ML18059A602

LER 93-013-00:on 930427,loss of Onsite Ac Power Occurred Due to Both EDGs Being Simultaneously Inoperable.Rev Will Be Submitted to Electrical Section of TS Which Will Emulate NUREG-1432, STS for C-E Plants.

ML18059A602
Person / Time
Site:	Palisades
Issue date:	12/23/1993
From:	Hillman C CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:
Shared Package
ML18059A600	List: ML18059A599 ML18059A602
References
RTR-NUREG-1432 LER-93-013, LER-93-13, NUDOCS 9401070041
Download: ML18059A602 (4)

Text

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• I 1181 SUBMISSION DATE 1161 I I I ABSTRACT On April 27, 1993, at 0428 hours0.00495 days <br />0.119 hours <br />7.07672e-4 weeks <br />1.62854e-4 months <br />, with the plant operating at 100% ~ower, diesel generator (DG) 1-1 was test started and loaded to approximately 500 Wprior to removing G 1-2 from service to gerform preventive maintenance. After ap~roximately 5 minutes of operation, the load on G 1-1 dropped to zero and DG 1-1 was dee ared inoperable. In accordance with our technical specifications, DG 1-2 was started and loaded to verify operability; however, by paralleling DG 1-2 to the electrical distribution grid to accept load, DG 1-2 was rendered inoperable for a period of five minutes, in accordance with our operating procedures. Therefore, both DGs were simultaneously inoperable, Technical Specification 3.0.3 (plant shutdown within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />) was entered, and an Unusual Event was declared in accordance with our emergency operating procedures.

The cause of this event was paralleling DG 1-2 to the e1ectrical distribution grid and rendering it inoperable while DG 1-1 was also inoperable. Paralleling DG 1-2 was determined to be necessary to verify there was no common mode failure and to ensure DG 1-2 operability.

Corrective action for this includes submitting a revision to the electrical section of our technical specifications which will emulate the NUREG 1432, "Standard Technical Specifications for CE Plants," electrical section.

9401070041 931223 PDR ADOCK 05000255 S PDR r

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NRC F.,..., 3HA U.S. NUCLEAR REGULATORY COMMISSION 19-831 APPROVED OMB NO. 3160-0104 EXPIRES: 8/31 /86 LICENSEE EVENT REPORT (LERI TEXT CONTINUATION FACILITY NAME 111 DOCKET NUMBER 121 LER NUMBER 131 PAGE 141 SEQUENTIAL REVISION YEAR NUMBER NUMBER Palisades Plant ol5lololol215ls el3 01 i 13 _ 0 I 0 0 I 2 OF 0 I 4 EVENT DESCRIPTION On April 27, 1993, at 0428 hours0.00495 days <br />0.119 hours <br />7.07672e-4 weeks <br />1.62854e-4 months <br />, with the plant operating at 100% power, diesel generator [EK] (DG) 1-1 was test started prior to removing DG 1-2 from service to perform prevent1ve maintenance as required by Palisades Technical Specification 3.7.2i.

Diesel generator 1-1 was successfully started and loaded to approximately SOOKW. After approximately 5 minutes of operation, the control room operator observed that the load on DG 1-1 was dropping from 500KW. The control room operator attempted to restore load but could not. The control room DG "raise limit" alarm actuated with zero KW on DG 1-1.

The control room operator then opened the DG 1-1 output breaker.

In accordance with Technical Specification 3.7.2i, with DG 1-1 inoperable, DG 1-2 must be started to verify operability and then shutdown, with the controls left in the automatic mode. Therefore, DG 1-2 was started as required. In addition, DG 1-2 was paralleled to the electrical distribution grid to verify the DG would accept and maintain an electrical load to assure that no common mode failure existed for the two diesel generators. This was considered necessary to assure operability as required by Technical Specification 3.7.2i.

By paralleling DG 1-2 to the Irid, DG 1-2 was rendered inoperable in accordance with our Standard Operating Procedure SOP) 22, "Emergency Diesel Generators." When a DG is paralleled to the grid, the D is incapable of performing its intended safety function.

Therefore, while DG 1-2 was in the parallel mode, both DGs were simultaneously inoperable. There is no action statement in the Palisades Technical Specifications for both diesel generators being simultaneously inoperable, therefore, the plant implemented the requirement of Technical Specification 3.0.3, and an Unusual Event (UE) was declared in accordance with Emergency Implementin~ Procedure (EI) 1, "Activation of the Site Emergency Plan/Emergency Classification. The UE was declared at 0428 hours0.00495 days <br />0.119 hours <br />7.07672e-4 weeks <br />1.62854e-4 months <br /> on April 27, 1993 because of the loss of on-site emergency AC power. The UE was terminated five minutes later at 0433 on when DG 1-2 was declared operable after it-was no longer paralleled to the electrical distribution grid. The plant also exited the Technical Specification 3.0.3 action requirement.

This event is reportable in accordance with 10CFR50.73(a)(2)(i)(B) as a condition prohibited by plant technical specifications in that both emergency diesel generators were simultaneously inoperable.

CAUSE OF THE EVENT The cause of this event was paralleling DG 1-2 to the electrical distribution grid and rendering it inoperable while DG 1-1 was also inoperable. Paralleling DG 1-2 was determined to be necessary to verify there was no common mode failure and to ensure* DG 1-2 operability.

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' (8-831 APPROVED OMB NO. 3160.0104 EXPIRES: 8/31 /B&

LICENSEE EVENT REPORT (LERI TEXT CONTINUATION

.I FACILITY NAME 111 DOCKET NUMBER 121 LER NUMBER 131 PAGE 141 SEQUENTIAL REVISION YEAR NUMBER NUMBER Palisades Plant 0 I5 I0 I0 I0 I2 I5 I5 I 9 I 3 I - I 0 I 1 I 3 I - I0 I 0 I 0 I 3 I I 0 I 4 OF ANALYSIS OF THE EVENT Palisades Standard Operating Procedure (SOP) 22, "Emergency Diesel Generators," provides direction to the operators concerning d1ese1 generator test startin~ and electrical loading. In that procedure, the operators are given options regard1ng the starting and loading of a diesel generator depending upon whether or not one of the DGs is inoperable. DG 1-1 had been successfully started to verify operability and was being electrically loaded when it failed. In accordance with the technical specifications and the procedure, the opposite DG (DG 1-2) was started to verify operability. Since DG 1-1 failed when it was accepting electrical load, the operators followed SOP 22, Step 4.1.lc, which requires that DG 1-2 be test started, paralleled to the electrical distribution grid, electrically loaded, and declared inoperable. In accordance with SOP 22, Step 4.1.lc.2, DG 1-2 was declared inoperable because it was paralleled to the grid.

Therefore, with DG 1-1 inoperable because it failed to maintain electrical load and DG 1-2 inoperable because it was paralleled to the electrical distribution grid, both diesel generators were simultaneously inoperable.

For this event, the operators could not confirm whether the inability of DG 1-1 to maintain load was a diesel generator problem or an electrical distribution system problem, therefore, simply starting DG 1-2 would not have verified its operability. In this instance, starting and loading of DG 1-2 was procedurally required to verify that a common mode failure did not exist.

Subsequent investigation as to the cause of the DG 1-1 failure determined that the fuel oil booster pump had experienced excessive wear. The.wear on the fuel oil booster pump caused reduced pumping capacity and air intrusion into the pump casing, resulting in starving DG 1-1 as it became loaded.

NUREG 1432, "Standard Technical Specifications for CE Plants," Section 3.8.1 discusses diesel generator LCOs. In the "Required Actions" .section, with one DG inoperable, the plant would have had 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to determine whether the second DG was inoperable because of a common mode failure. Therefore, had Palisades implemented standard technical specifications, we would have had 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to perform the common mode failure testing, would not have entered the Technical Specification 3.0.3 action statement, and would not have a reportable occurrence. In addition, the Standard Technical Specifications allow for the (simultaneous) inoperability of two DGs, with a required action to restore one DG to operable status within. 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />. Again, had we implemented standard technical specifications, we would have had 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> to restore the second DG to operable status, would not have entered the Technical Specification 3.0.3 action statement, and would not have a reportable occurrence.

Safety Significance The safety significance of this event is small because the operators were aware that DG 1-2 would be rendered inoperable by their actions, in accordance with SOP 22. The plant was in a stable, operating condition at the time of the event, and there were no unplanned activities in progress. DG 1-2 had been verified operable with no apP.arent common mode failure, therefore, DG 1-2 could have been restored to an "operable' status in accordance with SOP 22.

~ NRC Fcr.:m 381A U.S. NUCLEAR REGULATORY COMMISSION 19-83) APPROVED OMB NO. 31~104 EXPIRES: 8/31186 LICENSEE EVENT REPORT (LERI TEXT CONTINUATION

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F°'CIUTY NAA'E (1)

SEQUENTIAL REVISION YEAR NUMBER NUMBER Palisades Plarit 01 11 3 - o I o o 14 OF 0I 4 CORRECTIVE ACTION A corrective action for this event is to submit a rev1s1on to the electrical section of the Palisades Technical Specifications. One of the changes that will be included is a revision to the action statement(s) regarding diesel generator operability which emulates NUREG 1432, "Standard Technical Specifications for CE Plants," Section 3.8.1.

ADDITIONAL INFORMATION Licensee Event Report (LER) 93001 reported a similar occurrence of both diesel generators being simultaneous inoperable. The cause of the event reported in LER 93001 was personnel error and is not related to the event reported herein.