ML13308B438
| ML13308B438 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 03/22/1978 |
| From: | Head J SOUTHERN CALIFORNIA EDISON CO. |
| To: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| References | |
| IEB-78-04, IEB-78-4, NUDOCS 8102190195 | |
| Download: ML13308B438 (3) | |
Text
Southern California Edison Company C
P. 0. BOX 800 2244 WALNUT GROVE AVENUE J. T. HEAD, JR.
ROSEMEAD, CALIFORNIA 91770 TELEPHONE VICE PRESIDENT 213-572-1472 March 22, 1978 A
U.S. Nuclear Regulatory Commission MAR 27 1978 Office of Inspection and Enforcement It RsGION V Region V ECEIOT Walnut Creek Plaza, Suite 202 EMENT 1990 North California Boulevard 1
Walnut Creek, California 94596 Attention:
Mr. R. H. Engelken, Director Docket No. 50-206 San Onofre Unit No. 1
Dear Sir:
IE Bulletin No. 78-04 Environmental Qualification of Certain Stem Mounted Limit Switches Reference is-made to your correspondence of February 21, 1978, forwarding the subject IE Bulletin. This Bulletin discussed potential problems resulting from the use of seismically or environmentally unqualified limit switches on safety related equipment inside primary containment.
This letter documents the results of our investigation of this matter.
Responses to individual items specified in the Bulletin are listed below:
Item 1:
"Determine if your facility utilizes or plans to utilize NAMCO D2400X or EA-170-302 SNAP LOCK switches in any safety related equipment in the primary containment, including the valve control circuitry previously discussed."
Response
Both types of limit switches mentioned above are used inside containment at San Onofre Unit 1.
The switches are used in position indication circuitry on various safety-related valves.
None of these switches, however, are used in valve control circuits.
-2 The use of NAMCO D2400X limit switches in the position indication circuitry of certain containment isolation valves is identified in response to ITEM 6.15 of Volume VI of the San Onofre Unit 1 Final Safety Analysis Report (FSAR).
The response identifies the need for post-accident operability of such limit switches in order to monitor the position of the containment isolation valves.
This monitoring instrumentation is among the instrumentation which can be used to maintain post-accident surveillance of the containment.
Item 2:
"If any such applications are identified, review these applications to determine the adequacy or qualification testing for these switches and submit the qualification documentation or references to the NRC for review."
Response
The documentation for the limit switches used in the position indication circuitry of various safety-related valves was reviewed.
It was found that documentation verifying compliance with all aspects of the procurement specification was not available.
The absence of complete environmental qualification documentation for the limit switches used in the containment isolation valve position indication circuitry identifed in the FSAR resulted in the replacement of NAMCO D2400X limit switches with NAMCO EA-170-302 SNAP LOCK switches for those valves.
Subsequent discovery of inadequate environmental qualification documentation for the NAMCO EA-170-302 SNAP LOCK limit switches is being dispositioned as non-conforming material in accordance with our Quality Assurance program.
Item 3:
If evidence is not available to support a conclusion of adequacy, submit your plans and programs, including schedules, for corrective action."
Response
Limit switches discussed above, including those utilized in the position indication circuitry of certain containment isolation valves as discussed in the FSAR, are not used as a "latch-in" feature as discussed in IE Bulletin 78-04 or Westinghouse Bulletin NSD-TB-77-B.
The limit switches are used only to provide valve position indication.
The failure of these limit switches in a post-accident environment could result in an erroneous indication of valve position, but no postulated failure could cause valve niovement; therefore, limit switch failure does not jeopardize the safe operation of any safety-related equipment following a postulated accident.
SC The absence of complete environmental qualification documentation for the replacement limit.switches used in the containment isola tion valve position indication circuitry identified in the FSAR, which suggests the possiblity of erroneous valve position indica tion, is being dispositioned as identified in response (2) above.
No corrective action, other than corrective action that may be shown to be necessary in connection with disposition of the non conforming material identified above, is planned.
If I can be of any further assistance, please contact me.
Sincerely, cc: U.S. Nuclear Regulatory Commission Office of Inspection & Enforcement Division of Reactor Inspection Programs