ML19276F850
| ML19276F850 | |
| Person / Time | |
|---|---|
| Issue date: | 01/18/1978 |
| From: | Case E Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19276F851 | List: |
| References | |
| SECY-78-026, SECY-78-26, NUDOCS 7904120367 | |
| Download: ML19276F850 (25) | |
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UNITED STATES NUCLEAn REGULATORY CO.'.tMtssiCN CONSENT CALENDAR ITEM
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The Cc.=issioners
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,e-Ecsen G. Case, Acting Directcr Office of Nuclear Reac:ct Regulation F
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- h A Lee '/. Gessick, Executive Direc cr for Operation 7 m E
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Sec'ect:
PROPOSED ACTION PLAN FOR MCDIFYING ThE SYSTEM (ECCS) RULE IN 10 CFR S 50.46 AND A PART 50 c'u rec s e :
To cctain Cc. mission approval of the staff's creposed acticn p1an.
Issua:
When and hev should the "Acceptar.ca Criteria for Emergen Core Cooling Systems (ECCS) for Light-Water-C:oled Nuclear Power Plants" be modified to taka into account anc (2) c:erating experience? gained in tne licensing p
- 1) experience
-Discussien:
Backcreund:
Nuclear Reactor Regulation en the formula possible changes to the Emergency Ccre Cccling System (E
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rule (10 CFR S 50.46~and.Acpencix K to 10 CFR Part EO).
briefing incluced a discussica of (1) staff and industry The experience in icalementing the rule and (2) results frem the At the conclusion of this briefing, the Ccem staff to prcpose an action plan indicating when and how the rule mignt be mcdifiec."
A Ccamissien Infermatica Report"* presenting the staff's
'sien en July 1,'1977.pregress en the proposed action plan was se THIS DOCUMENT CONTAINS That report discussed:
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~ E P00R QUAUTY PAGES The background cf the-ECCS rule and the licensing ~ exp L.
rience in using the rule, new research results Reference me.ecrandum frem the Secretary tc the Executive Dire catec April 5, 1977.
- eraticns, K2 Cc.missica Information Recer, SECY-77-358, dated July 1, 1977 Centact:
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obtained since the rule was promu.lgated in 1974, and coerating and other experience gained that can be related to tne rule.
3.
The preposed decision criteria for rule change, i.e.
1.
Maintain adequate level of safety.
2.
Remove unwarranted conservatiscs.
3.
Maintain licensing ecmentum consistent with safety.
4.
Enhance generic resolution of ECCS issues where practical.
C.
The four alternatives considered for rule change, i.e.
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- 1. =?No Rula Change at this Tite.
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Change Certain Technical as welf as Non-Technical 2.
Requirements within Existing Rule Framework.
(a)
Procedure-Oriented Changes
- (b)
Research-Oriented Changes (c) Operating Experience-Oriented Changes 3.
Recast ECCS Regulations into New Framework with Mora ~
General Principles.. -
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4.
. Rescind Most ECCS Regulations and Replaca All but
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3asic Criteria with Regulatory _ Guides.
Methods for assessing the impact of a change on khe D.
overall conservatism in the rule, including a recommenda-tion en the method believed to be best at this time-
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For all alternatives except number T, technica7 evaluation of the impact of a change on the overall conservatism of the rule is required.
The paper also stated that the staff would discuss the consid-erations for possible ECCS rule change with the ACRS before making recc=:endations and providing an action plan for imple-menting the recommendations.
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The Cecaissioners 3
ACRS Briefincs On July 26, 1977, the staff met with the ACRS ECCS Subcccmit-tee and its censultants.
Some industry representatives were also in attendance at this meeting and provided their views.
There was extansive dialogue among the staff, the succcemittee and the subcccaittee's consultants regarding the reasons for considering a rule change at this time, the various proposed alternatives for rule change, and the proposed methods for assessing the impact of any proposed changes on the overall conservatism provided by the present rule.
The representatives of reactor manufacturers present at the meeting expressed the need for a more flexible interpretation of the ECCS rule to avoid needless waste of technical manpower
_and collars on ECCS recalculations for model corrections at
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the construction permit stage.
(See Enclosures A and B for
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industry letters and the staff's response regarding these concerns.)
It was the industry representatives' opinion that this can be acccmplished within the legal framework of the present rule.
The ACRS ECCS Subccraittee commented that while they are not in a position to offer legal advice to the staff o
on how to implement the rule, the Cccaission should.be aware of the ECCS recalculation problem and continue to explore what means exist under the present rule to cope with the problem.
'The vendor representatives al.so were.in general agreement that if resolution of' this recalculation problem can only be acccm-plished by rulemaking, then.it is better not.to change the rule.at this, t.ime.,, _Thi.s i.s because a rule change night initi-ate another time ' consuming and costly hearing and the end-result might not provide any substantial benefit in terms of power generation econcaics.
The staff agrees wi~th the reactor manufacturers' comments that ccmplete ECCS recalculations due ta micor analysis errors
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detected during-CP reviews-are not necessary and that they are expensive and delaying without any significant safety benefit. _
Because of tha. complexity of ECCS analyses and'the continuing refinement of ECCS analysis methods, errors (e.g., reprogram-ming errors) will in all probabilicy continue to occur.
However, the staff does not agree that flexibility in recal-culation requirements can be accommodated simply through more flexible interpretations of the existing requirements, as suggested by the industry representatives.
Rather, this flexibility must be cbtained through changes to the existing rule.
Another significant comment of the vendor representatives relative to the rigidity of certain parts of the rule was that
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The Cccaissioners 4
l their companies do not spend much effort en safety R&D in areas where it cannot be used directly in the licensing process.
On Sectember 9, 1977, the staff met with the full ACRS regarding pcssible approaches to ECCS rule changes.
At the beginning of this meeting, the ACRS ECCS Subccamittee chairman presented the subcccmittee's view that they "are not ready to recommend any major relaxation in Appendix X to be made at this time."
The subccamittee concluded that more work needs to be done by the staff in developing a suitable method for quantifying safety margins and in developing precedures whereby reasonable safety margins will be preserved.
Fellowing the ECCS Subccraittee report, the staff presented its censiderations for rule change at this time, alternatives for change and proposed methods for assessing the impact of a
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change en the overall conservatism provided by the rule.
While there was not unanimous agreement among the Ccmmittee members, the ACRS adopted the.ECCS Subccemittee recommendation and provided the staff with the folicwing statement (Enclo-sure C):
"During its 209th meeting the Committee discussed with the NRC staff fcur possible alternatives with respect to preposed changes in Appendix K.
The Ccmmittee concluded, as reflected.
- in the transcript at this meeting, that it endorses Alterna-tive 1 at this time."
(These are the saw Alternatives stated on page 2, above.)
"The ACRS Subccraittee on ECCS will continue'to work with the ~
NRC staff, both in Reactor Regulation and in Safety Research, in their efforts to develop methods for quantifying safety margins which exist in Appendix K and for preserving safety margins taking. into account new results which reduce the
- - - uncertainties in the data bases..The.ACRS Subcommittee will
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report back to the Ccmmittee at an appropriate time (approx-icately 6-8 months)."
Rationale for Staff's Recommended Action Plan The primary technical concerns of the ACRS centered on the current inability to quantify the conservatism of the ECCS rule and therefore the staff's ability to adequately assess the icpact of proposed rule changes on the overall conservatism of the rule.
While the ACPS subccamittee seemed to agree in principle with the staff's proposed methodology for making such assessments, they were not ready to endorse proceeding with rule changes that impact the'overall conservatism until the methodolccy has been more fully developed.
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Another consideration expressed by some ACRS members was the potential for time consuming and costly rulemaking' hearings.
This factor clearly appeared to be the principal consideration in the industry representatives' views on the desirability of ECCS rule changes at this time; however, one industry repre-sentative (utility consultant) stated that he believed utili-ties operating nuclear power plants would certainly be inter-ested in getting some relief in operating limitations.
The staff agrees with the ACRS that more work is requirt s to develop the methodology for assessing the impact of a change on the overall conservatism of the rule and plans to undertake this work.
The staff also agrees that for technical changes based on available new research information (fission product decay heat and zirconium-water reaction rate), the assessment
. of the impact of a change on the overall conservatism of the rule should be ccepleted prior to initiating rulemaking.
However,.the staff does not believe that it should wait until its assessment methodology has been fully developed before initiating rulemaking to effect procedure-oriented changes.
Therefore, the staff believes that the Commission should pro-ceed with Alternative 2, but in two distinct steps:
a l.
Initiate rulemaking now for the procedure-oriented changes discussed in Enclosure D (Alternative 2a froa page 2).
The procedure-oriented rule changes are expected to have
-little impact on the overall conservatism of the rule and such changes are anticipated to require a minimum of time and effort to implement.
It is also believed that
- _ procedure-cciented changes _.would not likely lead to the ;
need for a rulemaking hearing since they have little,'if any, impact on the overall conservati'sa of the rule.
2.
'In paralleT with 'I above, we should initiate development of the bases for a second rulemaking action to be taken later to incorporate new research and, if found appro-priate, operating experience.
(These are Alternatives 25 and possiblg 2c. fro.s page 2.) This effort would include -
assessing the impact of proposed changes on the overall conservatism of the rule.
As part of the ovarall assess-ment of conservatism, a systematic review of all relevant information will be performed to ensure that it is appro-priately considered in the assessment.
Favorable new data on decay heat and zirconium-water reaction will be considered together with all new information including adverse results, for example, discrepancies in the pretest prediction of significant research test resuits, uncertain-ties associated with the prediction of counter-current flow phenomena and core spray distribution, and the
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possibility of steam generater tube failures.
If, during this review, it is determined that any information requires core specific treatment than is presently provided in the Appendix K rule or in present licensing practices, then an appropriate rule change request will be initiated.
The research-oriented rule changes, however, are expected to raise significant questions on the overall conservatism of the rule, and a rulemaking hearing is more likely for these changes.
The proposed research-oriented rule changes will be a first step toward icplementing the Commission's general policy that new experimptal evidence or improved analysis should be considered where it is relevant.
This policy was stated in the 1973 Ccr.:sission Opinion
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. ECCS rulemaking as follows, "As new knowledge is acquired, the Cc= mission will analyze it; and at an-appropriate time consider
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the possibility of amending the rule we announce today'."
(Commission Cpinion, page 1088.)' The-staff believes that an appropriata time has now arrived to reconsider the require-ments of Appendix K in light of available information.
Signif-icant new research results on decay heat generation and metal-water reaction rate are now available and should be utilized with due consideration for maintaining adequate overall conser-vatism of the rule. We should not wait for other research programs whose results may indicate the need for ECCS rule change (i.e., discharge models, ECCS storage during bicwdown, BWR spray cooling heat transfer rates, etc.) since they are not expected to be ccmpleted for another three to four, years.
.Thereforeit.isthestaff'scpinionthatsufficient5dditic'nal data has beccme available such that a reevaluation of'present licensing requirements for ECCS analysis is justified and consistent with the Cc= mission's intent.
The staff has consi~dered the ACRS~and industry representa-tives' views relative.to.the_ decision criteria and the varicus
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alternatives (discussed" in detaiT in the previous information I
paper, SECY-77-358) and recommends proceeding with Alternatives 2a and 2b, taking 2c into consideration as may be apprcpriate (Alternatives stated on page 2, above).
This reccomendation is based on the fact that:
a)
Specific needs for change have been identified regarding procedural difficulties and new research information.
^CLI-73-39, Cpinion of the Ccamission in the matter of Rulemaking Hearing Acceptance Criteria For Emergency Cere Cooling Systems Fcr Light-Water-Cecled Nuclear Power Reactors, Decemoer 28, 1973.
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b)
Operating and other experience-oriented changes in ECCS analysis requirements (e.g., countercurrent flow phenomena, core spray distribution) have already been implemented by the staff.
Although such changes in ECCS analysis are not explicitly called out in the rule, the staff has not had significant problems in recuiring changes of this character when necessary and the staff believes that such items do not constitute specific needs for rule changes at this time.
Some cperating experience that could potentially affect ECCS performance is under generic review by the staff (steam generator tube failures). If during the overall assessment of conservatism of the rule it is determined that any experience-oriented information requires more specific treatment than is presently pro-vided in the ECCS rule, an appropriate rule change to
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account for this experience will be included.
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The recommended program can be accomplished within the manpower resources presently allocated in a reasonable time.
It is the staff's opinion that this general approach is harmo-nious with the intent of the ACRS.
Upon approval of the proposed plan, we intend to inform the public (via a Federal Register notice or~other appropriate means) and the industry (through a letter from E.G. Case to J. E. Ward of the Atomic Industrial Forum) about the proposed action plan.
The industry letter will respond to M_r. Ward's_ suggestions (see Enclo-sure B) concerning proposed _ECCS rule changes.
Recommendations:
1.
That NRR have SD initiate rulemaking for procedure-oriented changes (See Enclosure D for details)~to be made to certain parts of 10 CFR 50 and Appendix K to 10 CFR 50.
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That NRR, with input from RES, initiate develop =ent of a request for Timited technical changes to certain parts of
~i 10 CFR 50 ~and: Appendi'x K to 10 CFR 50 (See Enclosure D '
for details)_ This request will include an assessment of the icpact of these changes on the overall conservatism of the rule.
These changes will focus on the incorpora-tien of new research information in the areas of fission product decay heat and zirconium-water reaction, and the assessment of overall conservatism will also account for relevant new information obtained from operating experi-ence and on going research efforts that are not presently addressed in the rule.
Any information included in this assessment that is considered to require specific treat-cent in Ine rule will be proposed for incorporation in the rule change.
For any changes requested (or made),
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adequate overall conservatism of the rule shall be provided censistent with the intent of the 1973 Ccmmission Opinion.
3.
That the Ccamission approve the plan (Enclosure 0) for acccamlishing the above actions.
Cecrdinacien:
The Offices of Standards Development and Nuclear Regulatory Research concur in the reccamended action plan.
Tha Office of the Executive Legal Director has no legal objection.
The Office of the General Counsel has no legal objection.
Comments of the Office of Policy Evaluation are respcnded to in Enclosure E.
Scheduline:
For affir ation at an open meeting during ~the week of February 20, 1978.
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Edson G. Case, Acting Director Office of Nuclear Reactor Regulation
Enclosures:
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"A" - Letter from Glenn G. Sherwood, GE, to the Honorable Marcus A. Rowden, Chairman, USNRC, " Inter pretation of 10 CFR S 50.46 and Appendix K",
dated April 1,1977; and NRC's Response, Letter frca Lee V.
Gossick, EDO, to Glenn G.' Sherwood, GE, dated July 25, 1977 "B"
- Letter frca John E.' Ward, AIF, to
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Edson Case, USHRC, dated August 22,.-' -
1977
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"C" - Letter frem R. F. Fi aley, ACES to Lee V. Gossick, EDO, " Proposed
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Revision of 10 CFR Part 50,_Appen-dix K," dated September 13,,1977 "D" - Action Plan for ECCS Rule Chance "E" - Response to OPE Ccaments
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Cemissicners' corments or consent ji ould be provided directly to the Office of _
h tne Secretary by close of business iuesday, January 31, 1978 Co.missicn staff office coments, if any, should be subrritted to the Ccmmissioners NLT January 25, 1978, with an info Mation copy to the Office of the Secretary.
If the paper is of such a nature that it requires additional time for analytical review ar.d ccmer.t the Comt.issioners and the Secretariat should be apprised of when ccren-cay be ex:ected.
DIST?I5UTION:
Co. r.i s s i cr.ers C:=.ission Staff Offices Exec. Dir. for Opers.
Secretariat