ML20084F907

Forwards Review of Engineered Safeguard Sys Design,In Response to NRC 720803 Request Re Flooding Capabilities

ML20084F907
Person / Time
Site:	Dresden
Issue date:	10/13/1972
From:	Butterfield L COMMONWEALTH EDISON CO.
To:	Skovholt D US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084F870	List: ML20084F883 ML20084F907
References
5600, NUDOCS 8304210314
Download: ML20084F907 (3)

Text

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\ &< bommOmvealth Edison Company ONE F i 84 S T NATIONAL PLAZA

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POST OFFtct sos For e C M a c A G O, ILLIP*OIS 60690 October 13, 1972

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ll . ,, 1 Mr. Donald J. Skovholt - ' 90

?37 30 Assistant Director for Operating Reactors 'i 4 s

h,/s Directorate of Licensing Y[f .

U. S. Atomic Energy Commission Wash ing *.on , D. C. 20545

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Subject:

Review of Dresden Station Facilities to Resist Floodina Capabilities

Dear Mr. Skovholt:

Your letter of August 3, 1972 reauested that the ,

Dresden Station Facilities be reviewed in light of the flooding incident at Quad-Cities to provide assurance that Dresden Station is not susceptible to the same type l of incident. The attached report provides our analysis of the Dresden Station facilities.

If you have further questions, please do not hesitate to call on us.

One original and 39 copies of this report are provided for your use.  !

l Very truly yours, >

L. D. Butterfield, Jr.

Nuclear Licensing Administrator i

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The decirn or enrineerm r":- mn r4 "ystema consi"r ip-mort sut~mer eence ros t r o- r ^ v i e t.- a for r.e three iresdr ,d Lnree areas or concern id en t i i- . 'b orens o .' ' c c r c o rn uenti-fied or ~ resden Jnit 1; on Unita 1 3 it we' determined tn.. onree safewuard systens coula te sutcerced as a re: lt of failures of m'ipmcat which w". at doni.no: to meat tt e c rit eria of Cla ss I, 1 s o i r a.i c construction or f ailu re of r s ir le class I c ~ .ponent. ..

• ho three "resden Unit 25 3 s tandby diesel genera tor cooling water puM s are locsted nt 31evat lon h9C '-b" in the cribhouse (see attached Prawinr; M-10). 0his is 17'-h" below high rivar water level

ECE'-0". "f a fntlure of the circuletine water pumps or piping in the crithouse occurred, the three (D-2, D-2/3, ano D-3) diesel p.anerator cooling water punps would be submerced and inoperable.

If a diesel generator cooling water pump or the associated piping - . 1 should fail, it woulf result in submergence of the other two (2) pum;s. _

The four contn inment cooling water pitnps on each Unit are . , , . .

loented in the tuvLine buildin;s n t Elevntion L95'-0" ( see attached

'r s wi n ; M-5). These .amrs are above the elev < tion of the condensate ;fga,.#

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pump room (Elevation hM '-6") and the main condenser pit (Elevation >

4dl'-0"). Although the cont 91nnent cooling service water pamps are (PfTj well above the lowes t eleve tions in the turbine b ulidin g, they are belcw river water lovel, therefore n failure of the circule ting water ($CJ.

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s ys tem in a unit could result in submergence of the four containment 7 cooling service weter ; umps for that unit. Tf failure of a contain- #4 L..

ment cooling service water pumr. or t he associated piping were postu- [.is Inted, it could reaalt in submercence of the other three ( 3 ) pamps. [6 ? 7

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Redesign of the diesel gennrntor coolinu w a t er sy s tem and ,

containment cooling service wnter systems is in prorress. The diesel generator cooling water pmnps and motor will be replaced with eqairment desirner for submerced nnd dry operetion. These pamps will hJ[

no purenased in accordance v:ith the original criter ia. The present  % ;K .* -

= matinate indicates the new pumps will be delivered by late February >JE^

1G73 The pumps will be instelled as quickly es possible and should be available for testing and service by April 1973 To preclude sub-mergence of the contninment cooling service water pumps by circulating water, the main condenser pits will be sealed with C19ss I watertight access doors and ventilation closares. In addition, instrumentation to alnrm water level in the condenser pit and trip the circulating water pumps will be provided as described in our Quad Cities report dated July 10, 1972. We plan to romplete these designs the week of October 16, 1972. To preclude loss of all containment cooling watar pumps on a unit due to a single f ailure in the containment cooling sarvice water system, we are presently evaluating designs for separ- r ating the pumps bv Class I, watertight berriers. We plan to complete thin desirn by the week of October 30, 1972.

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- O O Continued operation of Dresden Units 2&3 is justified pending completion of the above described modification; because in the un-likely event one of the three safeguards systems is inoperable due to submergenet, the units will be maintained in a safe condition.

If the three diesel generator cooling water pumps are submerged making the diesel genore. tor inoperable, the two units can be brought to the cold shutdown condition using normal procedures, equipment and off-site power. In the highly unlikely event the diesel gener-ators are inoperable due to submerEence of the cooling water pumps coincident wi th a total loss of off-site pouer supplics, the units would coran and reactor cooling would be provided by the isolation cordensers supplied make-up water by the diesel-driven fire protec-tion system pump.

If the four (h) containment cooling service water pumps on one unit are inoperable due to subnerFence, the affected unit will be brought to the cold shutdown condition usine normal procedures and equipment. If the containment cooline rervice water pumps are in-operable coincident with a loss of off-site pouer, the affected unit will be brought to the cold shutdown cond ition using normal shutdown cooling equipmont powered by the standby diesel generators.

If the containment cooling service water pumps are inopereble co-incident with n loss of the normal shutdown cooling system on the affected unit, reactor cooling will be provided by the main conden-ser or the isolation condenser.

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