HISTORY OF CLEANUP STANDARDS/CRITERIA AT
NUCLEAR TEST AND ACCIDENT SITES
Bruce W. Church
BWC Enterprises, Inc.
POB 158
Logandale, NV 89021
ABSTRACT
Remedial actions or "Cleanups" have been going on at various nuclear test and accident sites since the sixties. Various criteria have been used to accomplish a reduction of exposure/dose from radiation or from radioactive materials to people who would later occupy or use the site in an assumed land use/lifestyle scenario. E.T. Bramlitt (1), defined cleanups as "the act of making a contaminated site relatively free of Pu (i.e., radioactivity) so that it may be used without radiological safety restrictions." This is also very close to the definition applied to other cleanups such as the actions taken on the Uranium Mill Tailings Remedial Action project sites. Is it correct?
This paper will set out the historical and current criteria as published, discuss the characteristics of major cleanup actions, and discuss intervention philosophy, which has a part to play, in setting criteria. The paper will also highlight the current paradox that technicians and administrators encounter when using specified dose values to drive a specified pathway model. Officials have found that the soil concentration values calculated, even when they are within the specified dose values, can be too high to be politically and publicly acceptable.
INTRODUCTION
Historically the criteria used are often based on the prevailing dose standard of the time, e.g., National Council on Radiological Protection and Measurements (NCRP) recommendations, Federal Radiation Council (FRC) guidance, and International Commission on Radiological Protection (ICRP) documents. This guidance is often propagated into various governmental regulations and/or operating orders.
Watching the dose guidance recede toward zero or background, as politically correct philosophy, has been alarming. The application of ALARA (2&3), has been interpreted by some as background. It has also been employed to reduce doses (attributed to projected land use scenarios from cleaned-up land) to a fraction of the published values of the standard setting organizations cited above for protection of the public. Currently the three US governmental agencies that set cleanup criteria have declared remediated facilities consuming 100% of the annual dose standard published by our National (NCRP), and International (ICRP) standard setting bodies (1mSv/y), unacceptable. The Agencies have, therefore, independently decided to set criteria 15-30% of the annual dose to a member of the public (2&4). Reasoning behind the 15 or 30% is difficult to understand and is lost somewhere in mentioning acceptable cancer risk at one in one million and wanting to use only a small fraction of the dose standard. This is confusing because the standard setting bodies claim they consider the cancer risk from public sources, i.e., medical exposures and background and recommend that variable natural sources, e.g., Radon, be influenced only by intervention (5). It is also surprising that agency personnel believe the various proposed values have any meaningful difference between them and that these levels have any significant risk (6). If it is as they imply, we have standards upon standards as each group attempts to set their own. Somemay find this approach acceptable as a very conservative point of view. The problem, however, to this needless lowering of standards, is that it significantly and directly influences cleanup costs and increases real risk to operators, e.g., transportation.
DISCUSSION
Atmospheric Test Sites:
The principal criterion in Table I, show large variations both in numerical values and application, of the individual cleanup objectives. The following summary review is intended to illustrate these differences. The tables that support the text include, below the site name the years of operation or event date, followed by the year a cleanup (or cleanups) were done.
Table I. Atmospheric Nuclear Weapon Test Sites
Bikini Atoll--Following the 1967 radiological survey, an Atomic Energy Commission's "ad hoc committee," determined that the islands of Bikini and Eneu could be readied for reoccupation (7&8). During February 1969 a general cleanup removed and disposed of all nuclear test debris and prepped the two islands' agricultural areas. Residual external radiation levels and samples of available food items were obtained. Prior radiological surveys had been done in 1964, 1967 and later in 1970, 1972 and 1975. Each survey repeated the type of data gathering. Coconut planting and house building commenced following the cleanup, with some Bikini families moving back to Bikini Island by 1970. The 1975 survey sampled local food crops that had produced enough fruit to sample and analyze. The dose predictions based on the sample data showed that when food crops matured the resulting whole body dose would exceed U.S. federal guidelines. Early in 1978 the dose predictions were confirmed by Brookhaven National Laboratory (BNL) measuring Cs-137 body burdens (9). Consequently, in August 1978 Trust Territory officials moved the people to Kili Island, where they remain.
Enewetak, Atoll--In 1977, a 3-year cleanup was initiated. This project cost, about $100 million, disposed of 104,097 cubic yards of soil and 5,883 cubic yards of contaminated metal debris in a nuclear crater. It also disposed of 253,650 cubic yards of noncontaminated metal debris in the lagoon. The effort required an Atoll work force of nearly one thousand people. Six servicemen, of the nearly three thousand who served there, lost their lives in various accidents. Sixty-three lost-time accidents also occurred (10).
Similar to Bikini, this cleanup did not address the residual fission product problem, e.g., Cs-137, etc., but focused on removing Pu contaminated soil (Enjibi Island was an exception, and soil was removed over the entire Island). Extensive deliberations took place regarding what the cleanup criteria should be. Initially, the AEC Task Group on Recommendations for Cleanup and Rehabilitation of Enewetak Atoll, recommended that a fraction of the FRC guide be used, and a statement on risk was issued (11). Later, a different committee, known as the Enewetak Advisory Committee, refined the guidance, incorporated a risk theme and developed criteria which they believed would be in harmony with the proposed EPA 1977 guidelines (12). The EPA guidance was to be equivalent to a lifetime risk of approx.14 premature cancer deaths per 100,000 persons exposed. These numbers correspond to a 3% chance of one cancer appearing in a population of two hundred people exposed to the EPA levels in their lifetime, or to a probability of one cancer every twenty-one hundred years (assuming a constant pop. size) (13).
As the cleanup concluded, homes were built to accomodate the returning native pop., however, within a year of their return more than 100 left Enewetak and returned to Ujelang because of shortages of locally grown food (14).
Maralinga, Australia--Maralinga was one of three sites used by the British for nuclear weapons testing in Australia (15). Events began with Royal Commission Hearings in the mid 80's. A Technical Advisory Group (TAG) was formed upon a recommendation at the hearings to investigate the aspects of future remedial action and to recommend cleanup options for the Australian Government to consider. The TAG report offered a suite of options. Out of these, the Government selected option 6c. In brief, this option suggested surface soil excavation and burial in deep trenches on site. Selected pits have been exhumed, and many shallow burial pits, filled with plutonium contaminated metal debris, are to be treated by insitu vitrification. The posting of signs which limit activities in the downwind plume areas, is accomplished (16).
This cleanup is similar to that of Enewetak, in that it is specifically targeting Pu in soil and debris buried in shallow pits. The Project will cost about $A 104 million, and will remove over 322,000 m 3 of soil (17). The objective is to return use of presently government controlled lands to former native owners. The soil removal criterion for rehabilitation is based on the annual risk of fatal cancer associated with the inhalation or ingestion of contaminated soil by inhabitants. This risk is not to exceed one in ten thousand accumulated by the fiftieth year. It was considered that the soil contamination contour corresponding to an annual committed dose of 5.0 mSv is the borderline between acceptability and unacceptability of risk (16).
Large amounts of metal and other materials were near the explosion of each of the 12 one point safe trials conducted at Taranaki. Because, of these materials, an area of about 2.5 km 2 was extensively contaminated with fragments and particles, (difference being visible or not visible to the naked eye). Concern that the fragments might cause or enter a wound on bare feet largely dictated the extent of the area for soil removal. The remediation plan not only specified the various earth works, but had to deal with restrictions on land use. For example, in the plume areas where excavating such large areas was not feasible, only casual travel and hunting will be allowed. The option for the aboriginal people to live in these areas was relinquished. This was because the cost and extensive environmental damage required to reduce the average Pu concentration to an acceptable risk level would make impossible a semitraditional Aboriginal lifestyle. Unlike the Marshall Islands situation, land owners participated in the development of cleanup objectives and plans, readily agreeing to the hunting and travel restrictions. Their participation helped to prevent severe and extensive damage to the environment.
Nevada Test Site--The Nevada Test Site and environs has approximately 8,500 acres (>3.7 Bq/g) contaminated with plutonium on the land surface because of one-point-safety tests and plutonium-dispersion tests (18). During the summer of 1996, an interim cleanup action was completed at the Double Tracks event site. An additional site (Clean Slate 1) was cleaned up in the spring of 1997. Both were part of the Operation Roller Coaster series. These two sites conformed to the criteria outlined in Table I. However, cleanup activities are considered to be interim actions because no definitive Pu in soil standard or guide exists. DOE/NV has recently negotiated a Federal Facility Agreement and Compliance Order (FFACO) with the State of Nevada. There has not been time for the State (lacking a federal Pu in soil standard), to decide on a Nevada standard for DOE to use. It has been contemplated, as suggested by the Double Tracks Environmental Assessment (19), that the cleanup criteria, expressed as a concentration, is "likely to be 14.8 Bq/g, but could be as low as 3.7 Bq/g." The value of 7.4 Bq/g as used is expected to be conservative (20).
The primary dose limit specified in DOE Order 5400.5, Chapter 4, for all DOE activities (including remedial actions) is expressed as a committed effective dose equivalent. This comes from the ICRP 60 risk-based system, which requires a summation of doses to various organs of the body using weighting factors to be applied to each major tissue and organ. Exposure to members of the public from all radiation sources (as a consequence of DOE activities) is not to exceed 1mSv/y. Though DOE and others have established guidelines for thorium and radium in soil, guidelines for residual concentrations for other radionuclides in soil have to be derived from the basic dose limit. This is done by creating an environmental pathway analysis, in which site data and default parameters are fed into a dose prediction model. In DOE's case they are required to use the RESRAD computer model developed by Argonne National Laboratory (21).
Because the "correct" land use and resultant pathway selection can be in the eye-of-the beholder, this method generally causes considerable discussion between regulators and regulatees. This is happening with the Nevada State Division of Environmental Protection (NSDEP). DOE Nevada had chosen to use a rancher land use scenario and resultant pathway assumptions (22), but Director of NSDEP has made it clear that he is not readily accepting the DOE/NV land use scenario (23). He has implied that future negotiations must be held before the matter of the "correct" land use and resultant cleanup criteria can be established.
Nuclear Weapon Accident Sites:
The three accidents discussed here have several similarities. They all involved nuclear material in a weaponized form, and the contamination spread came about by accident. As a result, no fission products were present to complicate cleanup, and because of the explosion and fire the Pu present is PuO 2 , in either a particulate form or fused onto various material surfaces. All three required cleanups with follow-up environmental monitoring.
Table II. Nuclear Weapon Accident Sites
Johnston Atoll (JA) ---The extensive contamination at JA resulted when the weapon about to be launched on a Thor rocket had to be destroyed on the pad just before liftoff, because of a launch malfunction, in 1962. An early cleanup consisted of pushing contaminated coral soil into the lagoon, and covering the area with clean soil. Nearby buildings and concrete were painted to lock up the contamination and keep it from resuspending and becoming available to the island work force. In addition to the on-pad destruct, two other high-altitude destructions caused particulate to fall onto the Atoll. Because of these events, particulate could be found sporadically over the entire atoll. The nature of this contamination led to several interim cleanups, which began in the early 80's, after technology was available to survey the entire Atoll. This material was removed, and consolidated at a controlled location. In addition, all the contaminated buildings and concrete were dissembled, packaged and shipped to the Nevada Test Site for disposal. In the late 80's a more aggressive cleanup of the stored contaminated coral (estimated at approx. 100,000 m 3 ) was initiated via Pu mining to save a large amount of material from being needlessly packaged and shipped for disposal. The cleanup criterion for declaring the material clean was based on the 1977 EPA draft screening guide (1&24).
As indicated in Table II, the cleanup of the coral soil stockpiled in and around LE-1, (launch emplacement no. 1) is continuing now. In early 1997 the Defense Special Weapons Agency (DSWA) advertised in the Commerce Business Daily, for qualified companies to prove, through demonstration that they were equipped to meet performance specifications. DSWA stated that the cleanup guide, for the about 185,000 metric tons of material to be cleaned, would be 0.5 Bq/g. This continued work will begin after the current contract is finished, about late summer 1998 (24).
Palomares, Spain ---On January 17, 1966, a U.S. Air force Bomber collided with its tanker and exploded above the town of Palomares, Spain. Of the four nuclear weapons onboard, three impacted very near the town and the fourth fell into the sea. The chemical high explosive of two of the four weapons detonated on impact bracketing the town of ~500 residents. PuO 2 , particulate contamination was distributed in varying degrees over a 226 ha area (~560 acres) consisting of brush land, farmland and an urban area. The other two weapons were recovered intact.
A tiered criterion was applied to the cleanup, which was completed by May 1966. In the most heavily contaminated area crops and soil were removed to a depth of 10 cm. These were then packaged and shipped to the United States for disposal. The next level of contamination required that canes be burned on the beach, crops buried and soil plowed to 30 cm. The remainder required that soil be plowed where possible to 30 cm (25).
A research/monitoring program began upon completion of the cleanup and soil restoration of the farmland. For reference, the contaminated area has been subdivided into three zones (zones 2, 3 and 5), corresponding to the number assigned to the weapons and where they impacted. Zone 5 is the urban zone. This program consisted of air sampling, soil sampling, crop sampling, and urine sampling and lung counting of residents. This work was carried out by members of the Spanish Junta De Energia Nuclear. A summary of the observations and conclusions of the research work appearing in various publications and presentations follow (26,27&28):
Table III. Composite Data Table, Palomares, Spain 1966-88
Measurements in residents (29)--At the time of the accident there were 485 people present in Palomares, because it was a holiday few were working in the nearby fields at the time of the accident. Over the 22 years of monitoring, 229 additional people became included (714 total). They either moved in or were born after the accident. Of this number 590 had urine sample results lower than the minimum detectable activity (MDA) of 0.37 mBq/d and 124 had values equal to or higher. Of the 124, 29 showed sample contamination, because samples were collected in Palomares. Starting in 1967 residents traveled to Madrid for sampling and annual examination. Estimations of dose were performed on those 55 people who were considered to really have suffered internal contamination. Lung counting, using the most sophisticated detectors for the time, indicated no Pu above the MDA of 814 Bq. From the urine sampling it was determined that 45 of the people had acute inhalation of particles, because chronic inhalation at the average concentration measured in air could not support the quantity observed in the urine. From this the date of intake could be assigned. For the remaining 10, who were not in the area on the day of the accident, the date of intake considered to be the most likely was assigned. The 70 year whole-body dose (committed effective dose equivalent, CEDE) for the initial 45 residents has a range of 20-200 mSv (0.29-2.9mSv/y). Based on the suppositions for the group of ten, 35-180 mSv is estimated. The remaining population (659 residents) are estimated to have received less than 20 mSv, CEDE. There were 10 residents 15 years or younger. Of these only one (<1 yr. old on Jan. 17, 66) has a CEDE higher than 200 mSv (242 mSv), the other 9 are in the range of 49-157 mSv.
Aerosol Measurements(26,27,28) -- Pu 239,240 in air exceeded the detection limit (1.8 E-6
Bq/m 3 ) for all years at all sampling stations, except in the urban zone for the years 71, 72,75 & 76. The frequency of air samples exceeding the detection limit diminished with time until a hilly and uncultivated parcel was plowed and transformed into a cultivatable parcel in 1974. Additional cultivation in the early 80's also contributed to increasing air concentrations (30). At station 2-2, near the new cultivatable land, higher annual concentration averages have occurred through the period. The maximum concentration occurred in 1967. For the Urban area the average concentration has been below a hundredth of the DAC (calculated for public) for Class Y Pu compounds. In the farming zone (2-2), the average concentration was below a tenth of the DAC (public) for Class Y Pu compounds. For the period 1966-69, the average concentration was below the DAC. Doses calculated for various organs were based on an average mass activity diameter (AMAD) of 1.0 m m for the particles inhaled, to be on the conservative side. The bone surfaces received the highest potential committed dose equivalent, the sum for each of the 15 yrs. (1966-80) has a value of 0.56 mSv for the urban zone and 5.42 mSv in zone 2-2. The contribution of the committed dose equivalents in the five organs of interest, to the potential CEDE during the 15-y period, is 0.054 mSv in the urban area and 0.52 mSv in zone 2-2 (27).
Measurements in Agriculture Products (31) -- The Palomares region of Spain is typical of Mediterranean agricultural areas that receive marginal rainfall (~20 cm/y) and require irrigation to sustain crops. Common crops of the area, are tomatoes, grain and alfalfa. The Pu concentration observed for washed tomatoes is 0.15 Bq/Kg and is generally a factor of 30 to 40 higher for the plants, stalks etc. of tomato plants, barley and alfalfa. The soil-crop concentration ratios are in the order of 10 -4 for tomatoes and 10-3 for the plant and the components of barley and alfalfa. The annual CEDE to individuals ingesting tomatoes is 1.5 m Sv. Other pathways, i.e., alfalfa, meat or milk, human is even less. Iranzo et.al. on the basis of the actual human experience observed at Palomares, recommend that the IAEA consider 1 man Sv of collective effective dose equivalent as a guideline to exempt quantities for practical application. They further recommend for the crop types experienced that 120 to 1200 kBq/m 2 would be an appropriate intervention level depending on the size of the contaminated area. The larger the area the higher the intervention level.
In brief summary it can be observed that only those available at the time of the accident and received acute exposures, received doses approaching and exceeding the annual dose limit for the public. Resuspension of the deposited Pu particulate, gives minimal dose to the receptor's organs. The CEDE is much less than the specified limits. Working, living and eating products grown in a contaminated area of the magnitude experienced at Palomares yields extreamly small doses and are much less than the accepted standards.
The data and experience recorded for Palomares are very important. To date the people of Palomares belong to a very good documented group, who since 1966 have lived and worked continuously as farmers, in a Pu contaminated environment. This is real experience involving a Pu soil cleanup where intervention was used, and should be influential in setting guidelines for Pu soil remediation work.
Thule, Greenland---On January 21, 1968, a B-52 carrying four nuclear weapons crashed and burned on the ice near the US Air Force base at Thule, Greenland. The plane was carrying 225,000 pounds of jet fuel and the resultant fire blackened an area of ice about 500 feet wide by 2100 feet long. Radiological surveys within days of the explosion determined that plutonium contamination existed around the crash site. The combination of darkness, storms, severe cold and remoteness severely hampered the recovery operations.
It was estimated that about 3,150± 20% grams of plutonium were distributed on the surface of the ice. About 99% of the contamination was confined to the blackened crust where the fuel had burned. The edge of the blackened area was close to the 0.9 mg/m 2 , isocontour line.
Snow samples were taken by Danish scientists at many locations away from the immediate crash site. The maximum contamination level observed was 14.8 kBq/m 2 . A major constraint of the clean up was that operations had to be finished by late April when the ice began to melt. Whatever plutonium remained on or in the ice would then disappear into the bay.
The cleanup removed all snow inside the blackened zone, an area about 60,000 m 2, at an average depth of 10 cm. The volume produced was 6,000 m 3. After all the aircraft debris had been removed from the ice, the snow in the blackened area was scraped into rows, picked up, and transferred into sixty-seven 25,000 gallon tanks. The contamination left in the ice was assessed via core sampling and an estimated 350 grams of Pu-239 were contained in ~2,000 tons of ice. Studies suggested that when samples of the ice melted all the plutonium contamination would sink to the bottom. An additional 48 cores were taken outside of the fractured area and indicated no contamination in or under the ice.
Follow-up environmental surveys by Danish scientists, assessing contamination of the marine environment, have been regular since the accident. They have determined that the maximum concentration under the crash site is about 1.85 Bq/g of Pu 239 in the sediments, and the inventory is about 1.1 TBq. The only pathway of interest to man is through the consumption of mussels. In 1974, the average concentration of plutonium in the soft parts of the mussels found within a radius of 20 km of the crash site was about 0.74 Bq/kg. If 100 g/d of mussels were consumed for 70 yrs, the estimated annual dose rate to the bone at the end of 70 yrs would be 0.75 mGy (32).
Processing Plant Sites:
Information on these sites has been included for comparison purposes, because these sites have had similar problems establishing cleanup criterions and/or standards. In particular, discussing Rocky Flats is important; as their experience parallels what is going on elsewhere.
Table IV. Processing Plant Sites
Rocky Flats Environmental Technology Site (RFETS)---An "Action Levels and Standards Framework for Surface Water, Ground Water and Soils Working Group" (nicknamed ALF), was established as part of the Rocky Flats Cleanup Agreement negotiations. Its mission was to "determine the derivation and application of the 0.15 mSv per year level and the derivation and potential application of the 0.75 mSv per year level." ALF recognized that the 0.15/0.75 requirements (0.75 mSv was later changed to 0.85 mSv in the draft EPA 196 guide) were based on EPA's draft 40 CFR 196, Radiation Site Cleanup Regulations. These regulations are intended for the release of government property. Because the Rocky Flats Cleanup Agreement (RFCA), identifies future land-use scenarios (which exclude release of government property and permit no residential land use), pertinent sections of the draft regulation were used as guidance for ALF. ALF chose radiation dose as the primary criterion for assessing radio nuclide action levels after considering the EPA's draft 40 CFR 196, NRC's decommissioning requirements, DOE's Order 5400.5, "Radiation Protection of the Public and the Environment," and DOE's 10 CFR 834. Because these regulations are all radiation dose-based, they believed that this was compelling evidence that the radiation protection community is recommending the use of radiation doses to limit environmental levels of radionuclides. They also accepted that the dose assessment process incorporates all pertinent facets of the EPA's CERCLA risk assessment process.
To translate the radiation dose requirements into soil action levels, it is necessary to first model radio nuclide transport within the environment to a human receptor and then assess the receptor's radiation dose. The computer code "RESRAD," developed by the Argonne Natl. Lab. (21) for DOE, was selected as the model to calculate the radiation dose to individuals, as well as to derive action levels for radio nuclides in soil. RESRAD will be used to compute doses for scenarios that include residential, open space, and office workers. Though not required by the RFCA, ALF is recommending a future resident on the former site be considered because over the one thousand years, institutional controls may disappear. ALF discussed and agreed upon seventy different input parameters for RESRAD, using site-specific values whenever possible, to tailor the action levels to RFETS. When site-specific values were not available, the RESRAD default information was used. The code was used to evaluate the office workers' exposure scenario, the open space exposure scenario and the hypothetical future resident exposure scenario over the 1,000 year modeling period. The values shown in Table IV are output of the modeling effort.
The action levels calculated are only applicable to a single radio nuclide in the environment, which is not true at RFETS. When multiple isotopes such as U-234, U-235, U-238, Am-241, and Pu-239, 240 are found together, it must be ensured that the sum-of-ratios of the radiation doses from all radionuclides present do not exceed the action level basis. The values for Pu-239, 240 shown in Table IV, were calculated using the ratio sum to the various dose levels, considering Am-241 as also being present (33).
Noting that the report and values being discussed were developed by a combined working group of DOE, State and Federal Regulators are important. After the completed report had extensive public interaction and review, it was submitted to an independent consultant hired by the RFETS Citizen Advisory Board. This reviewer gave a positive concurrence to the values calculated using the parameters and model specified. However, the Citizens Advisory Board has had difficulty accepting the levels as too high, and has petitioned DOE to again conduct independent calculations of the radio nuclide levels. DOE has committed to fund such a independent review and a Citizens Group has been convened to oversee the review (34&3).
UMTRA/FUSRAP Sites---Congress passed the Uranium Mill Tailing Radiation Control Act (UMTRA) in 1978. The cost of the program to the Federal Government was expected to be $180 million (35). In 1996, 20 of 24 sites were completed, and the remaining two sites are scheduled for completion in 97 or 98. Cost to the Federal Government, based on the FY 1998 budget, has reached $1.45 billion (36). Regulations implementing this law stipulated that to reach the dose guide of 15 mrem per year, that radioisotopes to be cleaned up, e.g., Ra-226, etc., should not exceed 0.2 Bq/g, 0-5 cm deep, and for successive 15 cm layers not more than 0.56 Bq/g.
For the Formerly Utilized Sites Remedial Action Program (FUSRAP), which involves hundreds of small (and not so small) sites, the cleanup criterion is set by DOE Order 5400.5, and/or proposed 10 CFR 834. For the Radium isotopes, the concentration levels are the same as the UMTRA sites, but for other radio nuclides, RESRAD is used to calculate the soil concentration that would equal the specified total effective dose equivalent.
FINDINGS AND CONCLUSIONS
The debate over cleanup standards has been going on now for several decades. Particularly over what should be the allowed concentration for Pu-239 in soil. The EPA has attempted twice to promulgate standards, first, in 1977, and again in 1996 to each time withdraw them because of negative comments and non-concurrence by operating agencies. Recently (Oct., 97) the Institute for Energy and Environmental Research, in their report "Containing the Cold War Mess," levied heavy criticism against the Dept. Of Energy, Office of Environmental Management, claiming that, "DOE is now proceeding in an ad hoc way that all but guarantees large discrepancies in protection between sites," (3). They cite the differences between what Rocky Flats' RESRAD calculates as meeting the specified dose level (24 Bq/g) and that published for Johnston Atoll (~0.56 Bq/g)(1) as a large discrepancy.
This author, as one who has followed and participated in this debate over these many years, views these charges as very hollow, carrying little merit. The reasons are many. The subject is a very complex one, where emotion plays heavily, cost is a significant factor, land use projections are difficult, and technical considerations have a very difficult time carrying the day. This was illustrated by situations discussed both at Rocky Flats and the NTS.
It is clear that large differences exist between the concentration values, used at various sites present and past. The challenge is to decide what this all means, if anything at all. At each cleanup, special circumstances exist, and cleanups are often dictated by the resources available. For example, the Enewetak Cleanup became limited in scope to a Pu cleanup, only because Congress appropriated a small fixed amount and specified that military troops would carry out the cleanup as a way to save money. It made it very difficult for decision makers to deal with problems of immediate Cs-137 inventory reduction. A Cs-137 soil cleanup would require restoration of soil to the Atoll for agricultural use. It could be readily shown that an undertaking of that magnitude would require billions not millions. As Cs-137 has a half-life of only 30 years, versus 24,110 yrs for Pu-239, the best that could obviously be done with the resource allotted was to remove the longer-lived material. This could be described by some as an over-simplification of a complex debate, but it was what this author concluded as he watched events unfold.
As a member of the TAG the author participated in developing a slate of options for the cleanup of Maralinga to be considered by the Australian Government. These ranged from the status quo, at a cost of a few $A million per year, to cleaning where use of the land would be without restrictions. The cost for the latter was about a $A billion. As discussed above, the Australian Govt. decided they could not afford the $A billion and the stakeholders were not interested in seeing major devegetation to achieve it. They were willing to settle for something less, i.e., restrictions, rather, than have large areas of their land made unproductive for many decades to come.
In deliberation of cleanup criterions, there must be room somewhere to embrace the philosophy of intervention as introduced in ICRP 60 (5). The ICRP make it clear in their first principles for those engaged in a practice, vis a vis "people at work" that "No practice involving exposures to radiation should be adopted unless it produces sufficient benefit to the exposed individuals or to society to offset the radiation detriment it causes."
The ICRP rcommendations for intervention are somewhat different as illustrated by the following principles: (a) "The proposed intervention should do more good than harm, i.e., the reduction in detriment resulting from the reduction in dose should be sufficient to justify the harm and the costs, including social costs, of the intervention. (b) The form, scale, and duration of the intervention should be optimized so that the net benefit of the reduction of dose, i.e., the benefit of the reduction in radiation detriment, less the detriment associated with the intervention, should be maximized. There will be some level of a projected dose above which because of serious deterministic effects, intervention will almost always be justified." The Commission further states that, "In most situations, intervention cannot be applied at the source and has to be applied in the environment and to individuals' freedom of action. The dose limits recommended by the commission are intended for use in the control of practices. The use of these dose limits, or of any other pre-determined dose limits, as the basis for deciding on intervention might involve measures that would be out of all proportion to the benefit obtained and would then conflict with the principle of justification. The Commission therefore recommends against the application of dose limits for deciding the need for, or scope of, intervention."
Examples abound of how intervention is applied in society, for instance, Radon in homes. Standard setting bodies do not recommend that people abandon their homes to achieve background, only when the exposure is sufficient to cause potential significant detriment do they recommend remedial action to limit the exposure. ICRP 60, and the Basic Safety Standards of the International Atomic Energy Agency (37), have both recommended action levels for intervention consideration corresponding to an annual effective dose range of 3-10 mSv/y.
This Author strongly endorses the ICRP stance that each cleanup action should be evaluated on its own merits. What would be the basis of providing a guarantee of protection between sites, or cleaning up to background? To illustrate the problem one has only to compare the relative costs of cleaning up the NTS. For example, in DOE/NV-399 (18), it was estimated that ~500 acres were contaminated to a level greater than 37.0 Bq/g, 8,500 acres >3.7 Bq/g and 90,000 acres >0.37 Bq/g. Recent cleanup experience in NV indicated costs of 0.509 $ million/acre (38). The Standard used was 7.4 Bq/g. If NV continues to use 7.4 Bq/g, for the 3,275 acres > this criteria, cost would be 1.67 $billion. If a cleanup to background was the standard, the costs in Nevada alone would escalate from an estimated 46 $billion for the >0.37 Bq/g to near a $trillion for background.
It is obvious that the current system is not working. One reason for this is that the interpretation of the promulgated guidelines developed for controlling prospective doses (i.e., the dose from practices) has been mistakenly applied in situations requiring back fitting or intervention.
To answer the question posed in the abstract, this author must argue that no country can afford the definition, "cleanup is the act of making a contaminated site relatively free of radioactivity, so that it may be used without radiological safety restrictions." It may apply at some sites, but as has been illustrated it makes sense to retain all options and truly evaluate each site and situation on its own merits, and not be bound to a standard, particularly one as harsh as background. Other wise serious economic and social impact will be traded for very little reduction in public detriment.
ACKNOWLEDGMENTS
Thanks are given to Mr. Terry Vaeth, Mr. Steve Mellington and Mr. Scotty Afong of the US Department of Energy, Nevada Operations Office, who provided the resources for this effort, under PO No. DA-AP08-96NV13073. In addition thanks are appropriate for Dr. Keith Lokan of the Australian Radiation Laboratory, Yallambie, Victoria, Australia, for assistance with references and discussion. To Mrs. Martha DeMarr and Mr. Jeff Gordon of the Coordination and Information Center, Bechtel Nevada, Las Vegas, Nevada for assistance with reference materials. To Dr. Edward Bramlitt, Bramlitt Technical Services, Albuquerque, NM, Mr. Steve Slaten, U.S. Dept. of Energy, Rocky Flats Environmental Technology Site, and Dr Joseph Shinn, Lawrence Livermore National Laboratory for discussion and references.
REFERENCES