 INES 2 |
PRESSURE TUBE FAILURE AND SMALL LOCA IN EMBALSE NPP AFTER GARTER SPRING INSPECTION AND RELOCATION |
During a long planned shutdown of Embalse NPP, which started in October 1995, several activities were performed. The main task was garter spring spacers inspection and its relocation using the SLARETTE Mark III tool.
During examination of pressure tube L-12 and A-14 the operator had many difficulties in relocating spacers and the machine electrical protection was tripped several times.
On November 24, an examination of pressure tube A-14 was perfomed and a hole of 9 mm in diameter and 1.7 mm deep was found, probably caused by electric erosion. Because of that, the replacement of pressure tube A-14 was decided.
On December 13, the station began to start-up activities and, on December 16, it reached full power. On December 18, there was an increase of annulus gas system pressure and of the tritium concentraion in the reactor building. The visual inspection showed the presence of water in the annulus gas collecting tank. The station was led to cold shutdown to decrease pressure in the primary coolant and the leakage rate. Further inspecton of pressure tube L-12 showed a 7 mm long crossing hole.
On December 29, fuel channel replacement was concluded and on January 2, the station reached 100% power.
Assessment of the causes is underway.
Event date: Mon, 18-12-1995
