only lately to a 1-page document. You get this permit by submitting the required information contained in TO. 00-11ON-3. This information is to provide answers to essentially the following questions:
a. Who will handle the source and what is his training?
b. Where will it be used?
c. Who will act as radiation protection officer?
d. What instrumentation is available?
e. Are film badge services provided?
f. Are the people cognizant of applicable directives?
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The application is then forwarded to the USAF Radioisotope Committee located in the Surgeon’s Office, AFLC. This Committee reviews and approves the use of isotopes Air Force-wide and also acts as the official liaison with the AEC in regard to licensing of isotopes within the Air Force. As a guideline for training we require that the individual have as a minimum attended the PMEL Technician Course at Lowry AFB. This course contains about 60 hours of instruction on the calibration of instruments and handling of radioactive calibration sources. For the radiation protection officer, we require a minimum of training equivalent to the 2-week Basic Radiological Health Course that most of you have had. We would prefer that the Sanitary and Industrial Hygiene Engineer be appointed as Radiation Protection officer, but in some cases this cannot be done. The Committee then reviews the application and approves the Permit if all information is in order. Upon approval, SAAMA will ship the source to the base.
4. Now let us assume that you are going to make a survey on a PME laboratory or any other organization that is using isotopes. The first thing you should establish, besides what sources they have, is “are the sources under control of the individual user.” In this respect the AEC defines a “restricted area” as any area to which access is controlled for purposes of radiation protection. In TO. 00-11ON-3 it is called a “controlled area” in order not to create confusion with regard to “classified areas.” What does this mean? Merely that no one but the designated individuals should be able to get at the isotopes. For the standard Pu-239 calibration sources, it could be merely a locked desk drawer; for the Cs-137 it means locking the source container and shield itself. It is preferable that this be in a locked closet or cabinet, but this is not an absolute requirement.
a. Each container or area that has in it licensed material must have a warning sign “Caution Radioactive Material.” (Slide i) This is irrespective of the radiation intensity. This is a standard Air Force form described in TO, 00-I1ON-3, and conforms with 1OCFR2O. If the container is used to store the isotope, it must also contain the name of the isotope, quantity, and data of measurement. So this sign identifies that radioactive material is present, but gives no information regarding the levels of radiation in the environment.
b. If the radiation intensity is greater than 2. 5 mr/hr but less than 100 mr/hr, there must be a sign saying “Caution Radiation Area.” (Slide 2) It is advisable to put this up where people will encounter the radiation field, either at the entrance to an area or at the 2.5 mr/hr level. This means that the sign must be put up whenever a source is to be removed from storage and. used. In most PME laboratories there will be a line drawn on the floor indicating the radiation area that requires the sign. Check it. If you are on a base that does hate industrial radiography, the same is true about placing your ropes and signs, so that any time there exist s a radiation field of 2.5 to 1OO mr/hr the “Caution Radiation Area” sign is displayed.
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c. If the intensity should be above 100 mr/hr, then a sign saying “Caution High Radiation Area” (Slide 3) must be displayed. In addition, you must have some visual or audible signal if a person should enter the area. Both TO. 00-11ON- 3 and 1OCFR2O specify the conditions required. The door to the room containing a Co- 60 teletherapy unit, therefore, would have both a “Caution Radioactive Material” and “Radiation Area” sign.
d. If you should be using isotopes, such that the possibility exists of an airborne hazard, then the following sign should be posted: “Caution Airborne Radioactivity Area.” (Slide 4) This means that concentration of activity exceeds the limits given in 1OCFR2O or AFP i60-6-7, “Maximum Permissible Body Burdens and Maximum Permissible Concentrations of Radionuclides in Air and in Water for Occupational Exposure.” In fact, if you are using isotopes which could become airborne, both the USAF Radioisotope Committee and t he AEC will request information on airborne concentrations and this implies that you have an air sampling program. In other words, these signs were designed to tell people that radioactive material is present and then the type and degree of hazard.
6. You will also need to ask:
a. What is going to be done with the isotopes?
b. How will it be done?
c. What actions will be taken if something goes wrong?
For the standard Air Force items most of the answers are provided in applicable technical orders, but let us go through what the answers might be with regard to the Cs-137 source:
a. The source should be used only to calibrate radiac instruments. It should not be used for training monitoring teams.
b. A definite area should be laid out to perform the calibration. Proper signs should be available to delineate the radiation areas.
c. Watch them perform some calibrations. Are the instruments handled so that only the hands enter the main beam?
d. What SOP is available if the source should happen to fall out of the shield?
The answers to these types of questions are sometimes not so simple.with other uses of isotopes. Industrial radiography, for instance, where the location varies from day to day and where there might be a problem returning the source to the shield. In these cases, it would be desirable to have
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some written rules that must be followed. We are having many licenses returned by the AEC because the SOP’s were not directed to the individual handling the isotopes and required looking at other documents in order to fully understand them. In other words, none of the typical SOP style “so and so will be done in accordance with paragraph 2b(4), Section 5, AFM 160-23.” This dosen’t really tell the person what to doll
7. Personnel monitoring is another aspect that must be considered. You will usually have to recommend a system. In most cases the film badges are sufficient. As a rule of thumb, I would say that any time you use a “Caution High Radiation Area” sign you might wish to supplement the film badge with a pocket dosimeter that can be read at the end of each working day. This might well be the case of our calibration laboratories that have AN/UDMA 100-curie Cs-137 source. I also want to point out that if you have an overexposure to isotopes, that is more than 1.25 rem/quarter, you must report it to the ACE. I suggest you pass the information on to the USAF Radioisotope Committee so that we can report it to the proper AEC Compliance Region. Neutron badges present a special problem and you should contact the USAF Radiological Health Laboratory. Please do not say you are using DT-60’s. They were not designed to record levels below about 25 roentgen.
8. Finally, there is the requirement that if you have sealed sources you must check them at 6-month intervals to see that they are not leaking. This is primarily to make sure that the area does not become contaminated. The AEC also requires that the test be sensitive enough to detect 0.005 microcuri.es of activity. This means that you cannot perform a proper leak test utilizing only standard Air Force radiac equipment. The thin window of the PDR-27 will give you an indication when you approach 0.05 microcuries and a field test using the PDR-27 is described in TO. 11H4-8-5-l. In order to detect 0. 005 microcuries, you will need a thin end window GM tube coupled to a scaler. The technical order is written so that you may mail the swab to the Regional Environmental Health Laboratories in the US, the 7112th Central Medical Group in Europe, and the 5th Epidemiological Flight in Japan. Each of these places has equipment sensitive enough to detect 0. 005 microcuries. If you have the necessary equipment you may
count the swab yourself. I think the easiest way for me to tell you what to do is to show you. (Slide 5)
This shows a Cs-137 source in its shipping container. The source is bolted to the bottom of the container so that when you lay the container on its side it also acts as a coilimnator. You never remove the source - -you only remove the source plug. (Slide 6)
For the wipe we finally decided to use a pencil and a paper towel, primarily as these two items are available to every Air Force installation anywhere in
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the world. You cut out a strip of paper towel, wet it, and wrap it around
the pencil. If you wrap it tightly it will stick to the pencil without any additional means to hold it.
(Slide 7)
Then remove the source plug. This plug fits tightly around the source. Keep your face away from the beam hole. No use getting that Irradiated. Move away from the source and monitor the plug with the PDR-27. You should get absolutely zero unless it is contaminated. If you get a reading, you would suspect a faulty instrument or that the plug is contaminated and then you would expect a positive leak test. Run the wet swab all around the hole on the bottom of the plug, then along the sides of the plug.
(Slide 8)
Replace the plug then monitor the swab with the instrument, holding it as close to the swab as possible. If you get any reading at all I would suspect that the source is leaking and not use it until the results have been returned from the laboratory. I would also check the instrument by slowly moving the swab close to the probe and then removing it. The needle should go up scale as you move closer to the probe and drop to zero as you move away. If it dosen’t, be careful what conclusions you draw.
(Slides 9 and 10)
After you complete your field evaluation send the swab to your designated laboratory by wrapping it in paper, sealing the ends in with tape, or use aluminum foil or Saran wrap. Then put It in an envelope with the necessary information. Put the whole works in a mailing tube. Do not mix several swabs in the same envelope. The laboratories do get them that way!
9. Records. Now we come to the most overlooked portion of any program -records. The AEC is now inspecting our bases and has Inspected quite a few PME laboratories, and records are what they are looking for, so don’t think it can’t happen to you. The inspection reports, if discrepancies are found, arrive by registered mail to the Commanding Officer with 24 hours to reply. So what records do you need?
a. Surveys. Has a competent person made a survey of the situation? By this, the Medical Service is usually Implied; the sanitary and Industrial hygiene engineer or health physicist, if available. And most Important, f~ the survey on file and current?
b. Exposure records. Are records kept of the film badge results arid are they up-to-date? Captain Markarian will mention something about this tomorrow.
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c. Leak test. Are leak tests made at 6-month intervals and are the results recorded?
d. Disposal records. In most cases, disposal is made through TO.
00-1 1ON- 2~ and you would have shipment instructions. In cases where you meter a licjuid solution into the sewer, you have had a record of total amount disposed of by each. day.
10. Now, let us apply some of these principles or requirements by looking around an Air Force Base.
a. PME Laboratory.
(1) Co-SO calibration source, TO, 11H4-8-3-l. This source is
presently being removed from Air Force use and the same precautions apply as with the Cs-137 sources.
(2) Cs-137 calibration source, TO. 11H4-8-5-1.
(3) Pu-239 test sample, TO. 11H4-8-4-l. (Slides 11 and 12)
(4) Cs-137. 100-curieAN/UDM-1A (Slides 13 and 14)
This is a fairly large source requiring remote telescope reading.
b. On the aircraft.
(1) Tritium markers, exit signs, etc. TO. 00-lION-i. The
tritium markers do not present significant hazard but must be accounted for under present Code of Federal Regulations. One of the latest amendments to 1OCFR3O exempts tritium markers that pass certain acceptance requirements.. The markers usually consist of tritium bonded to the phosphor and encased in plastic.
(2) Depleted uranium counterweights. The C-140 and C-141 aircraft contain depleted uranium aircraft counterweights. These are located in the ailerons. The counterweights must be plated in order to be exempt from licensing. The Air Force counterweight will be plated. The potential radiation hazards arising from uranium are from inhalation of uranium
dusts and external radiation. The external hazards are for all practical
purposes due entirely to beta particles. The amount. of gamma radiation is negligible and the alpha particles are shielded by the plating. Depleted
uranium counterweights with a nickel cadmium plating of 5 mils thickness can be expected to have a surface dosage of beta particles of 125 mrem/hr. A person could therefore hold. a uranium counterweight in his bare hands
for a total of 12 hours per week for a year without exceeding 75 rem limit
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for the extremities. Since the replacement of counterweights Is a rare maintenance procedure, it is unlikely that exposures would reach this amount. In order to prevent any possible Inhalation problem, the plating should be kept Intact.
c. Radiac Instrument check source.
(1) Radium, AN/PDR-27 - TO. iiH4-7-3-101. Some problem has been encountered with this lately where people have broken off the plastic stick and have put a new one In the hole. Instrument cases have been found with several broken off radium sticks wedged into the bottom of the rubber storage area. New check sources were then placed on top.
(2) Strontium-90. AN/PDR-39. TO. ilH4-8-3-8i(82)(83). These sources contain 1 microcurie of Sr-90. If these are removed they should be. handled carefully so that they will not be damaged and begin to leak.
(3) Krypton-85. AN/PDR-43. These represent a minimal hazard but must be accounted for.
d. Luminous dial painting shops. TO’s 42A2-i-3. 00-11ON-5, and
5-1-5.
(Slide 15)
This is a problem primarily confined to AFLC. Just about every on? of the AFLC bases has a shop that does radium dial painting and some also use tritium paints. Prior to painting, the paint must be stripped which can be a messy operation . In the year and a half since I have been at Hq AFLC I know that on three of the bases the radium dial painting shop has been contaminated. On your base, just for fun, you could use a radiac instrument on any dial that glows in the dark. In some cases the people may be using radioactive paint of which they are unaware. One of the daughter products of radium is radon, a gas. This means you can quickly spread contamination.
e. Re-entry vehicles - TO. 1INRV4-2-1(2). Re-entry vehicles contain. Krypton-85 batteries. The usual battery contains a vial or container of 450 miillturies of Kr-85. Krypton is an inert gas and does not react, so that the maximum danger occurs when an individual is submerged in an atmosphere of Kr-85 gas. Under the typical maintenance conditions, it would be difficult to build up a sufficient concentration for any length of time. If you should suspect that one of the batteries has released krypton, evacuate the building and ventilate as much as possible! for 5 to 10 minutes..~ The battery does have associated with It a gamma flux of about 30 mr/hr at 3.” and less than 5 mr/hr at 12”. The primary exposure would be to the wrists. An analysis of exposures of wrist badges indicates that no significant. exposures are occurring. You should, however, check the maintenance area where the subassemblies containing Kr-85 batteries are handled.
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f. Polonium-2l0 anti-static bars. TO. 00-11 N-8. Some of the card sorters used in missile card programmers utilize a Po-210 antI-static bar. This bar contains 1700 microcuries of Po-2l0. It is primarily an alpha hazard and a requirement exists for performing a wipe test. A field evaluation Is described in the technical order, using a PAC-iS or PAC-2t. The swipes are then sent to the USAF Radiological Health Laboratory for more sensitive analysis.
g. Industrial radiography. TO. 33B3-I-i. Some of you may become involved with industrial radiography. It is difficult to discuss very much of it except to say that the AEC has a thick pamphlet out describing precautionary measures. There is also a special 1OCFR31 which deals exclusively with radiographic sources. If you run Into this problem, I will be glad to supply you with the necessary information.
h. Research Isotopes. AFR 160-124. These types o problems are at only a selected group of Air Force bases usually belonging to Air Force Systems Command. Most of the bases having an extensive research program have assigned a health physicist. Again, if you feel you have a problem along this line, I suggest you contact the USAF Radioisotope Committee.
i. Clinical isotopes. AFR 160-57. Here, again, this is~a specialized field restricted to about 6 or 8 hospitals in the Air Force. In general, diagnostic quantities do not present much of a problem except with the necessary paperwork required for an~ AEC license. The AEC quite rightly insists they know who. is going to use the isotopes and their experience. Otherwise, the basic principles outlined above apply. The diagnostic quantities are usually in the microcurie range and in most cases the patient is in an out-patient status and waste disposal is no problem. When you increase the program to therapeutic quantities, then the problems increase and special instructions are required for nurses, bed clothing, and sheets. In some cases. the patient may have to be isolated due to the high accompanying gamma flux, as in Gold-198 in intracavitary use for pallation of carcinomous patients. This is a subject that could easily take up the whole two hours. If you have a problem along this line, again I ask you to contact the USAF Radioisotope Committee for more detailed information.
j. Medical x-ray. This subject will be discussed by Captain Kendig.
11. Conclusion. And, that, gentlemen, concludes what I have to say. We have time now for about 5 minutes of questions.