ML20198N325

Supplements 981112 Reply to NRC NOV ,in Response to 981209 Request from J Yerokun for Description of Reasons for Changing Normal Makeup & Purification/Hpi Sys Valve Lineup & Basis Upon Which Util Found Change Acceptable

ML20198N325
Person / Time
Site:	Three Mile Island
Issue date:	12/24/1998
From:	Langenbach J GENERAL PUBLIC UTILITIES CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
1920-98-20716, NUDOCS 9901060096
Download: ML20198N325 (6)

Text

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GPU Nuclear. inc.

( Rout, "1 South NUCLEAR Post Office Box 480 Middletown. PA 17057-0480 Tel 717-944 7521 December 24, 1998 1920-98-20716 l

U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D. C. 20555 Gentlemen:

Subject:

Three Mile Island Nuclear Station, Unit 1 (TMI-1)

Operating License No. DPR-50 Docket No. 50-289 Reply to Notice of Violation Dated October 15,1998 - Supplement i The purpose of this letter is to supplement the November 12,1998 GPU Nuclear reply'to the NRC's Notice of Violation (NOV) dated October 15,1998. This is in response to a request from NRC Region I inspector Jimmi Yerokun on December 9,1998 for GPU Nuclear to desciibe our reasons for I changing the normal Makeup and Purification /High Pressure Injection (Makeup / HPI) System valve I lineup and the basis upon which we found that change to the operating procedures acceptable. The following presents some ofthe background regarding the need for this change and a sununary of the GPU Nuclear safety evaluation (Reference 1) that approved the change.

f' BACKGROUND: l

[ The HPI system function as described in the Final Safety Analysis Report (FSAR) is to provide emergency core cooling for conditions when Reactor Coolant System (RCS) pressure is above the

l. Low Pressure Injection (LPI) System capability. A simplified diagram of the applicable portion of the l Makeup (Mi D System valve a.rangement is shown in Figure 1 (Attached).

Until TMI-l Operating Cycle 12 which began in October 1997, the Makeup Pump suction header was lined up for nonnal plant operation with only one of the two sets of cross-connect valves (MU-V-68A and MU-V-68B) open between the suctions of the three Makeup Pumps. Makeup Pump MU-P-1B is normally operating taking suction from the Makeup Tank (MUT) to provide a source for nonnal RCS e ,? -ny l

9901060096 PDR 981224 7)

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1920-98-20716 Page 2 of 5 makeup and Reactor Coolant Pump (RCP) seal injection. MU-V-14A and MU-V-148, which must be closed during normal operation to prevent injection ofborated water from the Borated Water Storage Tank (BWST) into the RCS, both open automatically on an Emergency Safeguards (ES) Actuation Signal. Prior to Operating Cycle 12, MU-P-IC was aligned for ES operation along with MU-V-14B, ,

but the MU-P-lC suction header was isolated from the common suction header for MU-P-1 A and  !

MU-P-1B with MU-V-69A and MU-V-698 locked closed.

GPU Nuclear had been considering the change to operate with a common Makeup pump suction l

header for some time. The assessment of safety consequences and implications of a June 1985 '

inadvertent Emergency Safeguards Actuation System (ESAS) actuation, reported as LER 85-001, j concluded that if the event had occurred on the "B" side without the MU-P-lC suction valves '

first being opened, the event could have resulted in damage to Makeup Pump MU-P-lC (Reference 2). In a follow-up study, the improvement in Makeup Pump availability from maintaining both sets of suction cross connect valves open was evaluated. The study found that a l reduction in the calculated core damage frequency (CDF) could be achieved and recommended further consideration of making that change. This was reported to the NRC in 1989 (Reference 3).

During the TM1-1 Architect Engineer (AE) Engineering Design Inspection (50-289/96-201),

w hich ended in January 1997, the inspection team raised issues because of the fact that the MU-P-lC suction piping is not normally lined up to a source of water. The repon states in Open  !

Item (01) 96-201-02 that in the normal standby mode, the suction from the BWST and high pressure injection valve from makeup pump MU-P-lC are in the closed position, and the pump is isolated from the suction and discharge headers that are connected to makeup pumps l l

MU-P-1 A&B and the Makeup Tank (MUT). Since Makeup Pump MU-P-lC is not lined up to any water source until MU-V-14B opens and there are no interlocks or time delays, the inspection team was concerned that the effect on the pump due to a slow opening suction valve combined  ;

with a rapid start of the pump and a fast opening high pressure injection valve had not been I properly analyzed. Also the report states in O! 96-201-03 that the inspection team identified a potential for accurnulation of non-condensables, such as hydrogen, released from the stagnant water in the suction line because of the physical configuration of the line and considered that a positive pump suction pressure was not necessarily an indication of absence of gas accumulation i in the piping.

In February 1997 GPU Nuclear discovered that Makeup suction piping and components had potentially been stressed beyond design code allowable stresses on a number of occasions over a long period of time due to leakage through the Makeup Pump recirculation line check valves.

Having completed the safety evaluation for the change, GPU Nuclear committed in LER 97-003, Revision 1 to implement changes prior to the next operating cycle (TMI-1 Operating Cycle 12) to eliminate the possibility of over-pressurizing the Makeup suction piping during testing by changing the normal valve lineup for the Makeup System to maintain the Makeup Pump suction cross connect valves (MU-V-69A and MU-V-69B) open (Reference 4).

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PURPOSE OF THE CHANGE:

The following lists some of the benefits of the change to maintain the Makeup Pump suction cross H

connect valves (MU-V-69A and MU-V-69B) open:

l 1. Concerns associated with maintaining an isolated Makeup Pump suction header filled and vented are resolved. Maintaining cross connect valves (MU-V-69A and MU-V-698) open:

a. Provides greater assurance that the Makeup Pump MU-P-lC suction piping remains filled and l vented at di times, b.- Precludes damage to Makeup Pump MU-P-lC ifit were inadvertently started during l operation or testing without establishing a suction path from the MUT or the BWST,  ;

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c. Reduces the potential for damage to Makeup Pumps MU-P-1 A & MU-P-1B due to a failure of MU-V-14A to open on ES actuation, and I

d. Reduces the probability of Makeup Pump damage due to improper valve operations during Makeup System testing.

L 2. ' Resolves concerns associated with over-pressurization ofisolated Makeup Pump suction l piping and components during normal or emergency operation. This change eliminates the  !

potential to over-pressurize the Makeup suction piping due to leakage through recirculation line L check valves or other leakage paths on the pump discharge. With a common suction header any flow back through an idle pump will picked up by the operating pump without any significant pressure increase in pump suction. This change resolves over-pressurization concerns during l normal or emergency operating as identified in LER 97-003.

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3. Results in a lower calculated core damage frequency due to a reduction in the probability of Makeup Pump damage and the resulting increase in MU/HPl System availability. This was l . the conclusion of the Probabilistic Risk Assessment (PRA).  ;

l i SAFETY REVIEW:

1 The impact of operation with the Makeup pump suction cross connect valves open was evaluated using PRA methodology and the calculated core damage frequency was found to be lower if the  !

suction cross connect valves are maintained open (Reference 3).

The potential effect of this change on Makeup Pump NPSH was evaluated. The design basis scenano i for Makeup Pump NPSH concern is an HPI line "B" break where the operator opens MU-V-217 and starts a second MU Pump in response to the reactor trip. During the period of time until the BWST

valves (MU-V-14A/B) open, the MUT level & pressure and therefore NPSH available to the Makeup Pump is decreasing. The threat to the Makeup Pumps is terminated when ES actuates, which opens l MU-V-14-A/B, or when MU-V-14-A/B is opened by the operator. Operation with'a common suction header does not adversely effect this scenario. There is no procedure direction for the operator l- to start all three Makeup Pumps taking suction from the MUT. In fact, as part of the change in 1997, a

1920-98-20716 Page 4 of 5 Limit & Precaution statement has been added to the procedure (Reference 5) to specifically restrict such operations. When ES actuates all three pumps receive start signals, MU-V-14A and MU-V14B are signaled to open, and adequate NPSH is provided while the Makeup Pumps are drawing suction from the BWST. There is also adequate NPSH for three Makeup Pumps ifone MU-V-14 valve fails to open.

The potential for gas entrainment of the Makeup Pumps was evaluated because the change altered the operational configuration of the suction header. The evaluation considered the limiting design basis scenario where all three pumps are operating and MU-V-14A or MU-V-148 fails to open. The maximum MUT pressure curve is based on the minimum possible pressure in the Makeup Pump suction header when the minimum level in the BWST is reached. Operating limits on MUT pressure and level provide a conservative boundary to prevent gas entrainment with a common Makeup Pump suction header. In addition to the evaluated condition, the Abnormal Transient Procedures (ATPs) direct the operator to shift the Makeup Pump suction to LPI pump discharge prior to reaching the minimum level in the BWST. This adds conservative margin to the evaluation. The evaluated case for potential gas entrainment uses conservative assumptions and concluoes that adequate margin to gas binding of the Makeup Pumps is maintained by the specified initial conditions for pressure ad level in the MUT.

An evaluation of the single failure potential introduced by making the MUT (MU-T-1) a common HPl component was performed (Reference 7). Failure ofMU-V-27 or MU-V-28 to close, failure of MU-V-13 to close, failure of MU-V-18 to close, and Loss of DC power were among the failures considered in the evaluation. This evaluation concluded that the limiting case for potential gas binding is the failure ofMU-V-14A or MU-V-14B to open.

Maintaining the required Makeup Pump NPSH margin and the prevention of Makeup Pump gas entrainment during a LBLOCA are ensured by maintaining the MUT pressure vs. level relationship.

The instruments used to ensure these parameters (MUT level and pressure) are calibrated in accordance with QA program requirements and periodically MUT level (Reference 8) and pressure (Reference 9) are compared to independent instruments to verify their operability. This ensures that no single instrument failure will degrade the operator's ability to maintain the MUT pressure / level relationship and thereby ensure that the initial condition assumptions of the Makeup Pump NPSH and i gas entrainment analysis remain valid.

Loss of Coolant Accident (LOCA) analyses, which credit the capability of the HPI system, include consideration for a single failure. The effect of this change improves the HPI system performance using single failure assumption considerations. HPI system performance was evaluated in response to

active failures of BWST supply valves (MU-V-14A or MU-V-148) or Decay Heat Removal (DHR) l Pump supply valves (DH-V-7A or DH-V-7B) when piggyback operation was required. With a

' LER 98-009 reported that, due to an analytical error, there was a potential for Makeup Pump gas entrainment to occur during a LOCA if either MU-V-14A or MU-V-14B were to fail to open on an ES actuation. Temporary procedural changes were implemented immediately which placed additional restrictions on the Makeup Tank temperature and pressure limits to compensate for that error. Subsequent to GPU Nucicar submittal of the LER (Reference 6), permanent changes have been implemented that resolve the issue.

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I common Makeup Pump suction header, either DHR Pump can provide suction to either or both L ' Makeup Pumps. This change does not effect the HPI system response to any other active component i L failures. HPI is not required to provide long term cooling in any design basis event where single failure l' has not already been taken. Passive failures of the Makeup System are beyond the design basis. The  ;

l - Makeup System is not required for long term Reactor Coolant System boron concentration control.

[ CONCL,USION: j j In summary, maintaining the MU/HPI suction cross connect valves open during operation results in higher MU/HPI system reliability and a reduction in core damage frequency.

REFERENCES:

L 1. GPU Nuclear Safety Evaluation No. SE-000211-015, " Operation with MU Suction Cross -

L Connects Open," Revision 0, dated August 25,1997.

[. 2. G_PU Nuclear Letter No. 5211-85-2131, Hukill to NRC, "LER 85-001-0," dated July 26, l 1985.

L 3. GPU Nuclear Letter No. C311-89-2020, Hukill to NRC, "TMI-l Level 1 Probabilistic Risk l Assessment (PRA)," dated March 17,1989.

l ' 4.- GPU Nuclear Letter No. 6710-97-2423, Langenbach to NRC, " Licensee Event Report L (LER) No.97-003, Revision 1,". dated September 29,1997.

.5 Operating Procedure 1104-2, " Makeup & Purification System," (Current) Revision No. I 15, l l Effective December 18,1998. '

!: '6 GPU Nuclear Letter No. 1920-98-20519, Langenbach to NRC, "LER 98-009-00," dated September 18,1998.~

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7. ' GPU Nuclear Safety Evaluation No.'SE-000211-024," Revised Makeup Tank Pressure and

' Level Limits," dated December 9,1998.

8. Surveillance Procedure 1301-1, " Shift and Daily Checks," (Current) Revision No.130, i Effective December 21,1998, u

9.' Surveillance Procedure 1301-4.1, " Weekly Surveillance Checks," (Current) Revision No. 66, l Effective June 10,1998.

Sincerely,

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i i i

JamWN. Langenbach

l. ,

Vice President and Director, TMI MRK' j l

O .cc: TMI Senior Resident inspector i TMI-l Senior Project Manager

' Region Administrator i File No. 97062

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DH-T-1 MU-V-37 MU-V-36 L 2 Pl Train A r , MU-V-14A MU-V48A MU Pump A ,

Makeup -

LPI & BS PUMPS Tank Mu-v488 7 RCP Seal d - 7 injection MU-T-1 CS Normal t

i Make Up 1 P MU-V-12 JL MU-V-69A MU Pump B 1 I MU-V498 g i

, f 7 HPI Train B MU-V-14B MU Pump C I~~

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