SWRHL-56r PROTECTIVE ACTION TAKEN AT SCHOFIELD'S DAIRY HIKO, NEVADA FOLLOWING AN ACCIDENTAL RELEASE OF RADIOACTIVITY FROM THE NEVADA TEST SITE by John S. Coogan and Wayne A. Bliss Western Environmental Research Laboratory ENVIRONMENTAL PROTECTION AGENCY Pub I ished January I 972 This study performed under a Memorandum Understanding (No. SF 54 373) for the U. S. ATOMIC ENERGY COMMISSION of ------- "This report was prepared as an account of work sponsored by the United States Government. Neither the United States nor the United States Atomic Energy Commission, nor any of their employees, nor any of their contractors, subcontractors, or their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, or process disclosed, or represents that its use would not infringe privately-owned rights." Available from the National Technical Information Service, U. S. Department of Commerce Springfield, VA 22151 Price: paper copy $3.00; microfiche $.95. ObG ------- SWRHL-56r PROTECTIVE ACTION TAKEN AT SCHOFIELD'S DAIRY HIKO, NEVADA FOLLOWING AN ACCIDENTAL RELEASE OF RADIOACTIVITY FROM THE NEVADA TEST SITE by John S. Coogan and Wayne A. Bliss Western Environmental Research Laboratory* ENVIRONMENTAL PROTECTION AGENCY Published January 1972 This study performed under a Memorandum of Understanding (No. SF 54 373) for the U. S. ATOMIC ENERGY COMMISSION *Formerly Southwestern Radiological Health Laboratory, part of the U. S. Department of Health, Education, and Welfare, Public Health Service, Environmental Health Service, Environmental Control Administration, Bureau of Radiological Health. ------- INTRODUCTION Protective Action Guide is a term often cited in health physics with consider- ation to public exposure, but applied protective actions have been few. Any protective action is unique with respect to the many possible influences. This report defines a protective measure applied to decrease radioiodines in a dairy's milk production and the factors judged in choosing the mode of action. This action by the Western Environmental Research Laboratory (WERL) in concur- rence with the Atomic Energy Commission was taken at levels below the Federal Radiation Council guides and, although intended primarily as a feasibility study, was a prudent measure for minimizing the potential thyroid dose. On April 25, 1966, an underground nuclear test conducted at the Nevada Test Site released radioactivity to the atmosphere. Weather conditions were such that the effluent traveled from the Nevada Test Site in a northeasterly direc- tion. Levels of radioactivity detected by portable instrumentation in the immediate off-site area on the day of the test were low. The maximum exposure rate in the off-site area was 8 mR/h, 42 miles from surface ground zero in an unpopu- lated area. The highest exposure rate in a populated area was 1.5 mR/h at Hiko, Nevada, 63 miles from surface ground zero in Pahranagat Valley. Milk samples were collected in the Pahranagat Valley where family milk cows and dairy operations were present. In addition to milk samples, other environ- mental samples were collected simultaneously: natural vegetation, field forage, green chop, dry hay- grain, water, air and soil. Environmental samples were collected once daily with the exception of milk which was collected twice daily after the morning and evening milkings. All samples were immediately taken to the WERL in Las Vegas, Nevada, for laboratory analysis. All samples were analyzed on systems using a 4- by 4-inch Nal(Tl) crystal coupled to a 400-channel pulse neight analyzer. Results are reported in pCi/l for milk or pCi/kg for vegetation. Of the milk samples collected in the Pahranagat Valley, those from Schofield's Dairy at Hiko showed the highest concentrations of I3II. The location with the second highest concentration was about three-fourths of that observed from Schofield's Dairy; however, this sample was from a family cow, the entire pro- duction of which was utilized for sampling purposes. This report is concerned only with circumstances involving Schofield's Dairy. I ------- RADIOLOGICAL SITUATION Table I lists the initial radioiodine levels through the maximum observed following contamination at Schofield's Dairy. These samples were composites from cows of the main dairy herd. Table I. Radioiodine Levels in Milk From Schofield's Dairy Date and Time Col lection 4-25 4-26 4-26 4-27 4-27 of PM AM PM AM PM I3lj 320 1,900 3,300 4,400 4,800 pCi/1 I32j 490 3,100 1,100 1,900 I33j 1,000 6,100 20,000 15,000 12,000 I35j 800 4,300 1 1 ,000 2,500 1 ,000 Field forage samples for the same location gave the following values (Table 2). The dairy herd was not eating this vegetation but it should serve as a reference parameter in more areas than green chop (freshly cut growing alfalfa and wheat). Table 2. Radioiodine Levels in Field Forage From Schofield's Dairy Date of Col lection 4-25 4-25 4-26 4-26 I3IT 120,000 460,000 140,000 85,000 I32T T Tel 320,000 580,000 150,000 85,000 pCi/kg I33T 310,000 580,000 300,000 160,000 I35j 220,000 390,000 48,000 27,000 Schofield's Dairy was feeding green chop and grain exclusively to its one hundred and thirty-eight producing cows. The dairy was producing ------- approximately 650 gallons of milk per day which was transported to a Las 'Vegas processing plant at two-day intervals. Various means of determining whether radiation levels violate established guides have been proposed. However, the most important consideration in any situation of this sort is that radiation exposure should always be kept at a mi nimum level. Initial concentrations of radioiodine in milk from Schofield's Dairy were low. Past experience indicated that the maximum concentrations in milk would be reached at about five days after contamination. The levels of I on field forage pointed toward relatively high I concentrations in the milk. Data from past radioactive releases have shown that I in milk will reach a maximum concentration of 0.015 to 0.15 times the I concentrations on vege- tation. This indicated that the peak concentration of I in the mi Tk would fall in the range of 6,900 to 69,000 pCi/l. Ralph A. James, University of California, states a radiation field produced by unfractionated fission products of 0.032 mR/h at H+24 hours is the field 131 * corresponding to the FRC upper limit for range II of !• An actual gamma exposure rate of O.I mR/h was measured at Hiko 24 hours after the detonation. Based on this measurement and James' relationship, a concentration 131 ** of 8700 pCi/l of I in milk was estimated. Referring to "the FRC Report #5, page II, "Deposition of " I can vary greatly within a relatively small geo- graphical area. As a result, there can be large differences between I concen- trations in milk produced on farms only a few miles apart." Then the text goes on to state, "It is not possible to predict reliably the maximum concentrations of of I in milk from deposition data." The prior statements are referenced not to discredit the projected dose but to point out the uncertainty "Calculation of Radioactive Iodine Concentrations in Milk and Human Thyroid as a Result of Nuclear Explosions" Ralph A. James, University of California, Lawrence Radiation Laboratory, Livermore, California, February 14, 1964, Report #UCRL-77I6. From this measurement, greater than three times FRC Range II, that is, more than 8700 pCi/l of I3II in milk was projected. ------- involved in projecting milk contamination from ground deposition data. The Federal Radiation Council Report #5 states that from a single event a total intake of 600 nanocuries of I would result in a dose of about 10 rads to a two-gram thyroid. It is estimated that a peak concentration in milk of 60 to 70 nanocuries of I per liter could result in such thyroid doses. The FRC does'not include approximately 20 to 25% of the infinite thyroid dose which is obtained prior to the peak I concentration. It is deduced then that a maximum concentration of 60 to 70 nanocuries actually gives 12.5 to 13.3 Rad. Chapter 0524, Standards of Radiation Protection, U.S. Atomic Energy Commission, gives 1.5 rem/year as a stand- ard for thyroid dose to individuals of the population in an uncontrolled area. It follows that 1.5 rem results from 6,800 to 8,400 pCi/l. CONSIDERATIONS These guides are based on FRC recommendations for exposure of the general public for normal peacetime operations. Since Hiko is near the Nevada Test Site, there was no assurance that another exposure would not result within a year. Also, experience was needed in the application of preventive action and its effects on the dairy herd, the contaminant levels, and the public. The recommendation was made to the AEC to take protective action. The course of action was chosen after considering the following: A. The milk was being picked up from the producer dairy and shipped to Las Vegas, Nevada (at two-day intervals). The milk was being processed and delivered to the consumers within thirty-six hours after receipt by the pasteuriza- tion plant. Dilution at the pasteurization plant could not have been greater than a factor of seven after pro- portioning the milk in the plant's bulk tanks. The milk was not normally proportioned in the tanks and to do so would have created inconvenience and expense to the processor. ------- B. Disposing of the thirteen hundred gallons of milk would have caused the processor to operate below his consumer commitments since no other Grade A supply was available for milk replacement. Therefore, disposal of the milk was not a desirable protective action for this case. C. Storage facilities for this large volume were non-existent thereby eliminating the possibility of decreasing the hazard through radioactive decay. D. Diversion of the contaminated milk to milk products seemed a likely procedure which would have allowed a large reduction of the activity due to holding time. This possibility was discarded, however, because the producer would receive lower prices for milk which must be diverted. Furthermore, there were no milk product processing facilities in the nearby area. E. The remaining possibility was replacing the dairy's feed supply. This action was chosen as the most feasible protective action to be taken, and it is one of the actions recommended by the FRC for reduction of human exposure from '^'l. Intake of the contaminant would be cut to a minimum and contact with any persons other than the producer would be unnecessary. The only reduction in milk production would come from changing the cow's feed. Reimbursement for this decrease would be small. Replacement hay was available. This course would also yield useful information as to the effects of the protective action on the level of '3'l in milk. PROTECTIVE ACTION The following questions were then posed to the dairy operator: A. Would he cooperate in feeding dry hay if the hay was supplied without cost? ------- B. What type and what amount of feed would be necessary? C. How much, if any, hay was on hand at that time? D. What time interval was necessary for the herd to be switched to dry feed? E. What hay suppliers could he recommend? The manager of Schofield's Dairy was most cooperative and immediately agreed to switch to dry hay and grain as soon as it was available. The nearest supplier with suitable uncontaminated hay was contacted and delivery was made on April 27. Dry feeding was initiated on the evening of April 27. A small decrease of I in the milk was seen on April 28 and this decrease was quite marked by April 29. Time was required for the clean feed to purge the radioiodine already in the animals, but the following results show that I levels dropped by a factor of four within two days after the feed change. Table 3. Radioiodine Levels in Milk Following Change to Dry Feed Date and Time Col lection A- 9ft A 9Q of AM AM PM pCi/1 I3lj I32j I33j I35j / nnn — — f, 7nn — — T. 7nn A 7nn i Rnn i /inn 1 , 3UU — 1 , 4UU i nnn — _ 7"^n — Four cows were fed the regular diet of green chop and grain as a control to assess the effect of the protective action. The I levels in their milk decreased only about \0% per day. The milk from these cows was not used for human consumption. The following graph depicts the trends seen in both groups. It is estimated that this action reduced the I thyroid dose by 71%. Schofield's Dairy continued to feed dry hay for 16 days, time for 2-3 effective half-lives of I to pass and acceptable levels of I to be reached. The cows were then returned to their normal diet. ------- PIN STRIPE EVENT APRIL 25, 1966 Schofield Dairy, Hiko, Nevada I31I in Milk of Cows eating contaminated green chop (DecaycxT—O.7) 131I in Milk of Cows after changing to uncontaminated hay (Decay=xT—5.O) 4 cows remaining on contaminated feed uncontaminated feed placed before main herd ------- CONCLUSION The initial considerations of peak '^'l concentrations in vegetation at Schofield's Dairy pointed to maximum levels in milk about ten times higher than those reached. Using the James' model relationship, the estimated milk levels were within about a factor of two of the measured peak level. Two features become paramount in handling any situation where protective action may be needed. The first is to sample all possible sources which may delineate and quantitate the contamination. The second, a quick assess- ment of the total radiological situation is necessary before employing pro- tective action. This paper has assessed a specific case which may or may not be a precedent for planning similar protective actions. Any incident would have to be judged on the set of circumstances controlling its situation. The para- meters set forth here are those used to judge this situation and to deter- mine the course of action taken. Under different circumstances, other equally important issues may need to be considered by the group responsible for taking the necessary precautions. ------- DISTRIBUTION 15 Western Environmental Research Laboratory, Las Vegas, Nevada 16 Robert E. Miller, Manager, NVOO/AEC, Las Vegas, Nevada 17 Robert H. Thalgott, NVOO/AEC, Las Vegas, Nevada 18 Henry G. Vermillion, NVOO/AEC, Las Vegas, Nevada 19 Robert R. Loux, NVOO/AEC, Las Vegas, Nevada 20 Donald W. Hendricks, NVOO/AEC, Las Vegas, Nevada 21 Mail & Records, NVOO/AEC, Las Vegas, Nevada 22 Chief, NOB/DASA, NVOO/AEC, Las Vegas, Nevada 23 Ernest D. Campbell, NVOO/AEC, Las Vegas, Nevada 24 Technical Library, NVOO/AEC, Las Vegas, Nevada 25 Phi I ip W. AI I en, ARL/NOAA, NVOO/AEC, Las Vegas, Nevada 26 Martin B. Biles, DOS, USAEC, Washington, D. C. 27 Ralph S. Decker, Safety Div., SNSO, USAEC, Washington, D.C. 28 John P. Jewett, SNSO-N, Jackass Flats, Nevada 29 Assistant General Manager, DMA, USAEC, Washington, D.C. 30 John A. Harris, PI, USAEC, Washington, D.C. 31 John S. Kelly, DPNE, USAEC, Washington, D.C. 32 Charles Bild, Sandia Laboratories, Albuquerque, New Mexico 33 George E. Tucker, Sandia Laboratories, Albuquerque, New Mexico 34 Chief, Weapons Test Div., DNA, Washington, D. C. 35 Bernard W. Shore, LLL, Livermore, California 36 James E. Carothers, LLL, Livermore, California 37 Roger E. Batzel, LLL, Livermore, California 38 WilliamC. King, LLL, Mercury, Nevada 39 Howard A. Tewes, LLL, Livermore, California 40 Lawrence S. Germain, LLL, Livermore, California 41 L. Crooks, LLL, Mercury, Nevada 42 Harry J. Otway, LASL, Los Alamos, New Mexico 43 William E. Ogle, LASL, Los Alamos, New Mexico 44 Charles I. Browne, LASL, Los Alamos, New Mexico ------- Distri but ion(continued) 45 Harry S. Jordan, LASL, Los Alamos, New Mexico 46 Gilbert J. Ferber, ARL/NOAA, Silver Spring, Maryland 47 Stanley M. Greenfield, Assistant Administrator for Research & Monitoring, EPA, Washington, D. C. 48 Acting Deputy Assistant Administrator for Radiation Programs, EPA, RockviIle, Maryland 49 Paul C. Tompkins, Acting Director, Division of Criteria & Standards, Office of Radiation Programs, EPA, Rockvilie, Maryland 50 Ernest D. Harward, Acting Director, Division of Technology Assessment, Office of Radiation Programs, EPA, Rockvi Me, Maryland 51 - 52 Charles L. Weaver, Acting Director, Division of Surveillance & Inspection, Office of Radiation Programs, EPA, Rockvi Me, Maryland 53 Gordon Everett, Director, Office of Technical Analysis, EPA, Washington, D.C. 54 Bernd Kahn, Chief, Radiochem. & Nuclear Engineering, NERC, EPA, Cincinnati, 0. 55 Richard S. Davidson, Battelle Memorial Institute, Columbus, Ohio 56 R. Glen Fuller, Battelle Memorial Institute, Las Vegas, Nevada 57 Arden E. Bicker, REECo, Mercury, Nevada 58 Frank E. Abbott, USAEC, Golden, Colorado 59 John M. Ward, President, Desert Research Institute, University of Nevada, Reno 60 - 61 DTIE, USAEC, Oak Ridge, Tennessee ------- |