05000352/LER-1996-019, :on 961026,capability to Reject Electrical Load of RHR Pump Not Fully Verified.Caused by Inadequate Test Procedure.Tests Will Be Revised Prior to Next Performance & TS Change Request Is Being Pursued

:on 961026,capability to Reject Electrical Load of RHR Pump Not Fully Verified.Caused by Inadequate Test Procedure.Tests Will Be Revised Prior to Next Performance & TS Change Request Is Being Pursued

ML20134L394
Person / Time
Site:	Limerick
Issue date:	11/11/1996
From:	Kananter J PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:
Shared Package
ML20134L388	List: 05000352/LER-1996-019, :on 961026,capability to Reject Electrical Load of RHR Pump Not Fully Verified.Caused by Inadequate Test Procedure.Tests Will Be Revised Prior to Next Performance & TS Change Request Is Being Pursued
References
LER-96-019, LER-96-19, NUDOCS 9611200305
Download: ML20134L394 (4)

LER-1996-019, on 961026,capability to Reject Electrical Load of RHR Pump Not Fully Verified.Caused by Inadequate Test Procedure.Tests Will Be Revised Prior to Next Performance & TS Change Request Is Being Pursued

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv), System Actuation 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability
3521996019R00 - NRC Website

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NRC F0nM.26 U.S. NUCLEAR RfGULATORY COMMISSION APPROVED BY OMB NO. 3150 0104 (5 92)

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AND TO TH ER OC2050h MANAGEMENT AND BUDGET WASHING 0$000352 1 Oi 4 Li rick Generatine Station. Unit 1 TITLE (4) capability to reject the electrical load of an RilR pump not fully verified Ev'.

DATE (5)

LER NUMBER (6)

REPORT DATE (7)

OTHER FACILITIES INVOLVED (8)

SEQUENTIAL REVISION MONTH DAY YEAR YEAR MONTH DAY YEAR NUMBER NUMBER Limerick, Unit 2 05000353 FACILITV NAME DOCKET NUPEER

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MODE (9) 1 25.402tD) 20.405(c) 50.73(a)(2)(iv) 73.71(c) 23.405(alli)(1) 50.36(c)(1) 50.13(all2)(v) 13.llic)

PMR LEVEL (10) 100 iU.405ta)(1)(ii) 50.36(c)(2)

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NRC Fonn 266A) i LICENSEE CONTACT FOR THIS LER (12)

NAME TELEFn0NE NUMBER tinciuce Area t.cce)

James L. Kananter, Manager, Experience Assessment, Lcs (610) 718-3400 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

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CAUSE

SYSTEM COMPONENT MANUFACTURER

CAUSE

SYSTEM COMPONENT MANUFACTURER 0

SUPPLEMENTAL REPORT EXPECTED (14)

EXPECTED MUNTH DAY YEAR SUBMISSION YES X

NO (if yes, ccmolete EXPECTED SUBMISSION DATE).

DATE (15)

ABSTRACT tumit to 1400 5; aces, i.e.

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On 10/10/96, an engineering evaluation concluded that the previously established surveillance testing for the Emergency Diesel Generators (EDGs) may not have fully verified the capability to successfully reject an electrical load of equal to or greater than the specified electricalload of a Residual Heat Removal (RHR) pump motor (992 kW) as required by Technical Specifications (TS). This resulted in operation prohibited by TS and in a condition where at least two independent trains of a single safety system being inoperable due to a common cause. The testing procedures did reject the electricalload of an RHR pump motor while the RHR pump was operating at the designed post-accident flow rate. However, the actual electrical load was less than the TS value of 992 kW. By 10/11/96, an engineering evaluation was performed or the EDG was tested to verify the capability of each EDG to reject a load of 992 kW. Analysis of previous test results has concluded that the EDGs were capable of rejecting the specified electricalload of the RHR pump motor while maintaining the 4kV cafeguard bus within the TS limits for voltage and frequency. The cause of the event was an inadequate test procedure. As originally written, the test did not incorporate data from the pump / motor curves to ensure at least 992 kW of electrical load was actually rejected during the test. The tests will be revised prior to the next performance and a TS change request is being pursued.

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Unit Conditions Prior to the Event:

Unit 1 and Unit 2 were both in Operational Condition 1 (Power Operation) at 100% power level at the time of the discovery of this issue. There were no systems, structures or components inoperable or out of service that contributed to the event.

Description of the Event:

1 On October 10,1996, an engineering evaluation concluded that the previously established surveillance testing for the Emergency Diesel Generators (EDGs, Ells:DG) may not have fully verified the capability to successfully reject an electrical load of equal to or greater than the specified electrical load of a Residual Heat Removal pump motor (992 kW). The RHR pump motor is the single largest post accident electrical load on the 4kV safeguard bus.

Technical Specifications (TS) Surveillance Requirement (SR) 4.8.1.1.2.e.2 establishes this requirement along with limits for the specified voltage and frequency fluctuations immediately following the trip of the RHR pump motor. These tests are performed on each EDG and the associated safeguard bus and loads while the unit is shutdown and while the electrical bus is disconnected from the offsite electrical power source.

The testing procedures did reject the electrical load of an RHR pump motor while the RHR pump was operating at the designed post-accident flow rate of 10,000 gpm (approximately 940 to 992 kW). However, due to the characteristic of the pump / motor curves, the specified electrical load occurs at a flow rate between 7,000 and 9,000 gpm depending on the RHR pump. Therefore, the minimum prescribed electrical load of 992 kW was not always rejected during the testing. Additionally, for those tests that rejected less than 992 kW, an analysis using the actual test data was not performed to conclude whether the EDG would have been capable of rejecting the 992 kW while maintaining the voltage and frequency within the required limits. Since these tests were originally written to establish a RHR pump flow rate of 10,000 gpm, the TS SR was not always met for each EDG since original fuelload of Unit 1 and Unit 2. (i.e., October 26,1984, and June 22,1989, respectively).M

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05000 3 0F 4 Limerick cenerating Station, Unit 1 352 96 019 --

00 TEXT Ut more space us requireo, use acartionai copres at MC f ann sooA) (11) i Since this issue was not discovered until October 10,1996, the TS actions for each l

inoperable EDG were not previously taken within the specified TS Action limits resulting in operation prohibited by TS. Additionally, this condition resulted in at least two independent j

trains of a single safety system being administratively inoperable due to a common cause.

Therefore, this report is being submitted in accordance with the requirements of 10CFR50.73(a)(2)(i)(B) and 10CFR50.73(a)(2)(vii).

On October 10,1996, an engineering evaluation was performed using the most recent test i

results. Two (2) of the EDGs had been tested with a rejected load of greater than or equal to l

992 kW and were in surveillance. The evaluation further verified five (5) of the remaining six i

(6) EDGs were capable of rejecting a load of equal to or greater than 992 kW with voltage j

and frequency fluctuations within the TS limits. The test data for the eighth EDG was not i

immediately available and this EDG was successfully tested on October 11,1996.

i Analysis:

The consequences of this event were minimal in that no radioactive material was released, an accident did not occur, and the EDGs were not called upon to perform their design function. Analysis of previous test results has concluded that the EDGs were capable of j

rejecting the specified electrical load of the RHR pump motor (992 kW) while maintaining the i

4ky safeguard bus within the TS limits for voltage and frequency. Therefore, the EDGs were i

fully capable of performing their design function even though the analysis was not performed within the specified TS SR interval and TS ACTION limits.

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.Qause of the Event:

The cause of the event was an inadequate test procedure. As originally written to meet the TS, the procedure established a pre-test condition with the RHR pump operating at 10,000 gpm based on the assumption that this flow rate produced the specified electrical load for the j

motor and that 10,000 gpm represented the design basis flow for the RHR system. The tests did not incorporate the data from the pump / motor curves to ensure at least 992 kW of j

electrical load was actually rejected during the test.

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YEAR SEQUENTIAL REVISION 05000 4OF4 Limerick cenerating Station, Unit 1 352 96 019 --

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Corrective Actions

The test procedures will be revised prior to the next performance. The revisions will ensure 992 kW or more electrical load is rejected during the tests or that an analysis is performed that uses the test data to ensure that each EDG has the capability to successfully reject 992 kW.

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A TS change request is being pursued to revise the TS SR that will remove the "992 kW" text and establish a requirement to verify the capability to reject an electrical load of equal to or j

greater than the single largest post accident electrical load.

Previous Similar Occurrences:

None i

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