Text

LER 91-009-00:on 910215,results of PRA Indicated Change in Core Damage Frequency for Main Steamline Break in Inboard Mechanical Penetration Area on 901220.Caused by Lack of Seismic Gap Seals.Seismic Gap sealed.W/910315 Ltr
	ML18095A807
Person / Time
Site:	Salem
Issue date:	03/15/1991
From:	Labruna S, Pollack M; Public Service Enterprise Group
To:	; NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
	LER-91-009, LER-91-9, NUDOCS 9103210245
	Download: ML18095A807 (8)
	v • d • e

Public Service Electric and Gas Company P.O. Box 236 Hancocks Bridge, New Jersey 08038 Salem Generating Station

March 15, 1991 U. S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555

Dear Sir:

SALEM GENERATING STATION LICENSE NO. DPR-70

- DOCKET NO. 50-272 UNIT NO. 1 LICENSEE EVENT REPORT 91-009-00 This Licensee Event Report is being submitted pursuant to the requirements of the Code of Federal Regul~tions 10CFR 50.73(a) (2) (v) (A), (B), and (D). This report is required to be issued within thirty (30) days of event discovery.

~incerely yours, S.

LaBruna General Manager -

Salem Operations MJP:pc Distribution The Energy People 9103210245 910315 PDR ADOCK 05000272 1Jr1\

95-2189 (10M) 12-89

=; PDF<

NRC Form 388 19-83)

LICENSEE EVENT REPORT (LER)

U.S. NUCLEAR REGULATORY COMMISSION APPROVED OMll NO. Jl!i0-4104 EXPIRES: 8/31185 FACILITY NAME 111 DOCKET NUMBER 12) I PAOE (:I)

Salem Generating Station - Unit l o 15 Io Io Io I 2 f 7 I 2j 1 loF 01 7 TITLE 14)

High Energy Line Break Barrier Not Installed Due To Personnel Error EVENT DATE IB) LER NUMBER IBI REPORT DATE (71 OTHER FACILITIES INVOLVED Ill)

MONTH DAY YEAR YEAR tt SE~~~~~~AL tt ~~~~~ MONTH DAY YEAR FACILITY NAMES DOCKET NUMBERISl Salem Unit 2 o t s I o I o I o 13 I 11 l oI 2 l Is9 l 911 - ~ oj 9 - ol o q 3 l Is 9 I1 OPERATING THll REPORT 11 IUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Ch<<:lr on* or moro of th* fo//owin11/ 1111 I

MOOE Ill t-~~--.~~....&...~--l l'OWER

] 20.402(bl 20.40lll1111 l(I) -- 20.40ll(cl ll0.3411cll1l - x ll0.7311)(2)11*1 ll0.73(.ll:ilM 73.71lbl 73.71(c)

LEVEL - ~

1101 11 0 I 0 20.40lll1ll1HUI ll0.311(cll21 ....__ ll0.73111121(¥11) OTHER (Sp<<:lfy in Ab1tnct

~""""'""""'"""~"""'"'~;;,.,,+o---i bolow *nd In T**t. NRC Form

-==:~:::

ll0.73(1)12)(1) ll0.7311l12llv111llAI 366A}

....__ ll0.7311l12JIUI ll0.7311H21Mlllllll

~

ll0.73(1112111111 ll0.7311l12llxl LICENSEE CONTACT FOR THIS LER (12)

NAME TELEPHONE NUMBER AREA CODE M. J. Pollack - LER Coordinator 6i O 19 3 1 3 19 1- I 2 1O I 2t 2 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT 1131 CAUSE SYSTEM COMPONENT MANUFAC- MANUFAC*

TURER SYSTEM COMPONENT TUR ER I I I I I I I I I I I I I I I I I I I I I I I I I I I I IUPPLEMENTAL REPORT EXPECTED 114) MONTH DAY Y~AR EXPECTED SUBMl$SION 11 YES (If yn, compl*to EXPECTED SVIJMISSION DA TEI r-xi ABSTRACT (l.lmlt IO 14()() ipacn, I.*.* opproxlmotoly fihHn lin11l**IPICO ty1>>wrltten /inn/ 11111 NO DATE.1151 I I I On 2/15/91, a Probabilistic Risk Assessment (PRA) of an unsealed portion of the seismic gap between the Inboard Mechanical P~netration Area and the Electrical Penetration Are.a was completed. Results show change in the core damage frequency to be significantly increased (i.e., due to concern for a Main Steamline break in the Inboard Mechanical Penetration Area). The vertical run of the seismic gap for the Unit 2 areas was found not sealed prior to discovery of the Unit 1 seal concern. The Unit 2 PRA was incorrect due to a personnel error.

The root cause of the seals not being in place is personnel error.

Apparently, the required seal was not installed during original plant construction (per structural design prints). The U-2 horizontal seismic gap was inspected on 2/19/91. It too was not properly sealed; however, anchored flashing was in place which would act as a steam flow barrier. The U-2 seismic gap was sealed on 2/22/91. The missing portion of the U-1 seismic gap seal will be installed prior to startup of U-1. An analysis is being completed which assesses the operability of the Electrical Penetration Area MCCs with the seismic gap not sealed. The remaining seismic gap area (both Units) has been inspected by the PSRG. To date, the safety significant penetrations with inadequate seals have been repaired with the exception of the Unit 1 seismic gap seal (which will be sealed during the current outage). The PRA assessment engineer was counseled on the need to maintain attention to detail. A random sampling of DEFs will be reviewed. Administrative controls, to control Appendix R penetrations, will be extended to include HEBA penetration impairments.

NRC Fotm 3118 19-831

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION I

' Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 1 5000272 91-009-00 2 of 7 PLANT AND SYSTEM IDENTIFICATION:

Westinghouse - Pressurized Water Reactor Energy Industry Identification System (EIIS) codes are identified in the text as (xx)

IDENTIFICATION OF OCCURRENCE:

Concern for effects of a High Energy Line Break due to a breached barrier between mechanical and electrical penetration areas Event Date: 12/20/90 Discovery Date: 2/15/91 Report Date: 3/15/91 This report was initiated by Incident Report No.91-101.

CONDITIONS PRIOR TO OCCURRENCE:

December 20, 1990: Mode 1 Reactor Power 100%

February 8, 1990: Mode 1 - Unit shutdown in progress in support of ninth refueling outage preparation DESCRIPTION OF OCCURRENCE:

On December 20, 1990, during normal power operation, a Penetration Seal Review Group (PSRG) walkdown identified an unsealed portion of the seismic gap between the Inboard Mechanical Penetration Area and the Electrical Penetration Area. This gap is an annular sector 6" wide by 5.5' high around the outside of the Containment at 120' elevation. The seismic gap seal would prevent the steam environment of a Main Steamline Break (MSLB) in the Inboard Mechanical Penetration Area from entering the mild environment of the Electrical Penetration Area.

The PSRG program is tasked to only review areas associated with 10CFRSO Appendix R concerns (i.e., fire barrier integrity). Even though this finding was outside the scope of the project, they pursued a resolution. A work order was initiated to seal the subject area in accordance with the work control process procedure (NC.NA-AP.ZZ-0009(Q)).

Previous to this specific finding, a similar condition was identified in May 1990 for Unit 2. The same areas were affected. A vertical run along the seismic gap was not sealed per design. An analysis completed in November 1990 indicated that there was no equipment in the "Air Handling Area" (another name for the Electrical Penetration Area) whose failure would result in increased core damage risk (reference Discrepancy Evaluation Form DES-90-01573). This analysis proved to be incorrect because it was not recognized (by the engineer performing the assessment) that the "Air Handling Area" was another name for the "Electrical Penetration Area" (100' Elevation).

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION

~

Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 1 5000272 91-009-00 3 of 7 DESCRIPTION OF OCCURRENCE: (cont'd)

Although there was minimal safety significance identified, the Unit 2 seismic gap section was sealed in November 1990.

On February 8, 1991, recognizing that a portion of the Unit,l seismic gap had not been sealed, a request to evaluate the safety significance, including a Probabilistic Risk Assessment (PRA) analysis, was initiated (reference Deficiency Evaluation Form, DES-91-00066). On February 15, 1991, the PRA assessment was completed. Results of the PRA show that change in the core damage frequency is calculated to be 2.76E-5/Yr. The core damage frequency normally attributed to Salem Unit 1 is 5.8E-5/Yr.

Due to the potential for the identified condition to challenge the operability of safety related equipment, the Nuclear Regulatory Commission (NRC) was notified on February 15, 1991 at 1743 hours0.0202 days 0.484 hours 0.00288 weeks 6.632115e-4 months as required by Code of Federal Regulations 10CFR 50.72(b) (2) (iii).

APPARENT CAUSE OF OCCURRENCE:

The root cause of not having the seismic gap seal(s) (both Units) installed is attributed to personnel error. Apparently, the required seal(s) were not installed, during original plant construction (per structural design prints). This could not be conclusively determined whether the subject section of the seismic gap seal was removed or was never installed; however, it is considered unlikely that the missing portion of the seal would have been removed.

ANALYSIS OF OCCURRENCE:

The Updated Final Safety Evaluation Report (UFSAR) Section 3.6.5.10 discusses leak tight areas of the contiguous zone; however, it does not detail specific requirements for the Inboard Mechanical Penetration Area. Engineering Field Directive No. S-C-VAR-MFD-0508-1 (issued in 1988) addresses this area and other areas of similar concern. The Field Directive was originally issued in response to LER 272/87-017-02 which identified a concern pertaining to leakage paths in the Steam Driven Auxiliary Feedwater Pump enclosures (for both Unit 1 and Unit 2). Another LER 272/87-017-02 corrective action required a walkdown of other protective pipe rupture enclosures.

This was completed; however, the seismic gap penetration areas were not clearly identified as part of the scope of this inspection.

Subsequently, they were not visually inspected as were the other penetrations.

The design basis of leak-tightness for the seismic gap seal between the Electrical Penetration Area and the Mechanical Penetration Area is to ensure that the Electrical Penetration Area (temperature <

120°F) is not subject to the harsh environment of a MSLB (temperature~ 375°F).

The effects of a postulated double-ended guillotine MSLB in the

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION

~

Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 1 5000272 91-009-00 4 of 7 ANALYSIS-OF OCCURRENCE: (cont'd)

Inboard Mechanical Penetration Area (causing steam to enter through the deficient seal) may potentially cause the three Vital Motor Control Centers (MCCs) in the Electrical Penetration Areas to become inoperable. The MCCs control various ventilation and cooling equipment including:

1) Room Coolers for the: a) No. 1 Auxiliary Feedwater Pump Room; b) No. 1 Safety Injection Pump Room; c) Nos. 11 and 12 Component Cooling Pump Room; d) Nos. 11 and 12 Residual Heat Removal Pump Rooms; e) Nos. 11 and 12 Containment Spray Pump Room and Nos. 11, 12 and 13 Charging Pump Rooms

2) Fans for the: a) Filters 11 and 12 Switchgear Area Supply; b) Nos. 11, 12, and 13 SWGR Room Exhaust (64' and 84' elevations); c) Nos. 11 and 12 Electrical Penetration Exhaust; d) Nos. 11 and 12 Circulation Fans for the 84' El.

Piping Corridor; e) No. 11 Control Area A/C System Emergency Supply; f) No. 12 Emergency A/C Supply; g) No. 13 Air Conditioning; h) No. 1 Battery Room Exhaust; i) Nos. 11 and 12 Reactor Shield Ventilation; and j) Nos. 11, 12, 13 and 14 Reactor Vessel Nozzle Support Ventilation

3) Chiller Condenser Water Recirculation Pump

4) Heat Tracing for lB and lC 230 Volt 1-phase An engineering review of the "loss" of the above equipment shows that the most critical equipment are the room coolers for the:

Charging Pump - Two of the three affected charging pumps would be used for high head safety injection in the mitigation of a design base accident; they are 100% redundant of each other Safety Injection Pump - both pumps (100% redundant to each other) would be affected; they would be used to mitigate the consequences of a design base accident by providing intermediate head safety injection RHR Pump - there are 2 pumps (100% redundant to each other) which are used to remove residual core heat during shutdown conditions and to mitigate the consequences of a design base accident by providing low head safety injection The room coolers, in conjunction with the once through ventilation system, are designed to limit the ambient temperature at vital pumping equipment. This helps assure long-term and reliable operation of the vital equipment. Based upon PSE&G Engineering Evaluation S-C-ABV-NEE-0504E, "Engineering Evaluation on the Effect An Inoperable Room Cooler Has on the Operability of Vital Pumps",

operability of the vital pumps is affected by the availability of

Salem Generating Station DOCKET NUMBER LICENSEE EVENT REPORT (LER) TEXT CONTINUATION LER NUMBER PAGE Unit 1 5000272 91-009-00 5 of 7 ANALYSIS OF OCCURRENCE: (cont'd) associated Room Coolers. Therefore, with a Room Cooler inoperable the vital pumps in that room are considered inoperable.

The MCCs are qualified for 96 hours0.00111 days 0.0267 hours 1.587302e-4 weeks 3.6528e-5 months at 131°F and 90% relative humidity. Detailed analysis of the effects of a MSLB on the MCC's is continuing. Preliminary modeling for this analysis includes: 1) A pressurized Inboard Mechanical Penetration Area with steam temperature reaching 375°F when blowdown ends at 10 minutes; 2)

Inlet ventilation flow to the Electrical Penetration Area as permitted by the pressure therein; and 3) modeling of the MCC units with venting and natural circulation, as applicable.

The Salem Unit 2 seismic gap was inspected on February 19, 1991. A portion of the horizontal run was found not properly sealed (per design); however, anchored flashing was in place. This flashing would have acted as a steam flow barrier even though it would deform under a pressure of 5.8 psig. Engineering is evaluating if the flashing would have provided sufficient protection to mitigate the consequences of a MSLB in the Mechanical Penetration Area.

Seals common to both Appendix R and High Energy Line Break Accident (HEBA) barriers (734 seals) have been inspected as part of the PSRG program. Approximately 11% (74) of the inspected seals were discovered to have openings requiring repair. Out of this 74 seals, 24 have been determined to have no safety significance and an additional 14 have been determined to have negligible affect on the environmental parameters of the targeted areas. Analysis to assess the safety impact of the remaining 36 impaired seals in on going.

All but three (3) Unit 2 penetration seals have been repaired. These three (3) seals have been analysed as having no significant safety impact.

Approximately 700 seals are part of barriers considered in pipe break analysis events which are not considered to be 10CFR50 Appendix R fire barriers. These seals have not been in~pected as part of the PSRG program.

As identified previously, LER 272/87-017-02 required completion of a visual inspection of HEBA areas required to be maintained airtight.

This inspection did not include review of the seismic gap locations (both Units) due to an Engineering oversight. However, as addressed by the inspection, the design basis break in the Mechanical Penetration Areas, at 78' and 100' elevations and the Pipe Alley, is in a 6" main steam line to the Auxiliary Feedwater Turbine Pump. PRA analysis indicates no near term safety significance associated with this postulated break. The visual walkdown found no Unit 1 unsealed penetrations. Two (2) unsealed areas in the Unit 2 Letdown Heat Exchanger Room were identified (i.e., no others were identified).

The design break is in a 2" eves line and the break locations are sleeved and restrained. PRA analysis indicates this postulated break

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 1 5000272 91-009-00 6 of 7 ANALYSIS OF OCCURRENCE: (cont'd) is not of near term safety significance based on as found conditions. Section 3.6.5.10 of the UFSAR indicates that all steam generated by this break can be carried away by the normal ventilation exhaust system. Based on the above discussion,. it is judged that a postulated HELB will have no significant affect on equipment operability in the target areas.

Due to the lack of a seismic gap seal, between the Mechanical Penetration Area and the Electrical Penetration Area, this event is reportable to the NRC in accordance with Code of Federal Regulations 10CFR 50. 73 (a) (2) (v) (A), (B) and (D).

CORRECTIVE ACTION:

The Unit 2 seismic gap (with flashing) was sealed (in accordance with the field directive and design prints) on February 22, 1991.

The missing portion of the Unit 1 seismic gap seal will be installed upon completion of the current refueling outage, prior to startup of Salem Unit 1.

An engineering analysis is being completed which assesses the operability of the Electrical Penetration Area MCCs with the seismic gap not sealed.

Of the 74 seals, identified as deficient during the PSRG inspections, 59 seals have been repaired as of November 1990. An additional 12 non safety significant seals (associated with Unit 1) have been repaired during the current Unit 1 refueling outage. The remaining 3 non safety significant Unit 2 seals will be repaired during the next Unit 2 outage of sufficient duration (i.e., due to ALARA concerns).

The unsealed portion of the Unit 1 seismic gap will be repaired during the current refueling outage (prior to restart).

Analysis of the impact on equipment operability of the 36 penetration impaired seals (of the original 74 identified) is on going.

The scope of the PSRG project has been increased to now include inspection and analysis of HEBA barrier penetrations not associated with Appendix R. Visual inspections for Unit 1 penetrations will be completed during the current outage. The accessible Unit 2 penetration inspections will be initiated upon completion of Unit 1 inspections. Those penetrations, not accessible during operation, will be inspected during the next Unit 2 outage of sufficient duration.

This event has been reviewed by Engineering management. The PRA assessment engineer was counseled. The need to maintain attention to detail and to challenge assumptions used in performing calculations was stressed.

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION

Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 1 5000272 91-009-00 7 of 7 CORRECTIVE ACTION: (cont'd)

A 10% random sampling of DEFs will be reviewed to ensure analysis results were assessed correctly. Included in this sampling will be the DEFs associated with the HEBA barrier concerns first identified in May 1990. Results of the random sampling assessment will be used to determine additional corrective actions as appropriate.

Administrative controls, to control Appendix R penetrations, will be extended to include HEBA penetration impairments.

/"")~,;;::

/}/j:,~~Di.c~<c-~

General Manager -

Salem Operations MJP:pc SORC Mtg.91-027

ML18095A807

Text

Dear Sir:

Navigation menu

Search