ML20044E541

LER 93-009-00:on 930421,found That Design of SBGTS Would Allow Operation That Would Result in Sys Damage If Containment Venting in Progress & Experience Loca.Operating Procedures 1-OP-10 & 1-OP-24 revised.W/930520 Ltr

ML20044E541
Person / Time
Site:	Brunswick
Issue date:	05/20/1993
From:	Jonathan Brown, Thearling G CAROLINA POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
BSEP-93-0075, BSEP-93-75, LER-93-009, LER-93-9, NUDOCS 9305250135
Download: ML20044E541 (4)

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CaroHna Power & Ught Company  !

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.i Brunswick Nuclear Project  ;

y. . P. O. Box 10429 s Southport, N.C. 28461-0429 i I.

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FILE: B09-13510C 10CFR50.73 i SERIAL: BSEP-93-0075 l I

U.S. Nuclear Regulatory Commission ]

ATTN: Document Control Desk Washington, D. C. 20555 ,

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t BRUNSWICK STEAM ELECTRIC PLANT UNIT 1 AND 2

• DOCKET NO. 50-325 AND 50-324 LICENSE NO.-DRP-71 AND DPR-62 LICENSEE EVENT REPORT 1-93-009 Gentlemen:

t In accordance with. Title 10 of the Code of Federal Regulations, the enclosed' Licensee Event Report is submitted. This report fulfills the requirement for'a written report within thirty ~ (30) days of a reportable occurrence and -is submitted in accordance with the format set forth in NUREG-1022, September 1983.

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very truly yours, h

' ;. -' M. Brown, Plant Manager'UL't 1 Brunswick Nuclear Plant y

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Enclosure cc: Mr. S. D; Ebneter Mr. P. D. Milano Mra R. L. Prevatte

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NRC FORM 366 U.S. NUCLEAR REGULAVORV COMMISSION APPROVED OMB NO. 3150-0104 (5/92) EXPIRES: 5/31/95 E STIM AT E D BURDE N PE R RE SPONSE TC COMPLY WIT H THIS INEDRM AT ON C OLLE CTION RE QUE ET: !>C O HRS. F ORW ARD LICENSEE EVENT REPORT (LER) CwME,ns m ouD,No evRDEN is,,M ATE To wE i.OweN AND RECORDS MANAGEMENT BFiANCH [MNf;B 7714L U.S. NUCLE AL ttEOutATORY CDMMISSCN W ASHINGTON. DC 205% DOC 1. AND TO THE F APE RWORF FIEDUCT CN PROJE CT 0150 01 Dat et rrCE OF M ANAGEMENT AND BUDGET, W ASHtNGTON DC 20503.

F ACIUTY %AME til doc t:ET NUMBER (21 FAGE {3)

Brunswick Steam Electric Plant, Unit 1 05000325 1 of 3 TITLE I41 DESIGN OF STANDBY GIiS TREATMENT SYSTEM WOULD ALLOW OPERATION THAT WOULD RESULT IN SYSTEM DAMAGE IF CONTAINMENT VENTING WERE IN PROGRESS AND THE UNIT EXPERIENCED A LOSS OF COOLANT ACCIDENT.

EVENT DATE (5) LER NUMBER (6) REPORT DATE (7) OTHER FACILITIES INVOLVED (B) f ACILITY NAME DOCKET NUVBER MONT H DAV YEAR YE AF; MONTH DAY YEAR BSEP UNIT 2 05000-324 04 21 93 93 00 05 20 93 ' 'C " Y * ^

• E doc 5 ET "$ *BEa 35000 THis REPORT is SUBMITTED PURSUANT TO THE HEOUIREMENTS OF 10 CFR 4: IChack or, or more of the followingM11)

OPERATING ,

MODE 2 20 402(b) 20.405(c) 50.73taH2Hrv) 73 71(b) 20.405(aH1 Hi) 50 ?HcH11 X 50 73taH2)M 73 71fc)

WEL 00) 00 20 405f aH1Hnl 50 361cH2) 50 73taH2Hvid OTHER 20 405taH1Hiii) 50.73f aH2Hil 50 73(aH2HviiiHAl 15pecsfy in Atistract 20 405(aH1Hiv) 50.73(aH2Hid 50 73!aH2HvisiHD) and Ted

, 20 405taH1Hv) 50.73(aH2Hm) 50.73(aH2Hx)

LICENSEE CONTACT FOR THIS LER (12)

NAME TELEP90NE NUVBE9 Glen Thearling, Regulatory Compliance Sr. Specia3ist (919) 457-2038 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS FEPORT (13)

^ COMPONENT CAUSE EYSTE M C OMPONE NT M ANuT ACTURE R CAUSE SYSTEM M ANUF ACT URE R l'

SUPPLEMENTAL REPOF

• 4 TPECTED (14) EXPECTED "UN'" C^* "^"

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of m compm. ExPECTtr suEsMissioN cATE DATE (15)

ABSTRACT { Limit to 1400 spaces. i e _ approximately h? teen sing 6e space typewritten tir es) (16)

Both Units had been Shutdown for a dual Unit outage that began April 21, 1992. On April 21, 1993, a follow-up evaluation of a design basis documentation review of the Standby Gas Treatment (SBOT) system found that current drywell venting procedures non-conservatively use the large Containment Atmospheric Control butterfly valves ( 18 " ) as the exhaust pathway through the SBGT trains to the plant stack. With this vent path, SBGT was not protected from over pressurization damage if a Loss of Coolant Accident (LOCA) occurred when the Primary containment was being vented. Calculations show that the SBGT filters would be subjected to 5.4 psig one second after a LOCA with a maximum pressure of 23.3 psig at the filters. These pressures exceed the SEGT filter design pressure of 2.0 psig.

Calculations have shown that the existing 2" bypass lines, around the large CAC valves, will limit pressure at the SEGT f11ter inlets to 0.35 psig. The Unit 2 Operating Procedures (ops) have been revised to require Primary Containment venting through the 2" valves when aligned through the SBGT system and the Unit 1 ops will be revised prior to the end of the current Refueling outage.

This procedural deficien g (per NUREG-1022 cause classification) is of minimal safety significance as an actual LOCA has not occurred and must happen in conjunction with the limited time the Primary Containment valves are cpen for venting.

NRC FORhl 366A U. S. NUCLEAR REGULATORY COMMISSION APPROVED OMB NO. 3150-0104 (5/92) EXPlRES: 5/31/95 i E ST tMATED DURDEN PER RE SPONf:E TO COMPLY WITH THIS l IN8 DRM ATION COLRCTlDN RE QUE ST: 50.0 HAS. FORWARD LICENSEE EVENT REPORT (LER) COuMENTSR[cARamo Buro [N ESuu ATno mE *ORwioN wo  :

TEXT CONTINUATION RECOMDS M ANAME NT MANCH fMNBB 7714L U.S. NUCLEAP 1 REGUL ATDRY COMMISSION, WASHINGTON. DC 20b$6-0001, AND TO I THE FAPERWORtt REDUCTION PROJE CT f3150-C1041 OmCE OF M ANAGEMENT AND BUDGET. WASHINGTOk, DC 20503.

FAC1UTY NAME II) DOCKET NUMBER (2) LER NUMBER (6) PAGE (31  !

SE QUE NTiAL RE VISION Brunswick Steam Electric Plant """ """*'"

Unit 1 05000325 2 of 3 93 00 l 1

EXT W rr> ore space is seguned, use additional NRC form 366A 's) (1h i

TITLE DESIGN OF STANDBY GAS TRFI/IKENT SYSTEM WOULD ALLOW CPERATION THAT WOULD RESULT IN SYSTEM DAMAGE IF CCNTAINMENT VEMING WERE IN PROGRESS AND THE UNIT EXPERIENCED A LOSS OF COOLANT ACCIDENT.  !

INITIAL CONDITIONS Both Units had been in Shutdown for a dual Unit cutage that began April 2: 1992.

i EVENT NARRATIVE ,

i i

On April 21, 1993, a follow-up evaluaticn of a design basis documentation review revealed  ;

an operability concern during power operaticn with the drywell venting procedures allowing '

use of the large Containment Atmospheric Control (CAC) butterfly valves (18') as the exhaust pathway through the Standby Gas Treatment (SBGT) trains to the plant stack, i Operating in this manner could cause SBGT filter cverpressurization if a Loss of Coolant  ;

Accident (LOCA) occurred when venting the Primary Containment. (

The large CAC butterfly valves have been used along with the 2' bypass lines for drywell i venting through the SBGT system since initial Unit operation in the 1970s. In the November 2, 1979, correspondence between CP&L and the NRC related to the Standard Review Plan l' Section 6.2.4 (rev. 1) and Branch Technical Position CSB 6-4, on Containment Isolation issues, CP&L incorrectly stated that only the two 1/2" (post-LOCA) valves were used for periodic containment venting and therefore the post-LOCA equipment was protected from '[

damage in the event a LOCA occurred during the venting operation. This letter was incorporated into the Updated Final Safety Analysis Report (re". 0), issued in July of 1982, but no procedural changes were initiated. Additional correspondence to the NRC on  ;

January 20, 1983, indicated that testing had shown the use of the 1/2" valves was  ;

inappropriate for venting at power, but CP&L was willing to pursue the feasibility of using l intermediate size valves (Drywell Head vent) in lieu of the large valves. NRC concurrence on returning the intermediate valves to normal service was requested but resolution of this i issue was not completed. j Calculations show that if Primary Containment venting through the SBGT system is in i progress using the 16* drywell and 20" torus lines, and a LOCA occurs, the SBOT filters  ;

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would be subjected to 5.4 psig in one second, peaking at 23.3 psig. These pressures exceed the design pressure of 2.0 psig at the filters.

Use of the existing 2" bypass lines, around the large CAC valves, was shown by calculati 7ns to limit pressure at the SBGT filter inlet to 0.35 psig.

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NGC F6Rbl 366A U. S. NUCLEAR REGULATORY COMMISSION APPROVED OMB NO. 3150-0104 r (5/92) EXPIRES: 5/31/95  ;

• E SiiM ATED BURDEN PER Rf 5PONSE 10 COMPLY WITH THIS i LICENSEE EVENT REPORT (LER) Cl5%n" Ecd %'l3" DEN 75S'S4 T' T 18$MIT ONS  !

TEXT CONTINUATION RECORDF MANA Gl Mt NT BRANCH [MNEB 7714L U.S. NUCLI AR REGULATORY COMMt$s TON. WASHINGTON. DC 205%-0001, AND TO T HE FAPikwDRK REDO; TION PROJECT (3150-0104h OFF6CE OF M ANAGEMINT AND BUDGET, W ASHIN*, TON DC 20503.

FACILITY NAME (1) DOCKET NUMBER (2) LCR NUNIBER 16) PAGE (3) f SE QUE NTIAL RE VfstON Brunswick Steam Electric Plant 05000325 3 of 3 Unit 1 ,.

93 00 i

TE XT tif more space is required, use add tional NRC form 366A 'st 0 7) 7 CAUSE OF EVENT The November 2, 1979, correspondence indicating that only the 1/2" (post-LOCA) vent valves were used for pre-LOCA venting was not correct. The terminology (post-LOCA vent valves used pre-LOCA to protect the post-LOCA operability of SBGT) may have led to the confusion associated with this issue. While use of these valves was referenced in years of correspondence between the NRC and CP&L, the issue was lost in the overlapping CAC valve  !

cperability issues of the period and was not adequately tracked through to a final resolution.

CORPECTIVE APTIONS The Unit 2 SBGT system Operating Procedure (2-OP-10) has been revised to allow Primary g Containment venting through the SBGT system only with the 2" bypass lines, or when the Reactor is depressurized. The Unit 2 Containment Atmosphere Control system Operating Procedure (2-CP-24) was also revised to ensure the primary inerting/deinerting path is through the purge fans, if Primary Containment radiological conditions are acceptable, l rather than the SBGT. ,

The Unit 1 Operating Procedures (1-OP-10 and 1-OP-24 ) will be revised prior to the end of f the current Refueling Outage.

i An evaluation of the acceptability of using the drywell head vent line as an additional path for routine drywell venting operaticns will be completed by August 31, 1993. l 1

$AFETY ASSESSVENT I.

This deficiency is of minimal safety significance as an actual LOCA event has not 3 occurred and must happen in conjunction with the limited time the CAC valves are open i for venting.

1 PREVIOUS SIMILAR EVFNTS  ;

i See LER 1-93-05, LER 1-92-20, EIIS COMPONENT IDENTIFICATION System /Comnenent EIIS Code Standby Gas Treatment System BH e

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