ML19340A973
| ML19340A973 | |
| Person / Time | |
|---|---|
| Site: | Dresden, Byron, Braidwood, Quad Cities, Zion, LaSalle  |
| Issue date: | 01/06/1977 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Brian Lee COMMONWEALTH EDISON CO. |
| References | |
| NUDOCS 8009100918 | |
| Download: ML19340A973 (1) | |
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!CENTRl[ FLIES UNITro STATES NUCLEAR REGULATORY COMMISSION REGION lli 799 ROOSEVELT RO AD GLEN Et. LYN. ILt.lNOIS 60137 JAN B I977~
Commcnwealth Edison Company Docket Nos. 50-10, 50-237, 50-249 ATTN:
Mr. Byron Lee, Jr. -
Docket Nos. 50-254, 50-265 Vice President Docket Nos. 50-295, 50-304 P. O. Box 767 Docket Nos. 50-373, 50-374 Chicago, Illinois 60690 Docket Nos. 50-454, 50-455 Docket Nos. 50-456, 50-457 Gentlemen:
The enclosed IE Circular No. 77-01 is forwarded to you for your information. No v-itten response is required.
Should you have any questions concerning this matter contact the Director of this NRC Regional Office.
Sincerely,
-b James G. Kepp r Regional Director
Enclosure:
IE Circular No. 77-01 cc w/ enc 1:
Mr. b. B. Stephenson, Station Superintendent Mr. N. Kalivianakis, Station Superintendent Mr..J. Bitel, Plant Superintendent Mr. L. J. Burke, Site Project Superintendent Mr. G. Sorensen, Site Project Superintendent Mr. R. Cosaro, Project Superintendent tral Files Reproduction Unit NRC 20b PDR Local PDR W4 nthony Roisman, Esq.,
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January 4, 1977 IE Circular No. 77-01 MALFUNCTIONS OF LDf1 TORQUE VALVE, OPERATORS DESCRIPTION OF CIRCUMSTANCES:
On October 28, 1976, Portland General Electric Company reported that the two motor operated (Limitorque) valves located between the Refueling Water Storage Tank and the charging pump suction at the Trojan Nuclear Plant failed to open in response to a spurious safety injection (SI) signal. The malfunction in both valves resulted from the torque limit switch in the opening circuit becoming activated before the valve was fully of f its seat.
The lir e=ee's investigation revealed that in each case the valve had been manually closed hard on its seat following a maintenance operation.
The licensee's investigation of this occurrence revealed difficulty in the opening of three additional motor operated (Limitorque) valves in the inlet and outlet piping of the Boron Injection Tank.
Each of the valves failed to open in response to a single actuation of its manual control switch.
In each case, the cause for failure was attributed to premature activation of the valve's torque limit switch.
These valves had opened in response to the SI signal on October 28, 1976, following which they were closed normally using their motor operators.
Subsequent investigation by the licensee revealed that each of the valves which malfunctioned was equipped with a torque limit switch in the opening circuit, the actuation of which stops valve motion.
The valves are also equipped with an adjustable bypass switch which defeats the function of the torque limit switch when the valve is being moved from its full open or full closed position.
Each of the valves which malfunctioned was found to have its bypass switch adjusted such that it allowed the limit torque switch to be unby-passed and operable in the circuit before the valve was moved from its seat.
Examination by the licensee revealed similar improper adjustment of the bypass switches on several other motor operated valves in safety related systems.
Corrective actions by the 'Lcensee included the establishment of procedural controls to insure that valves which are manually closed are checked for proper operation (by cycling them open with the motor operator) prior to their being declared operational.
The
~ bypass switches on all similar motor operated valves were checked and their position in terms of proper valve travel adjusted.
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2-January 4, 1977 Circular No. 77 -
RECOMMENDED ACTION BY LICENSEES:
If valves similar to those described are in use in safety relat'ed systems, you should verify that'your procedures contain adequate provisions to insure that these valves are adequately checked for operation following maintenahce or manual closure, and that operating personnel are properly instructed to assure conformance with the procedures. You should also verify that measures are taken to insure the proper setting of torque limit switches and limit switch bypasses, to assure that the bypass function is not negated prematurely in either the opening or closing cycle.
No written response to this Circular is required.
If you require additional information regarding this matter, contact the Director of the appropriate NRC Regional Office.
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