Sellafield site

Radioisotope Scavenging. Clinoptilolite has a relatively high Si/Al ratio and has the ability to scavenge cesium radioisotopes from aqueous nuclear wastes. An example of its industrial-scale use is in the development of the site ion-exchange effluent plant (SIXEP) by British Nuclear Fuels at their Sellafield site. This uses a clinoptilohte, from Mud Hills, California, and meets the stringent performance requirements. The Cs selectivity of clinoptilolite has led to its possible use to reduce Cs radioisotope body burdens in sheep, and mordenite has been studied for the same use in reindeer. Mordenite also has been used to treat aqueous nuclear waste, as has an acid washed chabazite (AW500). 

Fig. 12.1. Radionuclides released from the Sellafield site as liquid discharges, in 1991. Figures are in TBq...

If the activity of each isotope discharged within a given period is divided by the activity in the reprocessed fuel, a factor is obtained which crudely represents the relative ease with which a species is discharged. This release factor will be specific to the Sellafield site, which passes the effluent through a variety of decontamination procedures prior to discharge including storage whilst short-lived radionuclides decay. 

Gray, J., Jones, S.R. Smith, A.D. (1995) Discharges to the environment from the Sellafield site, 1952-1992. Journal of Radiological Protection 15, 99-131. 

Table I shows average hydraulic conductivities and their standard deviations based on similar data collected by NIREX at the Sellafield site.

Table I. Hydraulic conductivy based on NIREX data from the Sellafield site (means and standard...

Formation 2 of Sellafield site are used. Thus, the distribution of the permeability of the pixel is lognormal. 

T-H-M-C processes are significantly affected by subsurface heterogeneity, which results in scale-dependence of the related parameters. To handle this scale-dependent behavior, we need to characterize this heterogeneity and consider its effects at different scales. In this study, we demonstrate that the measured permeability data from Sellafield site, UK, are very well described by fractional Levy motion (fLm), a stochastic fractal. This finding has important implications for modeling large-scale coupled processes in heterogeneous fractured rocks. 

While a number of researchers have used fLm to characterize subsurface heterogeneities in porous media (e.g., Painter, 1996 Liu and Molz, 1997 Molz and Liu, 1997 Liu et al., 2003), the usefulness of fLm for dealing with heterogeneity in fractured rocks has not been investigated in the literature. In this section, we present a brief introduction to fLm and then demonstrate the consistency between measured permeability data from the Sellafield site and fLm. 

A permeability data set for fractured rocks was collected from the short interval tests carried out at the Sellafield site (United Kingdom Nirex Limited, 1997). These tests were conducted over a 156 m length interval and typically tested 1 to 2 m lengths of the borehole. They are comprised of 100 pulse injection tests and six production tests. 

Audit of British Nuclear Fuels Limited (Sellafield site)... 

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