ML20203A078

Application for Amend to License DPR-35 UFSAR Section 10.7, Clarifying Design Basis for Salt Water Svc Water Sys

ML20203A078
Person / Time
Site:	Pilgrim
Issue date:	02/11/1998
From:	Olivier L BOSTON EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20203A083	List: ML20203A078 ML20203A111 ML20203A123
References
BECO-2.98.008, NUDOCS 9802230270
Download: ML20203A078 (11)

Text

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10CRF50SO scaron ear on Pilgrirn Nuclear Powar Station Rocky Hin Road Plymouth, Massachusetts 02300 LJ. Olivler Vce President Nuclear and Staten Director February 11, 1998 BECo Ltr. 2.98.008 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555-0001 Docket No. 50-293 License No. DPR.-35 Proposed: License Amendment to BECo UFSAR to Clarify the Design Basis

~ for the Salt Service Water (SSW) Syctem.

Boston Edison Company (BECo) hereby proposes to amend Operating License No. DPR-35 in accordance with 10CFR50.00. This proposed change modifies Pilgrim Nuclear Power Station UFSAR Section 10.7, Salt Service Water System, by providing clarification concerning single failures which may place the salt service water system in a configuration of one pump supplying both trains of heat exchangers for the first ten minutes of the worst case design basis accident. NRC review and approval of the proposed amendment is requested.

The requested change is described in Ahachment A. The marked-up UFSAR pages are provided in Attachment B. Attachment C contains the amended UFSAR pages.

Attachment D contains Calc. No. M-771, Rev. O, RBCCW Heatup Immediately Following a DBA-LOCA, and Attachment E contains the Summary and Results portions of Calc. No.

M500, Rev. 3, Range of Salt Service Water System Header Pressures and Pump Flows.

.J Olivier 9802230270 980211 - )

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Commonwatith of Massachusetts Country of Plymouth Then personally appeared before me, L.J. Olivier, who being duly sworn, did state that he is Vice President Nuclear, Station Director of Boston Edison Company and that he is duly authorized to execute and fiU the submittal contained herein in the name and on behalf of Boston Edison Company and that the statements are true to the best of his knowledge and belief.

My commission expiresb6bwle 30. 3 of 2..

' ' kk DATE

[__ t ! 0 'W NOTARY PUBl.lC Attachments:- A. Description of Proposed Change B. Marked-up UFSAR Pages C. Amended UFSAR Pages D. Calc. No. M 771, Rev. 0 E. Summary and Results of Calc. No. M500, Rev. 3 Regional Administrator, Region 1 Peter LaPorte, Director U.S. Nuclear Regulatory Commission Massachusetts Emergency Management e Agency Office of Emergency Preparedness

• 475 Allendale Road 400 Worcester Road King of Prussia, PA 19406 P.O. Box 1496 Framingham, Ma. 01701-0317 Senior Resident Inspector Pilgrim Nuclear Power Station Mr. Alan B. Wang Project Manager Project Directorate 1-3 '

Office of Nuclear Reactor Regulation Mail Stop: OWFN 1482 1 White Flint North 11555 Rockville Pike Rockville, MD 20852 Mr. Robert M. Hallisey, Director Radiation Control Program Center for Communicable Diseases Mass, Dept. of Public Health 305 South Street Jamaica Plain, MA 02130

ATTACHMENT A

. Description of Proposed Chance ELoposed Chance:

Boston Edison Company (BECo) proposes to modify, by amendment PNPS-UFSAR Section 10.7, Salt Service Water System, by identifying that certain single active failures do exist that could leave the salt service water (SSW) systern in a configuration with one SSW pump serving both SSW trains through oper crossover (division) valves for the first ten minutes of an accident.

Discussion:

The SSW system is properly designed as a common header arrangement with five (5) pumps in which any combination of pumps may be operating without damaging effects.

The system is designed with the cri'eria that the pumps will operate over a wide range of conditions. They are rugged single-stage vertical turbine design of bronze and monel construction with a total head and horsepower curve that are favorable for multi-pump header configurations. The SSW pumps supply four heat exchangers, two turbine building closed cooling water (TBCCW) and two reactor building closed cooling water (RBCCW). The TBCCW heat exchangars provide cooling to equipment located in the turbine building and station air conditioning systems. The RBCCW heat exchangers provide cooling to the core standby cooling system components and provide a heat sink for the residual heat removal heat exchangers.

The PNPS FSAR in section 10.7.1 states "The safety objective of the SSW system is to provide a heat sink for the Reactor Building Closed Cooling Water (RBCCW) system under transient and accident conditions", This safety objective consists of two sub-functions: the first is to supply cooling to the equipment area coolers and to the core standby cooling systems which would be raquired to operate under transient and accident conditions; the second sub-function is to aupply cooling to the residual heat removal (RHR) system for containment heat removal. The current licensing basis credits operator actions to iniuate containment cooling ten minutes after the event has initiated.

Review of the results of the single failure analysis performed for the SSW system shows that certain low probability single active failures do exist that can cause the loss of the automatic closing feature of the SSW motor-operated division valves MO-3808 and MO-3813 and the loss of SSW pumps in one train, which could leave the SSW system in a configuration with one SSW pump supplying both SSW trains through open cross connect header isolation valves, For example, this can occur when power is lost on one train of the 4160/480 VAC distribution system but not the other When this occurs, only the valve which senses undervoltage on its associated 480V load center will receive a command to close and only if the selector switch (used to determine the loop to which the spare SSW pump will be aligned) is selected to the opposite train. In other words, if the telector switch is positioned to the same train that has lost power, neither division valve will receive a signal to close.

l.. . .

Th3 pumps on the d:en:rgiz:d trcin will stop, and if only ono pump is running in th3 cn:rgiz d trcin, this pump may continuo to supply flow to both trains of SSW. A s:cond pump tay or may not start depending on actual heat exchanger valve positions and tidal conditions at the time of the event.

This system configuration can also occur if a fault on a nonsafety-related load occurs on either motor control center lMCC) serving the SSW pumps and the breaker associated with that load fails to trip. The supply breaker for the MCC will open to protect the bus, deenergizing the associated pumps without signaling either motor operated division valve to close.

The abilit) of the SSW system to operate without damage with one pump supplying both trains of SSW is addressed by PNPS calculation M500

• Range of Salt Service Water System Header Pressure and Pump nnws". This calculation demonstrated continuous  ;

operation of a single SSW pump with an open header and minimum system Nsistance is I acceptable. The cxpected pump flow rate under worst esse design conditions is within the tested performance of the pump, and the NPSH requirements are met at the low astronomical tide. Additionelly, with the aid of the current pump OEM, it has been determined that the SSW pumps can withstand operation under the full range of conditions and times required with no significant adverse effects. This includes conditions under which only one pump would be operating until operator action is taken.

No degradation or damage to the pump is expected under these circum *,tances.

Additional testing with a SSW pump runout for a test du ation of thirty ininutes showed that a SSW pump can operate under conditions of severe cavitation without any I degradation of performance or any noticeable material degradation of pump intemals. ,

l This test indicated the SSW pump NPSH required is considerably more favorable than previous estimates and concem with potential pump damage due to cavitation is not an issue.

However it was recognized that the SSW system would be operating at diminished capacity until t'perator action restored the ability to provide design heat removal. These actions might not occur until ten minutes after the bccident. The abihty of the SSW i systam to supply adequate coolir.g to the RBCCW system was considered in PNPS calculation M771,"RBCCW Heatup Fo!!owing a DBA LOCA". This calculation shows that even with no cnoling to the RBCCW system from SSW during the first ten minutes of the worst case DBA LOCA, the temperatures within the RBCCW system remain within ecceptable limits.

However, the FSAR clearly describes in section 10.7.5 the response of the SSW system to a complete ! cts of AC power. It assumes the system will be split by the closure of one of the two isolation valves upon complete loss of AC power. It does not address system response to partialloss of AC power. Even though the results of the aboy" described calculations show the SSW system will perform its prescribed function in ... intended manner, the family of single failures described above will place the SSW system in a configuration not previously analyzed. This is considered an unreviewed safety question.

Therefore, this design is submitted to the NRC for review and approval as an amendment to the station operating license. The aF - af the SSW system to perform its safety ob;tetive is not diminished by operation w a one pump /two loop configuration. We request NRC approval of the proposed license amendment at the earliest convenient time,

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D0 termination of No Sionificant Hazards Consideration

] The Code of Federal Regulations (10CFR 50.91) requires licensees requesting an l amendtnent to provide an analysis, using the standards in 10CFR 50.92, that determines whether a significant hazards consideration exists. The following analysis is provided in 4

accordance with 10CFR 50.91 and 10CFR 50.92 for the proposed amendment:

i

. a. The proposed amendment does not involve a simific.nt increase in the probability

or consequences of an accident previously eveluated.

Operation with one (1) SSW pump supplying two (2) SSW trains is not an accident or transient precursor and does not prevent the RBCCW system from providing adequate

cooling during an accident, Core cooling requires no SSW for the first ten rninutes, and no containment cooling is assumed for the first ten minutea Pump testing has proved nu SSW pump damage will result from this configuration so there will be no effect on the containment cooling function. The current licensing basis includes operator action after ten minutes to align the SSW system to achieve containment cooling. This amendment does not affect operator action after ten minutes since pump and valve manipulations are already required to align containment coolirig. Therefore, the changes do not involve a i algnificant increase in the probability or consequences of an accident previously j evaluated.

b. The proposed amendment does not create the possibility of a new or d_ifferent kind Of accident from any accident previousiv evaluated, 5

The SSW system operating modes are not accident precursors. They cannot influence

the types of accidents that can occur. The SSW pumps can withstand operation under l the full range of conditions and for the time periods considered under a one pump, two

, train system configuration with no adverse effects. The SSW system is properly designed as a common header arrangement with five (5) pumps in which any combination of one to five pumps may operate without damaging effects.

l c. The proposed imendment does not involve a sianificant reduction in the marain of

safety.

i l Operation with one (1) SSW pump supplying two (2) SSW trains does not linpact the ability to provide adequate core or containment cooling during an accident. Although SSW system flow will be diminished during the first ten minutes of the heident, no system flow at allis needed at that time. The current licensing basis credits operator action after ten minutes to align the RHR, RBCCW, and SSW systems for containment i cooling. Operators are expected to isolate the SSW loops or start additional SSW pumps as necessary given the existing specific conditions.

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l ATTACHMENT B Marked-up UFSAR Paaes 10.7-2B and 10.7.3 Page 1 of 3

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PNPS FSAR

' The pturps are separated into two loops electrically. In the event of the loss of the preferred ac power source, the twc SSW ptrrps on loop A are powered by diesel generator A. They provide cooling to RBCCW loop A (also powered by diesel generator A) which provides cooling to all Core Standby cooling System conponents loaded on diesel generator A. The two )

salt service water purrps on loop B have the same relationship, both to their standby ac power source, diesel generator B, and to RBCCW Loop B.

The fif th punp is loaded on a conrican energency service bus which can be powered from either standby ac power source.

There are a ntstber of single fai. lures that can r ssult in a SSW system configuration where one SSW pterp will be supplying flow to both trains of SSW daring the first ten minutes of an accident. Should this occur cperators are then expected to align the SSW system for optimal a perfontance by starting additional punpa and/or closing division valves as required. This mode of operation has been analyzed and detennined to be acceptable.  !

)

J 10.7-2b Rev 21 - Oct 1997 f

Initi: tion of st:ndby cc pow:r following loss of the pr f;rred cc pow r sourco will cutom:tically st rt at I::st one pump in each loop during normal conditions. Following a LOCA and loss of offsite power one and only one pump will start in each loop because of diesel load limitations. Additional pumps are started manually by the operator as additional cooling loads are established and diesel capacity is made available.

10.7.6 Safety Evaluation The SSW system is designed with sufficient redundancy so that no single active system component failure nor any single active component failure in any other system can prevent it from achieving its safety objective. 'wo independent closed loops with full heat transfer capacity on each loop are provided.

The 22 in dischcrge headers leave the Reactor Building at an elevation of 15 ft 7 in msl.

The two ;.arallel lines run approximately parallel to the shoreline with a 2.8 percent slope.

At a point approximately in line with the edge of the intake structure the lines turn and then parallel the centerline of the discharge structure with a 1.98 percent slope. At an elovation of -61/2 ft msl the two discharge lines turn and enter the side of the discharge structure sealwell.

Detection of leakage in the Reactor Building auxiliary bay is provided by two water level detectors mounted in each area, The detectors provide control room personnel with early indication of flooding such that personnel can be dispatched to the area to identify the source and offect isolation.

Dewatering of a major pipe rupture is accomplished by two 14 in draia lines in each area which direct the water to the torus compartment. The discharge of the drain lines is submerged in a water trough to ensure that a sufficient water seal exists between the torus compartment and the Reactor Building auxiliary bay.

The drain line dewatering capacity is sized on the maximum possible flooding rate which results from a single failure in any one line.

Numerous small diameter floor drains in the RBCCW compartments are plugged to prevent chloride and nitrate intrusions in radwaste, Therefore, normal leakage can accumulate to a level of four inches before overflowing the lip around the fourteen inch dewatering lines located in each of the RBCCW compartments. All safety related equipment in the RBCCW compartments will be unaffected by flooding four inches above the floor level. Normal leakage will not prevent safety related systems or components from performing their intended safety functions.

A major pipe break in this area will not result in a loss of both RBCCW and TBCCW Systems because the redundant portions of each system are separated by a watertight barrier. The watertight barrier consists of a watertight door and a spray barrier. The spray barrier is located in the pipeway immediately alsove the watertight door. Position switches provide station personnel with status information for the watertight door at all times.

w The existence of single failures which place the SSW system in the mode of one pump supplying both trains of heat exchangers for the first ten minutes of an accident has been i analyzed and found to be acceptable. Operator action is credited after ten n. iutes to realign the system for optimal performance.

N _ N ,<

10.7.3 Rev 21 - Oct 1997

l l ATTACHMENT C Amended UFSAR Paaes 10.7-2B and 10.7-3 Page 1 of 3

[HPS-FSAP, There are a nunber of single failures that can result in a SSW system configuration where one SSW punp will be supplying flow to both trains of SSW during the first ten minutes of an accident. Should this occur operators are then expected to align the SSW system for optinal perfortrance by starting additional purps and/or closing division valves as required. This node of operation has been analyzed and determined to be acceptable.

The purps are separated into two loops electrically. In the event of the loss of the preferred ac power source, the two SSW punps on loop A are powered by diesel generator A. They provide cooling to P1CCW loop A (also powered by diesel generator A) which provides cooling to all Core Standby Cooling System conponents loaded on diesel generator A. The two salt service water punps on loop B have the sane relationship, both to their standby ac power source, diesel generator B, and to RBCCW Loop B.

The fif th punp is loaded f n a contron emergency service bus which can be powered from either standby ac power source.

1 l

l 10.7 2b Rev 21 - Oct 1997

PNPS FSAR Initiation of standby ac power following loss of the preferred ac power source will automatically start at least one pump in each loop during normal corditions. Following a LOCA and loss of offsite power one and only one pump will start in each loop because of diesel load limitations. Additional pumps are started manually by the operator as additional cooling loads are established and diesel capacity is made available.

10.7.6 Safety Evaluation The SSW system is designed with sufficient redundancy so that no single active system I

' component failure nor any single active component failure in any other system can prevent it from achieving its safety objective. Two independent closed loops with full heat transfer capacity on each loop are provided.

The existence of single failures which place the SSW system in the mode of one pump supplying both trains of heat exchangers for the first ten minutes of an accident has been analyzed and found to be acceptable. Operator action is credited after ten minutes to realign the system for optimal performance.

The 22 in discharge headers leave the Reactor Building at an elevation of 15 ft 7 in mst.

The two parallellines run approximately parallel to the thoreline with a 2.8 percent slope.

At a point approximately in lir's with the edge of the Iraake structure the lines turn and then parallel the centedine of the discharge structure with a 1.98 percent slope. At an elevation of -61/2 ft mst the two discharge lines tum and enter the side of the discharge structure sealwell.

Detection of leakage in the Reactor Building auxiliary bay is provided by two water level detectors mounted in each area. The detectors provide control room personnel with early indication of flooding such that personnel can be dispatched to the area to identify the source and effect isolation.

Dewatering of a major pipe rupture is accomplished by two 14 in drain lines in each area which direct the water to the torus compartment. The discharge of the drain lines is submerged in a water trough to ensure that a sufficient water seal exists between the torus compartment and the Reactor Building auxiliary bay, The drain line dewatering capacity is sized on the meximum possible flooding rate which results from a single failure in any one line.

Numerous small diameter floor drains in the RBCCW compartments are plugged to prevent chloride and nitrate intrusions in radwaste. Therefore, normal leakage can accumulate to a level of four inches before overflowing the lip around the fourteen inch dewatering lines located in each of th > RBCCW compartments. All safety related equipment in the RBCCW compartments will be unaffected by flooding four inches above the floor level. Normal leakage will not prevent safety related systems or components from performing their intended safety functions.

10.7-3 Rev 21. Oct 1997 y . . . .

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