ML20077N317
| ML20077N317 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood, 05000000 |
| Issue date: | 09/08/1983 |
| From: | Swartz E COMMONWEALTH EDISON CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| 7185N, NUDOCS 8309130021 | |
| Download: ML20077N317 (3) | |
Text
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Commonwealth Edison O{
One first Nitional Plaza. Chicago, Illinois
'l Address Hiply to: Post Office Box 767 Chicago Hlinois 60690 September 8, 1983 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555
Subject:
Byron Station Units 1 and 2 Braidwood Station Units 1 and 2 Pipe Whip Restraint EAM Test Program NRC Docket Nos. 454/455 and 50-456/457 References (a):
B. J. Youngblood letter to D. L. Farrar dated July 21, 1983 (b):
AIF-CRLS letter to H. R. Denton dated March 28, 1983 (c):
AIF-CRLS letter to H. R. Denton dated July 14, 1983 (d):
NUREG/CR-2189 " Probability of Pipe Fracture in the Primary Coolant Loop of a PWR Plant"
Dear Mr. Denton:
The Commonwealth Edison Company is entering into a test program to confirm the adequacy of our Byron and Braidwood Stations pipe whip restraint designs which utilize energy absorbing material (EAM).
Reference (a) provided an NRR status report in this matter.
The purpose of this letter is to document our position concerning this issue.
Additionally, the purpose of this letter is to document recent discussions and agreements reached since the issuance of Reference (a), and to formally request NRR approval of our current EAM Test. Program as attached.
Reference (a) states that
...a delay in the resolution of this _ issue will result with possible impact on the licensing schedule of the Byron facility".
Th is statement is of obvious concern to the Commonwealth Edison Company.
From the outset of our discussions in this matter, it has always been our position that the Byron and Braidwood pipe whip restraint designs are adequate for their intended f unction.
The purpose of our entering into an EAM Test Program is strictly confirmatory in nature.
g lf0 8309130021 830908 PLR ADOCK 05000454 A
eb The conservatism contained in current pipe break criteria is a rapidly evolving issue between the Nuclear-Regulatory Commission and the nuclear industry.
The attached References- (b) and (c) provide an historical perspective.of this matter and a discussion of the current issues.
Regulatory action is being sought to eliminate the requirement for combining seismic and pipe break
. loadings for the design of piping systems and supports because simultaneous SSE and pipe. break are not considered credible.
- Also, favorable results by Westinghouse (WCAP No. 9570, Rev. 2Cl.3),
Lawrence-Livermore National Laboratory (LLNL), et.al. support the position that undetected defects in the RCS piping that could cause guillotine and full size longitudinal breaks are essentially incredible.
Regulatory action is additionally being sought to allow the application of this approach to other plant piping systems where similar. criteria can be met.
It.is significant to note that the results of LLNL's analyses documented in various volumes of P.eference (d) are based in large part on the use of our Zion Station as the demonstration plant for such analyses.
The f avorable conclusions reached by LLNL were based on a combination of factors including conservatism in design methods used, quality assurance measures applied during construction, and the-degree of in-service inspection (ISI) conducted during plant life.
The measures applied to our Byron and Braidwood Stations in these areas meet the currently applicable requirements similar to those requirements that were applied to our Zion Station and accounted for in the LLNL analytical results.
- Based on the above, and the f act that there is evidence to suggest that pipe whip restraints do not improve plant safety, it is our judgement that delay in the issuance of the Byron Station Unit 'l license because of our EAM Test Program and it's intended confirmatory-results, as stated in Reference (a), would not be supported from a safety perspective.
It remains our belief that the Byron and Braidwood pipe whip restraint designs are adequate for their intended function and that the purpose of the EAM Test Program is confirmatory in nature to verify our position.
~
In an attempt to resolve the NRR' concerns presented in Reference (a), various discussions were held with NRR Staff including those held on August 8 and 16, 1983 wherein various agreements were reached.
The attached marked-up test program reflects these agreements.
In particular, the test set-up at Hexcel-MCI utilizes a load cell with a maximum capacity of 350,000 pounds which in turn limits the test specimen size to a maximum a
volume of' 108 cubic inches.
Agreement was reached to modify the test set-up as shown in-the Attachment to utilize a " saddle plate" between:the EAM samples.
Additionally, it was agreed that testing the following six (6) sample sizes at 900 (6x6x3, 5x5x4, 4x4x4, 4x4x3, 4x4x2, and 3x3x3) given this arrangement utilizing the saddle plate would provide results to adequately address the issue of scaling.
L
.. However, we do not believe that Reference (a) accurately represents the status of the agreements reached concerning the testing of the FWR-35 restraint design.
Hexcel-MCI indicated that it was not possible for them to perform a dynamic test to simulate the FWR-35 restraint design utilizing a single EAM compression member with a single tension member.
It was, and remains our position that the functional adequacy of the FWR-35 design can be demonstrated through an analysis of the EAM test results.
Th e analytical model that will be utilized in this effort is attached for your review.
Regarding the EAM tesc acceptance criteria, it was agreed that if the test specimen (s) f ails to absorb the specified energy or if the crushing load is significantly different than that used for design, the adequacy of the affected pipe whip restraint design (s) will be re-evaluated.
NRC Staff written concurrence in our confirmatory EAM Test Program is requestej as soon as possible.
Please address any questions that you or your staff may have concerning this matter to this office.
One (1) signed original and fifteen (15) copies of this letter are provided for your use.
Due to the volume of the Attachments, only one (1) copy of each is being sent directly to Ms.
Janice A. Stevens.
Very truly yours, E. Douglas Swar Nuclear Licensing Administrator Attachments cc:
J. A. Stevens w/att.
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