ML20150C933
| ML20150C933 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 03/11/1988 |
| From: | NRC OFFICE OF SPECIAL PROJECTS |
| To: | |
| Shared Package | |
| ML20127A683 | List:
|
| References | |
| NUDOCS 8803220429 | |
| Download: ML20150C933 (2) | |
Text
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jo, UNITED STATES NUCLEAR REGULATORY COMMISSION 3
l WASHINGTON, D. C. 20555
%,-...../
SAFETY EVALUATION REPORT BY THE OFFICE OF SPECIAL PROJECTS EMPLOYEE CONCERN ELEMENT REPORT EN 23704 "BYPASS OF OVER-TORQUE SWITCHES TENNESSEE VALLEY AUTHORITY SEQUOYAH NUCLEAR POWER PLANT, UNITS 1 AND 2 DOCKET NOS. 50-327 AND 50-328 1.0 SUBJECT Category:
Engineering (20000)
Subcategory:
Element:
Bypass of Over-torque Switch (23704)
TVA Element Report EN 23704, Revision 2, dated January)26, 1987, was issued to address the generic implications of the Watts Bar (WBN employee concerns.
1 Employee concerns, i
The following concerns related to bypass of over-torque switches:
XX-85-020-001 I-85-612-SQN 2.0
SUMMARY
OF ISSUES Installation of torque switch bypasses for safety injection system (SIS) valve numbers 332 and 333, required by 1979 Engineering Charge Notice (EC1) 2257 was not completed.
1 3.0 EVALUATION 3
IE Bulletin No. 85-03, "Motor-Operated Valve Comon Mode Failures During Plant Transients Due to Improper Switch Settings," dated November 15, 1985 require that licensees develop and implement a program to ensure that torque switch settings on certain safety-related r:otor operated valves (MOVs) are selected, set and maintained correctly to acccamodate the maximum differential pressure expected on these valves during both normal and abnormal events.
IE Circular 81-31, "Torque Switch Electrical Bypass Circuit for Safeguard Service Valve Motors" of September 25, 1981 provides guidance for installing' bypasses on torque switches.
8803220429 880311 PDR ADOCK 05000328 P
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l In order to conform with the above requirements TVA elected to bypass the torque switches of SON and WBN active valves except where the valves need to be protected fro.n potential valve damage.
These -letter M0V's would have their torque switches bypassed for all-but the last few percent of travel to' the full closed position. As a result of employee concerns at WBN, TVA
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re-evaluated the bypassing of torque switches and dete mined that:
The design basis does not support bypassing the M0V's torque switches.
No explicit requirement existed to keep the active valve list at SQN updated.
MOV's added to the WBN active valve list were not added to the SQN list and this resulted in SIS H0Vs 332 and 333 (at SQN) not having their torque switches bypassed.
Standard drawings did not provide clear criteria for selecting torque and limit switch configurations.
A further review by TVA, in mid-1986 identified 48 additional M0V's torque switches that should have been bypassed.
TVA's corrective action plan included the following:
Issuance of criteria for POV torque switch bypars design.
Preparation of an up-to-date active valve list including justifications for not listing passive valves.
Revision of FSAR to clarify the design basis for M0V torque switches.
Revision of standard drawings for NOV's to clarify and define design.
Orawing review on all active valves to verify compliance with MOV torque switch bypass design.
4.0 CONCLUSION
The NRC staff concludes that the licensee's investigetion of the employee concerns was adequate and the resolution described in Element Report EN 23704-SON, Revision 2, is acceptable,