ML18102A795
| ML18102A795 | |
| Person / Time | |
|---|---|
| Site: | Salem  |
| Issue date: | 01/28/1997 |
| From: | Eric Simpson Public Service Enterprise Group |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-96-06, GL-96-6, LR-N97072, NUDOCS 9702040234 | |
| Download: ML18102A795 (5) | |
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' Company E. C. Simpson Public Service Electric and Gas Company P.O. Box 236, Hancocks Bridge, NJ 08038 609-339-1700 Senior Vice President - Nuclear Engineering JAN 2 81997 LR-N97072 U.S. Nuclear Regulatory Commission Document Control Desk Washington DC 20555 GENERIC LETTER 96-06120 DAY RESPONSE ASSURANCE OF EQUIPMENT OPERABILITY AND CONTAINMENT INTEGRITY DURING DESIGN BASIS ACCIDENT CONDITIONS SALEM GENERATING STATION UNIT NOS. 1 AND 2 DOCKET NOS. 50-272 AND 50-311 Gentlemen, As required by Generic Letter (GL) 96-06, Public Service Electric and Gas (PSE&G) submits the following information in satisfaction of the 120 day information request. It should be noted that PSE&G has been in communication with your staff regarding the concerns addressed in Generic Letter 96-06 as they relate to the Salem Unit 1 and 2 facilities. PSE&G's approach to resolution of GL 96-06 is in part, based on the clarifications received during those discussions.
Waterhammer and Two-Phase Flow The Salem Containment Fan Coil Unit (CFCU) Service Water System (SWS) piping loops contain a vertical drop from the outlet of the CFCU to the point where they discharge fo the Delaware River. Drainage in this piping occurs upon loss of flow (Loss of Qffsite Power (LOOP) event) and continues until the downstream flow control valve closes. This results in a water column separation (void formation) in the downcomer leg and low pressures (approaching 0 psia) at the highest piping elevation in the CFCU coils. Waterhammer occurs upon restart of the SWS pumps when the void closes. For cases involving Loss of Coolant Accidents (LOCA) or main Steam Line Break (MSLB) events with coincident LOOP, thermal expansion of the water in the CFCU closes the initial void in the downcomer. Continued expansion of the fluid when the system is water solid results in an overpressure condition within the piping. Continued heat input prior to reestablishing flow results in two-phase (steam voiding) fluid conditions developing in the upper CFCU coils. Waterhammer occurs following
- j restart of the SWS pumps when the steam void collapses.
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JAN 281997 Document Control Desk LR-N97072 2
Currently, PSE&G is planning to modify the CFCU SWS piping arrangements to eliminate the potential for waterhammer, two-phase flow and thermal overpressurization following design basis accident conditions. A Failure Modes and Effects Analysis (FMEA) is aiso being prepared to identify single failures within the CFCU SWS piping loops which could result in system voiding under accident conditions. Proposed modifications are being evaluated using the Salem SWS hydraulic model to confirm that the SWS will continue to meet
- licensing and design basis requirements. A post modification test program is also under development. The objective for this test program is to evaluate system response during normal and off-normal conditions to assure that GL 96-06 concerns have been appropriately addressed, and that no new transient initiators have been introduced through the modification process.
Current plans call for the installation of a surge volume on the CFCU inlet piping to maintain water solid conditions within the piping. Additional valves.and control elements will be provided where necessary to address single failures.
Due to the short lead time for material procurement and the limited availability of materials compatible with the existing SWS design, the Salem Unit 2 restart schedule will be impacted. Alternative.designs to reduce the scope and schedule impact of the required modifications are also under consideration.
Modifications to Salem Unit 1 and 2 will be completed prior to restart of the affected Unit.
Thermal Overpressurization Piping systems penetrating Containment and closed portions of piping systems inside Containment have been evaluated to determine the effects of thermally induced overpressurization. A list of fluid lines penetrating containment was compiled and screened to identify lines susceptible to this condition. Screening was based on elimination of lines on the following basis:
The line is gas filled, The line will relieve back to the Reactor Coolant System (RCS) through an existing check valve, The line has an installed relief valve available, or The line is periodically exercised at power and its normal temperature exceeds the expected post-accident temperature.
95-4933
Document Control Desk LR-N97072 3
For those remaining piping configurations, resolution is through one of the following approaches:
Document piping system operability against the appropriate Code requirements, Analytically demonstrate that the isolation valve will act as a controlled leakage point, Where practical, affected sections of piping will be drained by procedure during system alignment, or Installation of relief valves.
The associated procedure revisions and modifications will be completed prior to restart of the affected Unit.
An initial assessment of instrumentation lines penetrating Containment has been completed. No modifications are anticipated on the basis of this assessment.
Formal documentation of this analysis is ongoing and will be completed prior to entry to Mode 4 for the affected Salem Unit.
Scenarios Considered The conditions referenced in Generic Letter 96-06 have been evaluated against the design basis accident (OBA) scenarios applicable to the Salem. These DBA's are generally applied throughout the industry as standard cases to be assessed. PSE&G continues to monitor industry feedback to determine its impact on the proposed resolution for Salem Unit 1 and 2.
Operability Assessment Salem Unit 1 is shutdown and defueled. Consequently the concerns outlined in GL 96-06 do not challenge operability of the Containment or its supporting systems.
Salem Unit 2 is being prepared for restart and is in Mode 5, Cold Shutdown.
The Salem Unit 2 CFCU's are currently available to provide normal cooling to the Containment. Reasonable assurance of operability exists on the basis that LOCA and MSLB events are not credible during this mode of operation due to the limited amount of stored energy in the Reactor Coolant and Main Steam systems. LOOP events are the bounding condition for analysis during Mode 5.
LOOP events have occurred on several occasions during past plant operation.
95-4933
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Document Control Desk LR-N97072
~AN 281991 4
The limited amount of leakage and lack of structural damage observed following these waterhammer events indicates that margin exists within the current design.
Dissimilar metal weld connections at which leakage was observed were replaced as part of the SWS piping material upgrade program. Additionally, this material upgrade program replaced original piping materials with stronger AL-6X material with no reduction in wall thickness. The result is a stronger piping system with improved design margins.
Should you have any questions regarding this information, please feel free to contact us.
Affidavit E. C. Simpson, Senior Vice President Nuclear Engineering C
Mr. H. Miller, Administrator - Region I U. S. Nuclear Regulatory Commission 475 Allendale Road King of Prussia, PA 19406 Mr. L. N. Olshan, Licensing Project Manager - Salem U. S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Mail Stop 14E21 Rockville, MD 20852 Mr. C. Marschall (X24)
USNRC Senior Resident Inspector Mr. K. Tosch, Manager, IV Bureau of Nuclear Engineering 33 Arctic Parkway CN 415 Trenton, NJ 08625 95-4933
..... l' REF: LR-N97072 STATE OF NEW JERSEY)
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COUNTY OF SALEM
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E. C. Simpson, being duly sworn according to law deposes and says:
I am Senior Vice President - Nuclear Engineering for the Public Service Electric and Gas Company, and as such, I find the matters set forth in the above referenced letter, concerning the Salem, Unit Nos. 1 and 2 are true to the best of my knowledge.
l<IMBERL Y JO BROWN NOTARY PUBLIC OF NEW JERSEY My Commission expires on ___
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