ML20168A453

Final ASP Analysis - Davis-Besse (LER 346-77-016)

ML20168A453
Person / Time
Site:	Davis Besse
Issue date:	06/16/2020
From:	Christopher Hunter NRC/RES/DRA/PRB
To:
Littlejohn J (301) 415-0428
References
LER 1977-016-00
Download: ML20168A453 (4)

Text

October 7, 1977 Half-trip of SFRCS Causes RCS Pressure Rise at Davis-Besse 1 lure sequence was:

purious half-trip of the SFRCS occurred, which initiated closure of a dwater valve, resulting in loss of water to one steam generator.

reduction in heat removal resulted in operation of the pressurizer ief valve, which failed open after 9 open/close cycles.

operator manually tripped the reactor;, within six minutes the RCS was saturation pressure/temperature.

pressurizer level went to maximum.

roximately 25 minutes later the operator realized the relief valve was ck open and closed the block valve, terminating the transient.

ve action:

SFRCS was monitored to detect spurious signals.

ns were also being developed to add additional SFRCS alarm windows and l in alarm conditions.

issing PORV control circuit relay was installed.

urpose of failed system or component:

am generator isolation during a steam line break.

bility of system per WASH 1400:

• SFRCS - type systems were not considered in WASH-1400.

bility of component per WASH 1400:

• availabilitie are in units of per demand D-1 . Failure rates are in per hour HR-'.

No No No No Yes No No Yes No No No No Yes Yes SIC 130788 - Actual Occurrence for Spurious Half-Trip fo SFRCS Causes RCS Pressure Rise at Davis-Besse I

Secondary Injection and LPR/HPI Core Heat Removal tross-Connect Damage 1

2 3

4 5

6 7

NSIC 130788 - Sequence of Interest for Spurious Half-Trip of SFRCS Causes RCS Pressure Rise at Davis-Besse 1 failure requires operator error in failing to close PORV block valve.

SION NUMBER: 130788 R: October 7, 1977 ENT: September 24, 1977 OLVED: Pressure relief of RC system INVOLVED: Valve ose relay missing from relief valve control circuit (PORV failure).

F INTEREST: Stuck open PORV - small LOCA.

URRENCE: Spurious 1/2 trip of steam and feedwater rupture control system.

ME: Davis-Besse 1 BER: 50-346 PE: PWR CTRICAL RATING: 906 MWe E: 0.5 yr

&W ENGINEERS: Bechtel Toledo Edison Co.

21. mi3es eaat o~f Toledo, Ohio N/A ATING CONDITION: 9% power TURE TYPE OF FAILURE: (ýD inadequate performance; (b) failed to start; (c) made inoperable; (d)__________

METHOD: Operational error.

No cause found for the 1/2 trip valve stuck open because pilot valve stem failed.