ML19329B328

Discusses Facility RHR Design

ML19329B328
Person / Time
Site:	Davis Besse
Issue date:	08/01/1975
From:	Novak T Office of Nuclear Reactor Regulation
To:	Grimes B Office of Nuclear Reactor Regulation
References
NUDOCS 8002040760
Download: ML19329B328 (4)

Text

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- eentral, File p -} j D NRR Reading Fil RSB Reading F' AUG 011975 Brian Crimas Chiaf, Accident Analysis Branch, TR.

THRU: Robert L. Baer, Section A Leader, Reactor Syntans Branch, TR DAVIS-BESSX 1 H R DESIGN Toledo Edison Company has justified their capability to bring their plant to below 212*F vithin 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> (in spite of a single active component failure) by installing a manual bypass around the RHR suction valves inside contain:nent.

Enclosed is a discussion which provides the resulting doses to the operator and to the site bcundary. Please review this material for acceptability of radiological consequences.

Since we are currently writing our SER input, your conclusions by August 11, 1975 would be appreciated.

Orip*1 signed By T.11. Suvak Thomas M. Novak, Chief Reactor Systems Branch Division of Technical Review cc: C. Ifazatis L. Engle R. Baer 80020407(,o f

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D-B 7.6.1 (10/4/74)

From our review of the Decay Heat Re= oval (DER) System (Sections 7.6.1.1, 6.3.2.16, and Figure 6.17), we have concluded that this_svater is recnirad fer esfetv. #, a,,

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The present cesign does not meet e single failure criterion with respect to failure (to en) of either of two serially connected isolation valves 'DH11 & DH12) in the suction line of the (DHR) pu=ps.

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We will'reynfre that the (WR) svstem A ardsn -a e_t *h sincie rn' ore _cri:-rton trc= tae stancocint or assuring decay neat renova 2 (

.e., cold shutdown and from the stand-point of precluding q;crnrNiCU c)f the system, and that the associates instru=antation, control and elec-trical systers conform with IEEE Std 279-1971 and IEEE Std 308-1971. Therefore, modify your design to meet these requirements, or justify the present design on scce other defined basis.

RESPONSE

%vstc= chances.. = Cma Tie.: The manual b've1=s has been changed as follows:

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1.

The removable section of piping has been inserted per=anently into the bypass.

2.

Both valves on the bypass will be designed for primary system pressure 10 and

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3.

The two " bypass" valves will be locked closed, with the necessary administrator controls.

Single tallure of one or enc actor-operated isolation valves could be i

accen=odated by a ce=ber of the operations reaff entering the contain=enth af ter sufficient nurcine if deered nacersarv.

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valvn=1 JTne resultant uose to cae =an enterir.g the contain=ent is 0.23 re=.

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Itic site' boundary doses are shewn in figure P7.6.1-1.

The doses are based on the following assu=ptions:

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A primary system leak of 140 gpm is assuced to occur continuously.

(This is a b enk which the makeup purps can keep up with.)

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2.

Purging does not occur until 6.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> af ter thi this cine the onerator would diseever that the =ain direct'idr$'can not be used.

[Hewouletneninitiae the nucced 3.

The onerntor enters the contain=ent with a Scott air pack and takes Lten ainutes]to open the bypass valves and ext: centain=ent.

4 Entry into the containment cou1 A ha.ade after two hours.

The benefit of waiting core than two hours is minimal anc results in an increase Revision 10 December 1974 P7.6.1-1 4e ud

D-B in the site boundary dose. The site boundary dose resulting from a two hour purge would be 15.5 rem thyroid, 0.42 rem whole body.

5.

To reduce beta skin doses, protective el_oth g was assumed to be worn.

6 One percent failed fuel was assumed.

10 Thyroid dose to the operator is reduced significantly by the use of the Scott air pack and 17 311 casna Je c.ec11cible cc cared to the gama dose.

If the man were to enter the contaira::ent witnout purging, tne resdIcAnt ga==a dose would be only 0.91 rems.

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Revision 10 December 1974 P7.6.1-2

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' LOSES VS. TIME FIGURE P7.6.1-1 REVISICN 10 DECEMBER 1974

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