ML19339B315
| ML19339B315 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 01/06/1977 |
| From: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Groce R YANKEE ATOMIC ELECTRIC CO. |
| References | |
| NUDOCS 8011060726 | |
| Download: ML19339B315 (1) | |
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UNITED STATES
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NUCLEAR REGULATORY COMMISSION 1
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Yankee Atomic Electric Company Docket No. 50-29 E
l Attention:
Mr. Robert H. Groce R
Licensing Engineer f
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20 Turnpike Road y
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'a'estborough, Massachusetts 01581 t;.
E fi Genticmen:
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' ?l The enclosed IE Circular, 77-01 is forwarded to you for your infor-i nation. No written response is required.
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Should you have any questions concerning this matter, please contact
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this office.
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Sincerely, P
k-James P. O'Reilly Director F
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Enclosure:
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IE Circular No. 77-01
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H. Autio, Plant Superintendent T
1 Donald G. Allen, President
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NUCLEAR REGUl.ATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT i
WASHINGTON, D.C.
20555 i
IE Circular No. 77-01 L
5 Date: January 6, 1977
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Page.1 of 2 p
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MALFUNCTIONS OF LIMITORQUE VALVE OPERATORS
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2" DESCRIPTION OF CIRCUMSTANCES:
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On October 28, 1976, Portland General Electric Company reported that the i
two motor operated (Limitorque) valves located between the Refueling i
l Water Storage Tank and the charging pump suction at the Trojan Nuclear I
l Plant failed to open in response to a spurious safety injection (SI)
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j signal. The malfunction in both valves resulted from the torque limit
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j switch in the opening circuit becoming activated before the valve was 4
fully off its seat.
The licensee's investigation revealed that in each case the valve had h
been manually closed hard on its seat following a maintenance operation.
b The licensee's investigation of this occurrence revealed dif ficulty in si the opening of three additional motor operated (Limitorque) valves in i
the inlet and outlet piping of the Boron Injection Tank.
Each of the e
l 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 y
premature activation of the valve's torque limit switch.
These valves
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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 4
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 unbypassed and operable in the i
circuit before the valve was moved from its seat.
Examination by the l
licensee revealed similar improper adjustment of the bypass switches on l
several other =otor operated valves in safety related systems.
i Corrective actions by the licensee included the establishment of proce-dural controls to insure that valves which are manually closed are checked for proper operation (by cycling them open with the motor opera-tor) prior to their being declared operational.
N bypass switches on all similar =otor operated ralves were checked and cacir position in terms of proper valve travel adjusted.
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8 e-IE Circular No. 77-01 Date: January 6, 1977 S'
Page 2 of 2 ET RECOMMENDED ACTION BY LICENSEES:
I 7m If valves similar to those described are in use in safety related systems, E
you should verify that your procedures contain adequate provisions to E
insure that these valves are adequately checked for operation following
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maintenance or manual closure, and that operating personnel are properly E
instructed to assure conformance with the procedures.
You should also verify that measures are taken to insure the proper setting of torque Q
limit switches and limit switch bypasses, to assure that the bypass function is not negated prematurely in either the opening or closing I
cycle.
(hT No written response to this Circular is required.
If you require addi-F tional information regarding this matter, contact the Director, of the
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appropriate NRC Regional Office.
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