ML13333A445
| ML13333A445 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 11/19/1979 |
| From: | Baskin K Southern California Edison Co |
| To: | Ziemann D Office of Nuclear Reactor Regulation |
| References | |
| TASK-03-12, TASK-3-12, TASK-RR NUDOCS 7911280381 | |
| Download: ML13333A445 (4) | |
Text
Southern California Edison Company P. 0. BOX 800 2244 WALNUT GROVE AVENUE ROSEMEAD, CALIFORNIA 91770 K. P. BASKIN November 19, 1979 TELEPHONE
- MANAGER, GENERATION ENGINEERING 213-572-1401 Director of Nuclear Reactor Regulation Attention:
D. L. Ziemann, Chief Operating Reactors Branch No.
2 Division of Operating Reactors U.S. Nuclear Regulatory Commission Washington, D.C.
20555 Gentlemen:
Subject:
Docket No.
50-206 San Onofre Nuclear Generating Station Unit 1 My letters of February 24, 1978, and February 13, 1979,.provided information regarding the environmental qualification of safety-related electrical equipment at San Onofre Unit 1. In particular, the qualification of electrical cable.was addressed and the following specific types of safety-related cable utilized at San Onofre Unit 1 were identified:
GE, GE/Vulkene, Raychem and Rockbestos. These cables were shown to be qualified for the environments associated with design basis events.
As discussed below, one of the types of cable utilized at San Onofre Unit 1 was the subject of a report in accordance with the requirements of 10 CFR 50.55(e) in connection with our San Onofre Units 2&3 plants which are currently under construction. Although it is our conclusion at this time that this matter is not reportable in accordance with the San Onofre Unit 1 Technical Specifica tions or NRC regulations pertaining to an operating plant, we are proceeding with a detailed evaluation of this matter. It is our intention to inform you of the results of this evaluation to supplement our previous environmental qualification submittals. In addition, if indicated by the results of these evaluations, we will comply with any reporting requirements of our Technical Specifications and NRC regulations as appropriate. Pending completion'of these evaluations, it is our conclusion that there is no safety hazard associated with continued operation of San Onofre Unit 1 as discussed in the following paragraphs.
At the San Onofre Units 2&3 construction site it was observed that an ethylene-propylene rubber insulated cable manufactured by General Electric (hereafter called "GE cable"), includes manufacturing rework. As that term is defined in ANSI N 45.2.10-1973, rework of cable includes factory made conductor joints and insulation/jacket replacement and processing, or both. An investigation into the adequacy of this rework determined that rework, while relatively infrequent, is part of the normal manufacturing process for cable and is permitted under industry standards. Since GE cable is used inside containment, SCE further evaluated the qualification of the reworked cable toI
D. L. Ziemann, Chief November 19, 1979 withstand the adverse environment inside containment following a design basis event.
GE successfully performed environmental qualification tests on representative production samples of this cable in 1974-1975, but is unable to demonstrate that any of these samples included a section of reworked cable.
Although it was felt that the reworked GE cable is technically acceptable for all services, SCE felt that actual environmental qualification testing of production reworked cables should be provided.
In view of the above, SCE reported this matter to the Commission for San Onofre Units 2&3 on November 5, 1979, in accordance with 10 CFR 50.55(e).
The GE cable, a 600 Volt power cable, is manufactured by General Electric in its Bridgeport, Connecticut facility. It consists of copper conductor with ethylene-propylene rubber insulation and a GEOPRENE jacket on the individual conductors. For multi-conductor cables, there is an additional GEOPRENE jacket around the complete cable.
All cable raw materials undergo qualification and receiving inspection tests.
All single conductor cable and singles of multi-conductor cable undergo spark tests and wet dielectric tests in accordance with IPCEA standards. In addition, all completed multi-conductor cables are tested again in accordance with the aforementioned standards.
In the event cable rework is required during the fabrication process, detailed manufacturing instructions describe the rework procedures and also specify that the materials used in rework are the same as applied in the original cable.
Such rework is performed in accordance with the appropriate ASTM and IPCEA Standards and the factory inspectors who rework cable go through a training program prior to performing such rework. Since any rework is performed prior to the production tests on each shipping reel of cable, the reworked cable must undergo and pass the same spark tests and wet dielectric tests as all other cable.
In addition, at our request, General Electric has subjected samples of reworked production cable to additional flame and mechanical tests, and this cable has compared satisfactorily with non-reworked cable.
Although the manufacturing and rework processes lead GE personnel to conclude reworked cable and non-reworked cable are functionally equivalent, SCE has requested GE to perform additional qualification testing on production samples of reworked cable.
This program will involve a complete qualification of reworked GE cable for the environment associated with design basis events as set forth in IEEE 323 and 383.
GE has estimated this program will require four to six months. It is GE's expectation that the results will parallel the results of the original qualification tests on GE cable performed in 1974-1975.
At San Onofre Unit 1, the only application of this GE cable inside containment is on the residual heat removal (RHR) pump motors. This cable was added during the 1976-1977 refueling outage as part of our backfit modifications and is at least partially installed in rigid conduit. The only accident condition for which use of the RHR pumps is taken credit for is a main steam line break.
However, as described in our letter of March 25, 1977, an alternate cooldown method is available following a main steam line break without RHR service and is incorporated in our emergency operating instruction for a steam generator high energy pipe break. This alternate method involves maintaining maximum charging and letdown flows as well as utilizing one safety injection/feedwater pump train to provide water from the refueling water storage tank (RWST) to the steam generators. The water that spills out the break to the containment sump is then returned to the RWST utilizing the safety injection system recircula tion pumps and the refueling water pumps and is available for recirculation to the steam generators.
D. L. Ziemann, Chief November 19, 1979 In light of the manufacturing process identified with the GE cable, SCE has also investigated whether this same manufacturing process applies to other cable utilized in safety-related applications at San Onofre Unit 1. In particular, SCE has investigated the GE/Vulkene, Rockbestos, and Raychem cables which were identified in our February 13, 1979 submittal.
In general, a similar situation was found with the GE/Vulkene and Rockbestos cables; that is, cable rework is part of the manufacturing process. Rework is not permitted, however, in the manufacturing process of the Raychem cable. The cables are discussed further in the following paragraphs.
The Rockbestos cable has a copper conductor with a cross-linked polyethylene insulation.
Although there is no jacket on individual conductors, the overall cable has a jacket that is either cross-linked polyethylene or hypalon. This cable was environmentally qualified as described in our February 13, 1979 submittal, although manufacturing rework was not specifically addressed in that submittal.
However, we have learned that Rockbestos is currently conducting environmental qualification testing of samples of cable with manufacturing rework. It is our understanding that the results of this program to-date, including heat aging, radiation and wet dielectric test have been satisfactory.
The rest of the qualification testing is currently anticipated to be complete within four months.
The GE/Vulkene cable has a copper conductor with a cross-linked polyethylene insulation.
Single conductor power cable does not have a jacket.
Multi conductor cable has a jacket of either GEOPRENE or polyvinylchloride. Although cable representative of that installed at San Onofre Unit 1 is no longer available from the manufacturer, GE indicates that this cable was manufactured using the same process and controls described for the GE cable above; that is, reworked cable had the same material as original cable and was tested after the rework. In addition, from a material standpoint, this cable is similar to the Rockbestos cable described above. Based on this information, it is SCE's opinion that successful completion of the qualification testing on the reworked GE and Rockbestos cables will mean there is a high probability that reworked GE/Vulkene cable will also pass additional environmental testing.
The Raychem cable has a copper conductor with cross-linked polyethylene insulation.
There is no jacket on the individual conductors, but an overall jacket of cross-linked polyethylene.
The manufacturer of this cable does not permit either conductor or insulation repairs on this cable. Therefore, the concern with respect to reworked cable does not exist with this cable.
As a result of the identified concern pertaining to the lack of specific environmental qualification data for reworked cable, SCE is proceeding with environmental qualification testing of the GE cable associated with the RHR pump motors.
The currently ongoing tests on the Rockbestos cable will be followed and their applicability to San Onofre Unit 1 established. Since the GE/Vulkene cable installed at San Onofre Unit 1 is no longer available from the manufacturer, SCE will attempt to locate a sample of reworked cable at the station and utilizing this sample establish the capability of reworked GE/Vulkene cable to withstand the post accident environments either through testing or analysis. It is my intention to inform you of the results of all of these evaluations when they are complete to update our previous environmental qualification submittals. In addition, we will comply with the reporting requirements in our Technical Specifications and in the regulations as mentioned earlier.
9 D. L. Ziemann, Chief November 19, 1979 Pending completion of the above identified evaluations, SCE concludes that there is reasonable assurance that the continued operation of San Onofre Unit 1 does not endanger the health and safety of the public. This conclusion is based on the information presented above and our judgement and the judgement of the cable manufacturers, that when the environmental qualification tests are performed on reworked cable, the results of these tests will parallel the results of the original qualification tests. This judgement is supported by the fact that material used in rework is the same as the material in the original cable, rework is performed by appropriately qualified operators using documented procedures, and all tests done to date on reworked cable (electri cal, flame, mechanical, environmental) have shown acceptable results. There is no evidence which would indicate that the use of such cable will present any safety hazard.
If you have any questions regarding this matter, please let me know.
cc:
R. H. Engelken, Director Office of Inspection and Enforcement, Region V