ML17194B555

Forwards 7-day evaluation,out-of-plant Test Results & Action Plan Re Main Steam Line Snubber Failures.Investigation of Clamp Interference & Possibility of Thermal Growth Continuing

ML17194B555
Person / Time
Site:	Dresden
Issue date:	05/13/1983
From:	Rybak B COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML17194B556	List: ML17194B555 ML17194B557 ML20023D266
References
6577N, NUDOCS 8305200295
Download: ML17194B555 (3)

Text

Commonwea.dison One First National Plaza, Chicago, Illinois Address Reply to: Post Office Box 767 Chicago, Illinois 60690 May 13~ 1983 *

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'* SLO RMA RC SP OE ML Mr~ Jame~~G~ Keppler, Regional Administrator Directorate of Inspection and Enforcement - Region III U.S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn; IL 60137

Subject:

Dresden Station Unit 2

Dear Mr~ Keppler:

Main Steam Line Snubber Failure NRC Docket-No~ 50~237* *

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During a meeting which occurred in your offices on May 12; 1983 an action plan was deveioped to further pursue a resolution to the Dresden Unit 2 Main Steam Line Snubber (MSL) failures.

Attachment A is a listing of the actions which were committed to; along with a date for transmittal to your o.ffices:

Several of these items du~ fa~ ttansmittal by May 13, 1983 are*-

being sent to you via this l~tter~

These arei A.2 -

S&L 7-day Evaluation (Attachment B)

-s:1 Out of Plant Test Results (Attachment C)

C~l Review of Actual Installation of Dresden Units 2 an d 3 and Quad Cit i e s_ 1 and 2 ~

The.investigation of It~m C~l co~sisted of a review of design drawing and installation packages for all four uriits in question and included interviews with the* contractor at Dresden (this being performed as part of Item C~2)~ It has been determined that the Quad Cities units do not have the same potential for binding as exhibited at Dresden.

For the most part components supplied by the same vendor were us!.8.~. The few cases where a mix of components was used have been reviewed and the components do not exhibit the same potential for binding~

For Dresden Units 2 and 3 the use of components which enhance the chances of binding does-exis*t on other snubbers than just those found failed.

We do not feel that t~is presents an immediate safety ~oncern, however, for the following reasons:

1)

An inspection was performed on Dresden Unit 3 of all MSL snubbers.

No snubbers were found failed~

Also all MSL snubber pipe clamps were inspected and there were no physical signs of the damaging the pipe clamps~ Therefore; even though the thermal growth of the lines is not a size and a problem~ * *

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u transition tube kit the potential exists direction to cause

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.Z Kt::) I MAY 161993

J. G. Keppler 2 -

May 13, 1983

2)

On Dresden Unit 2 ~11 MSL respective snubbers have been tested.

The failed ones were replaced and their pipe clamps modified to alleviate the binding potential resulting from that specific snubber component arrangement~

Therefore the areas where the component use may have caused a problem have been fixed~

3)

At this time evidence on line growth does not conclusively support the binding theory~

As shown in the action plan there are ongoing investigations to further pursue this matter~

The include looking into why the condition exists (C.2) whether actual thermal growth supports this theory (c;3) and checking for evidence of clamp interference during the Dresden Unit 2 62-day outage (E.3)~

If there are any questions on the above~ please contact this office~

Per the action plan the next transmittal will be May 20; 1983.

Very truly yours, B;

Nuclear Licensing Administrator lm cc:

NRC Senior Resident Inspector - Dresden w/o Att~

R. Gilbert -

NRR w/Att~

6577N i:.:

t A.

In

1.

2.

3.

4.

B.

Out

1.

Plant Test Raw data - 5/5/83 S&L 7-day evaluation ATTACHMENT A

Dresden Station Unit 2 Snubber Action Plan

- 5/13/83 Correlate test data with analysis - 5/20/83 Provide monitoring of snubber loads - 4 weeks of Plant Test Test report - 5/13/83 C.

Insta 11 ati on Review

1.

Actual installation of D-2, D-3 and QC 1 and 2 - 5/13/83

2.

Why mismatch; why mismatch was not identified - 5/20/83

3.

Actual binding possible at five failed locations at D 5/27/83 D.

MSIV Loads

1.

MSIV analysis loads - 5/20/83

2.

Compare actual S/RV load with MSIV analyzed load - 5/20/83 E.

62-Day Inspection

1.

Check calibration of 2 snubbers with largest deviation

2.

Stroke test

3.

Plan £or making interference checks at clamps -

5/20/83 (RHM)

F.

PSCo.

1.

Autopsy of failed snubber JSA/tlf 5/6/83

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