INES-event
INES 1

DEVIATION FROM TECHNICAL SPECIFICATIONS

On November 15, the reactor operator observed an increasing temperature downstream one of the pressurizer safety valves indicating internal leakage. The operational manager decided, after consulting the plant engineering staff and the Ringhals Safety Committee, to reduce the Reactor Coolant System (RCS) operating pressure. At 15.1 MPa the internal leakage terminated. The normal operating pressure is 15.5 MPa.
On December 8, during a planned stop, the safety valve was replaced and the operational pressure was returned to 15.5 MPa.
In January while working with an experience feedback item it was found in the Technical Specifications that the lowest allowed RCS pressure is 15.3 MPa.
Justifation:
Defence-in-depth criteria
level 1 anomaly beyond the authorized operating regime.

Location: RINGHALS-4
Event date: Wed, 15-11-1995
Nuclear event report
Legenda & explanation