ML20040B933
| ML20040B933 | |
| Person / Time | |
|---|---|
| Issue date: | 01/05/1982 |
| From: | Minogue R NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| To: | Joseph Austin NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| Shared Package | |
| ML20040B934 | List: |
| References | |
| NUDOCS 8201270012 | |
| Download: ML20040B933 (2) | |
Text
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gurg UNITED STATES o,,
NUCLEAR REGULATORY COMMisslON g
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g WASHINGTON, D. C. 20555 3 1% -a!
JAN 5 1982
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MEMORANDUM FOR:
John H. Austin, Technical Assistant Office ~of Executive Director for Operations FROM:
Robert B. Minogue, Director Office of Nuclear Regulatory Research CRGR MEETING Off
SUBJECT:
LTR AUSTIN TO MINOGUE 12/28/81, E
JANUARY 14, 1982 REGARDING ELECTRICAL TERMINAL BLOCKS In your letter you state that "the CRGR is being asked whether IE should, as RES urges, recomend to all licensees the actions spelled out in the Sandia report."
I would like to point out that the RIL does not endorse all the Sandia recommendations.
Specifically, the Sandia report recomends the following actions that were not endorsed by the RIL:
- 1) elimination of the pressure relief hole in operating plants
- 2) elimination of terminal boxes for new plants
- 3) elimination of contaminants in operating plants.
t Our recommendations were based on an independent consideration of the research data and our understanding of the licensing process. The purpose of a RIL is to transmit a completed portion of research along with the RES evaluation of the relevancy of the research to the regulatory process.
It is NRR and IE's responsibility to implement the results or request additional data.
In addition, the following is my staff's reply to the other point that you raised, that the research data does not support the conclusion that terminal blocks should be cleaned.
This issue was addressed in the December 9, 1981, memorandum from Dircks to Ahearne which RES prepared. Specifically, I refer you to page 3 of the letter.
In summary, RES agrees that when the estimated error band associated with the research results is considered the reduced probability of failure obtained by eliminating dust from the terminal blocks is essentially within the data error band and although a trend is evident, a firm conclusion cannot be drawn. However, with regard to overall contamination there is clear evidence that the failure probability is significantly reduced by eliminating all contaminants.
Furthermore, the very nature of the low voltage breakdown failure mode identified in the research depends on moisture and some contamination to produce a conductive electrolyte on the surface of the insulating material of the terminal block. Therefore, for all cases except where containment spray will be an overriding factor with regard to introducing T. B.
surface contamination, a clear advantage should be obtained 9201270012 820126 PDR REVGP NROCRCR PDR I
4
. John H. Austin 2
by cleaning.
Even if containment spray is prevalent there will probably be some risk reduction from elimination of other contaminants end for some cases containment spray may not even get inside a terminal block enclosure.
'As discussed with you by my staff this issue is still being addressed as part of our on-going research program.
As a part of this program RES intends to conduct full 1.0CA tests on a statistically relevant sample of terminal blocks.
RES will keep you informed as new data is available.
M M N[
Robert B. Minogue, Director Office of Nuclear Regulatory Research cc:
V, Stello T. Murley R. Baer R. Bernero W. Johnston Z. Rostoczy D. Reiff l
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