ML20136G595
| ML20136G595 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 02/28/1985 |
| From: | Reamer C NRC COMMISSION (OCM) |
| To: | NRC COMMISSION (OCM) |
| Shared Package | |
| ML20136F570 | List: |
| References | |
| FOIA-84-885 NUDOCS 8508190561 | |
| Download: ML20136G595 (5) | |
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UNITED STATES NUCLEAR RE'ULATIRY COMMISSION g
E WASHWGTON, D. C. 20666 Y
s,.... 4 February 28, 1985 CHAIRMAN MEMORANDUM FOR THE FILES FROM:
C. W. Reamer
SUBJECT:
MEETING WITH SOUTHERN CALIFORNIA EDISON The Chairman met with Howard P. Allen, President, Southern California Edison Company (SCE), on Thursday, October 4, 1984.
The meeting began at 2:00 pm.
The subject of the meeting was the restart of San Onofre, Unit 1.
Also in attendance were Kenneth Baskin, Tom Micheletti and David Pigott, representing SCE, Herzel Plaine, NRC General Counsel, and Norman Haller and C.W. Reamer of Chairman Palladino's staff.
The meeting was scheduled in response to a request from SCE on October 2, 1984.
Mr. Allen opened the meeting by summarizing briefly the history of Unit 1 and the seismic upgrade matter.
He noted that the seismic upgrade effort culminated in the submittal of letters by SCE in 1982, which he characterized as " voluntary compliance," followed by the 1982 NRC order.
Mr. Allen then addressed SCE activities involving the California Public Utilities Commission (CPUC) and Unit 1.
He said CPUC told SCE, during the Unit 1 outage (i.e., the outage commencing in February 1982 and continuing today), that Unit I was not producing and that CPUC wanted to take it out of the rate base.
He said SCE responded by telling CPUC "we're close, bear with us."
He said SCE showed CPUC the February 8, 1984 Denton letter (Denton letter / copy attached) which SCE interpreted as saying "Do this and we'll authorize operation."
Mr. Allen said that at no time, in the 30-50 discussions between SCE and the NRC staff about the seismic upgrade, prior to June 1984, was there any indication by the NRC staff, or under-standing by SCE, that the 1982 NRC order was a license amendment.
He said that, had SCE known in 1982 that the 1982 order was an amendment, SCE would not have proceeded as it did and that SCE would have recognized the potential for delay.
He also said that the Denton letter did not suggest that the upgrade was anything other than voluntary compliance.
He noted that in a June 1984 meeting, members of the NRC staff said that, while procedures would need to be examined, the staff thought restart could occur without significant delay.
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W Mr. Allen said the question is: Is the 1982 order an amendment?
He said there was good legal authority on both sides of the question and that, given the equity considerations, the Commission should resolve the matter in favor of SCE's view that the 1982 order was not an amendment.
Mr. Allen said that if Unit 1 did not go on line as SCE represented to CPUC, SCE would lose credibility with CPUC.
Unit I would be taken out of the rate base and there could be public hearings that might involve substantial delays.
He said that CPUC might open the question of the prudence of expenditures for retrofitting the plant -- a first-of-a-kind inquiry.
The Chairman noted, at this point, that there was a question about whether Unit 1 met.5g.
Mr. Allen responded that SCE felt it prudent to use the money to upgrade Unit 1 to.679 rather than attempt to prove that the unit met.5g.
The Chairman asked whether NRC had assurance now that the unit met
.5g.
Mr. Allen responded that portions of the unit were built to "x" and that, according to Mr. Eisenhut, most of the portions which are not to "x" can be upgraded by 1986.
He said SCE relied on the Eisenhut statement.
Mr. Allen stated that Mr. Denton said he did not think a license amendment was involved, and that Mr. Denton thought that if SCE completed the items in the Denton letter, then the unit could be safely operated.
Mr. Allen said Mr. Denton thought that if SCE could provide new data on.5, then Denton could recommend 9
operation of Unit I under the Denton letter.
Mr. Baskin stated that SCE would do sample calculations, compare Unit 1 to other facilities (non-nuclear), and offer expert opinion which would demonstate that non-upgraded portions of Unit I meet.5g.
Mr.
Allen noted that SCE had developed this data.
He said that he could not say whether the plant will work at.5g but that SCE will provide the data to the staff and let the staff reach a conclusion.
Mr. Allen said that there was an additional issue, apart from the possible loss of Unit 1 as a result of CPUC proceedings.
He said SCE proceeded in voluntary compliance and that SCE acted on the basis of the Denton letter.
He said SCE had another option with CPUC which it did not pursue.
He stated that no utility with an old plant would decide to upgrade the plant if the results were likely to be the adverse results potentially facing Unit 1.
The Chairman said that the staff came to the Commission, saying that Sholl know tETs y applied and that it thought the Commission ought to before the staff acted.
He stated that the staff said it did not see another way out and that the staff believed the Commission should have the opportunity to interact.
Mr. Allen said the matter depended on whether or not the 1982 order is viewed as a license amendment.
Mr. Pigott noted that the Miller & Chevalier legal memorandum offered an alternative legal theory.
He said that if NRC follows the Sholly route (i.e., if NRC deems the 1982 order to be a license amendment), then it will forfeit a valuable legal tool and limit its ability to take quick action while it looks in more detail at a matter.
Mr. Plaine stated that NRC followed the alternative path in some cases, but that he was informed that a different route was followed in this instance, that the 1982 order did not contain pertinent " triggering language," for restart, and that SCE understood in 1982 that the order did not contain such language.
Mr. Micheletti stated that if Sholly is involved, then the trigger language is irrelevant.
Mr. Plaine responded that he was not addressing that point.
He said he agreed that not every order mndifies a license but that he was informed that this case appeared to have been handled differently.
'Mr. Allen stated that neither Denton nor Eisenhut thought the order was an amendment and that the order did not follow the procedures applicable to amendments to a license.
The Chairman stated that even if the 1982 order were admitted not to be clear, it set a pattern for action and that the SCE proposal now is to modify that pattern.
He asked the question, "Isn't this an amendment?"
Mr. Pigott answered "no" and referenced the Fitzpatrick case in which he said the staff allowed resumption of operation when some but not all of the conditions were completed.
He said the Fitzpatrick casep in substance, is identical to the Unit I case.
He said that NRC does not have to follow the license amendment course for Unit 1.
The Chairman then questioned why the staff was doing what it was doing.
Mr. Allen stated that possibly someone in the staff concluded that there was a Sholly issue and that it should be looked at because it could be a source of embarrassment for the Commission.
He said that SCE was shocked when it learned of the l
staff's view on the Sholly issue and that SCE would not have taken l
the route it took witE NRC or CPUC had it known that staff view.
He stated that the staff lawyers apparently changed their mind.
He said SCE was led down a path for two years and that it relied on NRC.
He said that if NRC believes there is substance to SCE's legal argument, then NRC should follow that argument on the basis of the equities.
He repeated that, otherwise, no utility is going to retrofit.
4
The Chairman asked why SCE did not complete all upgrade actions.
Mr. Allen stated that SCE would have completed the actions, had it known, but that Denton said it did not have to.
The Chairman stated that the Denton letter was 1984 but that the utility committed to the upgrade actions in 1982.
Mr. Baskin said that SCE committed to one set of criteria in 1982 but that the set subsequently seemed to be changing.
He said SCE decided to stop work and did not reach agreement with the NRC staff on the applicable criteria until 1983.
He said SCE had severe problems getting NRC staff agreement and understanding on the applicable criteria but that, once that was achieved, SCE submitted its 1983 proposal.
Mr. Allen said SCE would prefer no public hearing, but that SCE would abide by the Commission's decision.
He said SCE feels "we've been had."
The Chairman stated that perhaps the Commission, which is a collegial body, should schedule a publ,1c meeting at which the staff and the utility each would present its case.
Mr. Allen responded that SCE would cooperate but that it believed public proceedings could lead to public intervention and to the demand that SCE " prove that Unit 1 is built to
.5g."
He stated that the Commission could let the staff make the decision on restart of Unit 1 and tell the staff that it had the legal authority to do so.
The Chairman then said he understood the staff's position to be that it did not have the legal authority.
Mr. Allen responded that he was informed it was the staff lawyers' position.
The Chairman stated that there were technical issues and legal issues involved.
He said he did not want to prejudge the technical issues which might become involved in a hearing.
He noted that the legal issues were in a different posture.
Mr.
Allen said that he had tried to answer the legal issues and that, on the technical issues, the Denton letter set out the answer, supplemented by the SCE data to show that the ECCS was good to
.5g.
Mr. Plaine mentioned an August 11, 1982 letter from Denton to the public.
Mr. Pigott stated he was familiar with that letter and that the same letter was sent to Ralph Nader's group and other people who made 2.206 requests.
He stated that none of the people l
intervened in any licensing proceeding involving San Onofre.
Mr. Plaine wondered whether the 2.206 requests had been settled on l
the basis of the 1982 order and the August 11, 1982 letter to the public.
Mr. Pigott responded that the 2.206's had already been denied at the time of the June 1982 order and the August 1982 letter.
Mr. Allen observed that the discussion lent credence to the view that no one viewed the 1982 order as a license amendment.
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The Chairman stated that it was the NRC staff, not the Commission, that was now saying the 1982 order was an amendment.
He stated that there was also a no significant hazards consideration (NSHC) question.
Mr. Allen asked whether the General Counsel's staff was involved in the decision that the 1982 order was an amendment.
Mr. Plaine responded "no."
The Chairman said that the technical issues have overtones for the discussion, and that they create NSHC questions.
Mr. Allen said that SCE would accept the NRC's NSHC conclusion, but that SCE had been misled.
He asked why the February 1984 Denton letter was written if the 1982 order was viewed as an amendment.
Mr. Baskin stated that the NSHC question depends on the outcome of the license amendment issue because that outcome would create the licensing basis for the NSHC judgment.
Mr. Allen said he believed the license amendment issue held significant consequences for SCE customers and for industry retrofitting generally.
The Chairman said that the information Mr. Allen provided in the meeting would be helpful to resolving the issues and that the Commission needed to consider the information and the issues Mr. Allen said that SCE outside counsel planned to request a meeting witn OGC.
Mr. Plaine said he thought such a meeting should wait until OGC could collect all the facts.
The Chairman noted that a technical judgment remains to be made as well as a legal judgment.
The meeting closed at approximately 3:10 pm.
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UNITED STATES
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NUCLEAR REGULATORY COMMISSION
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.e February 8, 1984 Occket No. 50-206
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LS05-84-02-021 Mr. K. Baskin, Vice President Nuclear Engineering Licensing and Safety Denartnent Southern California Edison Company 2244 Walnut Grove Avenue Post Office Box 800 Rosemead, California 91770
Dear Mr. Baskin:
SUBJECT:
PROPOSED RESTART PLAN FOR SAN ONOFRE NUCt. EAR GENERATING STATION, UNIT NO. 1 We have reviewed your December 23, 1983 precosal for returning San Onofre Unit No. I to operation.
In addition, we have had the benefit of reetings with ycur staff on December 9 and 14, 1983 to discuss the details of your proposal.
Resumption of power operation for San Onofre 1 recuires NRC approval pursuant to the NRC Order dated August II,1982.
In general, we find that the plan and criteria which you have proposed will, when imolemented, be sufficient to demonstrate the CADability to achieve a hot standby condition for a postulated safe shutdewn earthouake (SSE), such that we could permit plant restart prior to the complete resolution of the SEP seismic issues for Unit No.1.
The staff will review the implerentation of this plan and resulting plant modifications and, if satisfactory, issue.
l its safety evaluation report authorizing plant restart.
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The enclosed evaluation describes the results of the staff's review of,ycur Restart Plan and identifies specific exceptions to the criteria you proposed. Where the staff does not agree with the specific criteria ycu proposed, we have attempted to identify compafable, alternate criteria.
Some of these evaluation criteria are considered acceptable only for short-term operation since they do not provide substantial margin to allow for uncertainties.
For long-tem operation, therefore, such criteria must be nodified to restore this margin. We have distinguished those criteria that are necessary and sufficient for plant restart from those that are acceptable for the inng-tem resolution of the seismic design basis tn facilitate your plancing.
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Mr. K. Baskin, We believe that the criteria, as modified, provide adequate assurance for the short-term, i.e. between plant restart and the next refueling outage, that the plant could safely shutdown after the postulated SSE. For the long-ters resolution of the seismic issues, however, we expect you to address both an established capability to achieve cold shutdown and the seismic capability of mitigating systems for transients and accidents that might result from a significant seismic event.
Based on our review, we believe that all the seismic issues should be sub-stantially resolved prior-to restart from the next refueling outage. These issues will be addressed in the integrated plant safety assessment report for San Onofre Unit T.
Implementation schedules will be developed as part of the " Integrated Living Schedule", as discussed in our letter dated January 20, 1984.
To meet your intended restart schedule of Sunner 1984, we will need timely responses to the issues raised in the enclosed evaluation.
In addition, there a w a number of licensing actions that must also be completed to support the issuance of a restart safety evaluation report. These actions have been discussed with your staff and we encourage you to expeditiously pursue their resolution.
Sincerely, f7.C.1,,
Harold R. Denton, Director Office of Nuclear Reactor Regulation
Enclosure:
As stated a
cc w/ enclosure:
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r-Mr. K. Saskin.
cc Charles R. Kocher, Assistant General Counsel James Beoletto, Esquire Southern California Edison Company Fest Office Box 800 Rosemead, California 91770 j
David R. Pfgott Orrick, Herrington & Sutcliffe 600 Montogmery Street San Francisco, California 94111 Harry B. Stoehr San Diego Gas & Electric Company P. O. Box 1831 San Ofego, California 92112 Resident Inscector/ San Onofre NPS c/o U.S.'NRC P. O. Box 4329 San Clemente, Ca11fornfa 92672 Mayor City of San Clemente San Clemente, California 92672 Chai rman Board of Supervisors County of San Diego San Diego, California 92101 2
California Department of Health
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A7TN: Joseph 0. Ward, Chief Radiation Control Unit v
Radiological Health Section 714 P Street, Room 498 Sacramento, California 95814 U.S. Environmental Protection Agency Region IX Office ATTN:
Regional Radiation Representative 215 Freemont Street San Francisco, California 94111 John B. Martin, Regional Administrator Nuclear Regulatory Cenmission, Region V 1450 Maria Lane Walnut Creek, California 94596
SAFETY EVALUATION REPORT RETURN TO SERVICE PLAN - SEISMIC REEVALUATION PROGRAM SAN ONOFRE NUCLEAR GENERATING STATION, UNIT NO. 1 l
INTRODUCTION i
In a letter dated December 23, 1983, the Southern California Edison Company (SCE) submitted a program description to address the seismic cacebility of San Onofre Unit 1 as part of the justification for returning the plant to operation. The issues related to the seismic design of the plant wera raised during the Systematic Evaluation Program (SEP) review of Topic III-6, " Seismic Design Considerations," and are described in the staff's evaluation dated November 16, 1981.
In June 1982, SCE comitted to structurally uograde San Onofre Unit 1 to withstand the postulated Safe Shutdown Earthcuake (SSE), which is the SEP site-specific g spectrun scaled to 0.67g. gund motion characterized by the modi' fed Housner The NP.C issued an order on August 11, 1982 confirming SCE's ccmmitment and reouiring that NPC. approval be obtained for res ta rt.
The plant has remained shutdown since that time and a significant number of-plant modifications have been completed.
However, substantial additional analyses and resulting plant modifications would be necessary to corolete the seismic upgrade program as it has been conducted thus far.
Consequently, SCE has proposed evaluation criteria to identify a limited number of plant modifications to demonstrate the ability of the plant to achieve and maintain a hot standby (mode 3) can'dition following the postulated SSE. These criteria would be used to screen previcus analyses of the struc-tures, systems and components within the SEP seismic reevaluation procram Implicit in this definition of capability to withstand the earthcuake sccee.
event and achieve and maintain a hot standby condition is adeouate integrity nf the reactor coolant pressure boundary and piping in the main steam and main feedwater systems such that there is reasonable assurance that an accident will not be induced by the seismic event.
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The criteria proposed by the licensee are intended to provide necessary ard i
sufficient justification that the plant can withstand the postulated SSE for the short-tern, to permit plant restart until all of the issues related to the seismic capability of the plant can be resolved.
The staff intends to address any outstanding issues related to thg seismic design in the integrated plant safety assessment of the issues raised in the SEP topic reviews.
The implementation schedules for the actions resulting from the SEP integrated assessment, as well as other pending licensing reouirements, will be established as part of the licensee's " Integrated Living Schedule." For the purpose of this review, the staff has assured that "short-term" is essentially between plant restart and the next subsecuent refueling outage; however, in practice, each long-term requirement would be appropriately incorporated into the integrated living schedule based on the perceived safety sionificance of the specific implementation requirement involved.
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4 EVALUATION The licensee has proposed six evaluation criteria, each discussed individually i
below, which would be used to identify the minimum number of plant modifications necessary to ensure a capability to achieve and maintain a hot standby condition following the postulated SSE.
To support this proposa!, the licensee has described the general implementartion procedures that weuld be used to apply the ' proposed evaluation criteria.
In previous evaluations, the staff has cencluded that the modified Housner spectrum scaled to 0.67g is an appropriate safe shutdown earthouake (SSE) for San Onofre Unit 1.
Based on the conservative nature of the sefsnic analyses conducted thus far, the staff agrees that capability to achieve and maintain a hot standby condition is sufficient for plant restart.
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There were several issues raised during the ccurse 'of the seismic reevaluation i
of San Onofre Unit I related to the adequacy of analysis methods, the lack of analyses to demonstrate seismic capability, and the effects of soil conditions.
Based on the seismic risk perspective and the information related to these issues obtained thus far, the staff concludes that the potential fer an SSE to occur coincident with unacceptable conditions related to these issues is sufficiently small that plant restart need not depend on their resolution nor would plant oceration in'the short-term pose an undue hazard to the public health and safety in the absence of their resolution, except as they relate to the het standby capability.
In order to demonstrate het standby capability, the Ifcensee has proposed to apply six evaluation criteria to the structurec (or structural elements) and 4
piping systems which must be upgraded for the plant to withstand the postulated earthquake. These criteria woulc be used with and supplemert previous seismic analyses of the plant design, with due consideration of the plant modifications completed thus far. The conclusions of the staff's review of each of these criteria and the manner by which they would be appli d are as follows:
1.
Conta.irment Building Response Soectra o
In order to accourt for the effects of embedment, the licensee has i
proposed to apply a modified floor respohse spectra for the evaluaH on j
of components inside the containment.
The licensee developed a revised floor response spectra, as shown in Figure 1, based on analyses and l
modelling pergreed by the Lawrence Livemore National Laboratnry (LLNL) for the NRC. - LLNL analyzed the San Onnfre Unit I auxiliary feedwater system as part of a generic research project.
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The staff agrees that a reduction factor may be appropriate to acccunt for embedment effects es shown by the prevfous earthquake recordinos.
Hewever, the staff has found that modellino technioues and analysis methods used in the LLNL analyses significantly overestimate that effect.
Those analyses were performed with the CLASSI computer code assuming vertically propagating seismic waves.
This approach is ecuivalent to a
" deconvolution" technique and results in an input ground motion for the analysis of the containment building which can be a factor of two to three lower than the free-field ground motion.
Extensive peer reviews of deconvolution.,pechnicueshavefoundthatthesetechnicuescouldbe unrealistic. 3-The staff has previously provided guidance on soil-structure interaction review which allows a reduction factor of up to 25: to the 'ree field ground motion when applied for the structural. analyses, decendino on the nature of the earthourke records u motion and local site conditions. yd to define the site-specific cround The reduction factor can be derived from an analysis of the earthouake data used 'or the development of desicn basis earthouake ground motion at the site. The specific reduction factor allowed depends upon the extent to which surface measurerents were used, the extent to which the site conditions match those where the strong motien data were recorded and the extent to which the site conditions justify such a reduction.
The resulting reduction factor would then be applied to calculated floor response spectra using the site-scecific ground motion as an inout at the foundation, provided that the floor response spectra are generated using linear-elastic, dynamic structural analyses.
The staff considers this approach appropriate for both restart arc' long-tem resolution.
2.
Damping Values for Piping Analyses
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The licensee has proposed to use the damoing values 'or piping systers recemended by the Task Grcup of the Pressure Vesset Pesearch Comittee (PVRC) of the Welding Research Council (WRCI, instead of the Regulatcry Guide 1.61 values.
The damping values recomended by PYRC reflect ar extensive review of. #
damping data and a reasonably conservative margin exists when using tha spectral analysis method. On this basis, the sta#f concludes that the croposed damping values are acceptable for both restart ard lono-tem.
If the tire history analysis method is used, justification for the use of damping values as recomended by PVRC should be provided fnr the long-rem operation.
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3.
Spectra Shifting Regulatory ' Guide 1.122 recoceends that the calculated dominant peaks of the floor response spectra be broadened to account for uncertainties in the structural frequencies owing to uncertainties in the material properties of the structure and scil and to approximatiers in the nodeling technfoues.
The licensee has proposed to use a spectral peak shifting method, as depicted in Figure 2, where the licensee,iudges that overstressing is caused by the additional energy associated with the broadened peak.
The staff considers the proposed method more realistic and, there#cre, acceptable for both restart and long-term, with two exceptions:
(a) This nethod is less ef'icient for independent multiple-support motion; i.e., different motion at dif#erent supports in a systen.
If such a situation arises in the evaluation of San Onofre' Unit 1, the staff will require that the licensee justify the appitcatice of any spectral shifting and demonstrate the statistical significarce on a case-by-case basis before restart.
(b)
The specific method proposed by the licensee is based on a *sggle spectral peak within a defined frecuency range of interest. -
However, in some cases there is more than one "doninant" peak within i
this range. Therefore, the staff will reouire that the licensee justify the application cf this technioue on a case-by-case basis before restart for those cases in which there is more than one'
" dominant" peak.
For the long-tenn, the staff will review the application of this technicue to assure that there are no other instances of multiple dominant peaks.
4 Functionality Criteria for Piping and Pipe Supports As'part of the seismic reevaluation crogran for San Onofro trit 1, the\\
licensee proposed allowable stress limits for pioing, o4ce supports, and ecuipment (e.g., purrps and valves) based on the ASME Code Ard the NPC guidelines.
These criteria have been re' erred to as the Balance of Plant Mechanical Ecuf pment and Piping 'PPEP criteria and their (80PPEP) r:riteria. For piret restart, the licensee has modified the 50 appifcation to address the functional capability cf the systems recuired fer hot standby. The staff nonnally distinguishes between criteria for functional capabilitv and criteria for integrity; in our review of the i
restart proposal we have considered the adecuacy of the revised stress linits with regard to functional capability for the purecse of assur'rg creper system operation.
The evaluation of the proposed criteria are as follows:
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(a) Piping The lic'ensee proposed that piping stresses should not exceed 2.0 Sy
'or carbon steel and 2.2 5y for stainless steel, based on oncoiro studies of the capacity of piping systems to with3tand higher stresses. Further, the licensee proposed to evaluate all of the stress contributions witn the appro'priate intersification factors
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in accordance with the ASME Code, except seismic anchnr movernent (SAM).
The staff believes that there is s'Jfficient evidence that piping systems will retain both inteority and function so long as the l
stresses are be!cw 2.0 Sy for both carben and stainless steel.
Therefore, the staff will accept a single limit of 2.0 Sy fer restart and allow SAM to be excluded because its contribution to the total stress is, in general, likely to be small except for those piping systems extending through different buildfres.
For those extreme cases, the iicensee statec that all piping systems required for restart have already been checked for SAM stresses and have been shewn acceptable in the final confiruration. Hcwever, for the long-tem the staff will reouf re a lower stress limit to account for uncertainties and the analyses will have to include FAM to confim that it is a small contributor. The staff will develop the soecific criteria for the long-tem evalcation in conjunction with the review of the licersee's implementation cf the restart procram; those criteria will also consider both fLnctional capability and integrity.
With respect to the piping evaluation precedure proposed by the licensee (Section 5.3.1 of Reference 5), the criteria for decouolinn of branch lines using a diameter ratio of 1/3 is acceptable 'or.'
should not be decoupled if either of the following are factors:Howeve restart.
(1)
If an anchor or ricid constraint on the branch pipe is e located near the run oipe and significartly restrains the movement of the run pioe, the branch pire should be included with the model of the,run pipe, up to the ancher (or up to and including the series of rigid constraints that effectively permits terminaticn of the problem at some point remote frcm the pipe run).
(2) The branch pipe should be included in the mathenatical l
model of the run pipe if more precise magnitude of reactions l
are required at terminal points (i.e., acuipment, penetrations, etc.) to determine their (the reactions) acceptability.
(b) Pipe Supports Based on the review of the Restart Plan, the staff concluded that the licensee has proposed an " energy balance" approach to determine whether pipe supports would fail under the postulated loading conditions and, if they de, whether the intact suoports could survive the load redistribution. However, the staff was subsecuently advised by the licensee that the proposed approach would only be applied to 3
determine the effects of support removal or failure on the pipino functionnlity and integrity to avoid the expense of a complete '
reanalysis.
The staff agrees in principle that the erergy balance approach is reasonable to estimate the effects o' sucoort removal or failure on the oiping runs, provided that the ifcensee demonstrates that the kinetic enerry has been conservatively estimated for the specific piping configurations involved, and evaluates the fatture modes and consecuences for pipe supports that are postulated to fail and are not removed prior to restart.
The licensee would evaluate overstressed pipe supports using simplified analysis technicues to determine their ductile capability and potential f.or failure.
Because of the comolex nature of the piping analysis, simplified analysis techniques will have to be selected on a case-by-case basis.
Therefore, the staff will reouf re that the licensee identify all of the supports calculated to exceed yield stress and will rudit the analysis techniques applied.
The staff will a'ccept a definition of failure of the pice supports at the yield stress, as defined by (1) the ASNE Code or (2) actual materials certifications; separate criteria exist 'or buckling and ancnor bolts.
On a case by case basis, the staff would consider a support functionally capable if the peak stress does not exceed a about 30% above the yield stress specified by the Code because of \\
the inherent ductility strength of the support system.
For the long-tenn, the staff believg that the SEP guidelines shculd be used to evaluate pipe supports J
(c)
Equipment The licensee has proposed to apply the 80PMEP criteria to ecuipment for restart.
The staff has previously cencluded that ecufoment capabilft" has been adecuately resolved because (1) the functional capability of equip-ment is being actively pursued for all operating plants under the Unresolved Safety Issue A 46, " Seismic Oualification of Ecuipment,"
and (2) the licensee had previously comitted to uegrade the integrity of equipment (f.e., to meet the acceptable stress limits) for the postulated SSE, including ecutpment supports. The staff will recuire that the licensee confirm that the eouipment in the systems recuired for hot standby have been upgraded, as ccrsnitted.
7 5.
Inelastic Criteria for Structural Members The licensee has proposed to evaluate structural steel mmbers (excludino pipe supports covered under 4.b above) using a ductility ratio as a measure of the plastic de#onnation capacity. The staff agrees with this type of approach and accepted the allowable duct 4}ity factors presented in the Itcensee's February 23, 1981 submittal. /-- The proposed criteria for restart specify higher ductility factors; however, the basis for these factors has not yet been provided.
The staff has found that the approach proposed by the licensee apoears to overestinate the yield displacement of structural eierents in the basic definition of the ductility ratio. itoreover, the licensee did not adecuately define the nethod of application for the proposed criteria.
The ductility factor is the ratio of the calcu' lated displacement cf a merb y to the " effective" elastic limit displacement, as shown in Figure 3.
- The highly non-linear load (i.e. resistance) displacenant relatienship is approximated with an " effective" load-displacement curve of ecual area, which pro.iects the effective elastic limit. An analogous relationship exists for bending moments if the yield moments and displacements are used, as depicted in Figure 4; however, the ifcensee has proposed to use the plastic moment capacity instead of yield displacement to define the ductility ratio.
In addition, the staff noted the following issues during the review of these proposed criterie:
(a) Because the relationship betweef the ratio of merents (M/H ) and the ratio of displacements (8/dy) is not defined. 't is noE clear why M/M is used to calculate the ductility retfo, instead of the displa8ement ratio.
(b)
The licersee did not justify the relationship (pp.1)i P/p,,Mx/g,, My/
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p 1)f= 88y or 8 #y is valid (c) The gereral relationship (?>t-
/
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roughly in the rance of 2-8Hz.
It is not clear what relationships I
would be used cutside this range.
(d) When a structural member is loaded to its plastic momert caeacitv, there are raterial fabrication and construction censiderations for possible failure modes which must be addressed. These include ounched holes in tension zones, sheared edces, the ratios of b/t and h/w, the strength of connections and connectors, etc.
(e) The licensee should justify the adecuacy of usica bending merent "M" (or rotational displacement "p") to calculate ductility facters for short and nedium spanned beams.
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(f) The licensee committed to develop criteria for connected remoers. 21 Neither the criteria nor their bases have been provided.
The concept of the use of ductility ratio, as a neasure of the degree to which a structural member can go into the inelastic rance and still retair its function, is acceptable to the staff for both restart and lano-term operation. However, the staff does not agree that the calculational method proposed by the ifcensee is acceptable.
The staff concludes that a duc*'lity ratio calculated based on the yield displacement instead of the plastic moment capacity of the beam is acceptable; other calculational technicues may be acceptable if the licensee can justify the nethod of application prior to restart.
6.
Qualification of Small Piping For piping with a nominal diameter of 21 in, and less, the licensee has proposed a field walkdown together with the documented earthcuake experience and test data, particularly recent tests perforced in Germany by ANCO for KWU, to demonstrate the structural integrity and function of these small-diameter piping systems.
The walkdown to be comoleted before restart would apply only to those systems required for hot standby.
The staff agrees that there is sufficient historical and experimental evidence that small-diameter piping systems have sufficient inherent resistance to large earthquakes to support plant restart. The staff also agrees that it is appropriate to conduct a walkdown of the hot standby systems, prior to plant restart, to identify any possible anomolous design and field conditions.
Specifically, the piping supports should be evaluated where there are large eccentric masses enunted cn the piping.
For the long-tem, however, the staff believes that some samoling analyses should-be conducted to confirm the applicability of the historical and.
experimental evidence and to investigate the capabdif ty of any unusual
- or unique design features so that adequate safety margins are preserved \\n the small-bore piping systems.
For efficiency, the nature and criteria i for selection of sample analyses should be defined before any clant walk-downs are condu ted so that candidate design and field cono4tions can be identified at the same time.
Therefore, the staff will work with the licensee to develop appropriate criteria'for sampling analyses prior to the conduct of a plant walkdown, i
CONCLUSION Based en the review of the licensee's proposed restart program, the staff concludes that the evaluation criteria, as modified by the staff's evaluatier, are adequate to assure hot standby capability in the event of a postulated SSE earthouake for the short-term until the seismic design issue can be cemoletely
)
resolved. Moreover, the staff concludes that het standby capability is sufficient to assure safe plant shutdown for the purpose of plant restart, l
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i In specific cases, the application or combination of the evaluation criteria' may not be accropriate.
The staff considers such cases to be unlikely and, therefore, will address this issue in the review of the licensee's impler:enta-tion of this program.
The staff has identified those areas where additional review are necessary to extend the restart. progran to completely resolve the seismic design basis' for San Onofre Unit 1.
The plant's capability to reach a cold shutdown condition and to mitigate possible transients and accidents resulting from a design-basis earthcuake will be resolved in the SEP integrated assessment.
REFERENCES 1.
Letter fron W. Paulson, MC, to R. Dietch, SCE, dated Seotember 16, 1982.
2.
LLNL Draft Report, "The Final Progress Report for the San Onofre Nuclaar Generating Station Unit 1, Auxiliary Feedwater System Project - Seismic Safety Margins Research Program," June 18, 1982.
3.
Transcript of the Proceedings of the U. S. Nuclear Regulatory Comnission's Advisory Consnittee on Reactor Safeguards (ACRS) Seismic Activity Subecmit-tee meeting, February 8,1977.
4 Letter fron D. M. Crutchfield, NRC,'to all SEP Licensees, " Guidelines for SEP Soil - Structure Interaction Reviews," dated December 15, 1980.
5.
Letter fren M. D. Medford, SCE, to 0. M. Crutchfield, NRC, dated December 23, 1983.
6.
Letter from W. A. Paulson, NRC, to R. Dietch, SCE, dated July 26, 1982.
7.
Letter frem K. P. Baskin, SCE, to 0. M. Crutchfield, NRC, dated February 23, 1981.
g 8.
N. M. Newmark and W. J. Hall, " Development n# Criteria for Seisnic Peview' of Selected Nuclear Power Plants," NRC NUREG/CR-0098, May 1978.
9.
Letter from M. O. Medford, SCE, to 0. M.,Crutchfield, NRC, dated January 6,1984 i
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