ML19270F910
| ML19270F910 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 03/20/1979 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Bryan J UNION ELECTRIC CO. |
| References | |
| NUDOCS 7904030039 | |
| Download: ML19270F910 (1) | |
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NR 20.979 Docket No. 50-483 Docket No. 50-486 Union Electric Company ATTN:
Mr. John K. Bryan Vice President - Nuclear P. O. Box 149 St. Iouis, MO 63166 Gentlemen:
The enclosed IE Circular No. 79-05 is forwarded to you for infor-mation.
If there are any qucations related to your understanding of the suggested actions, please contact this office.
Sincer'ly, James G. Keppler Director
Enclosure:
IE Circular No. 79-05 cc w/ encl:
Mr. W. H. Weber, Manager, Nuclear Construction Central F.*1es Director, NRR/DPM Director, NRR/ DOR PDR Iocal PDR NSIC TIC Region I & IV Ms. K. Drey Hon. C. J. Frass, Chairman Missouri Public Service y90403003g Commission RIII RIII orrice >
sudwAuck Fiore li/bk ler DATE > _ __3 /19_/_7_9_ _ ___ _
NRC Form 318A (RIII) (5-76) NRCM 02040
- U. 5. GOVERNMENT PRINTING OFFICE: 1978-253
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U.S. NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ESPORCEMENT REGION III March 20, 1979 IE Circular No. 79-05 MOISTURE LEAKAGE IN STRANDED WIRE CONDUCTORS Description of Circumstances:
During a staff review of the results of environmental qualification test of certain electrical equipment, the phenomenen of water penetration between an electrical conductor and its loosely fitting insulation sleeve was identified.
The staff determined it to be prudent to investi-gate this phenomenon and initiated an equipment checkout test at Sandia Laboratories using a few typical conductors used in nuclear plants.
The equipment checkout test for cable leaks performed at Sandia Laborato-les in August 1978, has shown that most stranded wire conductors, when sabjected to a differential pressure e. cross the conductor ends, will leak steam or moisture through the interstices of the strands of wire.
The test has also shown that solid conductors, under similar conditions, do not' leak.
Steam / moisture leakage through stranded conductors can occur during a Loss of Coolant Accident / Main Steam Line Break (LOCA/MSLB), if a differential pressure were to develop across the conductor ends; e.g.,
one end of the conductor is exposed to the accident environment (typically, in an
, - unsealed junction box) and the other end is isolated from the environ-ment (typically, inside a sealed component such as a sensor / transmitter).
In order to determine whether as-installed configurations exist a nuclear power plants which may result in degradaticn of safety-related functions due to moisture leakage in stranded wire conductors, inspection visits by NRC personnel were made in October to two nuclear plants, (one under construction, and the other operating).
During the inspections the detailed configuration of stranded conductor cables, and their termina-tions at splices, penetrations, junction boxes, transmit ters, motors, motor TE M P9 9 0memissu6 i)afe 7903260138 O