05000298/LER-1993-030

LER 93-030-00:on 930708,discovered Inadequate Inservice Testing of Svc Water Sys Check Valves Due to Flow Instrument Calibr Error & Personnel Error in Specifying Sys Flow Requirement.Revised Calibr Factor developed.W/930809 Ltr

ML20056D418
Person / Time
Site:	Cooper
Issue date:	08/09/1993
From:	Gardner R, Reeves D NEBRASKA PUBLIC POWER DISTRICT
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
CNSS933204, LER-93-030, LER-93-30, NUDOCS 9308160098
Download: ML20056D418 (4)

LER-2093-030,

Event date:
Report date:
2982093030R00 - NRC Website

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COOPER NUCLEAR ST ATioN m.

Nebraska Public Power District "" "" "d" *o"MMis"i"T" "'"

i CNSS933204 ,

August 9, 1993 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555

Dear Sir:

Cooper Nuclear Station Licensee Event Report 93-030, Revision 0, is forwarded as  :

I an attachment to this letter.

Sincerely, R. L. Gardner Plant Manager r

RLG/j u  !

Attachment  !

cc: J. L. Milhoan  ;

G. R. Horn  ;

J. M. Meacham R. E. Wilbur V. L. Wolstenholm  !

D. A.' Whitman INPO Records Center NRC Resident Inspector R. J. Singer CNS Training CNS Quality Assurance 130044  !

r I f 9308160098 930909 'N PDR ADOCK 05000299 r3 .

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APPROVED OMS NO. MeiOO104 I LICENSEE EVENT REPORT (LER) N'at *: "'" lt f

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Inadeauate In-Service Testing Of Service Water System Check Valves Due To Flow Instrument Calibration Error And Personnel Error In Specifying. System Flow Requirement EVENT DATE (El LER NUMBER EG) REPORT DATE (73 OTHf R f AC8UTIES INVOLVED (8)

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On July 8,1993, as a result of determining that the conversion of Service Water .

(SW) Flow Rate measured by an annubar flow monitoring device was incorrect, it was (

discovered that In-Service Testing (IST) of the SW Pump discharge check valves had not been performed in accordance with the requirements of Generic Letter (GL) 89-04.

In accordance with the GL requirement, verification that a check valve has stroked >

to its full open position requires the maximum accident condition flow rate be -

established through the valve. However, due to the flow instrument calibration ,

error, actual SW System flow was less than indicated by approximately eight and one-  ;

half percent. Additionally, the surveillance procedure used to verify SW Pump  :

discharge check valve operability on a quarterly basis did not require that the ,

maximum accident condition flow rate be established. At the time this condition was  !

discovered, required surveillance testing in preparation for startup from the 1993 Refueling Outage was being performed.

'i The cause of the IST test deficiency was due to the flow instrument calibration-error, an original design deficiency, and failure to recognize that the flow rate specified in the surveillance procedure for verifying operability of.the check ,

valves was not the maximum accident condition flow rate required by GL 89-04.  !

A revised calibration factor was developed and incorporated in the surveillance test  !

procedure, Additionally, the procedure was revised to establish the correct SW I System flow for the test and to correctly state the test acceptance criteria. l Assurance of SW System check valve operability was verified prior to startup from '

the 1993 Refueling Outage. ,i t

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0 l0 0l2 or 0l3 A. Event Description On July 1,1993, it was determined that the conversion of Service Water (SW) Flow Rate measured by an annubar flow monitoring device was incorrect. This discrepancy was evaluated for its impact on SW System operability. A calculation based upon the results of the A SW Subsystem surveillance test conducted on June 23, concluded that both Subsystems remained operable. A subsequent evaluation on July 8 determined that previous In-Service Testing (IST) of the SW Pump discharge check valves had not been performed in accordance with the requirements of Generic Letter (GL) 89-04, Guidance on Developing Acceptable Inservice Testing Programs. As specified in the GL, verification that a check valve has stroked to its full open position requires the flow rate through the valve to be the maximum required accident condition flow rate. However, due to the flow instrument calibration error, actual SW flow was less than indicated by nearly eight and one-half percent. Additionally, the surveillance procedure used to verify SW Pump discharge check valve operability on a quarterly basic required that a SW System flow rate of 6000 gpm be established, as opposed to the required maximum required accident condition flow rate of 6243 gpm, a difference of approximately four percent.

B. Plant Status Performing required surveillance testing in preparation for startup from the 1993 Refueling Outage.

C. Basis for Report Failure to perform quarterly SW check valve IST in accordance with ASME requirements, reportable in accordance with 10CFR50.73(a)(2)(1)(B) as a condition prohibited by Technical Specifications.

D. Cause Design and Personnel. The K factor associated with the conversion of annubar d/p to gpm was not correctly specified by the manufacturer when procured for installation in the system during original construction.

Additionally, Engineering personnel responsible for the IST Program did not recognize that the flow rate specified in the surveillance procedure for verifying operability of the check valves was not the maximum required accident condition flow rate required by Generic Letter 89-04.

E. Safety Sinnificance once per refueling cycle, the SW System is tested at a flow rate in excess of 6250 gpm during the post LOCA flow test, with the secondary result of assuring operability of the check valves. While the actual flow rate was less than indicated by approximately ten percent during tests conducted prior to this refueling outage, the flow rate obtained during past post-LOCA flow tests has been adequate to assure check valve NRC FO8EM 366A *U.S. LPOs 1996 520-589 00010

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G. Safety Sinnificance (continued) t operability in accordance with the GL requirement. Further, since' 't publication of Generic Letter 89-04, each check valve has been disassembled and inspected or replaced at an approximate 24 month -

interval. The combination of surveillance testing and periodic ,

inspections have assured operability of the valves.

F. Safety Implications i

To verify satisfactory operation of safety-related equipment, assurance of check valve operability such that SW flow is not restricted is most critical with the plant at rated power. ,

G. Corrective Action A revised calibration factor was developed and incorporated in the ,

surveillance test procedure. Additionally, the procedure was revised to establish the correct SW System flow for the test and to correctly l state the test acceptance criteria. Assurance of check valve- .

operability was obtained during testing of the B SW Subsystem with the revised procedure on July 8, 1993. Operability of the A SW Subsystem ,

check valves was verified based on performance of the A SW Subsystem ,

post LOCA flow test on June 23, 1993. '

The SW System is unique in that the specification of flow requirements l in the USAR includes an adjustment to ensure required- flow will be 'i obtained at low river levels. This condition is unique for' systems  !

contained in the IST Program. For this reason, this is considered.to be .!

an isolated occurrence. 1; t

Correction of the SW System annubar flow monitor K factor completed action taken in response to LEPs93-015 associated with_a similar flow. 4 instrument deficiency in the High Pressure Coolant Injection System, All safety-related flow instruments are considered to be fully operable.

H ., Similar Events l

93-015 High Pressure Coolant Injection System Design Discrepancy _ l Resulting In A Nonconservative Difference Between Actual And j Indicated Flow  ;

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