ML20084G660

Advises of Delay in Submittal of Torus Baffle Studies.Safety Evaluation Verifying Prudency of Continued Operation W/ Torus Baffles Encl

ML20084G660
Person / Time
Site:	Dresden
Issue date:	11/27/1972
From:	Butterfield L COMMONWEALTH EDISON CO.
To:	Skovholt D US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084G655	List: ML20084G653 ML20084G657 ML20084G660 ML20084G666 ML20084G682 ML20084G724
References
6521, NUDOCS 8304220195
Download: ML20084G660 (3)

Text

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• C H I C A G O. B L LI N OI S Address Reel, to l POST OPPICE SOE T47

• C n I C A G O, IL L lN OIS 40490 November 27, 1972 A p

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-o Mr. Dannld J. Skovholt

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Asslatanu Jirector for - "

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Operating Reactors Directorate of Licensing

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U.S. Atomic ncrgy Comission N

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Washington, D.C. 20545

Subject:

Dolay in Submittal of Torus Baffle Studies on Dresden Units 2 and 3, AEC Dkt Nos.

50-237 and 50-249

Dear Mr. Skovholt:

Your letter of August 2, 1972 requested information

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concerning the torus baffles presently installed in Dresden Units 2 and 3. It was anticipated that a full response would be available for you before November 1, 1972 so no '

notification had been sent to you indicating when the report would be submitted. The report is still not available and the delay has been caused by other subjects, such' as the torus hanger problem at Quad-cities, which have received a higher priority from both Commonwealth Edison and the General Electric Company in work assignments. The expected submittal date for the report is now February 1, 1973.

Commonwealth Edison is discussing with General Electric the desirability of removing the torus baffles from Dresden 2 and 3 at the next refueling outage for each unit. As a result, a safety evaluation has been prepared to verify that continued operation with the torus baffles installed is prudent. This evaluation is attached.

One signed original and 39 copies of this letter are provided for your use.

Very truly yours, 85,.1 2

30716 * '

h [O 00023 L.D. Eutterfield,Jr.

p Nuclear Licensing Administrator COPY SENT REGION _ ' ' _

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There are three potential concerns associated with operation with loose baf fles which will be discussed in the following three items.

1. _Interforence .rith cc? 11c7? un Thera is no potential for bn f fics to break up into sections or pieces because they are conposed of I beams or channels solidly welded together. Analyses for othar plants have shoun that the courso of a bloudewn and containment pressure response to a LOCA vill not be aZZected by loss of baffling. This has boon a subject on several dockets and is not an issue or a problem with the AEC.

Also, because there are other baffles between those which could possibly fail and the downcomers from the drywall, there is no concern about damage to the douncomers from loose baffles. The mechanism for baf fle damage is apparently the sudden expulsion of cold air from the relief discharge pipe. If bolts connecting the baffles to the torus fail first, the entire baffle is moved away frora the av discharge and falls to the bottom of the torus.

This cannot occur in a LOCA (DBA) where an air and steam mixture is moving in a relatively alow fashion from the drywell to the votwell. Thus, damage to baffles nont to douncomers during a LOCA need not be considered.

2. Dama o to Torus " alls A question could be raised concerning damage to the torus walls due to loose baffles. Because the baffles remain in one, heavy piece and are moved out of the area of high forces, the probability of further movement to cause damage is minimal. Examinations at plants where baffles have previously come loose have confirmed that effects consist of surface marring and abrasion of paint. Cnly repainting was required. Therefore, there is no reason for undue concern relative to this mode of failure.

3. Damace to Other Ecuipment In the Torus The only other equipment of interest in the torus are the suction intakes to the ECCS pumps. These are protected by heavy baskets made of metal plates, perforated with many i inlet holes and forming about a l' right cylinder. Although l they are not in the path of likely baffle movement, contact i

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. - 2-and dr.nge could bn pontulnted. Because the baffles are very large and would tend to renain in one piece, there is no apparent

- c c' . n n L ., 'o c .. it g - ;. I. cn; c.~c, loc 2 (or pkg;ing) of one inlet strainer "ea b~ n taken into account in the design and the rcraining strainers are ample to fulfill ECCS requircraents.

Therefore, there is no reason for undue concern relative to this toda o f f ailure .

Surrarv In cumnary, Commonwealth Edison concludes that continued operation ic justified for an interin period until such time as a planned outage is available to remove baffles.

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