Health impacts of large releases of radionuclides. Radioactive contamination of the marine environment.
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England↗
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Issues in establishing an aerosol radiological baseline for the waste isolation pilot plant near Carlsbad, New Mexico.
The Department of Energy has constructed a deep geologic repository for defense transuranic waste disposal. The Waste Isolation Pilot Plant, located in Southeastern New Mexico, is slated to receive transuranic waste by truck delivery beginning in 1998. The Environmental Evaluation Group (EEG) provides an independent evaluation of the impact on the health and environment in New Mexico of the WIPP project. Since 1985, the EEG has operated a network of air monitoring sites around WIPP and in nearby communities. The radionuclide concentration data from these air samples have been assembled into a useful baseline data base after resolution of a number of methodological and quality assurance issues. Investigation thresholds for the principal radionuclides have been calculated from combined data collected from several sites. These action levels will provide a critical quantitative basis for decisions of whether future airborne radionuclide measurements are attributable to accidental releases.
Air Pollutants, Radioactive↗
Airborne emission of enriched uranium at Tokai-mura, Japan.
A new strategy for characterisation of airborne uranium contamination based on elemental/isotopic analysis of tree bark is described. Bark samples collected at Tokai-mura (Japan) were subjected to high sensitivity ICP mass spectrometric analysis; for control purposes, samples from the remote Yakushima island (Southern Japan) and central Tokyo were also analysed. The uranium contents of tree bark for Tokyo and Yakushima were of similar magnitude to that at Tokai-mura (U, 0.01-1.0 microg/g - all samples), however, there were marked differences in isotope ratio values between the sites. Whereas natural uranium isotope ratio values (235U/238U, 0.0072) were observed for Yakushima and Tokyo, non-natural and natural signatures (235U/238U, 0.00697-0.01448) were realised at Tokai-mura. These findings are consistent with the release of enriched uranium at Tokai-mura.
Air Pollutants↗
NRC releases evaluation of effects of Baltimore tunnel fire on rail transportation of spent nuclear fuel.
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Baltimore↗
A radioiodine speciation, deposition, and dispersion model with uncertainty propagation for the Oak Ridge dose reconstruction.
Between 1944 and 1956, radioactive 131I was released into the atmosphere from operations at the Oak Ridge National Laboratory in Oak Ridge, TN. The releases occurred from stacks and from building vents and openings in three different chemical forms: elemental, organic, and particulate. During their transport in the atmosphere, different forms of iodine react differently with other atmospheric chemicals and moisture, and are removed from the plume at different rates by the processes of dry and wet deposition. A modified Gaussian plume model was developed to address the processes of radioiodine speciation, deposition, depletion, and dispersion in the atmosphere, and to propagate uncertainties in input parameter values through to the ground-level concentrations of 131I in air. A unique approach was used to develop an implicitly correlated set of hourly meteorological parameters for any day of a month for each month of the year from ten years of available data between 1987 and 1996. The model was validated for both annual average and short-term releases. For the annual average releases, the predictions of ground-level concentrations of 131I from the model were within a factor of 2 of measured field data. For two of the three sets of available weekly data, the measurements fell within the 95% subjective confidence interval of model predictions. Predictions of ground-level air concentrations were made on an annual average basis for the entire period of release and on a short-term, episodic basis for a 1954 accident.
Atmosphere↗
Uranium-235 and childhood leukaemia around Greenham Common airfield.
There has been considerable publicity recently concerning the possible release of enriched uranium from the Greenham Common USAF base near Newbury in Berkshire. Evidence for the release relies on an internal report of the Atomic Weapons Research Establishment at Aldermaston, the authors of which postulated that it resulted from a fire in 1958 involving a B47 bomber standing on the runway. Their report contained a much publicised contour map of excess 235U levels estimated from the ratio of 235U to 238U in 26 evergreen leaf samples examined. The current concern of the inhabitants of Newbury centres mostly on the incidence of leukaemia, which was known beforehand to be slightly elevated in parts of West Berkshire, at least for young children. A number of cases have received considerable press publicity, with suggestions that their homes are located close to the base or the flight-path. The reports are, however, anecdotal and are not based on a complete register of cases. We have examined the evidence for this putative association by re-analysing the uranium data and determining the spatial relationship to the base of cases of childhood leukaemia diagnosed in the years 1966-87. We conclude that, although the excess uranium found has a non-random distribution, it does not support the pattern depicted by the contours and bears no relation to the incidence of childhood leukaemia for the period we examined. In any case, the increase in level of environmental radiation as a result of the putative release must be very small and is at variance with the reporting in some of the national press.
Child↗
Reconstruction of radionuclide contamination of the Techa River caused by liquid waste discharge from radiochemical production at the Mayak Production Association.
Because of its importance to reconstructing radiation doses for ongoing epidemiological studies, a feasibility study was undertaken to determine if the source term of radioactive materials released to the Techa River from the Mayak Production Association, the first facility in the former Soviet Union for the production of plutonium, could be reconstructed from historical measurements made at a limited number of downriver locations. The feasibility study used historically measured water flow rates and total-beta radioactivity measurements, and considered the processes of radioactive decay and of sorption/desorption. A simple radionuclide mass balance approach was used. To determine the rate of input of radionuclides to the Techa River system, the Techa River was depicted as a series of segments for which measurements are available. For each segment of the river, a system of recurrent (with time) equations was compiled for radioactivity balance accounting for the radioactivity inflow at the inflowing end, activity discharge with water at the outflowing end, and the reduction of activity because of radioactive decay. The equations change with time to account for the changing nature of the river regime. Effective sorption constants for 90Sr and 137Cs, which characterize the transport of radionuclides among the river system components (water and bottom sediments), were defined based on the inventory of these radionuclides deposited at each of the studied river segments and data on water concentration and radioactive removal. All the information on radioactive contamination of the river system components during the period 1949-1996 was used. Solution of the series of equations provided information on the rate of input of these radionuclides into the upper end of the river. The pilot study indicated that it is possible to determine the historical releases of a wider suite of radionuclides using the historical monitoring data from numerous locations along the river, rather than relying on a more uncertain reconstruction of quantities released at the point of discharge. Radionuclides considered include 90Sr, 106Ru, 137Cs, and 144Ce. Estimated concentrations of selected radionuclides at various times are presented.
Feasibility Studies↗
Territory contamination with the radionuclides representing the fuel component of Chernobyl fallout.
The data obtained through a series of experiments were used to specify the correlation of activities of the fuel component radionuclides of Chernobyl fallout and to create the maps of the 30-km Chernobyl zone terrestrial density of contamination with 154Eu, 238Pu, 239+240Pu and 241Am (on 01.01.2000). In the year 2000, total inventories of the fuel component radionuclides in the upper 30-cm soil layer of the 30-km Chernobyl zone in Ukraine (outside the ChNPP industrial site, excluding the activity located in the radioactive waste storages and in the cooling pond) were estimated as: 90Sr--7.7 x 10(14) Bq; 137Cs--2.8 x 10(15) Bq; 154Eu--1.4 x 10(13) Bq; 238Pu--7.2 x 10(12) Bq; 239+240Pu--1.5 x 10(13) Bq; 241Am--1.8 x 10(13) Bq. These values correspond to 0.4-0.5% of their amounts in the ChNPP unit 4 at the moment of the accident. The current estimate is 3 times lower than the previous widely-cited estimates. Inventories of the fuel component radionuclides were also estimated in other objects within the 30-km zone and outside it. This allowed more accurate data to be obtained on the magnitude of a relative release of radionuclides in the fuel particles (FP) matrix during the Chernobyl accident outside the ChNPP industrial site. It amounts to 1.5+/-0.5% of these radionuclides in the reactor, which is 2 times lower than the previous estimates. Two-thirds of the radionuclides release in the FP was deposited on the territory of Ukraine.
Environmental Monitoring↗
Iodine-129 in thyroid and urine in Ukraine and Denmark.
Human thyroids collected from Gomel in Belarus, sheep thyroid from Jutland and human urine from Zealand in Denmark were analysed for 129I and 127I concentrations. The ratios of 129I/127I in human thyroid in Gomel are 2.65-11.0 x 10(-9) with an average of 7.21 x 10(-9), which is one order of magnitude higher than those from Asia and South America (10(-10)), but significantly lower than those observed in west Europe (10(-8)). A weak negative correlation (P < 0.05) between 129I/127I ratio in human thyroid and the age of the subjects was observed in Gomel. The average ratio of 129I/127I in sheep thyroids from Jutland of Denmark is 1.81 x 10(-7), which is two orders of magnitude higher than those in south hemisphere, and Asia. It is also significantly higher than those observed in other west European countries before 1984 and that in human thyroid in Gomel. The high thyroid 129I level in Jutland is attributed to the release of reprocessing plants in France and UK. The 129I/127I ratios in human urine in Zealand of Denmark are 0.86-2.86 x 10(-8). The possibility of using urine 129I to evaluate the thyroid exposure to 129I is investigated.
Adolescent↗
Radioactivity near the sunken submarine "Kursk" in the Southern Barents Sea.
Radioactivity measurements were conducted on seawater, sediment, and biota samples collected in the vicinity of the Russian submarine "Kursk" in September, 2000, within 1 month of the vessel's sinking in the Barents Sea to determine whether leakage of radioactivity from the vessel's two nuclear reactors had occurred and to assess the impact on one of the most productive fishing areas in the world. Levels of radioactivity in surface sediments and biota are within the range of values previously measured in the Barents Sea and can be ascribed to inputs from global fallout, European nuclear fuel reprocessing facilities, and the Chernobyl accident. However, levels of 1291 in seawater in the Southern Barents Sea increased by 500% between 1992 and 2000, and the 129I/137Cs ratio increased by more than an order of magnitude during this time, owing to long-range transport of releases from reprocessing facilities at Sellafield (U.K.) and La Hague (France). Although these results indicate that, at the time of sampling, leakage from the Kursk had a negligible impact on the environment, they also show that regional background levels of artificial radioactivity are varying rapidly on annual timescales and that Europe's nuclear reprocessing facilities are the leading contributor of anthropogenic radioactivity to the region.
Environmental Monitoring↗
Retrospective dosimetry related to chronic environmental exposure.
Radioactive contamination of the environment occurred in the early fifties as a result of the releases from the Mayak plutonium production complex (Southern Urals, Russia). The releases of liquid wastes into the Techa river resulted in chronic exposure of 30,000 residents of the riverside communities. Since 1951 90Sr body burdens have been measured for over half of this cohort. This paper presents the analysis of data on 90Sr in humans and describes the reconstruction of internal doses for these people.
Autopsy↗
Health impacts of large releases of radionuclides. Impacts on plant and animal populations.
Historical experiments and observations in radioactively contaminated environments have documented radiation impacts on natural plant communities and animal populations. General findings from these studies are reviewed. Despite much information on the response of individual organisms to radiation in the laboratory, the database is more limited and the interpretations more complex for natural populations and communities exposed to radionuclides. These complications are discussed as they pertain to plants and animals in natural environments. Paradigms concerning the recovery of radiation-damaged communities and ecosystems, and areas of needed research are discussed.
Animals↗
Reactive barriers for 137Cs retention.
137Cs was dispersed globally by cold war activities and, more recently, by the Chernobyl accident. Engineered extraction of 137Cs from soils and groundwaters is exceedingly difficult. Because the half-life of 137Cs is only 30.2 years, remediation might be more effective (and less costly) if 137Cs bioavailability could be demonstrably limited for even a few decades by use of a reactive barrier. Essentially permanent isolation must be demonstrated in those few settings where high nuclear level wastes contaminated the environment with 135Cs (half-life 2.3 x 10(6) years) in addition to 137Cs. Clays are potentially a low-cost barrier to Cs movement, though their long-term effectiveness remains untested. To identify optimal clays for Cs retention, Cs desorption was measured for five common clays: Wyoming Montmorillonite (SWy-1), Georgia Kaolinites (KGa-1 and KGa-2), Fithian Illite (F-Ill), and K-Metabentonite (K-Mbt). Exchange sites were pre-saturated with 0.16 M CsCl for 14 days and readily exchangeable Cs was removed by a series of LiNO3 and LiCl washes. Washed clays were then placed into dialysis bags and the Cs release to the deionized water outside the bags measured. Release rates from 75 to 139 days for SWy-1, K-Mbt and F-Ill were similar; 0.017% to 0.021% sorbed Cs released per day. Both kaolinites released Cs more rapidly (0.12% to 0.05% of the sorbed Cs per day). In a second set of experiments, clays were Cs-doped for 110 days and subjected to an extreme and prolonged rinsing process. All the clays exhibited some capacity for irreversible Cs uptake. However, the residual loading was greatest on K-Mbt (approximately 0.33 wt.% Cs). Thus, this clay would be the optimal material for constructing artifical reactive barriers.
Adsorption↗
Health impacts of large releases of radionuclides. Late somatic health effects.
This chapter reviews the risks of radiation-induced cancer for the dose range likely to occur after releases of radionuclides into the environment. Epidemiological evidence from exposed workers and the atomic bomb survivors of Hiroshima and Nagasaki is surveyed. Influences on such risk functions of individual related quantities (e.g. age, sex, nationality, time since exposure and organs exposed) and of radiation modality-related quantities (e.g. dose, dose rate and radiation quality) are also briefly discussed.
Accidents, Occupational↗
Comparative study of the PARK and ASTRAL post-accidental decision support software.
The French radioecological assessment model ASTRAL and the German model PARK have been developed to evaluate the radiological situation in the case of an accidental release of radionuclides and a widespread contamination of the environment. For decision makers it is of importance that the results on foodstuff contamination and on dose to humans are in fairly good agreement, when areas of the common border are affected. Therefore a comparative study has been done for two scenarios, assuming accidental releases on 1 June and 1 October. The study indicates that the models' structures and the transfer parameters are in good agreement. Only model principles for root vegetables are different in both models. Significant differences in results on the contamination of foodstuff and on dose to humans by ingestion are caused by different assumptions on dates of harvest and feeding methods of animals. A corresponding harmonization is essential with respect to decision making.
Animal Feed↗
Forecasting the consequences of accidental releases of radionuclides in the atmosphere from ensemble dispersion modelling.
The RTMOD system is presented as a tool for the intercomparison of long-range dispersion models as well as a system for support of decision making. RTMOD is an internet-based procedure that collects the results of more than 20 models used around the world to predict the transport and deposition of radioactive releases in the atmosphere. It allows the real-time acquisition of model results and their intercomparison. Taking advantage of the availability of several model results, the system can also be used as a tool to support decision making in case of emergency. The new concept of ensemble dispersion modelling is introduced which is the basis for the decision-making application of RTMOD. New statistical parameters are presented that allow gathering the results of several models to produce a single dispersion forecast. The devised parameters are presented and tested on the results of RTMOD exercises.
Air Movements↗
Health impacts of large releases of radionuclides. Interactions with human nutrition and other indices of population health.
The consumption of food is an important pathway involved in the internal contamination of humans. The site-related critical foodstuffs can be grouped into three main categories: dairy products; aquatic animals, such as fish, molluscs and crustaceans; and other typical foods. The concentration factor plays a more important role than the amount of a certain food consumed. Semi-natural and natural ecosystems are of special interest in this context because they can provide critical pathways for radionuclide transfer to humans, and they can also act as temporary sinks or long-term sources for radionuclides deposited from the atmosphere. From the viewpoint of population health, another important role is played by the countermeasures. The reference values commonly adopted in radiation protection are conservative and they have been established for planning practices that could provide future sources of irradiation. After a large release of radionuclides, the evaluation of the problem must be as realistic as possible, otherwise the countermeasures will imply consequences worse than those produced by the accident itself (without any further intervention). This criterion was clearly stated by the International Commission on Radiological Protection but it was frequently neglected after the Chernobyl accident. The results of a survey on the number of induced abortions following this incident are reported. These suggest that moral and ethical problems are involved above and beyond any economical implications.
Abortion, Spontaneous↗
Health impacts of large releases of radionuclides. Physical transport and chemical and biological processes in agricultural systems.
The purpose of radioecological models is to make realistic estimates of doses to the public after accidental releases of radionuclides into the environment. Important physical, chemical and biological processes involved in the dispersion and transport of radioactive substances in the atmosphere and along the food-chains are presented. The results of the EURAD (EURopean Acid Deposition) model, predicting the deposition patterns of 131I and 137Cs in Belarus and Ukraine after the Chernobyl accident, are discussed. An overview of the most important ecological processes--such as deposition, interception and translocation, weathering, transfers from soil to plants and from plants to animal/animal products, and seasonality in agricultural environments--is given. Examples corresponding to these individual processes, mainly experimental results after the Chernobyl accident and related to radiocaesium and radioiodine, are shown and discussed.
Agriculture↗