ML20086D134
| ML20086D134 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 05/31/1973 |
| From: | Searls F PACIFIC GAS & ELECTRIC CO. |
| To: | Kreusi F US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20086D132 | List: |
| References | |
| 10CFR-050.55E, 10CFR-50.55E, NUDOCS 8311300198 | |
| Download: ML20086D134 (2) | |
Text
-
O O
PACIFIC G-A S A N D E LE C T RI C C O M PANY MOtM l
77 OE ALE S TREET e S A N F R A NCISCO. C A LIFO R NI A 94106 *(415) 781 4211 P R E D E R I C K T. S E A R t. S
[l3fjj 3.*.;,.,. '....
y v.a m...m....m.
comu JOH N C. MOR RISS EY E *
.J se*aa.'
A550CIATE 61.EaAL COUNSEL e6s.
was,. da.
T'.".U.';,,'J".. '*'
wiuiau S. nuoE.
w,u Au..sO
~S M ALCOLM M. FunSUSH
.e.e.t 0-6.aa se C M A R L E S 7. V A N D E U S E N
[,\\,",*[,
,[,[
M ALCOLM A. M AC MILLOP D**
EG
,,g",
PHILIP A. C R A NE, J R.
g g,
.*:X~:::.
Mr. Frank E. Kreusi, Director C :?.'"J."".....
Directorate of Regulatory Operations
'"'*y*/$*
[..
U. S. Atomic Energy Commission r;;;,p;,;;,,,
Washington, D. C. 20545 Re:
Docket No. 50-275 Diablo Canyon Site Unit 1
Dear Mr. Kreusi:
On April 18, 1973, we notified the Office of the Direc-torate of Regulatory Operations, Region V, that an incident report-able under paragraph (e) (iii) of 10 CFR 50.55 appeared to have oc-curred affecting the integrity of the thermoplastic insulation jacket on 4.16 kv metalclad switchgear bus bars F, G, and H, non-vital 12 kv metalclad switchgear buses and related bus ducts for Unit 1, Diablo Canyon site.
This letter includes the written report summarizing our investigation.
The 12 kv and 4.16 kv systems provide distribution of elec-trical power for the auxiliary loads in the plant.
4.16 kv buses F, G, and H are the vital portions of.these systems and are fed from the diesel generators; the other buses have non-vital loads.
The systems are equipped with metalclad switchgear and power bus ducts made by General Electric Company.
The main conductors in the switch-gear and bus ducts consist of copper bus bars insulated with a thermo-plastic -jacket over the straight sections.
Joints are insulated with laps of irradiated polyethylene tape covered by glass tape impregnated with flame-retardant resin.
This covering is not the primary insulation of this equipment and, if defective, would not ordinarily lead to an electrical failure.
Porcelain or polyester fiberglass insulators at the supports and pene-trating points provide the main electrical insulation and.are unaffected by the incident described in the following paragraph.
During installation at the job site it was discovered that
/
s, J
8311300198 750615 a"
PDR ADOCK 05000275 y (C )'
3 0410 S
PDR h
4 o
o Mr. Frank.E.=Kreusi, Director May 31, 1973 Directorate of Regulatory Operations Page 2 L
cracking of the' thermoplastic insulation had occurred.
General Electric Company was informed of the problem, and a joint investiga--
~ tion into the cause was initiated.
A discrepancy report was prepared in accordance with - the PGandE quality. assurance program, and the -
problem was reviewed by a Material Review Board.
It was determined that the bus would be repaired in place in accordance with procedures and materials provided by General Electric and approved by PGandE..
The repair, consisting of replacing the cracked plastic insulating material with appropriate layers of irradiated polyethylene tape, glass tape, and varnish has been successfully completed.
The insulation system approved for the repairs meets the ANSI Standard C37.20 and all other industry _ standards for Class I insulation.
Very truly yours, i
a CC: Mr. R. W. Smith, Director Directorate of Regulatory Operations, Region V 5
4 L
-=w ve w