Biotic transport of radionuclides from a low-level radioactive waste site

In the United States, concern for human exposures to radioactivity associated with the disposal of low-level radioactive waste has resulted in a series of regulatory guides, environmental assessments, management practices, and modeling tools. A large number of radionuclide transport processes and mechanisms that may contribute to human exposure have been modeled, using computer programs to make the required calculations. The objective of our work was to evaluate the relevance of potential biological transport processes in the assessment of potential impacts at low-level waste (LLW) disposal sites. As part of this effort, we developed an order-of-magnitude estimate for potential dose to man resulting from biological transport by burrowing animals and by plant translocation at a reference low-level waste site in the arid west. We also made comparative dose-to-man estimates for a more commonly considered human intrusion exposure scenario. Parameter values for defining a reference arid LLW disposal site and biotic transport processes are based on data reported in current literature. Estimates of waste volumes for the western United States are based on information described by the U.S. Nuclear Regulatory Commission in the Draft Environmental Impact Statement in support of 10 CFR Part 61. Our estimates of the dose-to-man resulting from biotic transport are of the same order of magnitude as those resulting from a more commonly evaluated human intrusion scenario. The previously assumed lack of potential importance of biotic transport at LLW sites in earlier assessment studies is not confirmed by our findings. Our results indicate that long-term biological transport processes have the potential to influence LLW site performance, and should be carefully evaluated as part of the impact assessment process.     

疑似放射性废水伤口沾染医学应急处置1例

通过对一名疑似放射性废水沾染的头皮裂伤患者,采取快速的医学应急响应和科学有效的处置,排除了伤口的放射性污染,消除了患者的心理恐惧,患者伤口愈合良好。核事故时批量伤员的救治流程、心理干预方式,对于突发少量放射性沾染患者依然适用,本文总结了相关的处置流程,以供参考。     

Health effects of a thorium waste disposal site.

A case-control study of 112 households residing in the vicinity of a thorium waste disposal site found a higher prevalence of birth defects (RR 2.1) and liver diseases (RR 2.3) among exposed than the unexposed group. The numbers were quite small and the confidence intervals wide, however, so that no definite conclusions can be drawn from these data.     

Radionuclide export by deer mice at a solid radioactive waste disposal area in southeastern Idaho

Concentrations of 90Sr, 137Cs, 238Pu, 239+240Pu, and 241Am in deer mice tissues collected from a radioactive waste disposal area in southeastern Idaho were significantly (p less than 0.05) higher than those from a control area. The highest concentrations of Pu and Am occurred in pelts of deer mice inhabiting an area which had elevated surface and subsurface soil concentrations of these nuclides as compared to other Subsurface Disposal Area locations. Therefore, transuranic contamination in tissues likely originated from both soil depths. However, 137Cs and 90Sr in tissues likely originated from subsurface areas, since surface soils were below background concentrations for these nuclides. Based on a minimum of 6160 deer mice inhabiting the 36-ha waste disposal area over a 1-yr period, a total minimum inventory of 22.8 mu Ci radioactivity was contained in deer mice tissues. Of this estimate, 22.7 mu Ci activity was due to the radionuclides 90Sr and 137Cs. An estimated total of 8.4 mu Ci was transported from the disposal area in mice dispersing from the area. A calculated annual radionuclide inventory of 28.8 mu Ci in deer mice feces was deposited in and around the radioactive waste disposal area. Deer mice inhabiting the SDA are a mode of radionuclide uptake and transport; however, the environmental consequences of this transport mechanism are likely minimal. The results for deer mice, which make up 69% of the small mammal biomass, are discussed in relation to other small mammals within the disposal area. Other modes of transport associated with the deer mice, such as radionuclides in excavated soils associated with burrowing activities and predation, are also discussed.     

Illustrative assessment of human health issues arising from the potential release of chemotoxic substances from a generic geological disposal facility for radioactive waste

Many countries have a programme for developing an underground geological disposal facility for radioactive waste. A case study is provided herein on the illustrative assessment of human health issues arising from the potential release of chemotoxic and radioactive substances from a generic geological disposal facility (GDF) for radioactive waste. The illustrative assessment uses a source-pathway-receptor methodology and considers a number of human exposure pathways. Estimated exposures are compared with authoritative toxicological assessment criteria. The possibility of additive and synergistic effects resulting from exposures to mixtures of chemical contaminants or a combination of radiotoxic and chemotoxic substances is considered. The case study provides an illustration of how to assess human health issues arising from chemotoxic species released from a GDF for radioactive waste and highlights potential difficulties associated with a lack of data being available with which to assess synergistic effects. It also highlights how such difficulties can be addressed.     

A comparative radiological assessment of five European biosphere systems in the context of potential contamination of well water from the hypothetical disposal of radioactive waste.

In the framework of the BioMoSA project for the development of biosphere assessment models for radioactive waste disposal the Reference Biosphere Methodology developed in the IAEA programme BIOMASS was applied to five locations, situated in different European countries. Specific biosphere models were applied to assess the hypothetical contamination of a range of agricultural and environmental pathways and the dose to individuals, following contamination of well water. The results of these site-specific models developed by the different BioMoSA partners, and the individual normalised dose to the exposure groups were compared against each other. Ingestion of drinking water, fruit and vegetables were found to be among the most important pathways for almost all radionuclides. Stochastic calculations revealed that consumption habits, transfer factors, irrigation rates and distribution coefficients (Kd(s)) were the most important parameters that influence the end results. Variations in the confidence intervals were found to be higher for sorbing elements (e.g. (36)Cl, (237)Np, (99)Tc, (238)U, (129)I) than for mobile elements (e.g. (226)Ra, (79)Se, (135)Cs, (231)Pa, (239)Pu). The influence of daughter products, for which the distribution into the biosphere was calculated individually, was also shown to be important. This paper gives a brief overview of the deterministic and stochastic modelling results and the parameter sensitivity. A screening methodology was introduced to identify the most important pathways, simplify a generic biosphere tool and refine the existing models.     

新型薄壳屋盖在垃圾处置厂设计中的应用

新型薄壳层盖的结构合理,但它的设计计算工作量很大。作者在设计四川省德阳市垃圾处理厂时采用了简便的倒“Ｔ”梁理论计算方法。     

Development and comparison of five site-specific biosphere models for safety assessment of radioactive waste disposal.

This paper describes the development and application of site-specific biosphere models that might be used for assessment of potential exposures in the framework of performance assessment studies of nuclear waste disposals. Model development follows the Reference Biosphere Methodology that has been set up in the framework of the BIOMASS study. In this paper, the application is to real sites at five European locations for which environmental and agricultural conditions have been described and characterised. For each of the sites a biosphere model has been developed specifically assuming a release of radionuclides to waters that are used by humans, for example as drinking water for humans and cattle and as irrigation water. Among the ingestion pathways, the intakes of drinking water, cereals, leafy vegetables, potatoes, milk, beef and freshwater fish are included in all models. Annual individual doses were calculated, and uncertainties in the results were estimated by means of stochastic calculations. To enable a comparison, all results were normalised to an activity concentration in groundwater of 1 Bq m(-3) for each of the radionuclides considered ((36)Cl, (79)Se, (99)Tc, (129)I, (135)Cs, (226)Ra, (231)Pa, (230)Th, (237)Np, (239)Pu, and (238)U), i.e. those that are usually most relevant in performance assessment studies of nuclear waste disposals. Although the results do not give answers in absolute terms on potential future exposures, they indicate the spectrum of exposures that might occur in different environments and specify the interaction of environmental conditions, human habits and potential exposure.