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Management of Commercially Generated Radioactive Waste - U.S. ...

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6.109<br />

<strong>Waste</strong> Preparation Technology. Liquid waste might require pretreatment to ensure compa-<br />

tibility with the rock. No operating injection facilities exist at present for high-level<br />

acid wastes. Pretreatment for most industrial wastes comprises filtration and limited chem-<br />

ical treatment. Since well injection is usually being pursued to reduce waste processing<br />

requirements, chemical treatment is minimal, and may include the addition <strong>of</strong> biocides and<br />

chloride to prevent plugging <strong>of</strong> the well from bacterial growth (Hartman 1968).<br />

<strong>Waste</strong> preparation for shale-grout injection at ORNL has been the subject <strong>of</strong> extensive<br />

testing to develop an economical mix with good pumping and leach-rate characteristics (Moore<br />

et al. 1975, Hollister and Weimer 1968). Research indicates that the use <strong>of</strong> ash as a partial<br />

substitute for cement reduces costs and enhances strontium retention. Mixes incorporating<br />

various clays and grout shale have been tested. Leach rates <strong>of</strong> 3.2 x 10 - 5 g/cm 2 /day for<br />

strontium and 2.1 x 10- 6 g/cm2/day for cesium have been obtained. The latter value is<br />

approximately equivalent to the leach rate for borosilicate glass (ERDA 1977).<br />

Isolation and Safety. Isolation and safety analyses are based on<br />

* Definition <strong>of</strong> source term (concentration, form, location, time)<br />

* Characterization <strong>of</strong> pathway (transport velocity, chemical or physical changes, path<br />

length barriers, ecosystems involved)<br />

* Exposure and "dose-to-man" calculations for both specific groups and total population.<br />

A range <strong>of</strong> data values for the parameters can be analyzed to provide a probabilistic<br />

basis for the results. Methods involving modeling and analysis <strong>of</strong> failure processes have<br />

been employed for analyzing the performance <strong>of</strong> conventional disposal options (Logan and Ber-<br />

bano 1977) and would also be applicable to deep well injection concepts.<br />

R&D Requirements<br />

Since experience in the basic techniques required for well injection exists, the uncer-<br />

tainties associated with the design basis are related primarily to extrapolation <strong>of</strong> this<br />

experience to other waste forms, to other geologic settings, and to modified quantities and<br />

disposal rates. There are already techniques for preparing radioactive wastes in liquid or<br />

slurry form; however, there are uncertainties in formulating liquid wastes that would provide<br />

stability and compatibility with the disposal formation. For slurries, further R&D would be<br />

required for the development <strong>of</strong> optimum mixes, which would be related to the specific charac-<br />

teristics <strong>of</strong> the waste and disposal formation.<br />

Geologic formations suitable for the injection <strong>of</strong> waste would have to be identified and<br />

verified on a site-specific basis. The exploratory techniques needed to do this are in an<br />

early stage <strong>of</strong> development, and would require further R&D with particular emphasis on verify-<br />

ing local geologic structure, establishing local and regional geohydrologic conditions, de-<br />

termining thermal and mechanical properties and in situ stresses, and locating and orienting<br />

discontinuities.

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