ML20100J642

Interim Deficiency Repts 84-07 & 84-19 Re Crush Strength of Energy Absorbing Matl Supplied by Hexcel Used in Pipe Whip Restraints.Initially Reported on 841030.Hexcel Requested to Evaluate Matl W/Reduced Crush Strength

ML20100J642
Person / Time
Site:	Byron, Braidwood, 05000000
Issue date:	11/29/1984
From:	Danni Smith COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
84-07, 84-19, 84-7, 9480N, NUDOCS 8412100399
Download: ML20100J642 (3)

Text

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~.... y:# . Y CORNRORW981100 EdiSOR -.

p; 1 .:- C' / one First Ittiortil Pitts, Chicago, lihnois C ) Addrzss RIply 12 Post Office Box 767.

.{f _ Chicago, Illinois 60690 7

T November 29,~1984 ,

s.

Mr.: James G. Keppler:

- Regional Administrator U.S. Nuclear Regulatory Commission Region III,

-799; Roosevelt Road.-

Glen Ellyn, IL x 60137'

Subject:

Byron' Generating Station Units 1 and 2 Braidwood: Generating Station Units 1-and 2 10 CFR-50.55(e) 30-day. Report Energy Absorbing Material NRC-00cket-Nos.- 50-454/455 and 50-456/457-I Reference (a): E. ' D. Swartz letter to H.10 Denton .

dated November 15,'1984 h .

Dear Mr. Keppler:

I, '

'On October 30, 1984, Commonwealth Edison Company notified Mr..R.-Lerch of your office of'a' potential deficiency reportable

lpursuantito '10 CFR 50.55(e) regarding the" crush strength of energy n- absorbing material (EAM) used in pipe whip = restraints. This letter

[ ~ provides information.concerning'this matter.ito fulfill the ~

r . thirty-day' reporting requirement and is considered an interim p report. For tracking purposes, this potential deficiency was.

assigned' Numbers 64-07 at Byron and;84-19 at Braidwood.

~

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Description of Deficiency I

! - During testing of Byron energy-absorbing material-(EAM) et Hexcel, 'the supplier of the EAM, it' was discovered that some material used in the pipe whip. restraints had a lower than specified

= crush' strength. Hexcel's earlier production testing results-for-this material were reviewed and showed that, when tested prior to delivery, it met the~specified crush strength.

Analysis of Safety-Implications Deficient EAM:in pipe whip restraints could result in idamage to nearby equipment during postulated breaks of high energy lines. Case-by-case analyses would be necessary to determine the actual ' consequences of this deficiency; -Such analyses would~

-consider the consequences of whip restraint failure, the as-built capability of the-restraints and the actual expected loads, and the

' likelihood of the design basis breaks.

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-Corrective Action Taken Hexcel has been requested to provide an evaluation of the -

EAM piece which showed the most significant reduction in crush strength. Hexcel has informed us that the brazing process used to manufacture Byron /Braidwood EAM was revised in 1980. The new brazing process.used to manufacture EAM is considered-by-Hexcel to be a significant improvement over the original brazing process and-is not suspected of any discrepancy at this time.

Based on this information, the following steps have been taken to resolve the problem with respect to Byron /Braidwood stations:

'1. Westinahouse Designed Restraints Hexcel has informed us that the EAM used in Westinghouse designed restraints was manufactured using their current brazing process. Although this process is not considered suspect by Hexcel, they have been requested to . test a number of specimens from a core block manufactured using the current process to evaluate the material variability within the core block. The results from these tests, along with the details of the manufacturing process used for this test block and the core block used to fabricate Westinghouse designed restraints, will be evaluated to determine if any further corrective action is necessary.

2. Sargent &'Lundy-Designed Restraints

a. The number of restraints required for each unit has been re-evaluated by eliminating the arbitrary intermediate pipe breaks. . An analysis for elimination of intermediate pipe.

breaks has been submitted to NRR with a request for expeditious review in Reference (a).

b. After considering the potential deletions of those restraints which are associated with arbitrary intermediate breaks, there are 21 restraints in each unit at Byron /Braidwood Stations which utilize EAM. Although we believe that design adequacy of these restraints can be shown by further analysis using lower crush strenght, we plan to replace those EAM pieces from these 21 restraints which are associated with terminal breaks. The replacement material will be manufactured by Hexcel using their current brazing process. This approach has been chosen based on considerations of scheduling, feasibility of replacement and preservation of safety margin in restraint design.

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c. In order to address the issue of material variability for.

the new material, no less than four specimens from different parts of the core block will be tested to determine the crush strength. Design of restraints will be re-evaluated for any crush' strength values outside the specified range. In this evaluation, the information obtained from the. evaluation described in paragraph (1) will also~be considered.

We expect that all corrective action will be complete by January-15, 1985 and that a final report on the corrective actions taken will be filed by January. 31, 1985.

Please address any questions that you or your staff may have concerning this matter to th fice.

I Very truly o}rs,

& 31 Day . Smith Nuclear Licensing Administrator cc: Resident Inspector - Byron Resident Inspector - Braidwood Director of Inspection and Enforcement US Nuclear Regulatory Commission Washington, DC 20555 9480N