ML17289A441

LER 92-010-00:on 920303,standby Gas Treatment Differential Pressure Controller Setpoint Error Identified.Caused by Analysis Deficiency.Setpoint Methodology Program to Review Selected non-harsh Setpoints extended.W/920402 Ltr

ML17289A441
Person / Time
Site:	Columbia
Issue date:	04/02/1992
From:	John Baker, Fuller R WASHINGTON PUBLIC POWER SUPPLY SYSTEM
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
GO2-92-078, GO2-92-78, LER-92-010, LER-92-10, NUDOCS 9204100114
Download: ML17289A441 (7)

Text

ACCELERATED DIRIBUTION DEMONST TION SYSTEM.REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)ACCESSION NBR:9204100114-DOC.DATE: 92/04/02 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 92-010-00:on'920303,a nonconservative setpoint was being used on Standby Gas Treatment.

Caused by Analysis.-

Deficiencies.A plan to extend WNP-2 Setpoint Methodology Program to review selected nonharsh setpoints.W/920402 ltr.DISTRIBUTION'ODE IE22T COPIES RECEIVED: LTR (ENCL i SIZE: TITLE: 50.73/50.9, Licensee Event Report (LER), Incident Rpt, etc.NOTES D A RECIPIENT ID CODE/NAME PD5 LA ENG, P.L.I INTERNAL: ACNW AEOD/DOA AEOD/ROAB/DS P NRR/DLPQ/LHFB10 NRR/DOEA/OEAB NRR/DST SELB SD NRggiD3-:, BS.D1 RE~QLE~~OQ GN5 FILE 01 EXTERNAL: EGGG BRYCE,J.H NRC PDR NSIC.POORE,W.

f Ply 733~COPIES LTTR ENCL 1,1 1'I 2 2 1'2 2 1 1 1 1 1 1 1 1 1 1 1 1 3 3 1'1" 1 ACRS AEOD/DS P/TPAB NRR/DET/EMEB 7E NRR/DLPQ/LPEB10 NRR/DREP/PRPB11 NRR/DST/SICBSH3 NRR/DST/SRXB SE RES/DS IR/EI B 2 2 1 1,'1 1 1 1 2 2 1 1 1 1 1 1 L ST LOBBY WARD NSIC MURPHY,G.A

'NUDOCS FULL TXT 1 1 1 1 1 1'ECIPIENT COPIES ID CODE/NAME LTTR ENCL PD5 PD 1 1'D S D NOTE TO ALL"RIDS" RECIPIENTS PLEASE HELP US TO REDUCE WASTE!CONTACT THE DOCUMENT CONTROL DESK, ROOM Pl-37 (EXT.20079)TO ELIMINATE YOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!D D FULL TEXT CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUIRED: LTTR 32 ENCL 32 Sa WASHINGTON PUBLIC POWER SUPPLY SYSTEM P.O.Box 968~3000 George Washington Way~'ichland, Washington 99352 l April 2, 1992 G02-92-078 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 EVENT REPORT NO.92-010-00 Transmitted herewith is Licensee Event Report No.92-010-00 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..B WNP-2 P ant Manager (Mail Drop 927M)-JWB/lc Enclosure CC: Mr.J.B.Martin, NRC-Region V Mr, C.Sorensen, NRC Resident Inspector.(Mail Drop 901A, 2 Copies)INPO Records Center-Atlanta, GA Ms.Dottie Sherman, ANI Mr.D.L.Williams, BPA (Mail Drop 399)

LICENSEE EVEN REPORT (LER)FACILiTY NAHE (1)ashington Nuclear Plant-Unit 2 TITLE (4)DOCKET NUHB R ()PAGE (3)0 5 0 0 0 3 9 7 I OF Standby Gas Treatment System Differential Pressure Controller Setpoint Error EVENT DATE (5 LER NUMBER 6)REPORT DATE (7)OTHER FACILITIES INVOLVED 8 HONTH DAY YEAR YEAR SEQUENTIAL NUMBER EV I 5 ION UHBER MONTH DAY YEAR FACILITY NAHES CKE 50 UHB R (5)0 3 0 3 9 2 9 2 0 I 0 0 0 0 4 0 2 9 2 50 PERATING ODE (9)HIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREHENTS OF 10 CFR 5: (Check one or more of the following)

(11 4 POWER LEVEL (10)20.402(b)20.405(a)(1)(i) 20.405(a)(1)(ii) 20.405(a)(1)(iii) 20.405(a)(1)(iv) 20.405(a)(1)(v) 20.405(C)50.36(c)(1) 50.36(c)(2) 50.73(a)(2)(i) 50.73(a)(2)(ii) 50.73(a)(2)(iii) 50.73(a)(2)(iv)

X 50.73(a)(2)(v) 50.73(a)(2)(vii) 50 73(a)(2)(viii)(A) 50.73(a)(2)(viii)(B) 50.73(a)(2)(x) 77.71(b)73.73(c)THER (Specify in Abstract elow and in Text, NRC orm 366A)NAME LICENSEE CONTACT FOR THIS LER (12)R.E.Fuller, Compliance Engineer REA CODE TELEPHONE NUMBER 0 9 7 7-4 1 4 8 COMPLETE ONE LINE FOR EACH COHPONENT FAILURE DESCRIBEO IN THIS REPORT (13)CAUSE SYSTEH COMPONEN'I HANUFACTURER EPORTABLE 0 NPRDS CAUSE SYSTEH COMPONENT HANUFACTURER EPORTABLE TO NPRDS SUPPLEMENTAL REPORT EXPECTED (14).YES (If yes, complete EXPECTED SUBHISSION DATE)X NO ABSTRACT (16)EXPECTED SUBMISSION HONTN DAY YEAR ATE (15)On March 3, 1992, a reportability evaluation was completed which concluded a nonconservative setpoint was being used on the Standby Gas Treatment (SGT)System differential pressure controllers (SGT-DPIC-1A1, 1A2, 1B1, and 1B2).The reportability evaluation concluded that the condition identified by a Design Engineer on August 28, 1991 was reportable.

The condition was determined to have the potential to prevent the SGT System from performing its safety function in response to a highly unlikely accident condition coincident with adverse environmental conditions and with instrument loop uncertainty at the 95%confidence level.This condition was identified as a result of the%NP-2 Setpoint Methodology Program., The SGT System was not required when the condition was identified.

The Plant was in Mode 4.No activities requiring SGT were allowed until the condition was corrected on September 10, 1991.The root cause of this condition was Analysis Deficiencies.

Further corrective actions include: 1)a plan to extend the WNP-2 Setpoint Methodology Program to review selected nonharsh environm'ent setpoints, and 2)perform an independent assessment of the Reportability Evaluation process.The safety significance of this condition is considered insignificant.

The probability of extremely unlikely design conditions occurring coincident with the instrument loop uncertainty being at the 95%confidence level is considered to have a negligible impact on the probability of exceeding 10CFR100 guidelines.

LICENSEE EVENT REPORT (LER)TEXT CONTINUATION AGILITY NAHE (1)Washington Nuclear Plant-Unit 2 DOCKET NUHBER (2)0 5 0 0 0 3'9 7 LER NUHBER (8)ear umber ev.No.2 010 0 AGE (3)2 F 5 ITLE (4)Standby Gas Treatment System Differential Pressure Controller Set oint Errol'ii n Power Level-0%Plant Mode-4 (Cold Shutdown)" D On March 3, 1992, a reportability evaluation was completed which concluded a nonconservative setpoint was being used on the Standby Gas Treatment (SGT)System differential pressure controllers (SGT-DPIC-lA1, 1A2, 1B1, and 1B2).The reportability evaluation concluded that the condition identified by a Design Engineer on August 28, 1991 was reportable.

The condition was determined to have the potential to prevent the SGT System from performing its safety function in response to a highly unlikely.accident condition coincident with adverse environmental conditions and with instrument loop uncertainty at the 95%confidence level.This condition was identified as a result of the WNP-2 Setpoint Methodology Program.The setpoint for the SGT System differential pressure controllers of negative 1.0-inch w.g.did not include a proper evaluation of the instrument loop uncertainties.

The differential pressure controller setpoint was determined to be insufficiently'negative because calculations showed that the combined uncertainties were larger than previously evaluated, The negative 1.0-inch w.g.setpoint could prevent the SGT System from.drawing all areas of Secondary Containment down to negative 0.25-inch w,g.unde'r the combination of extremely unlikely design conditions, with only one train of SGT operating and with the instrument loop uncertainty at the 95%confidence level.Immedi rrec ive Ac i n The SGT System was not required when the condition was identified.

The Plant was in Mode 4.No activities requiring SGT were allowed until the condition was corrected on September 10, 1991.F her Ev 1 i n nd orrective Acti n A.BU!hhEi L This event is considered reportable per 10 CFR 50.73(a)(2)(v)(C) as a condition alone that could have prevented the fulfillment of the safety function of structures and systems that are needed to control the release of radioactive material.The SGT System may not have perfor'med its safety function under the combination of extremely unlikely design conditions.

LICENSEE EVENT REPORT (LER)TEXT CONTINUATION AGILITY KAME'(1)llashington Nuclear Plant-Unit 2 DOCKET NUNBER (2)0 5 0 0 0 3 9 7 ear LER NUNBER (8)umber ev.No.2 10 0 AGE (3)3 F 5 ITLE (4)'I Standby Gas Treatment System Differential Pressure Controller Set oint Error Reportability of the differential pressure controller setpoint,error was determined on March 3, 1992 while reviewing the regulatory compliance issue backlog.The controller setpoint error was believed to be virtually equivalent to the SGT System flow limiter setpoint error described in LER 92-08, which had been verbally reported on March 1, 1992.Hence,'t,was concluded that verbal notification'was not necessary and that both issues would be discussed in a common LER.When developing the LER for the setpoint errors, it was determine'd that the conditions were not closely linked and should be reported separately.

Verbal notification regarding the controller setpoint error was made to the NRC at 1628 hours0.0188 days <br />0.452 hours <br />0.00269 weeks <br />6.19454e-4 months <br /> PST on March 27, 1992 per 10 CFR 50.72(b)(2)(iii)(C) as a condition alone that could have prevented the fulfillment of the safety function of structures or systems needed to control the release of the radioactive material.2.The reportability evaluation completed on March 3, 1992 concluded the condition identified by a Design Engineer on August 28, 1991 was reportable.

The setpoint was conservatively changed on September 10, 1991, prior to formal completion of the setpoint calculations for the differential pressure controllers.

The calculations were formally completed on March 15, 1992, which confirmed the reportable condition.

The delay in the reportability evaluation was due to the backlog of items requiring evaluation, This evaluation was part of the Reportability Evaluation backlog reduction effort, Recently Management attention has been focused on this issue.A goal has been established to maintain the number of items at a very low level.3.There were no structures, components, or systems inoperable prior to the discovery of the condition which contributed to the condition.

'4.As described in LER 88-23, Revision 1, dated September 30, 1988, the setpoint for the SGT'ystem differential pressure controllers was changed from negative 0.25-inch w.g.to negative 0.6-inch w.g.to'account for instrument loop uncertainties.

5.LER 89-40, Revision 1, dated June 19, 1990, indicated that significant pressure gradients as a function of elevation could occur in the Reactor Building from high wind and/or low outside temperature conditions.

For extreme environmental conditions, analyses determined that the lower portion of the Reactor Building must be held at a differential pressure of negative 0.75-inch w.g.to ensure the upper portion of the Reactor Building is maintained at the required negative 0.25-inch w.g.This is due to the difference in density of the air inside and outside the Reactor Building during cold weather conditions.

The differential pressure transmitters (REA-DPT-1A1 through 1A4 and REA-DPT-1B1 through 1B4)that provide the signal to the SGT System differential pressure controllers for Secondary Containment are LICENSEE-EVENT REPORT (L)TEXT CONTINUATION AGILITY NAHE (1)Mashington Nuclear Plant-Unit 2 DOCKET NUHBER (2)0 5'0 0 3 9 7 LER NUHBER (B)ear umber ev.No.2'0.0 AGE (3)4 F 5 iTLE (4)Standby Gas Treatment System Differential Pressure Controller Set oint Error located at the 572-foot elevation of the Reactor Building.Analyses further determined that the transmitters must sense a negative 0.66-inch w.g.differential pressure to ensure the upper portion of the Reactor Building is at a negative 0.25-inch w.g.This is defined to be the analytical limit for the differential pressure controllers.

The previous analytical limit had been negative 0.25-inch w.g.As a result of the new analytical limit for the SGT System differential pressure coritrollers, the setpoint was changed from negative 0.6-inch w.g, to negative 1.0-inch w.g.on September 1, 1989.The magnitude of the instrument loop uncertainties was determined to be the same and went unchanged.

6.Evaluation of the instrument loop uncertainties for the SGT System differential pressure controllers was performed per the WNP-2 Setpoint Methodology Program.The new methodology determined the uncertainties are larger than previously evaluated.

In conjunction with the new setpoint calculations, a new analytical limit of negative 0.71-inch-w,g.was determined based on 95%of the meteorological data for wind and temperature.

The previous analytical limit of negative 0.66-inch w.g.was based on the average monthly low temperatures.

7, For the new analytical limit on the controllers of negative 0.71-inch w.g., the minimum allowable differential pressure controller setpoint value was calculated to be negative 1.637--inches w.g.with instrument loop uncertainties.

The root cause of this condition was Analysis Deficiencies.

The analyses that supported the controller setpoint changes from negative 0.25-inch w.g.to negative 0.6-inch w.g.and from negative 0.6-'inch w.g, to negative 1.0-inch w.g.did not properly evaluate the instrument loop uncertainties under harsh environment conditions.

B: r rrective A i n The differential pressure controllers were subsequently changed with the setpoint set at negative 1.70-inch w.g,+0.05-inch w.g, on September 10, 1991.This provides a margin of'.013-inch w.g.between the minimum differential pressure controller setpoint of negative 1.65-inch w.g.with controller uncertainty error, and the minimum allowable differential pressure setpoint of negative 1.637-inch w.g.with instrument loop uncertainties.

LICENSEE EVENT REPORT (LER)TEXT CONTINUATION AGILITY NANE'(1)Washington Nuclear Plant-Unit 2 OOCKET NUNBER (2)~0 5 0 0 0 3 9 7 LER NUMBER (8)Year umber ev.No.2 10 0 AGE (3)5 F 5 ITLE (4)Standby Gas Treatment System Differential Pressure Controller Set oint Error 2.3.'valuation of setpoints for equipment in harsh environments has been completed per the WNP-2 Setpoint Methodology Program.Although beyond the scope of our original Setpoint Methodology Program, the Supply System is planning to extend its review to selected nonharsh environment setpoints.

Based on current planning, this is estimated to be a 4-1/2 year effort.An independent assessment will be performed on the Reportability Evaluation process, This evaluation will determine how improvements can be made in the overall process taking into account information obtained from other utilities.

The independent assessment will be completed by July 1, 1992.Efffii~The.safety significance of this condition is considered insignificant.

The probability of adverse environmental conditions occurring that would require a differential pressure at the analytical limit coincident with accident conditions that would require the SGT System to perform its safety function is small.This probability combined with the probability that 1)the instrument loop uncertainty is at the 95%confidence level and that 2)only one SGT train is available is considered to have a negligible impact on the probability of exceeding 10CFR100 guidelines.

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