INES-event
INES 1

REVEAL OF INADVERTENTLY CLOSED MANUAL SERVICE VALVES AT VERIFICATION TESTS OF THE SCRAM SYSTEM BEFORE PREPARATIONS TO RESTART

During test of the hydraulic scram system with cold water after service of an electrical rod drive it was revealed that a group of rods did not respond to demand. The reason was that a manual service valve was closed. All the other corresponding valves were also closed. Normally these valves are closed when the reactor vessel head is put on or off. These procedures are governed by specific instructions. Due to misconception the operating personnel supposed that the valves were already open.
Basis for the rating: Chapter 4.4b, deviation from written instruction.
BASIS FOR RATING:
DIFFICULTIES IN RATING:

Location: FORSMARK-2
Event date: Tue, 10-09-1991
Nuclear event report
Legenda & explanation