ML17354A326

LER 96-011-00:on 961009,potential for Overpressurizing Post Accident Containment Vent Filter Housings Occurred.Caused by Improper Change Mgt.Monitoring Sys Operating Procedures revised.W/961106 Ltr

ML17354A326
Person / Time
Site:	Turkey Point
Issue date:	11/06/1996
From:	Jim Hickey, Hovey R FLORIDA POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
L-96-292, LER-96-011-01, LER-96-11-1, NUDOCS 9611140236
Download: ML17354A326 (8)

Text

CATEGORY j.REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)ACCESSION NBR:9611140236 DOC.DATE: 96/11/06 NOTARIZED:

NO DOCKET g FACIL:50-250 Turkey Point Plant, Unit 3, Florida Power and Light C 05000250 AUTH.NAME AUTHOR AFFILIATION HI CKEY, J.A.Florida Power&Light Co.HOVEY,R.J.

Florida Power a Light Co.RECIP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER 96-011-00:on 961009,potential for overpressurizing post accident containment vent filter housings occurred.Caused by improper change mangement.Monitor sys operating procedures were revised.W/961106 ltr.DISTRIBUTION CODE: IE22T COPIES RECEIVED:LTR I ENCL I BISE: Ll TITLE: 50.73/50.9 Licensee Event Report (LER), Incident Rpt, etc.NOTES: E RECIPIENT ID CODE/NAME PD2-3 PD INTERNA Ee RAB FILE CENT NRR/DRCH/HHFB NRR/DRCH/HOLB NRR/DRPM/PECB NRR/DSSA/SRXB RGN2 FILE 01 EXTERNAL: L ST LOBBY WARD NOAC MURPHY,G.A NRC PDR COPIES LTTR ENCL 1 1 2 2 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 RECIPIENT ID CODE/NAME CROTEAUPR AEOD/SPD/RRAB NRR/DE/ECGB NRR/DE/EMEB NRR/DRCH/HICB NRR/DRCH/HQMB NRR/DSSA/SPLB RES/DSIR/EIB LITCO BRYCE,J H NOAC POORE,W.NUDOCS FULL TXT COPIES LTTR ENCL 1 1 2 2 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 D E NOTE TO ALL"RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WASTE.TO HAVE YOUR NAME OR ORGANIZATION REMOVED FROM DISTRIBUTION LISTS OR REDUCE THE NUMBER OF COPIES RECEIVED BY YOU OR YOUR ORGANIZATION, CONTACT THE DOCUMENT CONTROL DESK (DCD)ON EXTENSION 415-2083 FULL TEXT CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUIRED: LTTR 25 ENCL 25 FPL NOv Ol'9gI L-96-292 10 CFR 50.73 U.S.Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C.20555 Re: Turkey Point Units 3 and 4 Docket Nos.50-250 and 50-251 Reportable Event: 96-011-00 Potential for'Over Pressurizing the Post Accident Containment Vent The attached Licensee Event Report, 250/96-011-00, is being provided in accordance with 10 CFR 50.73(a)(2)(v)(C).Should there be any questions, please contact us.Very truly yours, R.J.Hovey Vice President Turkey Point Plant JAH Attachment CC: S.D.Ebneter, Regional Administrator, Region II, USNRC T.P.Johnson, Senior Resident Inspector, USNRC, Turkey Point Plant 5'6iii40236 96ii06 PDR ADQCK 05000250 S PDR:,JP~()g-L)

FACILITY NAHE (I)LICENSEE EVENT REPORT LER DOCKCT NUMBER 2 PACE 3 TURKEY POINT UNIT 3 05000250 I OF 5 TITLC (4)POTENTIAL FOR OVERPRESSURIZING THE POST ACCIDENT CONTAINMENT VENT FILTER HOUSINGS MON f.'VENT DATf'DAY YR YR SC I RI LER NUMBER 6 RPT DATE 7 MON DAY YR OTHER f'AC ILITIES INV.8 FACILITY NAMES DOCKCT I S 10 09 96 OPCRAT INC MODC (9)96 011 00 11 06 96 TURKEY POINT UNIT 4 05000251 POWER LEVEL (10)100 LICENSEE CONTACT FOR THIS LER (12)James A.Hickey, Licensing Engineer Tele hone Number (305)246-6668 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)CAUSE SYSTEM COMPONE:NT MANUFACTURCR NPRDS?CAUSF.SYSTEH COMPONENT MANUFACTURER NPRDS?SUPPLEMENTAL REPORT EXPECTED (14)NO YCS (it yos, comPloto CXPECTCD SUBMISSION DATE)EXPECTED SUBMISSION DATE (15)MONTH DAY YEAR ABSTRACT (16)At 1620 on October 9, 1996, based on a procedural review, Florida Power&Light Company determined that a condition existed which had the potential to overpressurize the Post Accident Containment Vent (PACV)filter housings during post accident conditions.

The Post Accident Hydrogen Monitors (PAHM)are placed inservice within thirty minutes after a valid Engineered Safety Feature actuation.

Assuming a large break Loss of Coolant Accident and the failure of the"A" train PAHM containment suction isolation valve, procedural guidance existed which would have cross-tied the"B" train PAHM containment suction to the"A" train PAHM.The cross-tied suction would provide post accident sampling capability and two electronic channels of hydrogen monitoring.

The specific valve alignment used to cross-tie the PAHM/Post Accident Sampling (PASS)suction lines would have resulted in pressurizing the PACV filter housings.The PACV filter housings are not designed to operate under the containment conditions which would exist within the first few hours of a large break Loss of Coolant Accident.The PACV filter housings would be expected to fail and cause an unanticipated monitored release.The root cause of the event was improper change management.

The Containment Post Accident Monitor Systems Operating Procedures were revised on October 09, 1996, to eliminate the steps to cross-tie the PAHM/PASS suction lines.

t 1 LICENSEE EVENT REPORT (LER)TEXT CONTINUATION FACILITY NAME TURKEY POINT UNIT 3 DOCKET NUMBER 05000250 LER NUMBER 96-011-00 PAGE NO.2 QF 5 I.DESCRIPTION OF THE EVENT At 1620 on October 9, 1996, based on a procedural review, Florida Power&Light Company (FPL)determined that a condition existed which had the potential to overpressurize the Post Accident Containment Vent filter housings[WE:fit]during post accident conditions.

The Post Accident Containment Vent System (PACV)was recently upgraded to support a thermal power uprate.The NRC resident inspector raised a question concerning minor procedural discrepancies between Unit 3 and Unit for placing PACV inservice.

FPL initiated procedure revisions to resolve the discrepancies.

FPL expanded the procedure review to include those systems which interface with the PACV.The procedure review identified a potential Post Accident Hydrogen Monitor System (PAHM)[WE:45]/Post Accident Sampling System (PASS)[WE:45]

alignment which could overpressurize the PACV filter housings.Condition Report 96-1263 was initiated at 1000 on October 9, 1996, to perform an operability assessment of PACV, PAHM, and PASS.The PACV System is shared between Units 3 and 4.The PACV System consists of a particulate filter[WE:fit]and charcoal filter[WE:fit]with valves and piping to support post accident con'tainment venting.The PAHM and PASS sample supply lines tap into the PACV supply piping, (see Figure 1).The Post Accident Hydrogen Monitors are placed in service within thirty minutes after a valid Engineered Safety Feature actuation.

Procedure 3/4-0P-094,"Containment Post Accident Monitoring Systems" directs the opening of HV-3/4-1[WE:smv]to provide a suction source for the"A" train PAHM/PASS[WE:45].If valve HV-3/4-1 failed to open the operator was directed to cross-tie the sample suction lines by opening HV-3/4-2[WE:smv]and HV 3/4-4[WE:smv].This action would apply containment pressure to the PACV filter housings via normally open HV-2[WE:isv]and HV-7[WE:isv].The PACV filter housings had a design pressure of 5 psig.If pressure in excess of 5 psig were applied to the PACV filter housings, the housings would likely have failed.The PACV filter housings failure would have resulted in an unanticipated monitored release.Based on this sequence of events, at 1620 on October 9, 1996, FPL determined procedural guidance for potentially overpressurizing the PACV filter housings did exist.The NRCOC was notified at 1732 on October 9, 1996 in accordance with 10 CFR 50.72 (b)(2)(iii)(C).The investigation concluded that PASS was not required to support single failure criteria and the operable"B" PAHM satisfied the requirements for containment hydrogen monitoring.

Therefore, the alternate PAHM and PASS sample alignment was not needed to meet any operability requirements.

Procedures 3/4-OP-094 were revised to eliminate the procedural guidance for cross-tying the suction sources in the event of a failure of HV-3/4-1 to open.

t t LICENSEE EVENT REPORT (LER)TEXT CONTINUATION FACILITY NAME TURKEY POINT UNIT 3 DOCKET NUMBER 05000250 LER NUMBER 96-011-00 PAGE NO.30F5 II.CAUSE OF THE EVENT The root cause of the event was improper change management.

The original operating configuration for the PACV filter housings showed inlet valve HV-2 as closed.In 1990 FPL identified potential dose concerns associated with the need to locally open HV-2 under post accident conditions.

Based on these dose concerns FPL changed the system alignment for the PACV filter inlet valves from normally closed to normally open.The decision to open the PACV filter inlet valves did not adequately assess the effect of the valve realignment on systems which interface with PACV, specifically, the alternate PAHM and PASS suction alignment referenced in 3/4-0P-094.

III.ANALYSIS OF THE EVENT The alternate PAHM and PASS alignment had the potential to over pressurize the PACV filter housings.This action could have resulted in an unanticipated monitored release.The release from a faulted filter housing would flow through the Auxiliary Building, Auxiliary Building Exhaust Filters[NF:fit]

and Fans[NF:fan], and exit via the Plant Vent Stack which is monitored via R-14[WE:45].

FPL performed a dose assessment using the following assumptions:

A Double Ended Pump Suction (DEPS)break would occur at time zero.The DEPS break would bound all other containment response events.The PAHM and PASS alternate alignment would be completed about thirty minutes following the event.Reach rod operated valve HV-3/4-4 would be closed at about sixty minutes following the event.This action would terminate the release.Total release duration would be thirty minutes.No core damage or fuel melt would occur during the first hour.However, a partial or full gap release to containment is likely.A realistic source term is assumed based on NUREG-1465,"Accident Source Terms for Light-Water Nuclear Power Plants." NUREG-1465 indicates that during the first hour post-accident, the volatile material released to containment consists of the noble gas gap activity (5%of total core inventory) and halogens in the gap (5%of total core inventory)

.FPL assumed a gap activity of 10%of total core inventory and 10%of total core inventory halogen dispersal.

t t LICENSEE EVENT REPORT (LER)TEXT CONTINUATION FACILITY NAME TURKEY POINT UNIT 3 DOCKET NUMBER 05000250 LER NUMBER 96-011-00 PAGE NO.4 OF 5 As a result of the gap release to containment, the whole body dose to a member of the public would be about 2 Rem at the exclusion boundary.For the same release the thyroid dose to a member of the public would be about 24 Rem.These doses are in addition to the exclusion boundary doses previously calculated for a LOCA.Including the LOCA doses a member of the public at the exclusion boundary would receive about 3 Rem whole body and 47.6 Rem thyroid.Based on this realistic source term, 10 CFR 100 guidelines would not be exceeded.The following conditions must occur to support the postulated scenario: 1.A large break LOCA 2.Fuel rod bursting 3.Containment pressure greater than 5 psig 4.A mechanical failure of HV-3/4-1 to open Utik.izing the guidance of NUREG/CR-4550, the probability of a large break LOCA is 5.0E-4/Yr.

The generic probability of a Manual Valve failing to operate is 3.5E-4/Yr.

The valve design of HV-3/4-1 includes a reach rod, therefore the valve failure probability was raised by a factor of ten.The probability of a large break LOCA and failure of HV-3/4-1 is 1.8E-G/Xr.

The faulted PACV system was reviewed for impact on PASS and PAHM system operability.

Both systems would remain operable during the event.This event is reportable under the requirements of 10 CFR 50.73 (a)(2)(v)(C).IV.CORRECTIVE ACTIONS 1.Operating Procedures 3-OP-094 and 4-OP-094 have been revised to eliminate the alternate PAHM and PASS sample suction source flow path.2.A review and walkdown of similar infrequently used systems for consistency in procedural guidance between Units 3 and 4 and system interface implications will be performed.

The similar infrequently used systems include the Post Accident Hydrogen Monitors, Post Accident Sample System, and Hydrogen Recombiners.

3.FPL will evaluate the normal Post Accident Containment Vent system alignment for additional procedural improvements.

LICENSEE EVENT REPORT (LER)TEXT CONTINUATION FACELiTY HAP"-TURKEY POINT UNIT 3 BOCK.T iVCHBER 05000250 LFR!iUMBFR 96-011-00 BAG"=iio.5 OF 5 V.ADDITXONAL INFORMATION In 1990 as a result of Local Leak Rate Testing on Unit 3 during refueling, the operating Unit 4 PACV was inoperable for greater than the allowed outage time.Reference LER 251/90-002-01.

Figure 1 shows the basic relationships between PACV, PAHM, and PASS.EXIS codes are shown in the format[EIIS SYSTEM: IEEE component function identifier, second component function identifier (if appropriate)).

Figure 1 CHARCOAL FILTER HEPA FILTER 38" PAHM 4EI PAHM UNIT 3 HV-3-3 HY-4-4 HY-W3 HV-3-1 HY-3-2 HY-4-2 HY-4-1 PAHM/PASS%4Alt PAHM/PASS