ML13310B032
| ML13310B032 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 10/17/1983 |
| From: | Krieger R Southern California Edison Co |
| To: | Crutchfield D Office of Nuclear Reactor Regulation |
| References | |
| TASK-03-10.A, TASK-3-10.A, TASK-RR ACL:9394, NUDOCS 8310250196 | |
| Download: ML13310B032 (2) | |
Text
Southern California Edison Company P.0 BOX 800 2244 WALNUT GROVE AVENUE ROSEMEAD, CALIFORNIA 91770 October 17, 1983 Director.of Nuclear Reactor Regulation Attention: D. M. Crutchfield, Chief Operating Reactors Branch No. 5 Division of Licensing U. S. Nuclear Regulatory Commission Washington, D.,C.
20555 Gentlemen:
Subject:
Docket No. 50-206 SEP Topic III-10.A Thermal Overload Protection for Motors of MOV's San Onofre Nuclear Generating Station Unit 1 By letter dated July 24, 1981 you transmitted the NRC staff safety evaluation for the subject topic. The evaluation concluded that the electrical circuits for valves MOV 720A and B should be modified to satisfy the review guidelines since the valve motor starters contained thermal overload devices. The review guidelines were primarily based on the Regulatory Guide 1.106, Thermal Overload Protection for Electric Motors on Motor-Operated Valves..
The staff safety evaluation is based on the Technical Evaluation for SEP Topic III-lO.A provided by letter dated.July 3, 1980. The assessment indicated that based on a review of the safety-related motor-operated valve schematics, four valve motor circuits contained thermal overload devices. Two valves (MOV 813 and 814) in the Residual Heat Removal System were not required to change state in a short period of time during or following an accident and were not actuated automatically by an accident signal.
Modification of the valve motors to bypass the thermal overload devices is not necessary.
The remaining two valves (MOV 720A and B) are in the Component Cooling Water System. The assessment indicated that a report prepared by NUS for SCE previously recommended that the thermal overload devices for these valves be bypassed. The recommendations are to be implemented if it is determined they are necessary as part of the integrated assessment. Based on the information provided in the July 3, 1980 Technical Evaluation the following information should be considered as part of the integrated assessment..
As previously indicated MOV 720A and B are part of the Component Cooling Water System. Each valve is located on the discharge side of a Component Cooling Water Heat Exchanger. During normal plant operation one valve is open to allow use of one heat exchanger. The other valve is maintained closed. The heat exchangers are alternated on a weekly basis.
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Either MOV 720A or B would be openfor one-week and the other valve would be closed.
9t6310250196 831017 PDR ADOCK 05000206 P
Mr. 0.
October 17, 1983 In the event of an accident which requires safety injection, both valves are opened to allow use of both Component Cooling Water heat exchanger trains. The valves, MOV 720A and B, are interlocked to the Saltwater Cooling pumps, G13A and B, respectively. The Saltwater Cooling System provides cooling water to the Component Cooling Water heat exchangers. On safety injection, since one Saltwater Cooling pump is operating, the remaining pump is automatically started. Upon starting, the interlocked motor operated valve will automatically open. Either MOV 720A and B would be open due to normal operation and the closed valve will open due to automatic start of its respective Saltwater Cooling pump. The Emergency Core Cooling System at San Onofre Unit 1 is designed for operation with one Component Cooling Water heat exchanger.
The intent of the guidance provided in Regulatory Guide 1.106., is to protect intermittent-duty motors, which may have successive starts at short intervals. The successive starts could cause a heating effect which may actuate the thermal overload device and prevent the motor from starting. This will interfere with the intended safety function of either opening or closing the valve.
The valves under consideration in this SEP Topic are one time operation valves. Upon receipt of a safety injection signal the valve which is closed in the Component Cooling Water System will open upon auto-start of its respective Saltwater Cooling pump. As indicated above the remaining valve will already be open as a result of normal plant operation.and therefore no valve operation would be required. During the accident condition these valves, MOV 720A and B, will remain in the open position and will not require further operation. Even in the event of Loss of Offsite Power concurrent with safety injection the valve which is open will remain open. Upon initiation of safety injection equipment on the Onsite Power System the closed valve will open when its respective Saltwater Cooling pump is auto-started.
Based on the operation of MOV 720A and B and the requirements of Regulatory Guide 1.106, the concern of this SEP Topic does not apply to MOV 720A and B. Modification of the valve circults to comply with the guidance of Regulatory Guide 1.106 is not necessary and should not be considered as part of the integrated assessment.
If you have any questions regarding this information, please let me know.
Very truly yours, R. W. Krieger Supervising Engineer San Onofre Unit 1 Licensing ACL:9394