ML20198H897

Response to Aslab 860103 Memorandum & Order Re Hydrogen Control Rule.Consideration of Accidents Involving Station Blackout W/Rcic Unnecessary to Determine Adequacy of Preliminary Analysis

ML20198H897
Person / Time
Site:	Perry
Issue date:	01/29/1986
From:	Woodhead C NRC OFFICE OF THE EXECUTIVE LEGAL DIRECTOR (OELD)
To:
Shared Package
ML20198H899	List: ML20198H897 ML20198H919
References
CON-#186-889, REF-GTECI-A-44, REF-GTECI-EL, TASK-A-44, TASK-OR OL, NUDOCS 8601310123
Download: ML20198H897 (10)

Text

W January 29, 1986

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NUCLEAR REGULATORY COMMISSION C.~ ~ "% [cI Q ,k5 BEFORE THE ATOMIC SAFETY AND LICENSING APPEAL BOARD c -

In the Matter of )

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CLEVELAND ELECTRIC ILLUMINATING ) Docket No. 50-440 OL COPPANY, ET AL, ) 50-441 OL

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(Perry Nuclear Power Plant, )

Units 1 and 2) )

NRC STAFF RESPONSE TO APPEAL BOARD OVESTIONS CONCERNING THE HYDROGEN CONTROL PULE I. INTRODUCTION By Pemorandum and Order dated January 3, 1986 the Atomic Safety and Licensing Appeal Board (Appeal Board) indicated that a decision could be reached on the pending appeals of the Concluding Partial Initial Decision (CPID) 1/ without the need for oral argument, but that a few questions remained to be explored after an examination of the briefs filed by the parties. Consequently, the Appeal Board directed the parties to supple-ment their briefs with responses to two questions set out in the Memoran-I dum and Order. The NRC Staff hereby provides its response to the Appeal Board questions.

1/ LBP-85-35, 22 NRC 514 (1985).  ;

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II. DISCUSSION The two, two-part questions E asked by tte Aopeal Board concern (1) the propriety of considering certain evidence at the hearing regarding the hydrogen control -issue and (2) the particular requirements of the hydro-gencontrolrule,10CFR950.44(c)(3)(iv-vii). The Staff responds to the Appeal Board cuesticas serially below and in the atteched Staff affidavit. Because each question has two parts, the Staff has addressed them separately.

y 7he two cuestions posed are: l

1. No accident scenarios that would result in [75% metal-water reaction 1 bydrogen production are specified, but the [ hydrogen contro?) rule states that scenarios accepted by the NRC staff "must be accompanied by sufficient supporting justification to shcw that they describe the behavior of the reactor system during and following an accident resulting in a degraded core."

10 CFR 50.a4(c)(3)(vi)(B)(3). In light of this directive, was it proper for the Licensing Board, in connection with its assessment of the applicants' prelirr.inary hydrogen control analysis, to admit and to consider evidence concerning assutrptions related to specific details of the accident, such as cortainment spray availability, station blackout, and the operability of the Reactor Core Isolation Cooling System? If rot, does the rule nevertheless recuire the applicants' final analysis to include a detennination with respect to the appropriateness of such assurrptions?

2. Taking into account your answer to Question 1, as well as the requirement of section 50,44(c)(3)(vf)(B)(5)(i) that contain-ment structural integrity must be r.aintained throughout the hydrogen generation and control scenario, what is the justiff-cation for the applicant's and the staff's reliance on an analysts that cpparently requires the operation of the contain-ment spray system as a heat removal device in order to maintain containment integrity? Given this re<;uirement, does not the contaitur.ent spray become a necessary part of the hydrogen control systent and hence fall within the scope of the rew hydrogen rule? See L6P-85-35, 22 WRC 514, 542 (1985).

Q.1(a) The Licensing Board Correctly Admitted and Considered Testimony At Hearing Concerning Underlying Assumptions of the Preliminary ,

Analysis =

! The Staff believes the evidence concerning the underlying assumptions of the Applicants' preliminary hydrogen control analysis was properly admitted and considered by the Licensing Board. Sufficient information to evaluateconclusionsonthedefinedissuemustbemadeavailable,S/andin this prcceeding sufficient evidence was, in fact, the basis for the Licens-ing Board's finding that Applicants' preliminary analysis satisfied the requirements of 10 CFR iS0.44.

The Applicants' preliminary analysis assumed operation of containment spray, and assumed the availability of A.C. power during or after hydrogen burns for the two accident scenarios analyzed AI in the preliminary hydrogen control analysis, AffidavitofA.Notafrancesco(Affidavit),f4. As indicated by the CPID, the record contains substantial evidence (in the I SER and FSAR) supporting the assumption of containment spray operation, and the other analysis assumptions, 22 NRC 548-49. Since these were 1 assumptions of Applicants' preliminary analysis, the exploration of the underlying assumption that contaiment spray would operate and any other i assumptions in the selected and Staff-approved accident scenarios was a t-1

-3/ Virginia Electric and Power Company (North Anna Nuclear Power l Station, Units 1 and 2), ALAB-555, 10 NRC 23, 27 (1979) 4/ Simply put, the two accident scenarios chosen for the analysis were a stuck open safety relief valve (SORV) and a small break LOCA, both i of which led to a degraded core.

proper subject for consideration concerning the adequacy of the preliminary hydrogen control analysis.

Powever, as pointed out by the Licensing Board, the appropriateness of the two accident scenarios (and their underlying assumptions) contained in the preliminary analysis was neither challenged nor directly explored at hearing. 22 NRC 537. Rather, the thrust of intervenor's argument was that in addition to these scenarios, in which some safety systems were assumed to function (and for which there was record support), the Appli-cants should also address scenarios in which safety systems would not

, function. Specifically, Intervenor attempted to interject into the hear-ing hypothetical questions concerning the consequences of failure of con-tainment spray during hydrogen burning and failure of all A.C. power sources. Tr. 3444-45, 3428-38. Despite the rather liberal scope of inquiry permitted by the Licensing Board5_/, Intervenor was not able to establish a foundation challenging the assumption that these systems would, in fact, function.

Thus, the actual underlying assumptions of the preliminary analysis (which were, generally, that certain safety-related systems would function properly) were appropriate for consideration by the Licensing Board - and for challenge by intervenors- in order to determine whether the preliminary analysis provided "a satisfactory basis for a decision to support interirn operation at full power until the final analysis has been 5/ The Licensing Board did explain that because the boundary between the preliminary and final analysis described in the hydrogen control rule was not defined, the Board allowed cross-examination beyond the bounds of a reasonable preliminary analysis. 22 NRC at 548.  !

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- 5-corpleted" as required by 10 CFR $ 50.44(c)(3)(vii)(B). To make this judgment, the Licensing Board necessarily and properly should admit and consider evidence concerning the bases of the preliminary analysis. In this regard, the Licensing Board noted that containment spray as well as other safety systems were subject to separate detailed analyses so that the reliability of these systems, while ultimately connected to proper -

functioning of the hydrogen control system, need not be addressed at length in the preliminary hydrogen control analysis in the absence of a basis for questioning the reliability of these systems. 22 NRC 549. In the absence of any challenge to the reliability of such systems, cross-examination and testimony corcerning the consequences of containment spray unavailability, station blackout and RCIC operation was not evi-dence essential to the Licensing Board's decision detcrmining that the Applicants' preliminary analysis of two scenarios was sufficient to satisfy the requirements of 10 CFR 50.44, 22 NRC at 548-49.

Thus, in response to the first cuestion posed by the Appeal Board, the NRC staff concludes that it was proper for the Licensing Board to permit inquiry into these subjects to the extent that such inquiry served to explore the bases and assumptiens of the preliminary analysis that certain safety systems would operate. In the absence of any challenge to the reliability of such systems, further inquiry into the consequences of the failure of safety systems was unnecessary but the Board's action in j permitting such inquiry was hannless.

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01(b). The Staff Will Require a Wide Range of Potential Conditions For The Final Analysis of Hydrogen Control Systems The second part of the Appeal Board's Question 1 inquires as to ,

whether the three specified subjects ultimately must be addressed in the final analysis.

The hydrogen control rule itself does not specify the exact scope of the " final analysis"; rather it requires that the analysis satisfy the performance standards set forth in 10 CFR 550.44(c)(vi)(B) esing accident scenarios " accepted by the NPC staff. These scenarios must be accompanied by sufficient supporting justification to show that they describe the behavior of the reactor system during and following an accident resulting in a degraded core". 10 CFR 550.44(c)(vi)(B)(3).

Thus, the Staff is given a wide range of discretion in determining the exact details of acceptable analyses. In this connection, the Staff has indicated that it will require that " final analyses" encompass a wide range of potential conditions using information from test programs which are now in development, particularly the Hydrogen Control Owners Group (HCOG) experimental testing program. The conditions to be analyzed are to include containment response with and without containment spray operation. Affidavit ,1 8.

The objective of the final analysis is to assure that the hydrogen control system will in fact function to adequately control hydrogca generated as a result of a dearaded core accident. The related test prcgrams are to provide erpirical information to assess the potential range of conditions over which the selected systems can be relied upon to function. Thus, although the final analysis is intended to confirm the conclusions reached in the preliminary analysis and will cover the same

two basic scenarios, the Staff will require that the final analysis consider a broader range of parameters associated with these scenarios.

The extension of parameters will include considerations of the effects of availability [and nonavailability) of Containment spray, to be based in part on empirical data being developed from a quarter scale test facility. Affidavit, f 6.

Hence, while the final analysis will be similar to the preliminary analysis, in that it will address the same two basic scenarios, it will be a much more in-depth assessment of the capability of the hydrogen control system to deal with a range of potential conditions under which it may be called on to function.

0.2(c) The Reliance On Effects of Containment Spray In The Preliminary Analysis Is Justified But Should Not Be Construed As Reliance For The Final Analysis The Appeal Board's second question inquires into the justification for " reliance" by Staff and Applicants on containment spray as an apparently required heat removal device to maintain containment integri ty.

The Staff, by accepting the preliminary analysis, did not intend to suggest that ultimate reliance was or should be placed on the containment spray. Testing programs now underway may show that containment spray is not necessary to maintain containment integrity during hydrogen burning.

Affidavit 18. In the absence of such test data and for the limited purpose of the preliminary analysis (to justify interim operation until completion of the final analysis), the Staff believes it was technically

reasonabletorelyoncontainmentspray(AffidaDit,?6.)andreliance was indeed placed on operation of containment spray as well as some other safety systems. The reliance is justified by the fact that these are l

safety-related systems which are subject to strinaent design, quality and l operability requirements to assure reliability. However, as indicated I above, the final analysis will require evaluation of a wider range of conditions including conditions in which containment spray is I unavailable. Such analysis may demonstrate that containment spray is not <

necessary to assure containment intergrity, it may confirm the need for containment spray, or it may provide other insights on the relationship, if any, between the operation of containment spray and containment integrity In the interim, the reliability and quality of this safety related systen provide, in the absence of any record evidence to the contrary, dn adequate basis for reliance on it to function to assist in hydrogen control.

Q.2(b) The Containment Spray Is A tk estary Part Of The Hydrogen Control System for P tyg 9 the Preliminary Analysis Finally, the Appeal Board inquires into the necessity of containment spray operation for proper functioning of the hydrogen control system, given the apparent reliance on the spray to maintain containment integrity.

While the preliminary analysis did assume operation of containment spray, the Staff, nevertheless, has not finally concluded that the spray is necessary to maintain containment integrity, since tests and the extended evaluation of the final analysis may show that temperatures frcm

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-g-hydrogen burning do not require the heat transfer effects of the spray or that other heat reduction measures could be taken. Affidavit, 5 8. For this reason, the Staff has not yet finally concluded that containment spray is a necessary part of the hydrogen control system at Perry and within the scope of the hydrocen control rule. However, since the pre-liminary analysis assumes operation of containment spray, the containment spray system could be viewed as a currently necessary part of the hydro-gen control system encompassed by the new rule.

IV. CONCLUSION In summary, consideration of accidents involving the unavailability of containment spray and station blackout with RCIC operation at hearing was not necessary to determine the adequacy of the preliminary analysis, althcugh evidence concerning the adequacy of the underlying assumptions of the preliminary analysis was necessary to a decision and therefore, properly admitted and considered. The necessary final analysis will be similar in scope to the preliminary analysis but will consider a broader range of parameters, including unavailability of containment spray.

The assumption in the preliminary analysis that containment spray will operate is justified by the fact that containment spray is a safety system subject to stringent operability requirements and there is no evidence demonstrating unreliability. Nevertheless, current reliance on containment spray operability in the preliminary analysis essentially makes containment spray a necessary part of the hydrogen control system,

at least until the need for containment spray is further examined in the final analysis.

Respectfully submitted, Colleen P. Woodhead Counsel for NRC Staff Dated at Bethesda, Maryland this 29th day of January,1986.

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