INES-event
INES 0

D2O leak from a calandria tube sheet plug

During unit shutdown heavy water leak developed from a calandria tube sheet plug which was installed earlier after removal of calandria tube at that lattice location (in bottom most row of channels). The heavy water leak into calandria vault was detected through he alarm from a moisture element located in calandria vault drain line. The source of leak was identified to be the plug gasket and plug was replaced with a new one. The integrity of the new plug was confirmed by helium leak test and by raising moderator level in calandria above the particular row. The spilled heavy water was collected through calandria vault drain line. Activity release during the vent was well within the technical specification limits. no safety system was challenged or required during the incident. The event is rated at level 0 on INES.

Location: KALPAKKAM-1
Event date: Sun, 07-01-1996
Nuclear event report
Legenda & explanation