INES-event
INES 1

PVNGS 2 STEAM GENERATOR TUBE RUPTURE

Palo Verde Unit 2 was operating at 98 percent power. At 0435, operators noticed a decrease in pressurizer pressure and level. Although additional charging flow was started, pressurizer level and pressure continued to decrease. The operators manually scrammed the reactor at 0447. Safety injection and containment isolation signals automatically initiated. After determining that a steam generator tube rupture existed, operators began to cool down and depressurize the reactor coolant system. The leak rate was estimated to be approximately 15 l/s (240 gal/min.). The release patchway through the steam jet air ejector was filtered and monitored. At 0728, the affected steam generator was isolated. Sometime after 0800, leakage was minimized when reactor coolant system pressure was reduced to match secondary system pressure. Field surveys outside the plant indicated dose rate readings no higher than background.

Location: PALO VERDE-2
Event date: Sun, 14-03-1993
Nuclear event report
Legenda & explanation