ML20062G059
| ML20062G059 | |
| Person / Time | |
|---|---|
| Issue date: | 11/20/1990 |
| From: | Chris Miller Office of Nuclear Reactor Regulation |
| To: | Kintner E ALWR UTILITY STEERING COMMITTEE |
| References | |
| PROJECT-669A NUDOCS 9011280377 | |
| Download: ML20062G059 (8) | |
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gn UNITED STATES ie'91i NUCLEAR REGULATORY COMMISSION s
WASHINGTON, D.C. 20086
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November 20, 1990 Project No. 669 Mr. E. E. Kintner, Chairman ALWR Utility Steering Committee GPU Nuclear Corporation One Upper Pond Road Parsippany, New Jersey 07054
Dear Mr. Kintner:
SUBJECT:
DISCUSSION QUESTIONS FOR THE NOVEMBER 29 30, 1990 MEETING ON THE EPRI PASSIVE ALWR REQUIREMENTS DOCUMENT In order to facilitate the November 29-30, 1990 meeting on the EPRI Requirements Document for advanced light-water reactors with passive safety systems, I am forwarding the enclosed discussion questions to inform you of some of the questions that the staff has raised during its preliminary reviews of the Passive Plant Requirements Document and the conceptual designs of Westinghouse Electric Corporation's AP-600 and General Electric Company's SBWR, This early feedback will assist in the development of the final agenda for the meeting so that we can have thorough technical discussions.
Some of these questions concern details of the designs that go beyond the scope of the Requirements Document.
However, due to the close relationship of the requirements to the actual designs, the staff believes that it-is important that i
the industry be aware of the staff's current thinking on these matters. Note that these questions represent the preliminary views of the staff and have not been presented to the Commission for approval as agency views.
Because the staff has not completed its determination regarding EPRI's September 6, 1990 request that the entire Passive Plant Requirements Document be withheld from public disclosure, the staff expects that most of the meeting will be closed. Please be prepared to provide both proprietary and non-proprietary n
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-2 November 20, 1990 versions of any discussion meterial that will be presented at the meeting.
If you have any questions concerning this matter, please contact the project manager, T. J. Kenyon, at (301) 492-1120.
Sir:erely, 1RIGl'JAL SIGNED BY CMILLER Charles L. Miller, Director Standardization Project Directorate Division of Reactor Projects - III, IV, V and Special Projects Office of Nuclear Reactor Regulation
Enclosure:
As stated cc w/ enclosure:
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/90 11/2c/90 11/Ac/90 11/W/90 11/1//90 DOCUMENT NAME: QUESTIONS FOR PASSIVE HTG l
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Mr. E. E. Kintner, Chairman Project No. 669 l
ALWR Utility Steering Comittee EPRI 1
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Mr. William Sugnet Nuclear Power Division Electric Power Research Institute P.O. Box 10412 Palo Alto, CA 94303 l
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ENCLOSURE DISCUSSION QUESTIONS FOR THE NOVEMBER 29 30, 1990 MEETING ON THE EPP.1 PASSIVE ALWR REQUIREliENTS DOCUMENT General What design considerations in SECY 90-016 will be incorporated into the l
l passive designs? What will not? What is the justification for non-inclusion of these design considerations into the possive designs? What makes the passive plant dest $ns different from the evolutionary designs?
(Note:
l Chapters 5, 6, and 9 of the p6ssive plant Requirements Document do not appear l
to reflect the Commission direction for fire protection enhancements.
How should non safety systems that used to be considered safety systems be treated? Are the passive systems sufficient to replace the active systems?
Examples:
I Safety-related ac power emergency diesel generator requirement offsite power requirements control room habitability b6tterycharging(after72 hours) ability to reach cold shutdown spent fuel pool cooling heaters for PCCS l
P6ssive RHR in lieu of emergency feedwater t
passive injection systems in lieu of active safety injection systems How much credit should be given for non-safety systems? What portions of Appendix B of 10,CFR Part 50 will these systems be required to meet?
Why shouldn't the single f ailure critoria be applied to passive components in fluid systems (such as check valves)? Should a multiple failure analysis be performed for selected systems? Are there failure modes unique to passive designs? Should one train of an active system be required to be available to work in conjunction with the passive systems to account for unknown events?
Will there be anything unique in the ALWR maintenance program? Should specific, detailed maintenance requirements be included in the certification?
Will the designer provide a specific maintenance and component replacement program that includes the frequency of testing and ins >ection of components?
Does the maintenance progrom include consideration of luman factors early-in its development?
Is there a need for a prototype? Are facilities available that can be used for benchmarking codes? Will the unique design of the control room require a prototype?
Is a simulator necessary for the control room before certification?
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. 4 Clarify what h me6nt in section 11.2.2 of Chapter 1 and 3.2 and 4.1.3.3 of Chapter 10 of the passive Regt.irements Document.
Passive ALWR An61ytical Issues What is the basis for determinir.g the adequacy of the vendor's models to evaluate passive plant reactor behavior?
Adequacy of vendor's separate effects testing for the passive d6 signs - Are separate effects tests adequate and sufficient?
Is an integral system test necessary? If so, is semiscale testing adequate?
Is some type of natural circulation testing necessary foi new configurations?
Are hest estimate calculations adequate? What conservatism is being employed l
in these analysis?
Hermal-HydraulicIssues i
W AP-600 What is offect of ncn-condensible gases on heat transfer in passive RHR heat exchanger heat transfer to the containment surface variation of non-condensible fraction throughout containment SBWR t
Due to differences in geometrical design, is an integral vessel test of the SBWR necessary to demonstrate its stability?
Containment Analys.is Will codes be available to model heat rejection flow paths with natural circulation flow patterns rather than forced flow conditions?
!!AP-600 What is the effect of local hot spots or thermal gradients on the containment surface due to internal structures and thermal stratification of the atmosphere?
What is the effect of revaporization of condensate inside containment on heat transfer from break to inner shell and equipment cualification?
Address how the natural circulaticn flow patterns could be disrupted and heat sources or sinks could be created in the containw nt by:
l initiation of containment spray flow location of structures presence of a standing flame
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How is the external passive containment cooling system performance affected by film thickness and stability of the water on the containment external containment coatings and surface wetabilty presence of chemical additives surface discontinuities (weld beac's, structural rein'orcement and penetrations,platealignment) velocity and distribution of air flow watyr entreir6er.t in the air flow How do you maintain wetting characteristics over the life of the plant?
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Are heaters necessary in the PCCS (for freeze protec+lon of a safety-related system)? If so, do they need to be safety grade and/or de powered?
GE SBWR What is effect of non-condensible gases in the 1:016 tion condenser on condensation heat transfer potential to interrupt flow effectiveness of vent to suppression poo'.
What is the effect of thermal str6+1'ication in the suppression pool?
Is a test necessary to assess mixing between separate pools inside containment (drywell, suppression pool regions)?
Instrumentation and Control Issues How will the batteries be sized to be able to support t
the control room l
analog control panel l
chillers environmental control of the control room heaters for the PCCS cancomputerfailure(duetosoftwareunreliability)resultinthelossofthe main control room? Will an analog backup system be provided?-
Are advanced safety-related IAC designs with cownon software more susceptible to common mode failure? Discuss proposed verification and validation program.
Is more diversity necessary for safety systems?
What separation and independence requirements for digital systems are you proposing?
What requirements for on-line testing and self-diagnostics are you proposing?
How do the advanced notety-related 18C _ designs reduce the effects of electromagneticinterference(EMI,RFI,EMP,andSWC)?-
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1 4-Tc what extent do the passive designs intend to incorporate expert / artificial intelligence systems into the designs?
Can use of the CAD / CAM systems it.troduce common mode failures?
Human Factors The staff believes that human factors considerations must be included early in the design process.
How are such considerattons being included early in the design stages of the >assive designs? How are the man-machine interfaces being acdressed for tae entire plant operation, mainteriance, refueling operations, etc.?
Are job task analyses (JTA) being performed for the passive designs?
Given the increased automation of the facility, what new approaches may be required to maintain operator vigilance? What is the appropriate level of staffing and qualification for operators?
What qualifications and education do you intend to require for the operating staff?
After an event, should the operator be allowed to intervene with the automatic safety systems and operate the plant immediately or be required to take no action for a given amount of time? Should the operator be operating equipment at the component level? or at the systems level?
Reliability. Testability. & Inspectability What should be included in a Reliability Assurance Program? How should l
reliability goals be established? How should the applicant kee) track of l
actual equipment reliability values to ensure the validity of tie reliability valuts assumed in the design analysis are maintained? How does the applicant ensure it stays within the reliability envelope? What actions must be taken by the applicant should the plant fall below the reliability levels?
l What should be the criteria to specify testing and inspection frequency?
Should a comparative reliability analysis be required (passive to evolutionary)? Whatcredit(ordebit)shouldbegivenforhumanfactors/ human interactions?
Industry experience suggests that component reliability may not be at the level necessary to support a design employing so few components. What measures are being employed to improve component reliability (in testing, design, and m61ntenance practices)?
Sheuld there be more reliance on divcrsity and redundancy to improve the reliability of the safety function?
How is the industry demonstrating the reliabilit of motor-operated valves (see Generic Letter 89-10 for current facilities ?
Check valves are relied on for accident mitigation.
These valves may prove less reliable than those in current facilities since there is a low delta P
l i across the valves end there are no pumps to provide a driving force to oren the valve.
Is qualification testing necessary? Should it be done before certification?
Thereactorvessel, pumps, valves,steemgeneratortubing(PWRs)fthefacility and component supports should be designed early in the development o to be fully inspectable and to include the capability to perform ASME Code,Section XI inservice testing.
Should the reactor internals be required to be periodically inspected as well to ensure no flow blockage?
How do you assure that the check valves will operate? Should the applicant perform on-line monitoring of check valves, full-flow testing, and/or back flow leak testing? Should non-safety related pumps and valves be tested?
Should the squib valves that are used in the safety depressurization system and in the SLCS undergo additional testing to verify operability? Should they be replaced on a periodic basis to ensure reliability?
Should other valve designs be censidered for these purposes to allow for testing, yet have the same reliability with zero leakage?
Structural Engineering large variations in actual thickness,)may occur in the unstiffened steel containment (shell thickness = 13/4" which, in combination with large openings, may result in lower buckling strength than that predicted analytically.
Is the industry proposing improved manuf,acturing methods to control the actual thickness of the containment? Is some testing of the design contemplated to address seismic interaction concerns?
Is the Lawrence Livermore seismic hazard curve being included in the generic hazard curve proposed by EPRI? EPRI should address inclusion of the LLNL results in the development of a generic (regional) best estimate hazard curve.
Materials Engineering The ALURs should use improved materials in the designs to reduce intergranular stress cerrosion cracking (IGSCC) and secondary side corrosion (i.e., using nuclear grade stainless steel for IGSCC prevention and Inconel 690 for SG tubes). Why are certain, less corrosion-resistant materials allowed to be used in the EPRI Requirements Document.
Should the secondary water chemistry control limits (PWRs) and primary water chemistry control limits (BWRs) be included in the certification?
What design features reduce unanticipated embrittlement due to low flux neutron irradiation of an P,pV support near the beltline?
In 1tght of your commitment to ALARA, is the industry considering the use of i
other materials (i.e., EPRI NOREM alloys) in lieu of stellite for hard-facing?
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