ML17312A797
| ML17312A797 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 06/01/1996 |
| From: | Wessman R NRC (Affiliation Not Assigned) |
| To: | NRC (Affiliation Not Assigned) |
| References | |
| NUDOCS 9606050116 | |
| Download: ML17312A797 (11) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 2055&4001 Rune i, 1996 LICENSEE:
Arizona Public Service Company FACILITY:
Palo Verde Nuclear Generating Station, Units 1, 2, and 3
SUBJECT:
SUMMARY
OF MEETING HELD ON APRIL 23,
- 1996, TO DISCUSS RISK-INFORMED INSERVICE TESTING A public meeting was held an April 23, 1996, at the Palo Verde Nuclear Generating Station (PVNGS) and continued on April 24 at the main offices of Arizona Public Service Company (APS) in Phoenix, Arizona, to discuss the licensee s submittal on risk-informed inservice testing (IST) of November 27,
- 1995, and the staff's request for additional information (RAI) of March 15, 1996.
PVNGS is one of two pilot plants (the other is Commanche Peak) submitting requests to use risk-informed IST.
A list of those attending this public meeting is attached.
BACKGROUND Richard
- Wessman, Chief of the Mechanical Engineering Branch in the Division of Engineering, Office of Nuclear Reactor Regulation (NRR), opened the meeting by stating that the NRC staff needed to clearly understand the licensee's probabilistic risk assessment (PRA) models, the process and criteria for risk ranking components, the methodology for adjusting component testing frequencies, the basis for extending a component testing frequency, and the feedback process used to adjust component testing based on deterministic information.
The NRC staff will use the information gained in evaluating the pilot plant submittals to write the standard review plan (SRP) and the regulatory guide (RG) on risk-informed IST.
Mark Rubin, a section chief in the Probabilistic Safety Assessment
- Branch,
.Division of Systems Safety and Analysis, NRR, stated that the Commission wanted to be involved in the process and that the Commission would be evaluating the potential risk increase resulting from implementation of the risk-informed IST progr as.
The staff will probably be asked to brief the Commission on the policy issues involved sometime this summer.
Jack Bailey, APS Vice President for Nuclear Engineering, stated that the work on IST was only part of the ongoing PVNGS PRA efforts.
APS management understands that the current effort will be an iterative process.
Tom Cannon, APS, stated that the RAI questions were well thought out and showed that the NRC is truly seeking to move the process forward.
ISCUSS ION After the introductions, the staff members from APS and NRC reviewed each question pertaining to PVNGS from the RAI of March 15, 1996.
APS staff had prepared draft responses to some of the RAI questions.
All participants discussed questions of a general nature.
Specific questions involving.only poR soock ooooohs',i
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IST or PRA issues were discussed in separate breakout sessions.
The key areas discussed, with the licensee at the meetings included the following:
Ensuring that the level of detail, the scope, and other quality-related aspects of the PRA are sufficient for the IST risk-ranking application and that the plant's PRA has been adequately reviewed.
Ensuring that risk ranking is robust and that components ranked as having low safety significance will remain low, independent of PRA uncertainties, conservatisms, and modeling assumptions.
This measure can be achieved by performing a series of sensitivity and uncertainty studies and also by relying on more than one risk-ranking importance measure.
More clearly defining the processes and criteria used to risk rank components to help the staff develop risk-informed regulatory guides and SRP sections.
Defining a process to show that the risk ranking is robust and is not sensitive to PRA assumptions and data.
In addition, APS and the NRC staff discussed the methodology used to determine the change in risk from changes in IST requirements and the acceptance criteria that would be applicable for any potential increases in risk.
Ensuring that the overall risk-informed IST program does not have an adverse effect on defense in depth or the plant's licensing basis.
Identifying the process and criteria (e.g., reliability information) used by the expert panel to rank components, particularly components or conditions not modeled in the PRA.
Establishing measures to identify important components not in the current IST program, as well as identifying the important failure modes of the more risk-significant components so that the effectiveness of the test strategy (i.e., methods and frequency) can be addressed.
APS and NRC also discussed the relationship of the licensee's proposed risk-informed IST program to draft American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASIDE Code) cases.
Basing the technical basis for test interval extensions on component
- design, service condition, and performance, as well as on the component's safety significance (i.e., not just on PRA alone).
Implementing a performance-based feedback mechanism to ensure that if a particular component's test interval is extended too far, the omission is expeditiously identified and corrected.
The risk-ranking process should also have performance-based fe'edback.
Defining the specific processes for implementing the risk-informed IST program at PVNGS (e.g.,
system versus component-type implementation
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schedule) and establishing the new starting point (test frequency and method) for each component or group of components.'t was also noted that the two pilot plants utilize component performance history differently to determine the final component classifications.
APS did not use the performance history of a component to help determine whether its classification was that of a more safety-significant component (HSSC) or a less safety-significant component (LSSC).
Actual testing frequencies of certain LSSC components at PVNGS may remain at the code frequency, depending on factors such as component performance history and environmental service conditions.
In contrast, Comanche Peak Steam Electric Station (CPSES) moved certain poorly performing components to NSSC, even though the PRA analysis may have suggested that they be classified as LSSC components.
Although similar components at each plant may have different classifications, the actual testing frequency for these components at each plant may be identical.
However, if both licensees were to employ different test methods for HSSC and LSSC (such as the use of ASHE Code Case OHN-1 for motor-operated valves that are MSSC), the different approaches would yield different component test programs.
CONCLUSIONS APS expects to supplement its submittal and respond to the staff's RAI by Hay 28, 1996.
The APS submittal will also contain, if necessary, a schedule of submission for RAI items that have not been addressed by APS.
The NRC staff anticipates authorizing an alternative to the existing ASNE Code testing requirements (pursuant to 10 CFR 50.55a(a)(3)(i))
as a pilot activity, pending completion of the staff's regulatory guidance related to risk-informed IST programs.
The staff will brief the Commission regarding the pilot plant program and related policy issues before authoriz>ng implementation of the IST program.
If the staff's interaction with the pilot licensees (for CPSES and PVNGS) is successfully completed and the risk-informed issues are resolved with the Commission, the staff will document the acceptability of the risk-informed IST pilot programs in safety evaluations.
.Or iainal signed by.:
RichaYd Wessman, Chief Mechanical Engineering Branch Division of Engineering Office of Nuclear Reactor Regulation Docket Nos.
STN 50-528, STN 50-529, and STN 50-530
Attachment:
Attendance List cc w/att:
See next page DISTRIBUTION:
HARD COPIES Docket File PUBLIC PDIV-2 Reading OGC ACRS DOCUMENT NAME:
PVIST.NTS i
E-HAIL WRusse11/FMiraglia RZimmerman JRoe EAdensam WBateman CThomas EPeyton EJordan NRC Participants NSatorius, EDO TPolich
- DKirsch, RIV OFC NAME DATE PDIV-2 PM PDIV-2 LA EpPePn CThomas:
96 96 OFFICIAL RECORD COPY MEB RWes man 5
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schedule) and establishing the new starting point (test frequency and method) for each component or group of components.
It was also noted that the two pilot plants utilize component performance history differently to determine the final component classifications.
APS did not use the performance history of a component to help determine whether its classification was that of a more safety-significant component (HSSC) or a less safety-significant component (LSSC).
Actual testing frequencies of certain LSSC components at PVNGS may remain at the code frequency, depending on factors such as component performance history and environmental service conditions.
In contrast, Comanche Peak Steam Electric Station (CPSES) moved certain poorly performing components to HSSC, even though the PRA analysis may have suggested that they be c'lassified as LSSC components.
Although similar components at each plant may have different classifications, the actual testing frequency for these components at each plant may be identical.
However, if both licensees were to employ different test methods for HSSC and LSSC (such as the use of ASHE Code Case OHN-1 for motor-operated valves that are HSSC), the different approaches would yield different component test programs.
CONCLUSIONS APS expects to supplement its submittal and respond to the staff's RAI by Hay 28, 1996.
The APS submittal will also contain, if necessary, a schedule of submission for RAI items that have not been addressed by APS.
The NRC staff anticipates authorizing an alternative to the existing ASME Code testing requirements (pursuant to 10 CFR 50.55a(a)(3)(i))
as a pilot activity, pending completion of the staff's regulatory guidance related to risk-informed IST programs.
The staff will brief the Commission regarding the pilot plant program and related policy issues before authorizing implementation of the IST program.
If the staff's interaction with the pilot licensees (for CPSES and PVNGS) is successfully completed and the risk-informed issues are resolved with the Commission, the staff will document the acceptability of the risk-
'nformed IST pilot programs in safety evaluations.
.Oriainal signed by.:
RichaT'd
- Wessman, Chief Mechanical Engineering Branch Division of Engineering Office of Nuclear Reactor Regulation Docket Nos.
STN 50-528, STN 50-529, and STN 50-530
Attachment:
Attendance List cc w/att:
See next page DISTRIBUTION:
HARD COPIES Docket File PUBLIC PDIV-2 Reading OGC ACRS DOCUMENT NAME:
PVIST.MTS E-NAIL WRussel 1 /FHiragl i a RZimmerman JRoe EAdensam WBateman CThomas EPeyton EJordan NRC Participants MSatorius, EDO TPolich
- DKirsch, RIV OFC PDIV-2 LA PDIV-2 PM MEB NAME EPPe Pe DATE 4
i 96 CThomas:
96 RWes man' 96 OFFICIAL RECORD COPY
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Arizona Public Service Company Palo Verde Nuclear Generating Station CC:
Nr. Steve Olea Arizona Corporation Commission 1200 W. Washington Street
- Phoenix, Arizona 85007 T. E. Oubre, Esq.
Southern California Edison Company P. 0.
Box 800
- Rosemead, California 91770 Senior Resident Inspector USNRC P. 0.
Box 40
- Buckeye, Arizona 85326 Regional Administrator, Region IV U. S. Nuclear Regulatory Commission Harris Tower
& Pavillion 611 Ryan Plaza Drive, Suite 400 Arlington, Texas 76011-8064
- Chairman, Naricopa County Board of Supervisors 301 W. Jefferson, 10th Floor
- Phoenix, Arizona 85003 Nr. Aubrey V. Godwin, Director Arizona Radiation Regulatory Agency 4814 South 40 Street
- Phoenix, Arizona 85040 Ms. Angela K. Krainik, Manager Nuclear Licensing Arizona Public Service Company P.O.
Box 52034
- Phoenix, Arizona 85072-2034 Nr. William L. Stewart Executive Vice President, Nuclear Arizona Public Service Company
, Post Office Box 53999
- Phoenix, Arizona 85072-3999 Hr. Roger D. Walker, Hanager Regulatory Affairs for Nuclear Engineering Organization Texas Utilities Electric Company 1601 Bryan Street, 12th Floor
- Dallas, TX 75201-3411
Attachment i
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~tt I~de.s Se Jack Bailey Tom Cannon Saragrace Knauf A.K. Krainik Brian Lindenlaub Roy Linthieum Glenn Michael Gerald Sowers Joanne Stahler Te ti i es lectric Co.
Carl Corbin Hossein Hamzehee R.B. Hays Roger D. Malker c
r n r nstitute Steve Floyd Hedhi Sarram Hike Cheok Joseph Colaccino Brad Hardin Dave Fischer Hark Rubin Charles Thomas Dick Messman e te te P.R. Davis Hoymayoon Desfuli Bob Youngblood o
ave t
n btator Hohamad Ali Azara ember the Public Andre N. Anderson C. Meseley Rowley
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