ML16340C793
| ML16340C793 | |
| Person / Time | |
|---|---|
| Site: | Summer, Diablo Canyon, 05000000, Atlantic Nuclear Power Plant |
| Issue date: | 07/23/1982 |
| From: | Jordan E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE) |
| To: | Eisenhut D Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML16340C794 | List: |
| References | |
| TAC-54356, NUDOCS 8209160095 | |
| Download: ML16340C793 (4) | |
Text
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UNITED STATES N CLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 JUL - J 1982 MEMORANDUM FOR:
Darrell G. Eisenhut, Director Division of Licensing Office of Nuclear Reactor Regulations FROM:
SUBJECT:
E. L. Jordan, Director Division of Engineering and equality Assurance Office of Inspection and Enforcement BOARD NOTIFICATION OF CONTROL ROD DRIVE GUIDE TUBE SUPPORT PIN FAILURES AT. WESTINGHOUSE PLANTS The purpose of this memorandum is to inform you of an-issue which we believe should be brought to the attention of the Atomic Safety Licensing Board Panel and the Atomic Safety Licensing Appeals Panel.
The issue involves the failures of the support pins that are attached to the bottom of the control rod drive guide tubes in Westinghouse designed reactors.
The support pins align the bottom of the control rod drive guide tube assembly into the top of the upper core plate in a manner that provides lateral support and accomodates thermal expansion of the guide 'tube relative to the core plate (see enclosed notice for details).
Westinghouse has analyzed the safety implications of a failed pin and concluded that a single pin failure is not a safety concern, either from the effects of a loose part or the failure of a single control rod assembly to fully insert upon a reactor trip signal.
Since the failures are due to stress corrosion cracking (SCC),
we believe that multiple pin failures are possible.
Such failures could introduce several loose parts into the reactor coolant system, and could also inhibit the insertion of several control rod assemblies upon a reactor trip signal.
For example, one can assume that SCC had progressed to the point where several pins are on the verge of failing.
(Note:
Such degradation was detected in a Japanese reactor).
With the above preconditioning of the pins, we can postulate that a
LOCA or other triggering event could induce higher than normal stresses on the'pins such that they could fail simultaneously.
We, therefore, plan to request additional analyses from Westinghouse regarding the potential for multiple pin failures and their effects on plant safety.
In addition, we plan to determine which actions are needed to resolve this concern.
Contact:
I. Villalva (301) 492-9635 t'209ih0095 820822 PDR ADOCK 05000275 j
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Based on the above; and the information contained in the enclosure, we believe that this matter is of sufficient safety significance to warrant board notification.
Edward L. Jordan, Director Division of Engineering and equality Assurance Office of Inspection and Enforcement
Enclosure:
IE information Notice No. 82-29 cc:
R.
C.
- DeYoung, IE J.
H. Sniezek, IE H.
P,. Denton, NRR G.
C. Lainis, NRR T. A. Ippolito, NRR J.
H. Taylor, IE L. I. Cobb, IE R. L. Baer, IE W.
R. llills, IE T. L. Harpster, IE I. Villalva, IE R. A. Holland, IE A. Pattou, IE
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