ML18058A415

LER 92-028-00:on 920331,results of Analysis of EDG Room Cooling Requirements Identified Potential Inability to Maintain DG Room Temp within Design Temp.Caused by non-1E Qualified Cooling Fan.Procedures revised.W/920430 Ltr

ML18058A415
Person / Time
Site:	Palisades
Issue date:	04/30/1992
From:	Roberts W, Slade G CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-92-028, LER-92-28, NUDOCS 9205070142
Download: ML18058A415 (5)

Text

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"' consumers Power* GB Slade General Manager POWERINli

. lllllCHlliAN'S i'llOliRESS Pali.sades Nuclear Plant: 27780 Blue Star Memorial Highway, Covert, Ml 49043 ..

April 30, 1992 .

Nuclear Regulatory Commission Docu~ent Control Desk Was~~ngton, DC 20555 DOCKET 50-255 - LICENSE DPR~20 - PALISADES PLANT -

LICENSEE EVENT REPORT 92-028 POTENTIAL INABILITY TO MAINTAIN DIESEL GENERATOR ROOM TEMPERATU~E QUALIFICATION DUE TO NON IE QUALIFIED COOLING FAN ~

Licensee Event Report (LER) 028 is attached. This event is reportable in accordance with 10 CFR 50.73(a)(2J(ii) as a condition outside th~ design basis of the plant .

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Gerald B Slade General Manager CC _Administrator, Region 111, USNRC NRC Resid~~~:Inspector ~ Palisades Attachment

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• On March 31, 1992, at approximately 1100 hours0.0127 days <br />0.306 hours <br />0.00182 weeks <br />4.1855e-4 months <br />, th~ pl~nt was in cold shutdown preparing to start u~ from a refueling outage. Results of analysis of the

~mergency diesel generator rooms cooling requirements and installed s*fety reJated cooling capability revealed that the existing cooling capability was not adequate to mainta1n the room temperature within the required design temperatures. Analysis results indicate that the existing configuration of having only 1 of the *2 emergency diesel generator room coolihg fans powered

, from i tlass IE source is not adequate to maintain the emergency diesel generator roorri tempEfrature below the design limit of 104°F, with a design outdoor temp~ratur~ of 95°F. **The analysis r~sults also showed that with one

. cooling fan in opefation, the room temperature could be maintained below the design limit only if the outdoor temperature does not e~ceed 75°F.,

Proc~d~res have been*revised to allow for re-energizing the non-safety rel~ted electrical bus that powers the second fan when the outdoor temperature exceeds 75°F. This condition was caused by an original design and construction error.

The rooms were designed to be cooled.by 2 safety related fans however, only one fan in each room is powered from a safety related power source.

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EVENT DESCRIPTION On March 31, 1992, at approximately 1100 hour0.0127 days <br />0.306 hours <br />0.00182 weeks <br />4.1855e-4 months <br />s~ the pl.ant .was in cold shutdown preparing to start up from a refueling outage. Results of analysis of the emergency diesel generator rooms cooling requirements and installed safety related cooling* capability revealed that the existing cooling capability was

• not adequate to maintain the room temperature within the required design temperatures. Analysis results indicate that the existing tonfiguration of having only I of the 2 emergency diesel generator room cooling fans [EK~FAN]

powered from a class IE source is not adequate to maintain the emergency diesel generator room temperature below the desigh limit of 104°F, with a d~sign outdoor temperature -0f 95~F. The analysis results also showed that with one cooling fan in operation, the room temperature.could be maintained below the design limit only if the outdoor temperature does not exceed 75°F.

• To permit plant operation at outside temperatures greater than 75°F; actions were taken such that power would be supplied to the second fan in each room when needed. System Operating* Piocedure (SOP) 22, ."Emergency Diesel Gerieratdrs", was revised to require that the-electrical bus that powers the non-safety room cooling fan be re-powered from the emergency diesel generator needing the cooling, within 30 to 40 minutes after the generator i~ started, if the outside air tefuperature is greater theri 75°F. This action is deemed as an interim action until a permanent class IE power source can be supplied to the second room cooling fan. The analysis also showed that under exi~ting

• plant conditions, the two cooling fans.would only be able to cool the room to a temperature of ll0°F verses the 104°F design temperature. The temperature

• rating of the limiting equipment in the rooms will be revised to allow operation of the equipment in a higher temperature environment.

This event is reportable in accordance with 10 CFR 50.73(a)(2)(ii) as a coridition outside *of the design basis of the plant.

CAUSE OF THE EVENT The root cause of the event was the inadequate implementation of the original emergency diesel generator room cooHng design. The original design fan sizing calcul~tions show that the original design intent was to have both of th~ room fans in operation to maintain.the diesel generators operable.

This event did not involve the failure of any equipment important to safety.

ANALYSIS OF THE EVENT.

In 1991 as part of the on-going Palisades Configuration Control Project a.

number of apparent discrepancies in circuit routing were id~ntified. The power ahd control circ~its, for one of the safety related emergency diesel gener~tor cooling fans, were two of the circuit~ determined to be misrouted.

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,..,. ,. ,.,.._ *.__--.Alie ........" 1171 Because of these two drcuit deficiencies a special Pi ant Review Coinmittee (PRC) meeting (91-030) was convened to address *the operability of the associated emergency diesel generator (_1-1). The committee found that actions were needed to provide alternate cooling for the (1-1) diesel generator .. These

• actions were established and remained in place until the fans cables could be rerouted to resolve the deficiency~ Jhe fan cables were rero~ted on Ottober 19, '1992. . .

Prior to this time, as part of an Appendix R safe shutdown analysis, an analysis had:been completed to assess the ability to cool the diesel generator room by natural convection rather than by forced convection.This analysis

• co~cluded that operiing the doors and blocki~g open the v~ntilation louvers would pro~ide adequate cool in~ to maintain the diesel generator ope~able. As a follow-up and as part~f lhe* corrective actions for the identified cable.*

routing discrepancies, an eval uat i o_n for the operability requirements for the diesel generator ventilatibn w~s assigned. *

• As a result, the System Engineering Department performed a preliminary analysi~ which concluded that natural circulation may not be sufficient to cool an operating diesel generator, and.when outside temperatures reach near the design limit, two room cooling fans may be needed. This issue was addressed at the regul~r PRC (92-038} meeting in October of 1991. The PRC concluded that based on a Plant Safety Engineering analysis that the diesel g~nerators were operable, but that an unreviewed safety q~estion may exist in

. that we wer~ outside the design basis of the.plant. At this time we did not have the knowledge th.at the original design had called for both room cooling fans to cool the .r.oom under maximum design* conditions: This was discovered*

when we requested the plant architect engineer to complete a formtl room HVAC analysis. Therefore, we believed that the original design was as the plant was configured, that is with one room cooling fan powered from a lf power source .

. As* a follow-up to the. PRC meeting the operability of the emergency diesel generator was discussed with the Palisades Senior Resident Inspector and the

• Region HI Reactor Projects Section Chief for Palisades. It was agreed that there was no imme'diate operability concern and a license amendment need not be pursued ~nless we p~6posed to perman~ntly accept the condition.

The plant architectural engineer was ask~d to perform a formal analysis ~f the emergency diesel generator room cooling requirements.* The results of their arialysis showed that both room cooling fans would be required to maintain the required room coqling above an outdoor temperature of 75°F .and that design limit of 104°F cannot be maintained with an outdoor temperature above approximately 88°F, even with both fans operating. Diesel generator operability will be assured for outdoor temperat~res above 75°F by ptocedural controls which require the operators to re-energizing the bus which feeds the non-IE powered fans. This procedural re-powering action will be in place until a modification can be completed to power the fans from a lE source:

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OOCKIT "'-I* IJI Palisades Plant 4 TDT ,, _ _ _ . _ . _ _ . . ,._..,..11,*171 05000 255 92-028 In addition, by the time the outdoor temperature exceeds 88°F, it is our intent to assure that the diesel gener*tor ca~ operate in an environment six degrees higher than was originally called for in the Palisades design ..

We are examining the vendor ambient temperature limitations for critical operational components on the emergency diesel generators and.have found that NEMA rated components are the limiting componentS. The NEMA standards provide for temperature rating of components at an ambient temperature of 104°F. The standard also provides guidelines for. operation of components at highef ambient temperatures. We believe that based on the small temperature difference between the rooms original desig~ rating and that which is now calculated (6°F), that we will have no problem adjusting the rating of the necessary components to meet "the 110° F limit ..

. CORRECTIVE ACTION Activities to improv~ tempe~at~re qualification of necessary equipment in the emergency diesel generator rooms to approximately 115°F will be completed by June 1, 1992. *

• A modification wii'l be implemented by September 30, 1992, which will power all emergency diesel generator room ventilation fans from cla~s lE power sources.

ADDITIONAL INFORMATION Recently submitted licensee event reports which also dealt with the subject of bperabil ity of the emergency diesel generator room cooling fans was LER 9.1-014.

• This emerg.ency diesel generator room cooling condition is an open item in NRC Inspection Report 91:01~, item 23. *