Isolating radioactive waste

Natural systems have been studied to provide data to support the ability of geological repositories to isolate radioactive wastes (e.g.,... 

The hydrolytic chemistry of Pu is important in that it affects the behavior and mobility of plutonium in the environment [A2] and in geologically isolated radioactive wastes that may be subjected to slow leaching by ground water. The absorption spectra of the Pu(TV) polymer is similar to that of the plutonium hydroxide precipitate Pu(0H)4 [L4]. Experimental data in Fig. 

Although the objective of the waste repository is to isolate radioactive wastes from humans, it is recognized that there are mechanisms which at some distant time... 

Isolation of radioactive wastes for long periods to allow adequate decay is sought by the use of multiple barriers. These include the waste form itself, the primary containers made of resistant materials, overpacks as secondary layers, buffer materials, concrete vaults, and finally the host rock or sod. Barriers limit water access to the waste and minimize contamination of water suppHes. The length of time wastes must remain secure is dependent on the regulatory limit of the maximum radiation exposure of individuals in the vicinity of the disposal site. 

Congress has decided that reprocessing will not be practiced in this country so that we will not be in the plutonium production business. This seems like a safe thing to do since this action will minimize terrorism threats. Reprocessing generates chemi cal wastes but greatly reduces the volume of the highly radioactive waste. It also isolates plutonium and unused fuel for possible use as new fuel. 

Shurr, G.W. "The Pierre Shale, Northern Great Plains a Potential Isolation Medium for Radioactive Waste", U.S. Geological Survey Open-File Report 77-776, 1977. 

Radioactive wastes are usually stored in underground tanks or in temporary storage at reactor sites for recycling or disposal (Whicker and Schultz 1982a). For low-level wastes, containment and isolation are the preferred disposal options, including burial, hydraulic injection into deep geological strata, and ocean disposal (Table 32.10). Options for the disposal of high-level wastes include... 

The reactors at Oklo and Bangombe provide great confidence in the feasibility of radioactive waste isolation. The reactors operated for 800 000 years and after two billion years, most of the radionuclides (except for iodine that has migrated away completely) and/or their decay products have migrated only a few metres. 

Tt is almost three years since the first American Chemical Society sym-posium on radioactive waste isolation and management was held in... 

The work presented here enables us to get a clearer picture of the problems involved in permanent isolation of radioactive wastes from the environment. 

The Department of Energy Program for Long-Term Isolation of Radioactive Waste... 

Over the last year or so, several papers have been published which have been concerned with the adequacy of the technology for providing for permanent isolation of radioactive wastes. In all cases the concerns that have been raised have focused on the second set of issues, rather than the first, so that the apparent dispute between those who say that there are no technical problems and those who say that there are still some to be solved is perhaps more a dispute as to what particular set of problems are being described. 

Without going into great detail about the issues described in these papers, I would like to make the point that the response of the waste isolation program to these papers will be to use them to help us to design a technical program plan to ensure that these issues are adequately addressed, as indeed they must be, before we can commit radioactive waste to irretrievable permanent disposal. 

The objective of geologic isolation of radioactive wastes is to preclude their reaching the biosphere until after they have decayed to the extent that they no longer constitute a health hazard. Concern over radioactive wastes from military, industrial and research uses has elicited many lines of commentary and deep concern from many individuals. In California, the concern about waste disposal was the focal point in establishing a moratorium on the construction of new reactors until a satisfactory waste disposal technology could be demonstrated. 

One of the more important factors affecting the isolation of radioactive waste is the rate of release of the radioactivity from the solid waste form to the environment. The most probable mechanism for release and transport of radioactivity from a solid waste form is by leaching of radioactive isotopes with groundwater. The objective of leach-testing various waste forms is to evaluate the rate at which specific hazardous radionuclides migrate from waste if and when the waste form comes in contact with groundwater. In this paper, measurement of leach rates of radioactive waste by a method which incorporates neutron activation is described. 

Much interest in the past few years has been generated in connection with problems of radioactive waste isolation in a growing nuclear economy. Many studies have been irfitiated to find the most suitable sites for waste repositories, and the environmental impact if breaches occur in such repositories. 

Figure 16.11 Water dilution volume for radionuclides in PWR spent fuel. (From National Research Council, A Study of the Isolation System for Geologic Disposal of Radioactive Waste, NAS, Washington, 1983.)...

In general terms, the goal of long-term waste storage is to isolate the radioactive waste from humans and the environment. The prevailing design strategy for waste repositories is that of multiple barriers (Fig. 16.12). 

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