ML17285A806

LER 89-040-00:on 890919,determined That Under Certain Meteorological Conditions,Situation Would Be Created Not within Licensing Basis Consideration for Secondary Containment Performance.Evaluation underway.W/891018 Ltr

ML17285A806
Person / Time
Site:	Columbia
Issue date:	10/18/1989
From:	Arbuckle J, Powers C WASHINGTON PUBLIC POWER SUPPLY SYSTEM
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-89-040, LER-89-40, NUDOCS 8910260184
Download: ML17285A806 (10)

Text

ACCELERATED DISTR33UTION 0 DEMONSTFMTION 0 SYSTEM REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR:8910260184 DOC.DATE: 89/10/18 NOTARIZED: NO DOCKET FACIL:50-397 WPPSS Nuclear Project, Unit 2, Washington Public Powe 05000397 AUTH. NAME AUTHOR AFFILIATION Washington Public Power Supply System

'RBUCKLE,J.D.

POWERS,C.M. Washington Public Power Supply System RECIP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER 89-040-00:on 890919,SGT sys capability not w/in license basis consideration for secondary containment performance.

W/8 ltr.

DISTRIBUTION CODE: IE22T COPIES RECEIVED: LTR I ENCL TITLE: 50.73/50.9 Licensee Event Report (LER), Incident Rpt, etc.

g SIZE:

NOTES:

RECIPIENT COPIES RECIPIENT. COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD5 LA 1 1 PD5 PD 1 1 SAMWORTH,R 1 1 INTERNAL: ACRS MICHELSON 1 1 ACRS MOELLER 2 2 ACRS WYLIE 1 1 AEOD/DOA 1 1 AEOD/DSP/TPAB 1 1 AEOD/ROAB/DSP 2 2 DEDRO 1 1 NRR/DEST/ESB 8D 1 1 NRR/DEST/ICSB 7 1 1 NRR/DEST/MEB 9H 1 1 NRR/DEST/MTB 9H 1 1 NRR/DEST/PSB 8D 1 1 NRR/DEST/RSB 8E 1 1 NRR/DEST/SGB 8D 1 1 NRR/DLPQ/PEB 10 1 NRR/DLPQ/HFB 10 NRR/DOEA/EAB NUDOCS-ABSTRACT ll 1 1

1 1

1 1

/ RPB 10 1

2 1

2 1

RES/DSIR/EIB 1- 1 RGN5 FILE 01 1 1 EXTERNAL: EG&G WILLIAMS,S 4 4 L ST LOBBY WARD 1 1 LPDR 1 1 NRC PDR 1 1 NSIC MAYS,G 1 1 NSIC MURPHY,G.A 1, 1 NUDOCS FULL TXT 1 1 D

pD D D

NOTE TO ALL "RIDS" RECIPIENIS:

PLEASE HELP US TO REDUCE WASTE! CONTACT THE DOCUMENT CONTROL DESK, ROOM P 1-37 (EXT. 20079) TO ELIMINATEYOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!

FULL TEXT CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUIRED: LTTR 38 ENCL 38

WASHINGTON PUBLIC POWER SUPPLY SYSTEM P.O. Box 968 ~ 3000 George Washington Way ~ Richland, Washington 99352 Docket No. 50-397 October 18, 1989 Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C . 20555

Subject:

NUCLEAR PLANT NO. 2 LICENSEE EVENT REPORT NO.89-040

Dear Sir:

Transmitted herewith is Licensee Event Report No.89-040 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.

Very truly yours, C. M. Pow s (M/D 927M)

WNP-2 Plant Manager CMP:lr

Enclosure:

Licensee Event Report No.89-040 cc: Mr. John B. Martin, NRC - Region V Mr. C. J. Bosted, NRC Site (M/D 901A )

INPO Records Center - Atlanta, GA Ms. Dottie Sherman, ANI Mr. D. L. Williams, BPA (M/D 399)

NRC Form 355 U.S. NUCLEAR REGULATORY COMMISSION (94)3) APPROVED OMB NO. 31100104 EXPIRES: 4/31/44 LICENSEE EVENT REPORT ILER) r DOCKET NUMBER (2( PAGE (3/

FACILITY NAME (ll Washington Nuclear Plant - Unit 2 I 0 s 00 o3 7iovO an y as rea ment ystem apa>> ty ot > s n License Basis Consideration t for Secondary Containment Performance Under Certain Conditions Due to Desi n EVENT DATE (SI LER NUMBER (5) REPORT DATE (7) OTHER FACILITIES INVOLVED ISi SEGVENTIAL IIEY6IQN OAY YEAA FACILITYNAMES DOCKET NUMBEAISI MONTH OAY YEAR YEAR NVM82 A :PA NI/MSEA MONTH 0 5 0 0 0 0 '9 1 9 8 9 8 9 4 0 0 0 1 0 1 8 8 9 0 5 0 0 0 THIS REPORT IS SUBMITTED PURSUANT T 0 THE REOUIREMENTS OF 10 CFR (II /Cntcc one or mort o/ tnt foiiovrrnP/ (11 OPERATING MODE (OI 20.402(bi 20.405(c) 50,73 (4 I (2 I I iv) 73.7((o)

POWE R 20.405( ~ I('llAl 50.35(cl(11 50.73(s)(2)(vl 73.71(c)

~EYEL OTHEA /Sotcify in Acrtrtcr 1 0 0 20,405(s) (11(ii) 50.35 Icl(2) 50.73(x)(2) (vEI otioyr tnd in Ttvt, NRC Form 20.405'(1)(OII S0.73( ~ ) (2 III) 50.73(s) (2)(viii)(Al 3664) 20,405( ~ l(1 l(iv) 50.73( ~ )(2) (ii) 50,73( ~ l(2)(viiil(8) 20.405(v ) (1 I (v) S0.73(sl(2l(iii) 50.73( ~ ) (2)(x I LICENSEE CONTACT FOR THIS LER (12)

NAME TELEPHONE NUMBER AREA CODE J . D. Arbuckle, Com liance En ineer 50 93 COMPLE'TE ONE LINE FOR EACH COMPONFNT FAILURE DESCRIBED IN THIS REPORT (13)

CAUSE SYSTEM COMPONENT MANVFAC IIEPOATABLE ~~srmb+~S" .

SYSTEM COMPONENT MANVFAC. EPOATABLE TURER TURER TO NPADS off/P j)'jxjj~P+mIS QI'jSIPj~j/gjij gpss~@~))Ij'p;,",.~T/

SUPPLEMENTAL REPORT EXPECTED (14I MONTH DAY YEAR EXPECTED SU 8 M I 5 5 I 0 N DATE (I SI YES llfym, comortrt fxPBCTfD SUBM/$$ /Df/ OATf/ X ABSTRACT /Limrt to /400 rotctr i.t,, toorovimtuiy Rfrttn rrnprt rptct ryptvvrrtttn /inN/ (15)

On September 19, 1989 it was determined by Engineering analysis that under certain meteorological conditions (moderate wind and low temperature), coincident with a DBA LOCA and assumed failure of one train of the Standby Gas Treatment (SGT) system, a situation would be created that is not within the licensing basis consideration for Secondary Containment performance.- The Engineering analysis was performed as a fur-ther corrective action for LER 88-023.

The WNP-2 FSAR states that the Secondary Containment will be maintained at minimum differential pressure of -0.25H W.G. following a postulated LOCA, and that this dif-ferential will be established within two minutes following the accident. Recent analysis, based upon Standby Gas Treatment, Secondary Containment, Standby Service Water and weather modeling, shows that during post-LOCA, or adverse weather, dif-ferential pressure of the Secondary Containment may not always meet the FSAR commit-ments. Certain combinations of post-LOCA single active failures and winter conditions adversely affect Secondary Containment and, as a result, increase Secondary Containment leakage.

N RC F orm 355 (9.83)

NRC Form 366A US. NUCLEAR REOULATORY COMMISSION (943)

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION APPROVED OMB NO, 3(50-0104 EXPIRES: 8/3(/88 FACILITY NAME O) DOCKET NUMBER (2) LER NUMBER (6) PACE (3) s<R sECUSNTIAL ohio'REvrsroN NUMSER i<VS NUMoell Washin ton Nuclear TEXT /I/ more Foeoe /F toorr/er/ ore rdde'os Plant - Unit 2 o s o o o 397 8 9 04 0 000 2>>0

/VRC Form 366AS/ (17)

Abstract (contd. )

As an immediate corrective action, a Justification for Continued Operation (JCO) was performed and concluded that operation of the Plant can continue while final resolu-tion of this issue is achieved. In addition, this situation was reviewed relative to the requirements of 10CFR50.59 and it viewed safety question. Accordingly, the NRC was formally notified of this was determined that it represents an unre-determination.

As a further corrective action, a test was run to confirm the leakage value used for the JCO. In addition, Design Basis changes will be evaluated to provide an SGT system that allows for adequate filtering of Secondary Containment for applicable meteorological conditions, and system draw down time, so as to meet 10CFR100 and GDC 19 limits, while taking credit for suppression pool scrubbing as allowed by Standard Review Plan 6.5.5.

This event did not affect the health and safety of either the public or Plant personnel.

Plant Conditions Power Level - 100%

Plant Mode - 1 (Power Operation)

Event Descri tion On September 19, 1989, it was determined by Engineering analysis that under certain meteorological conditions (moderate wind and low temperature), coincident with a DBA LOCA and assumed failure of one train of the Standby Gas Treatment (SGT) System, a situation would be created that is not within the licensing basis consideration for Secondary Containment performance. The Engineering analysis was performed as a fur-ther corrective action for LER 88-023, "Technical Specifiation Violation of Secon-dary Containment to Outside Differential Pressure Caused by Design due to Programmatic Errors."

The WNP-2 FSAR states that the Secondary Containment will be maintained at minimum differential pressure of -0.25U W.G. following a postulated LOCA, and that this dif-ferential will be established within two minutes following the accident. Recent analysis, based upon Standby Gas Treatment, Secondary Containment, Standby Service Water (SSW), and weather modeling, shows that during post-LOCA, or adverse weather, differential pressure of the Secondary Containment may not always meet the FSAR com-mitments. Certain combinations of post-LOCA single active failures and winter con-ditions adversely affect Secondary Containment and, as a result, increase Secondary Containment leakage.

The analysis uses the lowest monthly average temperature for January of 12'F in com-bination with the highest average monthly wind for January of 10.3 mph. On the average, temperature is below 12'F approximately 1.6% of the calendar year, and below O'F approximately 0.1% of the calendar year. Wind conditions above 10.3 mph wi 11 probably provide sufficient dispersion to preclude the need for maintaining the

-0.25" differential and; therefore, negates designing the SGT for worst case wind conditions.

NRC FORM 066A ~U~ S ~ CPOr (966 520 569~00070 (9.83)

NRC Fotm 3SSA UA. NUCLEAR REGULATORY COMMISSION (9431 LICENSEE EVENT REPORT (LER) TEXT CONTINUATION APPROVED OMB NO 3)50&104 EXPIRES: 8/31/88 FACILITY NAME (() DOCKET NUMBER (31 LER NUMBER (6) PAGE (3)

SEQUENTIAL P(E REVISION YEAR NVMSER "M NVMSER clear Pl ant - Unit 2 0 5 0 0 0 3 9 7 8 9 0 0 0 0 3o" 0 7 TEXT /// Itxvo <<ocoit toqund, Itto ddddoot///AC Form JSBA't/ ()7)

Wind increases the demand on the SGT to hold the leeward side and roof of the Reac-tor Building sufficiently negative while simultaneously increasing the differential and, thus, the inleakage on the windward side of the building. Differen- 'ressure tial temperature between the inside and outside of the building creates a differen-tial pressure gradient from the bottom to the top of the Secondary Containment due to the density difference of the air inside and outside the building during cold outside conditions. As a result, the lower portion of the building must be held at a high differential pressure (up to -0.75") to assure that a -0.25" differential exists at the building roofline. This overall greater differential pressure propor-tionally increases building inleakage. The effects of wind and winter temperatures result in the inability to hold the upper portion of the Secondary Containment at a

-0.25U differential in cold and mildly windy weather, and lengthens the time required to reach -0.25U differential in warmer and less windy weather.

Analysis shows that the time required to reach the steady state condition is a func-tion of the assumed meteorological conditions at the time of a postulated LOCA, type of single active failure coincident with the LOCA, and the Standby Service Water (SSW) temperature. The transient analysis clearly indicates that the limiting single active failure is the assumed loss of one SGT train. Based"upon single train design basis SGT flow and maximum Technical Specification allowable Secondary Con-tainment leakage, the upper-most inside surface areas of the Reactor Building cannot be maintained at a -0.25" W.G. with respect to atmospheric pressure during low temperature and high wind conditions. High SSW water temperature acts to extend the time required to reach a steady state condition, but does not effect the final steady state differential pressure.

With two fans redundantly powered in each train, the SGT is not susceptible to many of the single active failures that have a higher probability of occurrence relative to other events, e.g., failure of an emergency diesel generator to start. If one train does fail to start automatically, remote manual initiation and process moni-toring can occur through the control room. A design review of the system to deter-mine the susceptibility of an SGT train to single failure has not been performed.

Until that occurs, the likelihood of failure, or what would be necessary to remedy failure susceptibilities, is not known. (Local control is not possible due to the post-LOCA radiation fields that are postulated to be present in the vicinity of the SGT trains.) From a failure analysis perspective, the SGT train design at WNP-2 does have features that provide more reliable operation than are dictated by the minimum design requirements that allow for satisfying single failure criterion by the existence of a redundant train.

Testing conducted during the past calendar year of SGT flow/differential pressure capability, and testing of Secondary Containment integrity show that the SGT is capable of performance beyond design basis requirements, and that the Secondary Containment is significantly more leak-tight than required by Technical Specifica-tions. Actions have been taken over the past twelve months to further tighten the Secondary Containment boundary against leakage, e.g., Reactor Building Exhaust and Outside Air (REA and ROA) isolation valve seals have been replaced and the railroad bay door seals have been adjusted. Reanalysis using documented actual performance values for SGT flow capability and Secondary Containment leakage shows that the NRC FORM 3SSA 'V.S. GPOI 1SSS S)0-SS&I000)0 IS 43)

NRC Form 366A US. NUCLEAR REGULATORY COMMISSION (9431 LICENSEE EVENT REPORT (LER) TEXT CONTINUATION APPROVED OMB NO. 3160&104 EXPIRES: 8/31/88 FACILITY NAME (I) COCKET NUMBER (2) LER NUMBER (6) PAGE (3)

YEAR SEOVENTIAI. O)IO REVISION NVMEER ~:CVi NVMSER 39 89 0 0 0 0 OF 0 7 TEXT /// moro Foooo u /oqrrinei, Ir>> odi'0'ou/ H/IC %%dnn 3QLE 3/ (12) post-LOCA pressure stabilizes at -0.32U with an outside temperature of 12'F with a coincident 10.3 mph wind, which is well below the required -0.25". However, the

-0.25" level is not reached for approximately 3.5 minutes after the accident. Addi-tional margin to the design basis requirements is also available from the actual leakage performance of the Primary Containment. Table 1 outlines the results of analysis based upon licensing basis SGT and Secondary Containment performance fol-lowed by reanalysis results based on realistic SGT and Secondary Containment performance.

Table 1 also demonstrates that the plant can be maintained at the required negative pressures (albeit the time is greater than two minutes) with the current leak-tightness of the Secondary Containment and SGT capability at very low winter temperatures, i.e., -BOF with a 10 mph wind, and -23'F without wind. This is obtained provided that the leak-tightness of Secondary Containment and/or the flow capability of SGT do not degrade by more than 5%, a differential of -0.25" can be maintained at 12'F with a 10 mph wind. Requirements for residence time in the SGT charcoal filters is met with at the 5600 cfm flowrate for design basis active and passive failure scenarios.

Provided that the SGT set point pressure is sufficiently negative, the existing SGT pressure control loop instrumentation will assure that the SGT trains operate at 5600 cfm flow as required during all meteorological conditions. Exisitng loop instrumentation controls Secondary Containment pressure during windy conditions up to existing REA or SGT capacity.

Table 1 Parametric Evaluation of Secondary Containment/SGT Performance Sec. Roof Line Time To Outside Wind SGT Cont. Stdy State Reach Ev al ua ti on Descri pti on Temp Speed Flow Leakage Pressure -0.25U

('F) (mph) (cfm) (cfm) (RH20) (minutes)

Design Basis Performance of SGT and Secondary Containment 12 10.3, 4460 2240 -0.02 Never Realistic Secondary Containment 12 10.3 4460 1475 -0.156 Never Leakage, Design Basis SGT Flow Design Basis Sec. Cont. Leakage, Realistic SGT Capability 12 10.3 5600 2240 -0.12 Never Realistic Sec. Containment and Realistic SGT Capability 12 10.3 5600 1475 -0.323 3.5 NRC FOAM 366A ~ V.E ~ CPOr 1888-S20 SE'Jr00010 (983)

NRC Form 366A U.S. NUCLEAR REGULATORY COMMISSION (943)

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION APPROVED OMB NO. 3150&104 EXPIRES: B/31/BB FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

SEOVENTIAL o.~: REVISION NUMSER NVMSER Washin ton Nuclear Plant - Unit 2 o s o o o 397 89 0 4 0 0 0 0 5 OF 0 7 TEXT /// moro opoco /s r//I/rorL Iroo a////'orN/ HRC Fonrr 3SSA3/ (I7)

Reanalysis For Coldest Temperature Capability Realistic Sec. Containment and Realistic SGT Capability -23 5600 1475 -0.25 <10 Realistic Sec. Containment and Realistic SGT Capability 10.3 5600 1475 -0.25 <10 Reanalysis With 5% Margin Realistic Sec. Containment and Realistic SGT Capability 12 10.3 5320 1475 -0.282 Realistic Sec. Containment and Realistic SGT Capability 12 10.3 5600 1549 -0.295 3.6 Immediate Corrective Action A Justification for Continued Operation (JCO) was performed for WNP-2. The conclu-sion of the JCO is that operation of the Plant can continue while final resolution of this issue is achieved.

Further Evaluation and Corrective Action A. Further Evaluation

1. This event is reportable under 10CFR50.73(a)(2)(ii)(B) as a condition out-side of the Plant design basis.

2. The cause of this event is design related in that inadequate design cri-teria were used by the Architect/Engineer (Burns and Roe, Inc.) to deter-mine SGT draw down time.

3. Current NRC requirements for radiological analysis do not allow SGT credit until a full -0.25U differential pressure is established at all Secondary Containment boundary surfaces. A review of existing radiological anlayses indicates that both the post-LOCA offsite and control room doses will increase as a result of delayed reestablishment (beyond two minutes) of the -0.25U differential. However, reanalysis using current rules (Standard Review Plan 6.5.5) that allow credit for iodine scrubbing within the suppression pool are expected to result in offsite doses equivalent to those outlined by the FSAR assuming a ten minute Rno SGT credit" period to reestablish the full -0.25". The current condition of the SGT and Secon-dary Containment do not meet the FSAR description under all reasonable environmental conditions; however, the resultant doses are within the 10CFR100 and GDC 19 requirements.

NRC FORM SSEA ~ I/,S. GPOI 1966 520 569/00010 (983)

NRC Form 388A U.S. NUCLEAR REOULATORY COMMISSION (983)

LICENSEE EVENT REPORT HLER) TEXT CONTINUATION APPRO>'.3 OMB NO. 3150&104 EXPIRES, 8/31/BB FACILITY NAME (1I OOCKET NUMBER (3) LER NUMBER (8) PACE (3)

YEAR SSOVSNTIAL RdvrsroN gpss NVMSSR NVMddR Washington Nuclear Plant - Unit 2 o s o o o 397 8 9 0 0 0 0 6 OF 0 7

- TEXT ///moro s/rscois rsdrrr)or/ oss /)/'orrs////IC Forrrr 3SSA's/ I)7),

4. Although there were no structures, components or systems inoperable prior to the event which contributed to the event, the equipment affected by this problem are SGT system filter trains SGT-FU-lA and SGT-FU-1B.

B. Further Corrective Action

1. This situation was reviewed relative to the requirements of 10CFR50.59 and it was determined that it represents an unreviewed safety question.

Accordingly, the NRC was formally notified of this determination.

2. To confirm that, the aforementioned actual Secondary Containment leakage value has remained representative of the Plant condition, a test was run on September 26, 1989. The leakage was found to be 1228 cfm; thus, con-firming the 1475 cfm value used for the JCO.

3. Design Basis changes will be evaluated to provide an SGT system that allows for adequate filtering of Secondary Containment for applicable meteorological conditions, and system draw down time, so as to meet 10CFR100 and GDC 19 limits, while taking credit for suppression pool scrubbing as allowed by SRP 6.5.5.

4. Current system testing will be maintained to ensure Secondary Containment leakage and SGT flow capabilities are within the JCO analysis.

Safet Si nificance Given the current state of Secondary Containment integrity, the SGT can provide adequate differential pressure control with an adequate margin applied for vari a-tions in Secondary Containment leak-tightness and SGT flow performance. Based upon actual Plant conditions and system performance, the Secondary Containment pressure differentia) will remain greater than -0.25U during severely cold winter conditions; with temperatures as low as -23'F without wind and -8'F with a coincident 10 mph

'ind. Although formal calculations have not been prepared, preliminary calculations show that both offsite post accident doses remain well below 10CFR100 limits and, with credit for suppression pool scrubbing, not significantly different than the .

results now documented in the FSAR.

Similar Events LER 88-023 NRC FORM SddA >V ~ 8 ~ CPOr lddd 830 ddsc 00010 1983)

NRC Form 366A U.S. NUCLEAR REOULATORY COMMISSION (94)3 I LICENSEE EVENT REPORT (LER) TEXT CONTINUATION APPROVED OMB NO. 3(50-0104 EXPIRES: B/31/BB FACILITY NAME (II DOCKET NUMBER (2( LER NUMBER (6) PACE (3)

YEAR SEOUENTIAL NUMSEll ~~( NUMSElr 4/>>coil Washin ton Nuclear Plant - Unit 2 o s o o 0 3 9 7 8 9 0 4 0 0 0 0 7oFO 7 TEXT///moro /4)/rwsrL uso r//0'ors/ HRC Folm 356A'4/(ll)

EI IS Information'ext Reference EIIS Reference System Component Standby Gas Treatment (SGT) System BH Secondary Containment NG Standby Service Water (SSW) BS Emergency Diesel Generator EK . GEN Reactor Building Exhaust and Outside Air (REA and ROA) Isolation Valves VA I SV SGT-FU-lA and SGT-FU-1B BH FLT NRC FORM 388A AU.ST CPOr (988-920 $ 89r00010 (94)3)