United States Nuclear Regulatory Commission - Protecting People and the Environment


ACCESSION #:  9708050112

                       LICENSEE EVENT REPORT (LER)



FACILITY NAME:  San Onofre Nuclear Generating Station Unit 2

                                                          PAGE: 1 OF 1



DOCKET NUMBER:  05000361



TITLE:  Charging Subsystem Check Valve Failure



EVENT DATE:  06/26/97   LER #:  97-010-00   REPORT DATE:  07/28/97



OTHER FACILITIES INVOLVED:  Unit 3                  DOCKET NO:  05000362



OPERATING MODE:  1   POWER LEVEL:  100



THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR

SECTION:

50.73(a)(2)(i)

50.73(a)(2)(vii)

Other:  Part 21



LICENSEE CONTACT FOR THIS LER:

NAME:  R. W. Krieger, Vice President, Nuclear Generation

                                            TELEPHONE:  (714) 368-6255



COMPONENT FAILURE DESCRIPTION:

CAUSE:  B   SYSTEM:  CV   COMPONENT:  V    MANUFACTURER:  K085

REPORTABLE NPRDS:



SUPPLEMENTAL REPORT EXPECTED:  YES  EXPECTED SUBMISSION DATE: 08/11/97



ABSTRACT:



On 6/26/97 while Unit 3 was shutdown for refueling, Edison found a check

valve in the Charging Subsystem that would not open completely.  This

would cause the charging flow distribution to the Reactor Coolant System

to be different than that assumed in the safety analysis.  Because of the

similarity of the Unit 2 Charging Subsystem, Edison immediately entered

the Technical Specification action statement.  As a conservative action,

Edison also reduced Unit 2's power to about 90 percent, where charging

flow is not required for accident mitigation.  On 6/28/97, Edison tested

Unit 2 and found that a similar check valve also would not open

completely.  As required by the Technical Specifications, Edison shutdown

Unit 2 to repair the valve.  Completion of that shutdown is being

reported as required by 10CFR50.73(a)(2)(i).  Edison believes this valve

failure was caused by a design defect and is including 10CFR21

information in this report.



Edison replaced the faulty design valves in the charging injection lines

and auxiliary spray line in each unit with another type valve.  Edison's

evaluation of the cause(s) is on-going.  This LER will be revised.



Using an EPRI analysis program and actual, allowed, plant parameters,

Edison concluded that the condition resulted in a negligible increase in

plant risk and had no actual safety significance.



END OF ABSTRACT



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