Radiological safety aspects of radiation shielding window repair jobs at Kaiga Generating Station-Unit 1

Kaiga Generating Station (KGS) Unit-1 attained first criticality on September 26, 2000. Oil filled Radiation Shielding Windows (RSW) are installed in the cross Shielding Wall of Fuelling Machine Vaults (FMV) and Fuelling Machine Service Areas (FMSA) to provide gamma and neutron attenuation while viewing the end shield faces through the windows. A crack was observed in the inner side glass of the RSW of South Fuelling Machine Vault during commissioning of Unit -1. Neutron fields of 10-40 μSv/h were observed at different power levels on the south FMV RSW. Several shielding arrangements were tried to eliminate streaming neutron dose rates on the window surfaces in the accessible areas. The crack in the window was fixed with araldite, and the window was filled with silicon oil during October. Neutron dose rates were eliminated by this procedure. This report presents the design criteria, the RSW arrangement radiological conditions observed at different power levels and the attenuation factors observed with different shielding arrangements. (author)