ML20046B895

LER 93-008-01:on 930518,determined That Control Air Not Analyzed to Function During Seismic Event Due to Lack of Understanding Significance of Control Air Availability for Long Term DG Operation.Ufsar Will Be Updated

ML20046B895
Person / Time
Site:	Seabrook
Issue date:	07/30/1993
From:	Peschel J NORTH ATLANTIC ENERGY SERVICE CORP. (NAESCO)
To:
Shared Package
ML20046B894	List: ML20046B893 ML20046B895
References
LER-93-008, LER-93-8, NUDOCS 9308060381
Download: ML20046B895 (5)

Text

.

C FORM 365 U.S. NUCLEAR REGULATORY COPHISS10li APPROVED BY OMB NO. 3150-0104 (5-92) EXPIRES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH

$ Apo I*f

$#dI$ E0L CTION P JEST 0 IR LICENSEE EVENT REPORT (LER) n THE INTORMATION AND RECORDS MANAGEMENT BRANCH (MNBB 7714), U.S. NUCLEAR REGULATORY COMMISSION, (See reverse for required number of digits / characters for each block) WASHINGTON, DC 20555-0001, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.

I FACILITY KAME (1) DOCKETNUMBER(2) PAGE(3) 1 Seabrook Station 05000443 1 OF 5 l TITLE (4)

Control Air Not Analyzed to Function During Seismic Event EVENT DATE (5) - LER NUMBER (6) REPORT DATE (7) OTHER FACILITIES INVOLVED (8)

MONTH DAY YEAR YEAR SEQUENTIAL REVISION MONTH DAY YEAR NUMBER NUMBER 05000 FACILITY NAM DOCKET NUMBER 05 18 93 93 08 01 07 30 93 05000 OPERATING y THIS REPORT IS SbtlMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR Ut (Check one or more) (11)

N00E(9) 20.402(b) 20.405(c) 50.73(a)(2)(iv) 73.71(b)

POWER g _

20.405(a)(1)(i) 50.36(c)(1) X 50.73(a)(2)(v) 73.71(c)

LEVEL (10) 20.405(a)(1)(ii) 50.35(c)(2) 50.73(a)(2)(vii) OTHER 20.405(a)(1)(iii) 50.73(a)(2)(i) 50.73(a)(2)(v111)(A) (Specify in 20.405(a)(1)(iv) X 50.73(a)(2)(ii) Ab trac ow 50.73(a)(2)(viii)(B) 20.405(a)(1)(v) 50.73(a)(2)(iii) 50.73(a)(2)(x) NRC Form 366A)

LICENSEE CONTACT FOR THIS LER (12)

NAME TELEPHONE NUMBER (Include Area Code)

Mr. James M. Peschel, Regulatory Compliance Mgr. (603) 474-9521 Ext. 3772 COMPLETE ONE LDE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

CAUSE SYSTEM COMPONENT MANUFACTURER CAUSE SYSTEM COMPONENT R 0 E f MANUFACTURER SUPPLEMENTAL REPORT EXPECTED (14) EXPECTED MONTH DAY YEAR YES SUBMISSION I (If yes, complete EXPECTED SUBMISSION DATE). X NO DATE(15)

ABSTRACT (Limit to 1400 spaces, i.e.. approximately 15 single-spaced typewritten lines) (16)

North Atlantic Energy Services Corporation (North Atlantic) has identified a condition that is contrary to the design description stated in the Updated Final Safety Analysis Report (UFSAR). Specifically,it has been identified that failure of the air supply to the Emergency Diesel Generators (EDG) jacket cooling water temperature control valves during a seismic event  ;

could cause overcooling of the EDGs, which could potentially preclude long term operation of the engines. This is contrary to the UFSAR, which states that the functional performance of the cooling water system is not adversely affected by environmental occurrences, abnormal operation, accident conditions and loss of power. On May 18,1993, North Atlantic i reported this event pursuant to 10CFR50.72(b)(ii) as a condition outside the design basis of the plant.

The primary root cause of this event was a lack of understanding the significance of control air availability for long term diesel generator operation.

Immediate corrective actions for this occurrence included a Preliminary Operability Determination for the Emergency Diesel l Generators. The Operability Determination was supported by a Preliminary Engineering Evaluation which documented the  ;

seismic functionality of the diesel air start skid, utilizing available seismic documentation and Engineering judgement. The evaluation concluded that with the use of appropriate operator actions the EDG air start skid will function to support the EDG during a seismic event. The Operations Department revised EDG local alarm response procedures which will provide the method for restoring power to appropriate Motor Control Centers (MCCs), in event that the feeder breakers to the MCCs should trip during a seismic event. Long term corrective actions will include: updating the UFSAR and design documents to reflect appropriate safety classification of starting air components, and updating programs and procedures to ensure long term operability of the EDG.

NRC FORM 366 (5-92) 9308060381 930730 PDR ADOCK 05000443 S PDR

' - wRC IORK 366A U.S. NUCt EAR RIGULA10RY COPMIS$1CD APPROVLD fly OMil C3. 3150-0104 ,

l EXPIRES 5/31/95 (5 92) l ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH '

THIS INFORMATION COLLECTION REQUEST: 50.0 HRS.

FORWARD COMMENTS REGARDING BURuEN ESTIMATE TO LICENSEE EVENT REPORT (LER) THE INFORMATION AND RECORDS MANAGEMENT BRANCH TEXT CONTINUATION (MNBB 7714), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555-0001, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104), OfflCE OF MANAGEMENT AND BUDGFT, WA5HINGTON, DC 20503.

IACitllY MAME (1) DoCKLI m MilR (?) llR NtMllR (6? PAGI (3)

YEAR SLQUlN11AL REVIS]DN Seabrook Station NUMBER NUMBER 05000443 93 01 2 OF 5 08

~1LK1 (lI wre space is regoired, use additionai cupies of NRC /orn 3bbA) {t1)

Descrirition of Event North Atlantic has identified a condition that is contrary to the design description stated in the Updated Final Safety Analysis Report (UFSAR). Specifically, it has been identified that failure of the air supply to the Emergency Diesel Generators (EDG) jacket cooling water temperature control valves during a scismic event could cause overcooling of the EDGs, which potentially could preclude long term operation of the engin e s. This is contrary to the UFSAR, which states that the functional performance of the cooling water system is not adversely affected by environmental occurrences, abnormal operation, accident conditions and loss of power.

The design basis for the Diesel Generator Cooling Water System as stated in UFSAR Section 9.5.5.1 is not being met as discussed below:

The UFSAR states the following in Section 9.5.5.1 " Design Hases" for the Diesel Generator Cooling Water System:

"The f unctional performance of the Cooling Water System is not adversely affected by environmental occurrences, abnormal operation, accident conditions, and loss of offsite power."

Additionally, the following statement is made in UFSAR Section 9.5.6.3: ,

"A loss of air pressure in one of the two redundant supply lines to the engine could affect the supply of 20 psig control air to the diaphragm operated cooling water control valves. Under this condition, the unit will continue to operate but with lower jacket water and air cooler water temperatures since the control valves would go to the full open (maximum cooling) position

This UFSAR statement was based on the response to NRC Request for Additional Information (RAI) 430.111 which was incorporated in FSAR An :ndment 48 (January 1983).

i Contrary to the above statements in the UFSAR, the EDG manufacturer (Colt Industries) has determined that with the control valves in their maximum cooling positions, the relatively rapid cooling of the jacket water could cause engine damage to the cylinder liner /j a ck et, piston scuffing or piston seizure due to non-uniform component thermal expansion. On May 18,1993, North Atlantic reported this event pursuant to 10CFR$0.72(b)(ii) as a condition outside the design basis of the plant.

l NRC F ORM 366A (5-92) e i

r WRC F0PM 366A U.S. NUCLLAR REGULATOR 7 COMMISSION APPROVED BY OMB NO. 3150-0104 (5-92) EXPlRES 5/31/95 l

ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORMATION COLLECTION REQUEST:

50.0 HRS. FORWARD COMMENTS REGARDING LICENSEE EVENT REPORT (LER) BURDEN ESTIMATE TO THE INFORMATION AND RECORDS MANAGEMENT BRANCH (MNBB 7714), U.S.

TEXT CONTINUATION NUCLE AR REGULATORY COMMISSION, WASHINGTON, DC 20555-0001, AND TO THE PAPERWORK REDUCTION PROJECT , OFFICE OF MANAGEMENT AND ( 3150-0104 BUDGET, W A., }HINGTON,DC 20503.

IACILITY NAMI (1) DOCKET NUMBtR tFR NUMBER (6) PAGE (3) yggg SEQUENIIAL REVIS10 Seabrook Station NUMBER N 05000443 93 01 3 OF 5 08 ILKt (if more space is required, use addr t ronal copies of NRC f orm 3bt,A) (11)

The conditions which can result in EDG overcooling are described below. Each EDG is equipped with an independent starting and control air system. The starting air system consists of an air start compressor, air receivers and associated piping. The EDG air start compressors are relied upon to re-charge the air receivers to provide the required starting air and sufficient control air for long term operation. The air-start compressors are highly reliable units. 110 wever, they are not currently described in the UFSAR as being qualified to withstand a design basis scismic event and they are powered from seismic Motor Control Centers (MCCs) which supply non. nuclear safety loads. The event most likely to cause both EDG air start compressors to simultaneously malfunction is a design basis seismic event. The design basis assumes that all non-safety loads fail durir.g the design basis seismic event which could potentially cause the feeder breakers to the MCCs to trip open. Upon further investigation it was determined that only the feeder breaker to MCC 511 would trip open and power would remain uninterrupted to MCC 611. If the design basis seismic event were to adversely affect the air start compressors or their MCCs, the receivers would slowly bleed down over a period of 7-15 hours resulting in the jacket cooling water system temperature control valves going to their maximum cooling position. j l

l Safety Consequences i There were no adverse safety consequences as a result of the event. An evaluation performed by North Atlantic determined that EDG would continue to provide power during a scismic event.

Adverse safety consequences could have resulted during EDG operation if the compressors were unavailable to recharge the receivers. This co ild have resulted in the receivers slowly bleeding down if compensatory actions were not taken by the operators upon the receipt of the starting air receiver low and low-low alarms which are provided locally and in the main control room. These alarn.s would alert operators of the degrading condition of the receiver tanks. It is reasonable to expect that the operators would take compensatory actions to restore power to the air compressor when the starting air receivers reached the low and the low-low starting air pressure setpoints. The potential safety implications of this scenario are addressed below.

Potential Safety Implications A potential failure mode for a single train of emergency power existed that was previously unrecognized within the UFSAR and plant operating procedures. Since the need for control air to maintain long term operation of the EDG was not recognized, the starting air compressor and its appurtenances were not  ;

identified as critical components required for EDG operability. Therefore, a starting air compressor could I have been taken out of service without full recognition of the potential safety implications.  !

l ll Nin. t0kM M bA (5- W )

l

- hRC 6 0m 366A U.S. NUCll AR RI GUL A10RY COMMISSION APPROVtp BY OMB CO. 3150-0104 (5-92) EXPIRES 5/31/95 i

ESTIMATED Bl!RDEN PER RESPONSE TO COMPIY WITH 1HIS INFORMATION COLLECTION REQUEST:

50.0 HRS. FORWARD COMMENTS RECARDING LICENSEE EVENT REPORT (LER) BURDEN ESTIMATE TO THE INFORMATION AND kECORDS NANAGEMENT BRANCH (MNBB 7714), U.S.

TEXT CONTINUATION NUCLEAR REGUtA10RY COMMISSION, WASHINGTON, DC 20555-0001. AND TO THE PAPIRWORK REDUC 110N PROX C1 (3150-0104), OfflCE OF MANAGEMENT AND BUDGET, WASHING 10N, DC 20503.

fAClllIY NAMI (1) DOCKil MUMHIR LIR NUMBER (6) PAGE (3)

YEAR SEQUtNilAL REVIS10 Seabrook Station NUMM P N 05000443 93 01 4 OF 5 08 1L KI (lt more space is requ tred, use addlttoraI copies of NRC iorm J66A) {l1)

Root Cause The primary root cause of this event was a lack of understanding the significance of control air availability for long term EDG operation. During the initial design phase both the vendor (Collec) and United '

Engineers and Constructors (UE&C) did not identify that t l'c air compressors were critical to EDG operation. The primary design focus for the starting air system was assuring that enough air volume was present in the air receivers to ensure five 10 second starts of the EDG per Branch Technical Position Requirements. Long term availability of control air apparently was not considered by either Collec or UE&C during the design phase.

A lack of understanding by YNSD/PSNil/Coltec of the significance of control air for extended EDG ,

operation has been demonstrated. In September 1982 a potential Robertshaw temperature control valve  !

failure mechanism was reported pursuant to 10CFR50.55(e)(3). The failure mechanism that was reported could result in the valve controlling at a lower tempcrature resulting in EDG overcooling. The letter acknowledges that the EDG jacket water heat exchangers were designed to provide jacket cooling water at '

110*F with 90*F Service Water based on rated load operation. The letter further states " . at reduced load, and with colder Service Water, a control valve malfunction could cause overcooling in the engine, and a possible engine failure could constitute a substantial safety hazard" Contrary to this, FSAR Amendment 48 was issued five months later indicating that a loss of control air 'will not result in an engine shutdown or 3 degradation of engine perfor mance" The impact of a loss of control air pressure with reduced Service Water temperatures on the operation of the EDG was not considered.

Corrective Actions l Immediate corrective actions for this occurrence included the performance of a Preliminary Operability Deterrnination for the Emergency Diesel Generators which was supported by Engineering Evaluation Number 93-028. This evaluation documented the seismic functionality of the diesel air start skid, utilizing available ,

scismic documentation and Engineering judgement. Lingineering Evaluation Number 93-028(R1) confirmed '

i the seismic capability of the air start skid and concluded that through the use of available seismic documentation and operator action the EDG air start skid will function to support the EDG during a scismic event.

Operations Department management initially issued a standing operating order describing the rnethod for restoring power to MCC 511 and MCC 611, in event that the feeder breakers to the MCCs should trip during a seismic event. This guidance was subsequently incorporated into EDG local alarm response procedures.

This will provide procedural guidance for restoring power to these MCCs upon receipt of the air receiver low pressure alarm.

Mit EDM M W W riT

l i 1

. MRC I0I.M 366A U.S. NUCLLAR RE GULA10RY COMMISSION $'PPROVED BY OMB NO. 3150-0104 (5-92)

EXP]RES 5/31/95 l j ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORMATION COLLECTION REQUEST:

50.0 HRS. FORWARD COMMENTS REGARDING

, LICENSEE EVENT REPORT (LER) BURDEN ESilMATE TO THE INFORMATION AND RECORDS MANAGEMENT BRANCH (HNBB 7714), U.S.

TEXT CONTINUATION NUCLEAR REGUIATORY COMMISSION, WASHINGTON, DC 20555-0001, AND TO THE PAPERWORK REDUCTION PROJECT (3150 0104). OFFICE OF MANAGEMENT AND BUDGET. WASHINGTON, DC 20503. 1 IACll11Y NAMI (1) DOCKE I NUMBlR (fR NUMBER (6) PAGF (3)

YEAR SEQUENTIAL REV1510 Seabrook Station 05000443 5 OF 5 93 08 01 II.K 1 (11 more space is required, use additiona l copies of NRC f orm 366A) (11) l To ensure long term operational availability of the EDG control air system the following corrective actions will be taken:

1. The UFSAR and design documents will be updated to reflect appropriate safety classification of starting air components.

2. Programs and procedures will be updated to ensure long term operability of the EDG.

l Previous occurrences l

This is the first event where Seabrook Station has reported a potential for EDG overcooling due to unavailability of EDG control air. As discussed above, in September 1982 a report was made pursuant to j 10CFR50.55(c)(3) regarding a potential Robertshaw temperature control valve mechanical failure which could result in the valve controlling at a lower temperature and EDG overcooling.

At the time of discovery of this event, the plant was in MODE 1,100% power.

NFL FUhM AbX (5 M J