DRINK - A BIOGEOCHEMICAL SOURCE-TERM MODEL FOR LOW-LEVEL RADIOACTIVE-WASTE DISPOSAL SITES

Interactions between element chemistry and the ambient geochemistry pl ay a significant role in the control of radionuclide migration in the geosphere. These same interactions influence radionuclide release from near surface, low level radioactive waste, disposal sites once physic al containment has degraded. In situations where LLW contains signific ant amounts of metal and organic materials such as cellulose, microbia l degradation in conjunction with corrosion can significantly perturb the ambient geochemistry. These processes typically produce a transiti on from oxidising to reducing conditions and can influence radionuclid e migration through changes in both the dominant radionuclide species and mineral phases. The DRINK (DRIgg Near field Kinetic) code is a bio geochemical transport code designed to simulate the long term evolutio n of the UK low level radioactive waste disposal site at Drigg. Drigg is the UK's principal solid low level radioactive waste disposal site and has been receiving waste since 1959. The interaction between micro bial activity, the ambient geochemistry and radionuclide chemistry is central to the DRINK approach with the development of the ambient pH, redox potential and bulk geochemistry being directly influenced by mic robial activity. This paper describes the microbial aspects of the cod e, site data underpinning the microbial model, the microbiology/chemis try interface and provides an example of the code in action.