ML20168A720
| ML20168A720 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 06/16/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1976-015-00 | |
| Download: ML20168A720 (4) | |
Text
uction Valves to Decay Heat Pumps Fail to Open at Rancho Seco re sequence was:
g testing, neither sumnp isolation valve opened when an open signal pplied.
e action; alves were moved manually and then cycled electrically.. The bypass hes for the valve torque switches-was-adjusted to permit more motor before the bypass switches difopped. out.
rpose of failed system or component:
alves provide for fluid flow from the sump to the low pressure and pressure recirculation systems and the building spray system (while e recirculation mode) following a LOCA.
ility of system per WASH 1400:
- low pressure recirc: 1.3 x 10-2 /D high pressure recirc: 9 X 10-3/D ility of component per WASH 1400:
- motor operated valve, failure to operate. 1 x 10-3 /D vailabilitieQ are in units of per demand D-1 . Failure rates are in per hour HR-T
core Damage No No No - No LOCA and unit in shutdown.
NSIC 120995 - Actual Occurrence for Failure of Both Suction Valves to Decay Heat Pumps from Emergency Sump at Rancho Seco
Small Reactor Auxiliary ]High Low Pressure Potential Sequence LOCA Trip Feedwater and Secondary Heat Removal jInjection Pressure, Recirculation and LPR/HPI Cross-Connect Severe Core Damage No.
2 3
4 5
6 7
NSIC 120995 - Sequence of Interest for Both Sump Suction Valves to Decay Heat Pumps Fail to Open at Rancho Seco
CATEGORIZATION OF ACCIDENT SEQUENCE PRECURSORS CCESSION NUMBER- 120995 LER: November 22, 1976 F EVENT: November 11, '1976 INVOLVED: Decay heat NT INVOLVED: Pumps Switch setting incorrect.
E OF INTEREST: LOCA OCCURRENCE: Valves fail to open for decay heat system.
NAME: Rancho Seco NUMBER: 50-312 TYPE: PWR ELECTRICAL RATING: 918 MWe R AGE: 2.1 yr B&W CT- ENGINEERS: Bechtel RS: Sacramento Municipal Utility District N: .25 mi1les SE..of. Sacramento, CA N: 360(a) hours OPERATING CONDITION: Shut down.
FEATURE TYPE OF FAILURE: (a) inadequate performance; (b) failed to start; QDmade inoperable; (d) ______
ERY METHOD: During test.
T: Bypass switches for torque switches were dropping out before valve disc cleared seat resulting in torque switch stopping valve movement.