ML17195A760

Finds Proposal to Take Credit for Drywell Sprays as Early as 10 Minutes Following Onset of Transient Unacceptable,Based on Review of Spray Sys Dependencies & Operator Actions Needed to Initiate Sprays.Basis for Conclusion Provided

ML17195A760
Person / Time
Site:	Dresden, Quad Cities, 05000000
Issue date:	04/11/1985
From:	Vassallo D Office of Nuclear Reactor Regulation
To:	Farrar D COMMONWEALTH EDISON CO.
References
NUDOCS 8505010553
Download: ML17195A760 (6)

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.:Apr;il 11, 1985 sus~1ECT:,. *oRYWELL TEMPER-~TURE EQUIPMENT QUALIFICATION PROFILES

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Re:

Dresden, lini!s 2_ and* 3 anp.'.Quad Cities, Units 1 and 2 The drywell temperature equipment qualification profiles for six units, Hatch 1 and 2, Dreide~ 2 and 3 ~nd Quad Cities 1 and 2; are under review; The dr_ywel l pressure pfof'il~ *an'~ the wetwell pressure/temperature profiles used by the li~ens~~s ~o~*these six units in their equipment qualification program has previously been found acceptable by the NRC staff.

In order to continue our revie~ of.the drywell temperature equipment qualification profiles for these six units we need further information as described below.

The licensees for these six units have taken credit for early, manual initiation of the drywell spray s.vstem, i.e., 10 minutes into the transient, thus eliminating the long period of ~uperheated steam conditions that are present in the drywell temperature equipment qualification profiles for all of the other Mark I plants.

Rased on a review of the spray system dependencies and operator actions needed to initiate the sprays, the staff concludes that the licensee's proposal to take credit for dr.Ywell sprays as early as IO minutes following onset of a transient is unacceptable.

The basis for this conclusion is as follows:

1)

The availability of the drywell sprays is dependent on the need for the low pressure coolant injection system to maintain coverage of the reactor vessel core.

The Hatch, Units 1 and 2, control logic includes an interlock that physically prevents diversion of a low pressure coolant injection system to the drywell sprays until 10 minutes has elapsed and the core is at least two-thirds covered.

Although the Dresden/

Quad Cities plants do not incorporate this interlock, the staff is not expected to approve emergency operating procedures that do not meet these minimum conditions for system transfer.

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2)

Transfer of a low pressure coolant injection system to the drywell spra.vs requires the control room operators to make decisions and take certain manual actions. This process will take a significant amount of time and when combined with the required delay mentioned in 1) above, will result in a minimum drywell spray actuation time well in excess of 10 minutes following onset of a transie~t.

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r Mr. Dennis The staff has discussed this issue and our conclusions with the affected licensees and a possible approach for resolution has been identified.

The staff believes that with clearly defined procedures for initiating drywell sprays and a comprehensive study of how long the low pressure coolant injection system needs to be aligned to the reactor vessel, credit can be given for drywell spray initiation at approximately 30 minutes following onset of any transient.

In this regard, the staff has prepared drywell temperature profiles based on a 30 minute drywell spray initiation '(enclosed) and requests that the licensees:

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1)

Demonstrat~ f~t ail types and siz~s.:bf primary system* breaks, that the Operator Can*' remove, cl lOW pr.e*ssure.coolan.JA injection System from its reactor::-'(~SseT core. <:;ooling function ',~fter 20,r:ninutes following onset of the 'a.c.cjqe!'lt and.. $ti),l, ;nieP;t the.,vesse 1 core coo 1 ing and coverage requirements-. <.s~taf1'dafcll i.. cens~ng *ci.ss-utnptions should be used in this analysis;'in.c:lu<ding':'loss ofr:offsit~. power and the most limiting single failure ;n*_the's.afet.Y*sysfeins n'eeded-to mitigate' the accident.

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Demo~st'r~:te th.a~.'.t~~.. r-.o-ntro.l *,i::oo~ *'.1.n~,tr~me_n.tation and emergency operatfng-.'procedures 1 available 'to,the~cnntrol room operators are suffktent,1y c1e.. ~r*and simple"to foTlow:-so. as to allow for operator action to... i.nit,iate* t.he dry.wen spra.):ts'.:durinq the 10 minute interval after the.~fow~*R.reVillre system can safely be transferred to the drywell spray fµnct_i-'.6n.:~ The )inie *split ~bebieen the system transfer and operator actiOn, 20 m,inutes and* IQ.minutes, respectively, is based on the staff's understanding 9f the physical realities *of the situation.

Different time splits* can be utilized by the licensees, if justified, so long as the total time is equal to or less than 30 minutes, if the enclosed curves are,-tp.be.. used for equipment qualification purposes.

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The staff will review the :*;results ()f your responses to the above positions for completeness and accuracy~ To minimize any additional delays in the resolution of this issue, you should proceed to evaluate the equipment that will be exposed to the drywell temperature against the enclosed temperature profiles for your plants.

These profiles assume a drywell spray initiation time of 30 minutes and are based on analyses submitted by the licensees for their respective plants as modified by the staff using the CONTEMPT code for the revised drywe.11' spray initiation time.

Please provide the information requested within 30 days of receipt of this letter. If you have questions regarding this request, please contact your NRR Project Manager.

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Enclosure:

As stated cc w/enclosure:

See next page

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Mr.* Dennis L. Farrar Commonwealth Edison Company Ouad Cities Nuclear Power Station, Units 1 and 2 cc:

• Mr. B. C. O'Brien President Iowa-Illinois Gas and Electric Company 206 East Second Avenue Davenport, Iowa 52801 Robert G. Fitzgibbons, Jr.

Isham, Lincoln & Beale Three First National Plaza Suite 5200 Chicago, Illinois 60602 Mr. Nick Kalivianakis Plant Superintendent Quad Cities Nuclear Power Station 22710 - 206th Avenue - North Cordova, Illinois 61242 Resident Inspector U. S. Nuclear Regulatory Commission 22712 206th Avenue North Cordova, Illinois 61242 Chairman Rock Island County Board of Supervisors Rock Island County Court House Rock Island, Illinois 61201 James G. Keppler Regional Administrator Region III Office U. S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137 Susan N. Sekuler Assistant Attorney General Environmental Control Division 188 W. Randolph Street Suite 2315 Chicago, Illinois 60601 The Honorable Tom Corcoran United States House of Representatives Washington, D. C.

20515 Mr. Gary N. Wright Nuclear Facility Safety Illinois Department of Nuclear Safety 1035 Outer Park Drive, 5th Floor Springfield, Illinois 62704

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