ML20054G192

Ro:On 820507,during Operational Mode 5,shutdown Cooling Sys Relief Valve Opened to Mitigate RCS Pressure Transient. Caused by Manual Stopping of Low Pressure Safety Injection Pump.Operating Procedures Will Be Amended

ML20054G192
Person / Time
Site:	San Onofre
Issue date:	06/07/1982
From:	Ray H SOUTHERN CALIFORNIA EDISON CO.
To:	Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
References
NUDOCS 8206210236
Download: ML20054G192 (2)

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• P .O. B O X 128 S AN C L EMEN TE, C ALIFORNI A 92672 [w' C'o C, s' l June 7' 193*2 H.B. RAY TELEPHONE ST Af TON M AN AGg e (714) 492 F 700 V. 5. Nuclear Regulatory Commission Of fice of inspection and Enforcement Regior. V 1450 Maria Lane, Suite 210 L inu:. Craek, Cali fornia 94596 - 53C3 Attentian: Mr. R. H. Engelken, Regional Administra*.or Don Sir

Subject:

Docket No. 50-101 Special Re;, ort

$an Cno#re Nuclear Generating Station, Unit 2 Thi s subrdttii censt:tutes a Special Report in accorcance with lechnicai So ::fintion 6.0.2 of Appendix A to Operating License NPF-10 for

$1n Onc f re Sx iea 'isnerning S tetion Uni t 2. Action Statement c to Technical

%eci'icatien 3.4.3.2 1 -equires that such a Scecial Report be orecared v.ithin f nys in ;ne event that either :.ne Shutdown Cooling System (5DCS) Relief hive a- a ' actor "calant System (RCS) vent is used to mitigate an RCS pressuce trassiunt.

On May '7 1962 with San Oncfra Unit 2 in Ocerational Mode 5, the SDCS relief valve apared .o mit gate an RCS pressure transient.

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At tnn t i r. e o f t he e'. e n t the RCS .as solid, with no bubble in the pressurizer RC5 temperature ar.a pressure were 112 F and 350 osia. The SDCS aas in operat:cn utleicing one Lrw W-essure Sar.etv injection (LP -) . .

di pump and one Shutnn Cociinc; He n ;_ycnanger. Normal charg ug was in procress and letemn a.s a::nol: shed oy dive-ti .g apprc .: irate!j 26 go of LPS: discnarge into tne ietcown lire n 450 sia Tne RC3 pres:cre u s controlled by autor;ti; onernion of :.he - u pre sur_ regulating valve (EPVC2012). In this me:2 c' epera.icn t N tu :L p nsuri, m .uiator valve had oeen re-set to

-rd ' 1a. t.ra : ne as .ne _rd. curn c.scharge ore sure.

B206210236 820607 PDR ADOCK 05000361 S PDR

e Mr. R. H. Engelken June 7, 1982 The circumstance initiating the pressure transient was the manual stopping of the LPSI pump in order to align the second SOCS heat exchanger for service.

This action instantly reduced the letdown flow pressure to the RCS pressure of 350 psia. The back pressure regulator was still set at 450 psia; therefore, charging began to increase the RCS pressure rapidly. The shift operators promptly switched the back pressure regulator to manual and began opening this valve in an attempt to suppress the pressure transient. This action lowered the RCS pressure to 350 psia in about six minutes, but not before a pressure spike had occurred. By all indications, this spike exceeded the 406 psia setpoint on SDCS pressure relief valve (2PSV9349). The Plant computer trend recording of Pressurizer pressure indicated a momentary pressure spike of no greater than 460 psia, which was below the RCS pressure temperature limits of Technical Specification 3.4.8.1. Examination of the containment sump revealed approximately 30 gallons of water, indicating that the SOCS relief valve mitigated the pressure transient by lifting for about 40 seconds. This deduction correlates with the pressurizer pressure and letdown flow readings recorded every 30 seconds by the plant computer.

Corrective action to prevent recurrence is to amend operating procedures by requiring that the back pressure regulating valve be in the manual control mode whenever starting or stopping SI or charging pumps while the RCS is solid. Caution statements will also be added to the procedures requiring that the RCS pressure be closely monitored under these circumstances.

If there are any questions regarding the above or the attached, please contact me.

Sincerely, I <

cc: U.S. Nuclear Regulatory Commission Office of Inspection and Enforcement U. S. Nuclear Regulatory Commission Office of Management Information & Program Control (MIPC)

Institute of Nuclear Power Operations (INPO)

A. E. Chaffee (USNRC Resident Inspector San Onofre Unit 2)