ML19345C115
| ML19345C115 | |
| Person / Time | |
|---|---|
| Site: | River Bend  |
| Issue date: | 11/07/1980 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Draper E GULF STATES UTILITIES CO. |
| References | |
| NUDOCS 8012030899 | |
| Download: ML19345C115 (1) | |
Text
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UNITED STATES
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1 NUCLEAR REGULATORY COMMISSION hk 6 2
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- /, j REGION IV S,
,8 611 RYAN PLAZA DRIVE, SUITE 1000 ARLINGTON. TEXAS 76011 November 7, 1980 In Reply Refer To.
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Docket Nos.
50-458/IE. Information Notice No. 80-40 d
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50-459/IE Information Notice No. 80-40 S
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Gulf States Utilities m
rc Attn: Dr. E. Linn Draper, Jr.
i Vice President - Technology G
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Post Office Box 2951 Beaumont, Texas 77701 Gentlemen:-
This IE Information Notice is prnvided as an early notification of a possibly significant matter.
It is expected that recipients will review the information for possible applicability to their facilities. No specific action or response is requested at this time.
If further NRC evaluations so indicate, an IE Circular or Bulletin will be issued to recommend or request specific licensee actions.
If you have questions regarding this matter, please contact the Director of the appropriate NRC Regional Office.
Sincerely, g,k k! /
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V. Seyfrit fj!
Director
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Enclosures:
'1.
IE Information Notice No. 80-40 2.
List of Recently Issued IE Information Notices 80120SOFTi h
l 1
4 SSINS No.:
6835 Accession No.:
8008220269 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C. 20555 IE Information Notice No. 80-40 Date:
November 7, 1980 Page 1 of 2 EXCESSIVE NIROGEN SUPPLY PRESSURE ACTUATES SAFETY-RELIEF VALVE OPERATION TO CAUSE REACTOR DEPRESSURIZATION Description of Circumstances:
On October 7 and 31, 1980, the reactor coolant system was spuriously depres-surized at Boston Edison Company's Pilgrim Nuclear Power Station Unit No.1.
The Pilgrim Station Unit No. 1 uses a GE BWR. The depressJrizations resulted when excessive pressure in the nitrogen supply system caused the "A" Target Rock (TR) safety-relief ~ valve to open and remain open until the excessive supply pressure could be isolated, pneumatic operator pressure vented and the main steam system depressurized sufficiently to allow the main disk to reseat.
These twa events involved a failure in the pressure regulation of the supplf nitrogen and not a failure of the TR safety-relief valve to function as designed.
The safety-relief valves at Pilgrim are designed to be supplied, with other drywell instrumentation, from either the compressed air system or containment atmosphere control-system'(CACS).
The CACS uses nitrogen for containment inerting.
The supply for the safety-relief valves is provided from the CACS through an ambient air vaporizer and then through one of two parallel pressure regulators or a parallel bypass line.
Shortly before the time of each event a new supply of liquid nitrogen had been added to the storage tanks.
At the time of the events the two pressure regulators were in service with the bypass closed.
Nitrogen pressure supplying the valves increased to 160-165 psi.
This may have been caused by liquid nitrogen reaching the pressure regulators or by a failure in a pressure regulator.
The result was excessive pressure which was sufficient to leak through the solenoid actuator and initiate the oneumatic operator of the safety-relief valve.
The design normal operating pressure of the compressed air or nitrogen systems supplying the safety-relief valves is90-110 psi.
At a pressure of 145 psi the solenoid valve may begin to leak since excessive pressure acts to unseat the disk.
The supply pressure must then cecrease to 135 psi or less for the solenoid disk to reseat.
In addition, the design of the safety-relief valve is such that as the main steam ?ressure increases, less instrument pressure is necessary to initiate the pneumatic operator.
Approximately 3 to 5 pd at the pneumatic operator is sufficient to initiate the safety-relief valve opening.
IE Information Notice No.:
80-40 November 7, 1980 Page 2 of 2 Such a pressure begins to build with leakage through the solenoid actuator and was reached in the "A" valve at 160 psi supply pressure.
According to information from GE and TRC, approximately 180 psi pressure is necessary for all of the safety relief valves to open as result of supply overpressure.
It would appear that under such conditions of overpressure that safety-relief valve openings would be sequential rather than simultaneous.
The particular solenoid actuator valves used with these two-stage safety-relief valves are manufactured by TRC.
Their design is such that excessive control pressure tends to unse'at the solenoid valve disk.
The three-stage TR safety-relief
- valves use either AVC0 (Automatic Valve Company) or ASCO (Automatic Switch Company) solenoid valves according to information from GE.
The AVC0 solenoid valve has been tested to 300 psi and found not to leak and the ASCO solenoid valve tends to seat with increasing supply pressure.
Therefore, the NRC
- believes that the tendency for solenoid leakage and hence safety relief valve opening is confined to the two-stage safety-relief valve installations.
This information is provided as a notification of a possibly significant matter which is still under review by the NRC staff.
It is a:iticipated that the results of continuing NRC review will culminate in issuance of an IE Bulletin which will recommend or require specific licensee action.
In the interim, we expect that recipients will review the information for possible applicability to their facilities, particularly those with installations of the TR two-stage safety-relief valves.
If you have questions regarding this matter, please contact the Director of the appropriate NRC Regional Office.
L.
s IE Information Notice No. 80-40 November 7, 1980 LISTING-0F RECENTLY ISSUED IE INFORMATION NOTICES Information Subject Date Issued To Notice No.
Issued 80-33 Determination of-Tele-9/15/80 xil teletherapy therapy Timer Accuracy (G3) licensees 80-34 Boron Dilution of Reactor 9/26/80 All Pressurized Coolant During Steam Water Reactor Generator Decontamination Facilities holding power reactor Operating Licenses (0Ls) 80-35 Leaking and Dislodged 10/10/80 All categories G and Iodine-124 Implant Seeds G1 medical licensees 80-36 Failure of Steam 10/10/80 All nuclear power Generator Support Bolting reactor facilities holding Operating Licensees (0Ls) or Construction Permits (cps) 80-37 Containment Cooler Leaks 10/24/80 All nuclear power and Reactor Cavity _
facilities holding Flooding at Indian Point power reactor Operating Unit 2 Licenses (OLs) or Construction Permits (cps) 80-38 Cracking in Charging 10/30/80 All Pressurized Water Reactor Facilities holding power reactor Operating Licenses (OLs) and Construction Permits (cps) 80-39
. Malfunctions Of Solenoid 10/31/80 All light water reactor Valves Manufactured By' facilities holding Valcor Engineering Corporation power reactor OLs or cps Enclosure
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