ML17289B169

LER 93-001-00:on 930113,determined That Both Trains of Suppression Pool Cooling of RHR Sys Inoperable on 900806 Due to Design Deficiency of RHR Sys.Plant Procedure PPM 2.4.2, RHR Will Be Changed by 930301.W/930212 Ltr

ML17289B169
Person / Time
Site:	Columbia
Issue date:	02/12/1993
From:	John Baker, Fuller R WASHINGTON PUBLIC POWER SUPPLY SYSTEM
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-93-001, LER-93-1, NRC-292-1243, NUDOCS 9302220184
Download: ML17289B169 (9)

Text

ACCEI ERAT]iK) DOCUMENT DISTRIBUTION SYSTEM REGULAT~ INFORMATION DISTRIBUTION~ZSTEM (RIDS) i'ACCESSION NBR:9302220184 DOC.DATE: 93/02/12 NOTARIZED: NO DOCKET FACIL:50-397 WPPSS Nuclear Project, Unit 2, Washington Public Powe 05000397 AUTH. NAME AUTHOR AFFILIATION FULLER,R.E. Washington Public Power Supply System BAKER,J.W. Washington Public Power Supply System RECIP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER 93-001-00:on 930113,determined that both trains of suppression pool cooling of RHR sys inoperable on 900806 due to design deficiency of RHR sys.Plant Procedure PPM 2.4.2, RHR will be changed by 930301.W/undated ltr.

7 DISTRIBUTION CODE: IE22T COPIES RECEIVED:LTR ENCL SIZE:

TITLE: 50.73/50.9 Licensee Event Report (LER), Incident Rpt, etc.

NOTES:

RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD5 LA 1 1 PD5 PD 1 1 CLIFFORD,J 1 1 INTERNAL: ACNW 2 2 ACRS 2 2 AEOD/DOA 1 1 AEOD/DSP/TPAB 1 1 AEOD/ROAB/DSP 2 2 NRR/DET/EMEB 7E 1 1 NRR/DLPQ/LHFB10 1 1 NRR/DLPQ/LPEB10 1 1 NRR/DOEA/OEAB 1 1 NRR/DREP/PRPB11 2 2 NRR/DST/SELB 8D 1 1 NRR/DST/SICB8H3 1 1 N~

REG FILE SPLB8Dl 02 1

1 1

1 NRR/DST/SRXB 8E RES/DSIR/EIB 1

1 1

1 N ZLE 01 1 1 EXTERNAL: EG&G BRYCEiJ.H 2 2 L ST LOBBY WARD 1 1 NRC PDR 1 1 NSIC MURPHYgG.A 1 1 NSIC POOREgW. 1 1 NUDOCS FULL TXT 1 1 NOTE TO ALL"RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WASTETH CONTACT THE DOCUMENT CONTROL DESK, ROOM Pl-37 (EXT. 504-2065) TO ELIMINATEYOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED)

FULL TEXT CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUIRED: LTTR 31 ENCL 31

WASHINGTON PUBLIC POWER SUPPLY SYSTEM P.O. Box 968 ~ 3000 George Washington Way ~ Richland, Washington 99352 Docket No. 50-397 Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555

SUBJECT:

NUCLEAR PLANT WNP-2, OPERATING LICENSE NPF-21 LICENSEE EV1i2llT REPORT NO.93-001 Transmitted herewith is Licensee Event Report No.93-001 for the WNP-2 Plant. This report is submitted in response to the report requirements of 10CFR50.73 and discusses the items of reportability, corrective action taken, and action taken to preclude recurrence.

Sincerely, J. W. Baker WNP-2 Plant Manager (Mail Drop 927M)

JWB/REF/my Enclosure CC: Mr. J. B. Martin, NRC - Region V Mr. R. Barr, NRC Resident Inspector (Mail Drop 901A, 2 Copies)

INPO Records Center - Atlanta, GA Mr. D. L. Williams, BPA (Mail Drop 399) 9302220184 9302i2 PDR ADOCK 05000382 S PDR

LICENSEE EVEAEPORT (LER)

ACILITY NAME (1) DOCKET NUMB R ( ) PAGE (3)

Washin ton Nuclear Plant - Unit 2 0 5 0 0 0 3 9 7 I OF ITLE (4)

INOPERABLE SUPPRESSION POOL COOLING DUE TO POTENTIAL WATERHAMMER EVENT DATE 5) LER NUMBER 6 REPORT DATE 7 OTHER FACILITIES INVOLVED (6)

HONTM OAY YEAR YEAR SEQUENTIAL E VISION HOHTM DAY YEAR FACILITY NAMES CKET NUMB RS (s)

NUMBER UMBER 0 5 0 0 0 0 1 1 3 9 3 9 3 0 0 1 0 0 0 2 I 2 9 3 050 00 PERATING HIS REPORT IS SUBHITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR (IT (Check one or more of the follow!ng) (11)

ODE (9) 1 ONER LEVEL 0.402(b) 0.405(C) 0.73(a)(2)(iv) 77.71(b)

(10) 0.405(a)(1)(i) 0.36(c)(l) X 0.73(a)(2)(v) 73.73(c) 0.405(a)(1)(ii) 0.36(c)(2) 0.73(a)(2)(vii) THER (Specify in Abstract 20.405(a)(1)(iii) X 50.73(a)(2)(i) 0.73(a)(2)(viii)(A) elow and in Text, NRC 20.405(a)(1)(iv) 50.73(a)(2)(ii) 50.73(a)(2)(viii)(B) orm 366A) 20.405(a)(l)(v) 50.73(a)(2)(iii) 50.73(a)(2)(x)

LICENSEE CONTACT FOR THIS LER (12 TELEPHONE NUHBER REA CODE R. E. Fuller, Licensing Engineer -

5 0 9 7 7 4 1 4 8 COMPLETE ONE LIHE FOR EACH COMPONENT FAILURE DESCRIBED IH THIS REPORT (13)

CAUSE SYSTEM COMPOHEHT MANUFACTURER EPORTABLE CAUSE SYSTEH COMPONEHT MANUFACTURER EPORTABLE 0 NPRDS TO NPRDS SUPPLEMEHTAL REPORT EXPECTED (14) XPECTED SUSHI SSIOH MONTH DAY YEAR ATE (15)

YES (If yes, coIIpiete EXPECTED SUBMISSION DATE) HO TRACT (I el On January 13, 1993, a Licensing Engineer determined that both trains of Suppression Pool Cooling (SPC) of the Residual Heat Removal (RHR) System (RHR "A" AND "B") were inoperable on August 6, 1990. This represented a condition that could have prevented the RHR System from performing its SPC, Suppression Pool Spray (SPS), and Drywell Spray (DWS) safety functions. On December 22, 1992, engineering evaluations concluded that water hammer could fail the train of RHR in SPC due to a Loss of Power (LOP) coincident with a Loss of Coolant Accident (LOCA). Further review revealed that both trains were again operated concurrently: 'once in 1991 and twice in 1992. Per the Emergency Plans, these incidents also represented Unusual Events (UE).

A night order was issued immediately to declare any loop of RHR in SPC or SPS mode inoperable and enter the appropriate Technical Specification Action Statements (TSAS).

The root causes included: 1) A design deficiency of the RHR system because it cannot be operated in SPC during normal operation without compromising operability; 2) management methods that failed to identify this problem during review of a 1987 NRC Information Notice (IN), and 3) failure to follow procedures which led to inappropriate two train operation of SPC.

Leaking Main Steam Relief Valves (MSRV) will be reworked during the 1993 Refueling Outage to minimize leakage. Procedure changes will be made to indicate the inoperability of selected modes of RHR during operation of SPC and/or SPS. This LER will be made required reading for all Control Room supervision. An evaluation will be performed to determine the long term solution to the RHR design deficiency.

LICENSEE EVENT REPORT ( R)

TEXT CONTINUATION FACILITY NAHE (I) OOCKET NUHBER (2) LER NUHBER (8) AGE (3)

Year NUtnber ev. No.

Washington Nuclear Plant - Unit 2 0~ 0 I 3 9 I 7 0 ~ 5 ~ 0 ~ ~

~3 OIOI I OIO 2 OF 7 TITLE (4)

INOPERABLE SUPPRESSION POOL COOLING DUE TO POTENTIAL WATERHAMHER The safety significance of these events was negligible. This condition posed no threat to the health and safety of Plant personnel or the public.

Plan onditions Power Level - 100%

Plant Mode - 1 (Power Operation)

Even Descri i n On January 13, 1993, a Licensing Engineer determined that both trains of Suppression Pool Cooling (SPC) of the Residual Heat Removal (RHR) System (RHR "A" AND "B") were inoperable for 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> beginning on August 6, 1990. Previously, on October 23, 1992, a Problem Evaluation Request (PER) 292-1191 was issued for elevated Suppression Pool air space temperatures caused by leaking Main Steam Relief Valves (MSRV). During evaluation of the PER, a survey of other General Electric (GE) Boiling Water Reactor (BWR) plants revealed a possible water hammer problem with RHR in SPC following a LOP-LOCA. The WNP-2 engineering personnel were unaware of this potential vulnerability of RHR and thus issued PER 292-1243 on November 4, 1992, to document the problem. On December 22, 1992, engineering evaluations concluded that water hammer could fail the train of RHR in SPC or Suppression Pool Spray (SPS) due to a Loss of Power (LOP) coincident with a Loss of Coolant Accident (LOCA). Specifically, any LOP (e.g., failure to transfer from the normal transformer, TR-N, to the Startup transformer, TR-S) to the associated bus of RHR in SPC causes the corresponding RHR pump to stop. The LOP would allow portions of the associated RHR piping and heat exchanger to drain. A LOCA signal coincident with a LOP would result in an automatic start of the pump within 15 seconds following re-energization of the bus. The resulting water hammer from filling of the voided piping could cause failure in portions of the'associated RHR piping and/or heat exchanger, resulting in loss of the SPC, SPS, Drywell Spray (DWS), and Low Pressure Coolant Injection (LPCI) capability of the affected train.

Control Room logs were reviewed by the Licensing Engineer in support of a reportability evaluation for conditions when both SPC trains of RHR were inoperable, i.e., any combination of both trains operating in SPC or SPS concurrently or one train operating in SPC or SPS, and the other train out of service. A given train of RHR cannot be operated in more than one mode at a time. The review identified the concurrent operation of both SPC trains. This represented a condition that could have prevented the RHR System from performing its SPC, SPS, and DWS safety functions. The LPCI safety function was still capable of being performed by either RHR "C" or the Low Pressure Core Spray (LPCS) System.

LICENSEE EVENT REPORT R)

TEXT CONTINUATION ACILITY NAME (1)h DOCKET NUMBER (2) LER NUMBER (B) PAGE (3) ear Number ev. No.

Washington Nuclear Plan< - Unit 2 I3 OIOI 1 OIO 3 F 7 ITLE (4)

INOPERABLE SUPPRESSION POOL COOLING DUE TO POTENTIAL WATERHAMHER Immediate Correc ive Action A night order was issued on December 22, 1992, to declare any loop of RHR in SPC or SPS mode inoperable and enter the appropriate Technical Specification Action Statements (TSAS).

Fu her Evaluation and orrective Action A. ~Ph This event is considered reportable per 10CFR 50.73(a)(2)(v)(B) as a condition alone that could have prevented the fulfillment of the safety function of systems needed to remove residual heat. In addition, this condition is reportable per 10CFR 50.73(a)(2)(i)(B) as a condition prohibited by the plant's Technical Specifications (TS) Section 3.6.2.3. This event exceeded the TSAS allowable of 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> for the Plant to be in Hot Shutdown and 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to be in Cold Shutdown with both loops of SPC inoperable. NRC was verbally notified of this condition on January 13, 1992, per 10CFR 50.72(b)(2)(iii)(B). This event also satisfied the condition of an Unusual Event (UE) per PPM 13.1.1, Emergency Plans.

2. The NRC issued an Inspection and Enforcement Information Notice IN 87-10 on February 11, 1987, describing possible failure of the RHR train in SPC due to water hammer from a LOP-LOCA event. This IN was initiated based on the results of analyses performed at the Susquehanna Nuclear Power Plant on December 11, 1986. The notice indicated that Susquehanna limited operation of SPC to one train at a time in response to this deficiency.

On February 24, 1987, the Supply System's Nuclear Safety Assurance Group (NSAG) initiated an Operating Experience Review (OER 81078E) of IN 87-10. NSAG consulted only with a Shift Manager concerning the IN recommendation to limiting operation of SPC to one train at a time. Engineering personnel or the System Engineer were not contacted. The initial evaluation concluded that there was no Suppression Pool heat-up problem that would necessitate use of both trains concurrently. Although the procedures did not restrict two train operation, the Shift Manager considered the procedures adequate. The OER was closed on March 3, 1987, with no actions. It was still assumed that a train of RHR in SPC was operable.

3. While performing work on the Technical Specification Improvement Program (TSIP) in 1990, a Plant Technical engineer determined that the issue of two train operation had not been adequately addressed in the 1987 OER 81078E. NSAG limited their re-review of the OER to the procedure changes identified in IN 87-10 without consulting Engineering personnel or the System Engineer. Plant procedure PPM 2.4.2, Residual Heat Removal, was changed on October 8, 1990, to limit the SPC mode of RHR to one train operation per the

LICENSEE EVENT REPORT ( R)

TEXT CONTINUATION FACILITY NAHE (I) DOCKET NUHBER (2) LER NUHBER (B) PAGE (3)

Year umber ev. No.

Washington Nuclear Plant - Unit 2 l3 0~0~ 1 0~0 4 OF 7 TITLE (4)

INOPERABLE SUPPRESSION POOL COOLING DUE TO POTENTIAL WATERHAHHER recommended solution used by Susquehanna. However, the train of RHR in SPC was still considered operable. In addition, the 10CFR 50.59 review of the procedure change failed to identify the inoperable condition of the RHR train in SPC.

4. Based on the experience of Operations personnel, both trains of SPC would only have been operated during periods of MSRV testing. A review of Control Room logs since startup for only the periods of MSRV testing revealed three incidents of simultaneous operation of RHR "A" and "B". These incidents occurred from 0103 hours0.00119 days <br />0.0286 hours <br />1.703042e-4 weeks <br />3.91915e-5 months <br /> to 0546 hours0.00632 days <br />0.152 hours <br />9.027778e-4 weeks <br />2.07753e-4 months <br /> on September 30, 1991, from 0206 hours0.00238 days <br />0.0572 hours <br />3.406085e-4 weeks <br />7.8383e-5 months <br /> to 0810 hours0.00938 days <br />0.225 hours <br />0.00134 weeks <br />3.08205e-4 months <br /> on July 6, 1992, and from 1319 hours0.0153 days <br />0.366 hours <br />0.00218 weeks <br />5.018795e-4 months <br /> to 1542 hours0.0178 days <br />0.428 hours <br />0.00255 weeks <br />5.86731e-4 months <br /> on July 11, 1992. Since the Plant procedure PPM 2.4.2 was changed in 1990 to preclude two train operation of SPC, these incidents occurred because of failure to follow procedures by the Reactor Operators.

The Control Room logs between July 1 and December 20, 1992, were also reviewed for instances where at least one train of RHR was in SPC or SPS and other safety related equipment were inoperable. No occurrence was found that could have compromised the safety function of a system or the condition was prohibited by the TS given the RHR train in SPC or SPS was inoperable. Also, no other instance was found where a TS Limiting Condition of Operation (LCO) was exceeded.

B. ~Rot Cause The root cause of the vulnerability of the SPC mode of RHR to a LOP-LOCA was the inadequacy of the original design analysis.

2. A root cause that led to operating both trains of SPC simultaneously on August 6, 1990, was that management methods did not ensure appropriate technical input during review and closure of the OER on March 20, 1987. A multi-discipline review was not performed to ensure appropriate corrective actions would be implemented to preclude inappropriate operation of RHR.

s

3. A root cause that lead to inappropriate two loop operation of SPC in 1991 and 1992 was failure to follow procedures.

LICENSEE EVENT REPORT ( R)

TEXT CONTINUATION AGILITY NAME (I) . OOCKET NUMBER (2) LER NUMBER (8) AGE (3) umber ev. No.

Washington Nuclear Plant - Unit 2

~3 0~0~1 0~0 5 OF 7 TITLE (4)

INOPERABLE SUPPRESSION POOL COOLING DUE TO POTENTIAL WATERHAMMER C. Further Corrective Ac ion T ken The OER process was enhanced in 1991 to require the reviewer to obtain the appropriate independent and multi-discipline review prior to closure of the report.

2. The process of performing 10CFR 50.59 reviews and safety evaluations has been enhanced since 1990 to further assure changes to Plant operation and configuration are made within the Licensing Basis Documents (LBD). The enhancements include required training of persons preparing and reviewing 10CFR 50.59 reviews and safety evaluations, and procedure changes that provide additional guidance and clarification of the 10CFR 50.59 process. The experience to date indicates a continuing improvement in the quality of the 10CFR 50.59 reviews and safety evaluations as the enhancements take affect.

3. Due to MSRV leakage, one train of SPC is currently required to be operated from 6 to 14 hours1.62037e-4 days <br />0.00389 hours <br />2.314815e-5 weeks <br />5.327e-6 months <br /> per week. The SPC train in operation is declared inoperable and the appropriate TSAS in Sections 3.5.1, Emergency Core Cooling Systems (ECCS) Operating, and 3.6.2.3, Suppression Pool Cooling, are entered, Assuming one train of SPC would be operated a maximum of 15 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br /> per week, the probability of a severe water hammer from a LOP-LOCA was estimated to be 2.9E-7 events per year. This value coupled with the probability of coincident failure and unavailability of the remaining train of SPC results in an acceptably low increase in Core Damage Frequency (CDF).

4, An evaluation was completed to determine the appropriate maintenance activities required to significantly reduce the leaking MSRVs.

5. All Control Room operating crews and supervision have been trained regarding mandatory procedure compliance. The training emphasized that unauthorized departure from a Plant procedure is forbidden, especially in response to a recurring problem, even though the reasons for the problem are well understood. If difficulties are encountered while performing the procedure, it is management's expectations that performance of the procedure should be suspended, the Plant placed in a safe condition, and the conditions evaluated and appropriately resolved.

D. urther orr ive Acti n Plant procedure PPM 2.4.2, RHR, will be changed by March 1, 1993, to indicate that a train in SPC or SPS must be considered inoperable. The change will also indicate that any combination of two train operation of SPC and/or SPS: results in a loss of the safety function of SPC, SPS, and DWS, is required to be reported to the NRC within four hours, and is forbidden under non-emergency conditions.

LICENSEE EVENT REPORT R)

TEXT CONTINUATION AGILITY NAHE (i) DOCKET NUMBER (2) LER NUNBER (8) AGE (3) eel umbet'v. No.

Washington Nuclear Plant - Unit 2 3 9 7 6 0 Q 3 QQ1 00 6 F 7 ITLE (4)

INOPERABLE SUPPRESSION POOL COOLING DUE TO POTENTIAL WATERHAMMER

2. All Shift Managers and Control Room Supervisors will be required to read this LER by March 31, 1993.

3. The leaking MSRVs will be reworked, up to a maximum number of 12, by July 1, 1993, to significantly reduce MSRV leakage. Long Range Planning provides for rework of an additional 10 valves each outage as the need dictates.

4, 'lans will be developed by July 1, 1993, to perform an evaluation that will determine the long term solution to the RHR design deficiency and provide an expected completion date for the evaluation.

fet i nifi The safety significance of these events is negligible. The probability of a LOP-LOCA occurring during the four times both trains of SPC were operating was at least two orders of magnitude less than the estimated CDF for WNP-2 of 5.4E-5 events per year. Therefore, the increase to the CDF was insignificant. This condition posed no threat to the health and safety of Plant personnel or the public.

imil rE n One or more of the following original design deficiencies could have caused loss of the safety function of the respective system following a Loss-of-Offsite Power (LOOP) or LOCA.

LER 84-013 documents an original design deficiency where undersized fuses to the fan motors of the Containment Atmosphere Control (CAC) System would have prevented the CAC System from performing its safety function following a LOCA.

LER 92-007 documents an original design deficiency where location of restricting orifiices in the RHR return lines to the Suppression Pool could cause the loss of the safety function of the CAC System following a LOCA that required CAC operation.

LER 92-028 documents an original design deficiency where the Diesel Generator (DG) room normal air handling fans (DMA-FN-12, -22, and -32) would not restart following a LOOP, which could result in the loss of the safety function of the three DGs.

LICENSEE EVENT REPORT ( R)

TEXT CONTINUATION FACILITY NAME (1) OOCKET NUMBER (2) LER NUMBER (8) AGE (3) ear umber ev. No.

Washington Nuclear Plant - Unit 2 0 5 0 0 0 3 9 7 l3 OiOil Oi0 7 F 7 TITLE (4)

INOPERABLE SUPPRESSION POOL COOLING DUE TO POTENTIAL WATERHAMMER EII Inf rm ion Text Reference EIIS Reference

~S.;[em ~om onen Containment Atmosphere Control System BB Control Rod Drive System AA Emergency Power System for HPCS EK Plant AC Distribution System EA Main Steam System SB RV RHR/Containment Spray BO Suppression Pool System BT Diesel Building HVAC VJ