ML20213A041
| ML20213A041 | |
| Person / Time | |
|---|---|
| Site: | Three Mile Island  |
| Issue date: | 01/29/1987 |
| From: | NRC |
| To: | |
| Shared Package | |
| ML20213A011 | List: |
| References | |
| FOIA-86-608 NUDOCS 8702030070 | |
| Download: ML20213A041 (6) | |
Text
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e STATUS OF RADIOLOGICAL IMPACT STUDIES FR0r' THE ACCIDENT AT THREE MILE ISLAND As a result of the accicent at Three Mile Island, Unit 2, the ra-iological env irons of the site hav e been the suoject of intense, and comprenensive radiation monitoring and radiological impact studies. These inv estigations included assessment of the causes of the accident and of the radiation ex-posures and potential impacts, during and subsequent to the accident: to the workforce, the general population within 50 miles of the site, and the terrestrial and aquatic emironment relative to effects on domestic animals and wildlife. Many well known and respected agencies and organizations par-ticipated in this effort to assess any impact resulting from the accident.
Among those conducting the most comprehensive radiological assessments were:
Department of Energy (00E), Department of Health, Education and Welfare (HEW),
Eruironmental Protection" Agency (EPA), Comonwealth of Pennsylv ania, Metro-politan Edison Company, and the Nuclear Regulatory Commission (NRC).
The radiological monitoring programs which these groups initiated during the first few days after the accident included the placement of emironmental thermoluminescent dosimeters (TLDs) within a 20-mile . radius of the site, aer-ial and ground radiation surveys, monitoring of liquid effluents from the site, sampling and analysis of local milk, food, soil, vegetation, and grass samples, and analysis of surface and drinking water, in addition to these monitoring programs, the utility had TLDs and air particulate monitors in place at the time the accident began, in order to assess if there was any potential airborne contaminai. ion, a whole body counting system was set up in Middletown twelve p o g A - Of. - f.08 9\
8702030070 870129 PDR FOIA GANNIS86-608 PDR
days after the accident. Whole body counts of 753 men, women, and children living within 3 miles of TM1 were successfully performed during the following 21/2 months with no significant findings of radioactive contaminates in any of the individuals.
Radioactive Releases The principle radioactive materials released to the erwironment appear to be the noble gas isotopes of xenon and krypton, as well as trace amounts of radio-iodines, primarily 131 1 The primary xenon isotope released was 133 Xe. All of the krypton isotopes released during the accident have relatively short half-lives and no measureable quantities of these isotopes were detected immediately following the accident. Monitored venting of the TMI-2 reactor containment building a year after the accident (June 28-July 11,1980) resulted in a fur-ther release of approximately 44,000 curies (Ci) of 8 Kr. Estimates of the to-tal amount of noble gases released during the accident range from 2.4x10 6, g 6
13x10 Ci, with the lower estimate being the most accepted one. Between 14 and 15 Ci of I are believed to have escaped from the plant. Plant HEPA and char-coal filters presented particulates and most of the airborne radiciodines from escaping.
At least 17 isotopes in measureable quantities were released to the Susquehanna River from the TMI site in the 45 days following the accident. (The City of Lan-caster atjreement of 2/27/80 prohibited the discharging of any further accident' generated waste water into the Susquehanna River. This agreement was not violated)
Most of the isotopes released were released in low concentrations and at infrequent.
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inten als. Results of calculations to determine the maximum doses that an in-dividual would receive as a result of ingestion of water and fish from the Sus-quehanna River indicate that the health and safety of the public was not endan-gered, nor was there significant emironmental impact.
Environmental Monitoring and Sampling Results Assessment of the TLD and other monitoring data indicate that the major of fsite releases of radioactive materials occurred on the first day of the accident. Tne highest direct measurements were obtained on site [3000 mR/h (p+Y) and 400 mR/h (v) indicated in the plume mer the plant on March 29] and at nearby Kohr Island.
"The release quickly disspated and exposure levels on the ground on-site were or-ders of magnitude less" (NUREG/CR-1250, p. 389). Measurements indicated that the plume traveled to the north-northwest.
In general, following the accident, levels of 131 1 detected in air samples were on the order of a few picocuries per cubic meter (pCi/m 3) or less (the maximum permissible concentration (MPC) in air in an unrestricted area is 100 pCi/m3),
The highest obsemed I concentration of fsite was 110-120 pCi/m . This mea-surement was made on April 16, 1979, four days after changing of the filters in TMI's process ventilation was initiated.
Following the accident, thousands of emironmental samples (of air, water, milk, vegetation, soil, and f aodstuffs) were collected by the various groups monitoring the area. Of the radionuclides detected (139Cs , 89Sr aid 90Sr, 133Xe, and 1 311 )
in some of these samples, "only very low levels of radiciodines and radioxenons Fo i A-8f -4o8
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4 can be attributed to releases from the accioent "(NUREG/CR-1250, p. 389). The trace qua'ntities of radiocesium and radiostrontium detected in a few samples are attributed to residual global fallout from previously condu:tec nuclear wea-4 pons tests. Of the hundreds of samples of milk taken, small concentrations of 131 1 were detected in only a few samples. The highest concentration found
, was 41 pCi/l in a sample of goat's milk. This level is well below the EPA pro-tective action level for milk of 12,000 pCi/1. In an article in Science, E.
Marshall states that " China's most recent nuclear bomb test raised the iodine le< el in milk near Harrisburg to around 300 picocuries per liter". Of the m er 800 samples (of soil, grass, water, and air) collected by DOE,131 1 was found in only a few air and grass samples and this was at levels only slightly abwe the minimum detectable activities (MDAs). In an interagency EPA meno (9/11/79) to J.
Harley, K. Miller states that in situ gamma-ray spectra measurerents made at 7 DOE monitoring sites showed "no indication of unusual contamination at any of the sites". "The low levels of radiciodines and traces of radioxenons collected in emironmental samples taken from the area around the TMI Station confirm that releases of radioactive material from the accident were not significant, All of the offsite analytical results were significantly below regulatory limits" (NUREG/
CR-1250, p. 390).
t In the months following the TMI accident, there were several questions raised con -
cerning potential effects on animal and plant life in the TMI area. The Pennsyl '
i vania Department of Agriculture (PDA) conducted a number of surv eys to determi,ne-whether there were any unusual agricultural problems which could be related to IMI:
Some of the types of animal health problems imestigated included reproduction pro-blems, bone and muscle problems, and unexplained deaths. Reported ef fects on vege-Fo m-sG -Goe Cr \
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tation were also stuaied. The results of the aboie study found that "none of the reported plant and animal health effects...can be directly attributed to the operation or the accident at the TMI Nuclear Power Station" (NilREG-0738, p.29)
Estimates of Doses Radiological monitoring of the en/ironment by EPA, HEW, DOE, Metropolitan Edison, ano the Commonwealth of Pennsylv ania " confirmed that radiation levels of f site were quite low and remained so during the course of and subsequent to the accider.t" (NUREG/CR-1250, p. 398). TLD data indicated that the maximum dose would be re-ceived by an individual located on the east bank of the Susquehanna River. Esti-mates by the Ad Hoc Interagency Dose Assessment Group, the President's Task Group on Health Physics and Dosimetry, the Department of Energy, and others show that the maximum offsite individual dose was less than 100 mrem. The highest actual individual offsite dose indentified was received by an individual who was on near.
by Hill Island for short periods of time during the accident. The Ad Hoc Group and the fresident's Commission calculated the most probable dose to this in-dividual to be 37 and 50 mrem respectively.
I Several independent studies were performed using dif ferent methodologies to es-timate the collective dose to the population (approximately 2,164,000 people) living within a 50-mile radius of TMI. The results of these studies were simi-lar, with the maximum population dose estimates indicating that "the population dose could not have exceeded 5000 person-rems" (NUREG-1250, p. 399). The esti
- mated annual collective dose to this population from natural background radia-tion is about 240,000 person-rems.
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i The average dose to an individual in this population was estimated to be no more than 1.5 mrem. The HEW Public Health Service attempted to deter..1ne offsite ex-posure from photographic film present in stores in the TMl area during the firs-three days after the accident. They concluded that even if the fogging noted on the purcrased films was attributed to radiation exposure, the total dose would k less than 5 mrad.
Conclusion Tne President's Task Group on Health Physics and Dosimetry concludes that in spite of serious damage to the plant, most of the radiation was contained and ,
"t he actual release will have a negligible effect on the physical health of in-div iduals". The average individual dose of approximately 1 to 1.5 mrem is equiva-lent to about one percent of the yearly exposure dye to natural background radia-tion in the area. The President's Task Group states that "the major health effect of the accident was found to be mental stress".
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