ML20151T833

Requests Review & Comment Re Scope of Paragraph 50.44(g), Whether Technically Acceptable Inerted Containment Sys Could Satisfy Provision of Paragraph 50.44(g)

ML20151T833
Person / Time
Site:	Quad Cities
Issue date:	06/23/1987
From:	Janecek R BWR OWNERS GROUP, COMMONWEALTH EDISON CO.
To:	Dorian T NRC OFFICE OF THE GENERAL COUNSEL (OGC)
Shared Package
ML20151T837	List: ML20151T833 ML20195G520
References
BWROG-8737, NUDOCS 8804290166
Download: ML20151T833 (4)

Text

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IIE8 <. . n s /-% i LAJn OUJNERS' GROUP *a$ r* r 3 a = x. ch i-sa (312) 294-3971 l

l c/o COMMONVIALTE EDISON CO)fANY e Rm. 34 FN East e P.O. Box 767 e Chicago, IL 60690 h 7 BWROG-8737 g

Thomas Dorian Esquire  % \3 2>G l l

Office of General Counsel U.S. Nuclear Regulatory Coccission Washington, D.C. 20555 Dear Mr. Dorian During discussions between technical representatives of the NRC Staff ,,

and members of the Boiling Water Reactor Owners' Group ("BWROG") -l regarding combustible gas control require.ments, a specific question was l raised relating *.o the scope of paragraph 50.44(g}, viz., whethm a '

technically acceptable inerted containment system could satisfy the )

provisions of paragraph 50.44(g). As set forth mora fully belov, the l BVROG maintains that paragraph 50.44(g) does not preclude the ur.e of a l technically acceptable inerted containment system to satisfy cembustible I gas control system requirements. In addition, the BWROG submits that 10CFR50.44(c)(1) may be satisfied by an inerted containme We request your review and written co:: cent on this positier..gt optem.

The Commission initially promulgated regulations concerning control of combustible gases within containment in 1978, with the issuance of 10CFR50.44, "Standards for Combustible Gas Control Systems in Light Water Cooled Power Reactors" (43 Fed. Reg. 50162 (October 27, 1978)).

1 O An inerted containment system consists of valves, piping and other equipment associated with the contain=ent boundary out to and l including the first isolation valve necessary to operate after e l design basis LOCA to provide reasonable assurance that, with the l inerted containment required by technical specifications, concentrations of cembustible gases within the containment will be maintained belov fla. cable limits. (See 10CTR50.44(h)).

U Four members of the BWROG are holders of licenses for seven plants directly affected by the question presented in this letter. Those licensees and plants are Northeast Nuclear Energy Company (Millstone 1), Connonwealth Edison Company (Dresden 2 and 3 Quad Cities 1 and 2), Nebraska Public Power District (Cooper), and GPU Nuclear Corporation (Oyster Creek).

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' The Consnission intended the new requirements to clarify General Design Criterion 50, "Containment Design Basis," taking into account then-recent changes to the regulations concerning ECCS effectiveness (10CTR50.46) that imposed additional conservatisms in the design of Emergency Core Cooling Systens (See 43 Fed. Reg. 50163).3 The Consission provided different requirements for combustible gas '

control systems depending on the date the notice of opportunity for hearing on the construction permit was published. Separate requirements were established for plants with notices published after November 5, 1970, and plants with notices published between December 22, 1968, and November 5, 1970. For plants of the most recent vintage, the Cocunission allowed only combustible gas control systems which did not result in significant releases from containment (reconbinen were given as an example) (See 10CTR50.44(e)). For the second group of plants, purge and/or repressurization would also be permitted if certain release limits were met (See 10CTR50.44(f)).

Significant here, however, is Section 50.44(g), which applies to licensees for which notices of hearing on '

were published prior to December 22,1968.gheirconstructionpermits The section provides that those licensees may employ purging (and repressurization, where j

provided), if certain conditions regarding offsite rels.ases are '

satisfied. The Consnission also expressly provided that those licensses  :

may use alternative means of combustible gas control, stating: l

\' l Otherwise, the facility shall be provided with another type of combustible gas control system (a repressurization system is l

acceptable) designed to conform with the general requirements of I Criteria 41, 42, and 43 of [10CFR50.44(g))). l 1

W Prior to promulgation of Section 50.44, guidance regarding the control of combustible gases had been provided by Safety Guide 7.

The Com=ission viewed the new Section 50.44 as'provid$ng relief in most cases from prior restrictions, Le 2, to be assumed for the design of combustible gas contro; systems by taking into account the increased conservatism in ECCS analyses for plants satisfying the new 10CFR50.46 stan brds (See Regulatory Guide 1.', Revision 2 (November 1978); see also 43 Ted. Reg. 50162, 50163 (October 27, l 1978)).

b Each of the licensees noted above fall within the vintage of plants

governed by subpart (g) of 10CTR50.44. .

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Indeed, by its own terms, Section 50.44(g) does not preclude the use of any combustible gas control system, including an inerted containment system, that meets the specified technical requirements. Any conclusions to the contrary would directly conflict with the plain language of the regulation.

Consistent with the above interpretation is the definition of "combustible gas control system" adopted by the Co= mission in 1978.

The term "combustible gas control system" is defined in paragraph 50.44(h)(2) in terms of systems which do, or do not, rely on releases from containment, as follows:

A combustible gas control system is a system that operates after a LOCA to maintain the concentrations of combustible gaser within the containment, such as hydrogen, below flam= ability limits.

Combustible gas control systems are of two types: (i) systems that i allow controllbd release from containment, through filters if necessary, such as purging systems and repressurization systems, and (ii) systems that do not result in a significant release from conta; ament such as recombiners.

Thus, the Consission did not prescribe specific means of combustible gas control, but rather established functional descriptions without

/'~'h limi+,ation as to the type of system. A technically acceptable inerted

(/ containment system would satisfy that functional description.

Specifically, although an inerted containment system would be in place and operating before onset of a LOCA, it would actually operate, i.e.,

function, af ter a LOCA to maintain the concentrations of combustible gases within the containment below flam=4ble limits. In addition, an inerted contain=ent system would not result in significant releases free containment. Such a system, therefora, falls within the second definition of a combustible tas control system.

In addition to the above, 10CFR50.44 (c)(1) imposes require =ents ,

concerning combustible gas control immediately fellowing initiation of a LOCA. As noted above, an inerted containment system would operate from the enset of a LOCA and, thus, could be used to assure satisfaction of Section 50.44(c)(1). Indeed, the Coccission had contanplated use of inerting to assure satisfactory combustible gas control i==ediately following onset of a LOCA where existing reactor design or other combustible gas control systems could not provide adequate protection.

(See 10CFR50.44(c)(2).)

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\ t In sum =ary, the BWROG maintains that Section 50.44(g) does not preclude the use of an inerted containment system to satisfy combustible gas control requiraments. In addition, an inerted containment system could  ;

i be used to satisfy the provisions of Section 50.44(c)(1). We request t the Staff's review and comment on this position. If it would be helpful, we would be happy to meet with you to discuss this issue further.

The comments / positions provided in this letter have been endorsed by a substantial number of the mambers of the BWROG, however, it should not be interpreted as a commitment of any individual member to a specific course of action. Each member must formally endorse the BWROG position in order for that position to become the member's position.

Sincerely, gh (s)RYY=:2 22 *Y sr .-

R.F. Janecek, Chairman BWR Ovners' Group cc BWROG Primary Representatives Containment Vent Purge and Repressurization Coresittee D.N. Grace, BWROG Vice Chairman  !

T.A. Pickens, NSP H. Wyckoff, EPRI W.S. Green, INPO R. Huston, AIF

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