Remote Radiation and Visual Surveys of the Hot Cell Waste Vault and Spent Fuel Transfer Route at Kazakhstan’s BN-350 Reactor

Kazakhstan’s BN-350 fast reactor was shut down in 1999 and is in the process of being decommissioned in preparation for Safestore. A key achievement during 2010 was the removal of the known inventory of spent nuclear fuel (SNF) from the reactor to off-site secure storage. As a complementary activity, surveys of areas of the fuel discharge route where it was considered possible for fuel pins or fuel residues to have collected over many years of operation were also arranged to confirm that no significant amounts of fuel of remained at the plant. This paper reports on the remote radiation and visual (video and still photograph) surveys undertaken on the following areas of the BN-350 spent fuel route: • The waste storage repository or vault underneath the Post-Irradiation Examination Hot Cell in which non-destructive and destructive examination of irradiated fuels was undertaken throughout the operating life of the reactor. • The fuel transfer and washing cells within which irradiated fuel sub-assemblies were processed and residual sodium coolant removed. • The fuel storage ponds. Man access to several areas (particularly the waste vault) was not possible due to very high radiation levels from stored βγ-active wastes or residual contamination and in these cases specially engineered remote camera and radiation detector deployment systems were developed and used. In other areas, such as the ponds, limited man access was possible under prepared and controlled conditions. The survey results, together with associated radiochemical and radiation dose rate analysis, demonstrated that, despite several recorded handling incidents during Hot Cell operations, the maximum estimated amounts of nuclear material which could remain at BN-350 were sufficiently low to give no major safeguards concerns. The data also provides key information to guide decommissioning and dismantling planning in the future.