ML20213E121
| ML20213E121 | |
| Person / Time | |
|---|---|
| Site: | Columbia  |
| Issue date: | 03/04/1982 |
| From: | Johnston W Office of Nuclear Reactor Regulation |
| To: | Tedesco R Office of Nuclear Reactor Regulation |
| References | |
| CON-WNP-0485, CON-WNP-485, RTR-NUREG-0737, RTR-NUREG-737, TASK-2.E.4.2, TASK-2.K.3.28, TASK-TM NUDOCS 8204140065 | |
| Download: ML20213E121 (8) | |
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Docket flo. 50-397
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4 MEMORAtlDUM FOR:
Robert L. Tedesco, Assistant Director for Licensing Division of Licensing FROM:
William V. Johnston, Assistant Director Materials and Qualification Engineering Division of Engineering
SUBJECT:
WASHINGTON PUBLIC POWER SUPPLY SYSTEM (WPPSS) NUCLEAR PROJECT N0. 2 (WNP-2) IflPUT TO THE SUPPLEMENTAL SAFETY EVALUATION REPORT Plant Name: WPPSS Nuclear Project No. 2 (WNP-2)
Docket flo. : 50-397 Licensing Stage: flTOL Responsible Branch:
Licensing Branch flo. 2 Responsible Project Manager:
R. Auluck Review Status: Open The enclosed Supplemental Safety Evaluation Report (SSER) was prepared by DE:MQE, Equipment Qualification Branch.
The reviewer is M. F. Haughey.
This input covers the following open items:
1)
II.E.4.2 as it relates to the operability of the purge system isolation valves.
2)
II.V,.3.28 - Qualification of Accumulators on ADS valves.
We have identified additional information required of the applicant to resolve these items. These items remain OPEN at this time.
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Nuclear Project No. 2 (WNP-2)
Supplementary Sa fety Evaluation Report (SSER) Input Equipment Qualification Branch II.E.4.2 Containment Isolation Dependab'itity
[This evaluation addresses the issue of valve operability on the purge system isolation valves.
The Containment Systems Branch will address the remainder of this issue].
Requirement Containment purge valves that do not satisfy the operability criteria set forth in Branch Technical Position CSB 6-4 or the Staff Interim Position of October 23, 1979 must be sealed closed as defined in SRP 6.2.4, item II.6.f (NUP.EG-800) during operational condit ions 1, 2, 3, and 4.
Furthermore, these valves must be verified to be closed at least every 31 days.
Applicants must be in compliance with this position before they receive their operating license.
Discussion and Conclusion The following valves are classified as " active" valves and are included in the scope of this review:
Suppression pool inerting system isolation valves (valves CEP-V-3A, -4A, CSP-V-3 and -4)
Drywell inerting system isoaltion valves (valves CSP-V-1 and -2, CEP-V-1A and -2A)
Bypass purge system valves (valves CEP-V-18, -28, -3B and -48)
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. Qualification documentation was submitted informally for review on February 17, 1982 (the applicant has agreed to submit this in f o rma t i on formally at a later date).
Preliminary review of this information indicated that the valves were not analyzed for the dynamic torques which could be experienced by these valves as a result of the buildup of containment pressure in the event of a LOCA.
In discussions with the applicant it was agreed that the applicant would pursue this information through the manufacturer (BIF Valves) and submit this information at a later date.
The applican4 in his program for operability qualification for these valves,should use the worst case loads on the purge and vent valves, and show that the valve and associated equipment are acceptable.
Upstream piping' configurations which affect the approach flow profile to the valve can have a significant effect on the resulting dynamic torques on the valve.
SpecificalLy, elbows upst ream o f the valve when the valve shaft is out of plane with the bend of the elbow have been shown to have large effects on dynamic torques.
Disc orientation (flow direction) and closing direction can also be factors in increasing torques.
Demonstration that the case used to qualify the valve is the worst case should be provided.
A description of the method used to determine dynamic torques resulting from LOCA pressure loads should be included in the demonst rat ion.
Operatorse as welL as valvesi should be demonstrated to be operable with no parts overstressed during the worst case loads.
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- In determining dynamic loads resulting from LOCA pressure loads if the peak containment design pressure is not used as the pressure load through full st roke of the valve a justification for using I
Lower pressures should be provided.
If the valve closure time is used to justify lower pressures a test program should be proposed to provide continuing assurance th ats through the life of the plant, deteriating valve performance wiLL not affect the qualification of these valves.
The Equipment Quali fi cat ion B ranch will review the demonstration of operability documentation when it is complete and report on the results of the evaluation in a supplement to this re po rt.
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II.K.3.28 Verify Qualification of Accumulators on Automatic Depressurization System Valves Requirement Safety analysis reports claim that air or nitrogen accumulators for the automatic depressurization system (ADS) valves are provided with sufficient capacity to cycle the valves open five times at design pressures.
GE has also stated that the emergency core cooling (ECC) systems are designed to withstand a hostile environ-ment and still perform their function for 100 days following an accident.
Licensees and applicants must demonstrate that the ADS valves, accumulators, and associated equipment and instrumentation meet these requirements and are capable of performing their functions during and following exposure to hostile envir.onments, taking no credit for non-safety related equipment or in st rument at ion.
Additionally, air (or nit rogen) leakage through valves must be accounted for in order to assure that enough inventory of compressed air is available to cycle the ADS valves.
If this cannot be demon-strated, it must be shown that the accumulator design is still acceptable.
Discussion and Conclusion The WNP-2 ADS valve nitrogen supply system consists of two 100%
capacity air compressors; two nitrogen gas bottle banks for seven of the main steam valves which perform the ADS function; two remote nitrogen connections (one for each bank) and individual accumulators on each of-t he eighteen main steam safety /, relief valves.
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. Leakage through the accumulator check valves may disable the ADS before action is taken to provide the backup ai r supply.
Since the time when the ADS would be needed during or af ter an accident is dependent upon a variety of scenarios - specific unknowns such as equipment availabilitys operator actionse break sizer etc., the ADS should be available anytime the reactors is pressurized.
During discussions with the applicant on February 17 and 18, 1982 the applicant agreed to submit a program for periodic leakage testing to account for operator intervention time required from the system pressure alarm point in the control room to the acti-vation of the backup nitrogen supply systems.
Specific areas to be addressed in the test program are as outlined below.
1)
The number of times the ADS valves must be capable of cyclying and the minimum pressure required to achieve these actuations against either atomospheric or drywell design pressure as applicable.
2)
The action needed to introduce sufficient air pressure for ADS actuation using the backup systems.
The time and manpower required to accomplish this action.
3)
Plant procedures which instruct the operator to transfer the backup air system.
The control room indicators and alarms (including setpoints) which are available to alert the operator to the need for action.
How the operator would know that accumulator pressure had decayed to the minimum level where one ADS actuation against drywell pressure was still possible.
3-4)
A periodic test plan to be included in plant Technical Specifications to verify that each accumulator, (or the ADS air system as a whole), will maintain the minimum pressure discussed in (1) above for the time period to.
be provided in (2) above plus a margin of 30 minutes.
Loss of normal charging air (compressors) must be assumed and the timing should begin when the accumulator or system pressure is at the control room alarm setpoint.
The test plan prcposed should include test frequency, allowable leak rater and th+ actions to be taken if the leakage limit is exceeded.
5)
Sjnce the ADS accumulator system is important to sa fet yr it must meet the requirements of GDC 2 and 4.
Thereforer the applicant should seismically and environmentally qualify the ADS accumulator systems and associated control circuitry, from the ADS valve operator out to and including the accumulator system isolation check valve.
In addition,the applicant should seismically and environmentally qualify the nitrogen suppty backup systems for which credit is to be taken in the event of an accident.
Qualification of the backup systems, should inctude associated control circuitry, and interfacing piping and equip-ment from the backup system to the ADS valve.
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' The Equipment Qualification Branch will review the proposed test program when it is submittcd and report on the evaluation in a supplement to this report.
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