ML20215C080
| ML20215C080 | |
| Person / Time | |
|---|---|
| Site: | McGuire, Mcguire  |
| Issue date: | 12/01/1986 |
| From: | Tucker H DUKE POWER CO. |
| To: | Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| NUDOCS 8612150020 | |
| Download: ML20215C080 (3) | |
Text
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DUKE POWER GOMPANY P.O. Box 33189
- CHARLOTTE, N.O. 28242 HAL B. TUCKER
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December 1,1986~
Dr.LJ.I elson[ Grace, Regional Administrator
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N U.S. Nuclear Regulatory Commission
. Region II 101 Marietta St. NW, Suite 2900
, Atlanta, Georgia 30323
Subject:
McGuire Nuclear Station Docket Nos. 50-369,.50-370 IE Inspection Report 50-369/86-16 and 50-370/86-16 I
Dear Dr. Grace:
Please find attached supplemental information concerning the alleged violation which was identified in the above referenced Inspection Report. This is the supplemental response agreed upon-in the conference call of November 13, 1986 as noted in Mr. R.D. Walker's letter of November 20, 1986.
Very truly yours, l
-Hal B. Tucker JBD/137/jgm
'Attachnert xc t ' Mr. W.T. Orders NRC Resident Inspector McGuire Nuclear Station
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' DUKE POWER COMPANY
-McGUIRE NUCLEAR STATION SUPPLEMENTAL RESPONSE TO VIOLATION-IN INSPECTION REPORT 50-369/86-16 AND 50-370/86-16
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'During a.teleconference on November 13, 1986 between NRC and Duke, a request was made-for: followup information regarding the 1986 Unit 2 ILRT-report and addendum.
. The :two items requiring further discussion were:
'1.
Use of La.(rather-than.75 La) as the-acceptance criteria'of the "as-1 found"l analysis.
' ustification'of-calculations and assumptions'regarding leakage of-2.'
J
' penetration M375.
-La is' defined' as the " maximum allowable leakage rate at pressure Pa..."
.-McGuire Tech Specs and 10CFR50 Appendix J state that the surveillance acceptance criteria for ILRTs is a more restrictive 0.75 La.
In orderoto assess the proper applica' tion of these leakage criteria, the distinctioimust be made between penetrations on which maintenance was performad' prior ~to an ILRT and penetrations' isolated due to leaks during an ILRT.
- As' presently written, Appendix J requires the containment be tested in "as close
'to the "as is" condition as practical." Through interpretation, the NRC has approved penetration maintenance.during an ILRT outage, with the requirement that
'before and after maintenance 1eakages be determined so that a net " leakage
~
~ savings"_'can be calculated. 'An "as found" containment leak rate can then be determined by adding total. savings to the leak rate-(1,,) calculated by the ILRT.
For any penetrations isolated with an ILRT in progress, the post-repair leakage from a: local test would be required to determine total containment leakage. This case is directly addressed by Appendix J III-A.5(b):
" Acceptance criteria.
t (2)-Peak pressure tests shall be conducted L shall be less than 0.75 La.
If local leakage measurements are taken to effe$E repairs in order to meet the l
-acceptance criteria, these measurements shall be taken at a test pressure Pa."
1 Use of the 0.75 La acceptance criteria for surveillance containment leak rate, and the La acceptance criteria for "as found" containment leak rate ensures that the degradation margin is not exceeded, thus validating the surveillance frequency.
These interpretations are fully supported by the clarifications given by the proposed revision to Appendix J, dated October 29, 1986.
Individual assumptions used in the analysis of M375 are expanded as follows:
l-l 1.
The assumption of a total of 2 gpa H 0 leakage through penetration M375 9
L is conservative because af ter isolating M375 by closing 2WL23 about 0.5 L
gpa of NC system leakage was measured. This is normal NC system leakage. The total leakage is assumed to be going through M375.
The 2 gpm leakage is reported in LER-370-86-03.
l:
, 2.
The pressure drop across M375 was assumed to be 100 psi. Actual elevation differences indicate that 120 psi is a more realistic pressure drop. The 100 psi assumption is conservative because if 120 psi is substituted into the calculations in the " Addendum to the Reactor Centainment Building Integrated Leak Rate Test Conducted May 20 -
May 26,1986" (the Addendum), the equivalent leakage would be about 10%
less.
3.
The assumption of treating the leaking 2WL2A as an orifice with an equivalent diameter is reasonable at high Reynolds numbers.
Since flow and pressure drop are known or reasonably assumed, an equivalent orifice diameter can be calculated from the orifice equation. The Reynolds number for the water is calculated to be approximately 69,000.
For air the Re is approximately 50,000 per. calculations. These Re number values are large enough to ensure that turbulent flow exists and that geometry of flow cross section concerns are minimal. The value of the Re numbers also assures that the orifice coefficient for both cases is about 0.6 and can be assumed to be equal.
4.
It is assumed that 2WLIB is stuck open due to its limit switch problem.
Further calculations show that if it is assumed to be closed with the same equivalent diameter leak as 2WL2A, a larger equivalent diameter
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results; a 16% decrease in Re numbers results. However, this decrease is not sufficient to change either orifice coefficient. The final results of the Addendum would not be affected.
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