ML19250B750

Summary of 790725 Meeting W/Pwr Vendors,Aif & Utils Re Impact of TMI-2 Events on ATWS Resolution Plan NUREG-0460, Vol 3

ML19250B750
Person / Time
Issue date:	07/27/1979
From:	Thadani A Office of Nuclear Reactor Regulation
To:	Hanauer S NRC OFFICE OF ADMINISTRATION (ADM)
Shared Package
ML17054D123	List: ML19250B750
References
FOIA-80-587, REF-GTECI-A-09, REF-GTECI-IS, REF-GTECI-SY, TASK-A-09, TASK-A-9, TASK-OR TAC-08269, TAC-11037, TAC-8269, NUDOCS 7911050101
Download: ML19250B750 (9)

Text

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ENCLCSURE 1

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JUL 2 7 IWC Task Action Plan A-9 MEMCR;pCUM FOR:

S. H. Hanauer FRCM:

A. Thadani

SUBJECT:

NRC-INCUSTRY AT.VS MEETING SUt*, MARY The staff met with the PWR vendors, the* Atomic Industrial Forum (AIF) and several utility representatives to discuss the imcact of TMI-2 events on the AT45 resolution plan dascribed in Volume 3 of NUREG-0460.

The staff made the following initial remarks:

1) ATdS is still a safety concern and protection frem these events must be provided. Althougn plants need not be shutdcwn imediately because of relatively Icw likelihood of a severe ATWh in a PWR in the next couple of years, ATd5 resolution with suitable speed is necessary to permit an implementation plan which would assure an acceptably Icw risk feca AT.4S over the life of nuclear plants.

2) The staff would like to receive industry views on the imoact of TMI-2 on ATWS'and how to preceed frem now on to resolve ATdS. The staff noted that they intend to propose an ATdS solution to the Cermission preferably with but if necessary without the industry input.

3)

In view of TMI-2 accident, the staff expressed the folicwing general cen-cerns with the Vol. 3 preposed resolution and asked for industry coments.

a) What assurance do we have that the excessi.e calcylated pressures for scac designs mcdified ::er Alternative #3 would not result in loss of integrity of reactor coolant pressure boundary.

(Note - Scce designs may experience peak pressures - 2000 psi).

b) Wculd increasing the nurrber of safety valves as per Alternative #4 result in insufficient overall risk reductien? Would the prieary system integrity be maintained? Would it be better to have larger ca;acity valves?

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---e 2-S. H. Hanauer c) In view of questions a anc b above, the pressurizer relief and safety valves must be qualified for water relief to assure that the no::les, the valve body and the support structure integrity will be maintained and to estimate discharge ficw rate and the likelihood and effects of valve chatter.

d) In view of significant plant differences in the designs of auxiliary feedwater system, Emergency Core Cooling Systems and other systems, how would the industry provide assurances that plant specific features have been adecuately addressed in the "Farly Verification" approach for resolving ATWS as described in NUREG-0160, Vol. 3.

e) Other Lessons Learned from TMI-2 Following preliminary comments frem the NRC staff members, G. Sorensen of WPPS who is also the Chairman of the AIF ATWS committee, made the folicwing comments.

1) ATWS is not a safety issue but rather it is a licensing issue which needs resolution.

2) AIF in concert with the industry had reviewed ATWS in light of TMI-2 and had coacluded that the Alternative 44 fix (mitigation) in Vol. 3 of NUREG-0460 is not the correct solution to ATWS. The industry believes that the alternative #2 fix (Prevention - Electrical Portion of RPS) is t.ye appropriate ATWS solution.

3) Industry recognizes the TMI-2 impact on the role of the operator, his training aids and other lessons learned frem this event. The industry believes that there is no need to rus.: to resolve ATWS because of the low probability of ATWS and because some of the anticipated changes to plants as a result of TMI-2 accident review would direct resources to other issues.

Folicwing the AIF presentation, tne staff raised their cencerns that the ATWS resolution (not yet achieved) has been anything but hasty, that the NUREG dccu-ments on ATWS have been cut for sufficiently long time period, that protectice from ATWS is necessary, that TMI-2 event has raised concerns with the analyses assumptiens and therefore the staff needs industry technical assessment of the TMI-2 impact en ATWS.

The staff suggested that tne TMI-2 event indicates a need to answer at least the following specific questiens.

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1) Analyses indicate the sensitivity of peak pressure to AFWS design and actuation time for some plants.

Why should auxiliary feedwater actuation not be delayed beycnd technical specification values? What bases are available to assume AFWS actua-tien earlier than the technical specification value? How do the analyses take into censideration the limits on AFWS injection rate due to water hammer censiderations? How is the impact of ficw restrictors on scme AFWS designs considered in the ATWS analyses? How are the significant plant specific features of AFWS treated in the analyses?

2) As in question 1 above hcw are the differences in ECCS designs evaluated?

For example, for some ATWS events, the pressure and the pressurizer level remain high enough such that either the HPSI cannot be actuated (because of shut off head considerations) or the operator may fail to actuate HPSI because of insufficient available information.

3) Would single failure cause all PORVs to fail to open? If so, then analyses must be based on all PORVs failing to open. Further, several plants are operating today with PORVs isolated. For these plants credit cannot be taken for relieving capability of these valves.

4) What assurance do we have that the ATWS events with a stuck open safety valve have been correctly analyzed? What is the potential for core un-covering under this scenario? What is the importance of ECCS actuation, reactor coolant pumps operation, and the pressurizer safety / relief valve discharge model on the potential for uncovering of the core? Further, why shcold more valves not be assumed to stick open folicwing discharge of subcooled water.

5) For laag Larm shutdown, discuss the following:

a) available equipment, instrumentation and their qualifica*.icn.

(Must consider the effect of water discharged to the containment via ruptured quench tank).

b) impact of loss of offsite power c) continued operation of reactor ccolant pumps. Also censider tripping of reactor ecoli.nt pumps.

d) Describe natural circulation, including effects of ncn-cendensables.

Is reflux boiling mcde of operation anticipated? If so, justify.

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S. H. Hanauer e) Would one anticipate Boron precipitation problem? Also consider TMI-2 type problems with possible letdown line plugging frca Boron precipitation.

f) How are leakage problems from equipment outside containment considered?

6) Why should credit be given for operator action even after ten minutes fellowing an AT4S event initiation? TMI-2 experience does not provide encugh confidence in the ability of the operator to perfern correct acticns only in this short time period uncer high stress conditions.

In response to the staff concerns the industry made the folicwing coments.

AIF 1)

-le industry is frustrated because the staff concerns imply consideration of multiple failures and small LOCA which are beycnd the credible events to be considered under AT45.

(Note - safety valve stuck open (small LOCA) is considered an anticipated transient).

2)

Industry would like to wait for approximately six months before consider-ing AT4S evaluations to minimize duplicale expenditures.

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1) W has s,ubmitted responses to the 2/15/79 Mattson letter.

2) Calculated peak pressure of 2800 s 2900 psi (for Alt. #3) and proposed modifications in turbine trip and auxiliary feedwater system actuation ci rcuitry.

3) EPRI expects to issue a request for proposal to conduct tests on PORVs and safety valves and some results should be available by end of CY 79.

4) Recocrended that "Early Verification" approach shculd be continued.

g - Ed Shearer speaking for himself

1) TMI raises few questions like the behavior of S/R valves and the cperator action. Further, prevention is better than mitigation and that mitigation would mean more and more analyses.

2) Continue with early verificaticr..

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1) Basically agrees with the staff concerns.

Industry has longer list of items that could impact ATWS.

2) Stress analyses should be completed..

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3) Lik'elihood of additional failures beyond ATWS should be considered.

4) Prevention is better than mitigation.

B&W Owners Grouo

1) ATWS is not a safety problem.

2) Even if ATWS occurs, no significant risk to public health and safety.

3) TMI-2 suggests a desirability for realistic analyses. TMI-2 suggests a need to assure that analyses bound the facilities.

4) Wait until " Lessons Learned" and " Bulletins and Orders" issues are resolved before pushing ahead with ATWS.

After the above industry comments, the staff made the following concluding remares.

1) We don't intend to go too fast on ATWS.

2)

If Early Verification is to be pursued then there is a need to assure that earlier ATWS analyses are correct and review the industry TMI-2 related list.

In this regard the industry was invited to meet with the staff to discuss the technical issues which impact ATWS. The staff asked the indus-try to provide their assessment of TMI-2 impact on ATWS, the scope of effort to resolve these issues, and the schedule for performing this effort within 30 days.

3) We cannot wait another year to make progress in ATWS.

The list of attendees is in the enclosure.

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A. Thadani

Enclosure:

As stated cc: See next page 1270 075 6

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r S. Hanauer cc: Meeting Attendees ATWS Distribution PDR RSB Files T. Speis

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ENCLOSURE ATWS Meetine with Vendors & AIF July 25, 1979 Ashok Thadani NRC/ DSS Arthur McBride B&W Alan Hosler WPPSS Samir K. Sarkar FP&L Alan E. Ladieu YAEC Fred T. Stetson AIF Richard G. Rateick DECD Andrew J. Rushnok OEC M. Srinivasan NRC/ DSS F. Akstulewicz NRC/DSE G. Sorensen WPPSS/AIF T. Speis NRC/ DSS F. C. Cherny NRC/ DSS J. A. Norberg NRC/OSD Stuart Thickman TVA - EN DES Karl 0. Layer BBR J. Ted Enos AP&L Ted Myers TEco Robert Dieterick SMUD Michael J. Salerno CPCo S. Hardy Duerson B&W

' Bob Steither W

Gary Augustine if P. M. Abraham Duke Power Mark Wisenburg USTVA - Office of Power Michael Tokar NRC/ DSS Paul Scehnert NRC/ACRS David Bessette NRC/ACRS Steven Traisman Pacific Gas & Electric Sam Miranda W

Pat Loftus

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7 Fred Mosby 7yle Laboratory Roger Newton Wisconsin Electric Power Craig Grochmal Stone & Webster Charles A. Daverid Long Island Lighting Co.

Robert L. Stright SNUPPS Joseph M. Weiss GE Joseph A. Gonyeau Ncrthern States Pcwer 1270 077

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-2 Seth M. Coplan PiRC/DSE Clayton L. Pittiglio tiRC/DSE Kulin D. Desai f4RC/ DSS Fuat Odar tiRC/ DSS Kris Pare:ewski fiRC/DCR Roy Woods

iRC/DCR Harold Vander Molen F4RC/DCR Gururejarao Rangarao PAS:1Y Frank Mc? hatter B&W Steve Sanwartn BaW William R. Murray Virginia Electric & Power Co.

Sen Rodell VEPCD Don Swanson PGE Co.

Paul V. Holton Bechtel Tornmy Errington Mississippi Power & Light Ron Clausen Florida Power Corporation Charles B. Brinkman CE C. L. Kling CE William Benjamin Cormonwealth Edison Co.

Denny Kreps CE William E. Burchill CE A. E. Scherer CE Richard C. L. Olson Baltimore Gas & Electric Co.

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ENCLOSURE 2 Letter frem R. H. Bucholz (GE) to S. Hanauer, "AT45 Generic Analyses -

Content of December 1979 Submittal", dated Sep ember 5,1979.

Letter from J. H. Taylor (B&W) to S. Hanauer, "B&W Comitments for ATAS", dated September 13, 1979.

Letter A. E. Scherer (CE) to S. Hanauer, "NRC Request for Generic ATAS Infor.ation", dated August 31, 1979.

Letter L. O. DelGeorge (SWR 3 Cwners representative) to S. Hanauer, "ATWS BWR/3 Plants and 'lermorrt Yankee - Generic Analysis Supplement",

dated August 28, 1979.

Letter T. M. Anderson (W) to S. Hanauer, "AT4S", dated August 24, 1979.

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