 INES 1 |
DEGRADED WATER CHEMISTRY IN THE PRIMARY CIRCUIT DUE TO CEMENT MORTAR INGRESS INTO THE BORATED WATER STORAGE TANK |
The unit was in the maintenance outage in the stage of refueling. To prevent ground water filtration through the foundation into the Chemical and Volume Control Facility (CVCF) rooms cement mortar was being pumped through the drilled holes into the ground filling surrounding the building foundation. In the course of this effort cement mortar leaked through the foundation cavities (foundation defects) under the metallic liner of the borated water storage tank (BWST), tore it off the frame structure and through the resulting liner holes penetrated into the tank (pumping pressure 4 kgf/cm2). At this time coolant cleaning effort was under way and as a result cement containing water from the tank was pumped to the primary circuit, spent fuel and refueling pools. This caused degraded water chemistry as regards silicic acid, hardness salts and aluminum content.
Basis for rating:
No real initiator. Failed safety system equipment is intended for expected initiator.
Safety function availability - full.
Level 0 (A-1P) according to Table A1. Event reveals deficiencies in safety culture.
Event date: Thu, 16-04-1992
