ML16342C905
| ML16342C905 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 04/25/1995 |
| From: | Grimes B NRC (Affiliation Not Assigned) |
| To: | Yang D AFFILIATION NOT ASSIGNED |
| References | |
| IEIN-95-010, IEIN-95-10, NUDOCS 9504280222 | |
| Download: ML16342C905 (4) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON> O.C. 20SMi4001 April 25, f995 Mr. David Yang Peak Technical Services 1020 Wickham Drive
- Moraga, CA 94556
SUBJECT:
YOUR LETTER DATED FEBRUARY 17, 1995 REQUESTING CLARIFICATION OF NRC INFORMATION NOTICE 95-10 AND YOUR LETTER DATED FEBRUARY 17, 1995 COMMENTING ON THE DIABLO CANYON LICENSEE'S USE OF BECHTEL TOPICAL
- REPORT, BN-TOP-2, REV. 2, "DESIGN FOR PIPE BREAK EFFECTS"
Dear Mr. Yang:
This is in response to the subject letters.
Information Notice 95-10 was issued to alert commercial nuclear power plant licensees to the potential for loss of the automatic actuation function of engineered safety features as a
result of electrical faults in some non-class 1E input signals to the solid state protection system.
The information notice provided background information regarding the manner in which the problem was discovered and the corrective actions that were taken.
The solid state protection systems were declared inoperable at both of the facilities discussed in the information notice.
The decision to declare the solid state protection systems inoperable because of the identified design vulnerabilities was made by the licensees based on their interpretations o'f their design bases.
The responsibility for determining the operability of degraded or nonconforming
- systems, structures, and components rests with the licensee.
It is not NRC responsibility to make operability determinations.
Licensee operability decisions are necessarily based on initially available information and engineering judgment.
We do not believe it useful for the NRC to later re-evaluate licensee judgments made at the time of the event which were apparently conservative.
With regard to your comments concerning th'e Diablo Canyon licensee having incorrectly applied the Bechtel Model, in February 1974 the NRC staff published a safety evaluation report on the Bechtel model.
The Bechtel report was evaluated in light of the work presented by Hoody and others.
At that time the staff concluded that the approach by Bechtel was reasonable and therefore acceptable.
No new evidence has been presented to suggest that this 950msoma 9SQOaS PDR ADQCK 05000275 P
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Mr. Yang conclusion needs to be reconsidered.
Consequently, we do not believe that additional NRC guidance with respect to the interpretation of the model is warranted at this time.
Thank you for your comments.
Sincerely, Origina) Rig.",+<! by
- 8. D. Lid'r'/
l~ Brian K. Grimes, Director Division of Project Support Office of Nuclear Reactor Regulation DISTRIBUTION:
- BKGrimes, NRR 8~M~
Central Fil~7 AEChaffee, NRR OECB R/F DOPS/RF EFGoodwin, NRR Pg @~~ ~
- See previous concurrence DOCUMENT NAME:
G:~I,NICKiYANG.LTR To receive a copy of this document, indicate ln the born "C I
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