ML18085A326
| ML18085A326 | |
| Person / Time | |
|---|---|
| Site: | Salem  |
| Issue date: | 11/07/1980 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Schneider F Public Service Enterprise Group |
| References | |
| NUDOCS 8012030796 | |
| Download: ML18085A326 (4) | |
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UNITED STATES.
NUCLEAR REGULATORY*CQMMISSION REGION I 631 PARK AVENUE KING OF PRUSSIA, PENNSYLVANIA 19406 November 7, 1980 Docket Nos. 50-272 50-311 c.::Ji (J)
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C; t.;;1~*~2 Public Service Electric and Gas Company ATTN:
.Mr. F. W. Schneider Vice President ~ Production 80 Park Plaza - 15A Newark, New Jersey 07101 Gentlemen:
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The enclosed IE Information Notice No. 80-40, "Excessive Nitrogen Supply Pres.sure Actuates Safety-Relief Valve Operation to Cause Reactor Depressurization, 11 is forwarded to you for information.
No written response is. required.
If you desire additional information regarding this matter, please contact this office.
Enclosures:
Sincerely,
"~ce#.~
Boyce H. Grier Director 1-IE Infbrmation Notice No. 80-40
- 2.
.List of Recently Issued IE Information Notices CONTACT:
- 0. L.. Caphton (215-337-5266) cc w/encls:
F. P. Librizzi, _General Manager - Electric Production E. N. Schwalje, Manager - Quality Assurance R. L. Mittl, General Manager - Licensing and. Environment H. J. Midura, Manager - Salem Generating Station R. A. Uderitz, General Manager - Fuel Supply Department
UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION ANO ENFORCEMENT WASHINGTON, 0. c. *2osss November 7, 1980 SSINS No.:
6835 Accession No.:
8008220269 IN 80-40 IE Information Notice No.: 80-40:
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 d~pres surized at Boston Edison Company's Pilgrim Nuclear Power Station Unit No. 1.
The Pilgrim Station Unit 1 uses a GE BWR. The depressurizations resulted when excessive pressure in the nitrogen supply system caused the 11A 11 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 two events involved a failure in the pressure regulation of the supply 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 1 ine.
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
. pneumatic 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 decrease 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 pressure incr~ases, le.ss instrument pressure is necessary to initiate the pneumati:c operato~~. Approximately 3 to 5 psi at the pneumatic operator is sufficient.. to initiate'"tfhe safety-relief valve opening.
Such a pressure begins to build with leakage through the solenoid actuator and was reached in the 11A 11 valve at 160 psi supply pressure.
According to information from GE and TR, 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.
IN 80-40 Page 2 of 2 The particular solenoid actuator valves used with these two-stage safetyrelief valves are manufactured by TR.
Their design is such that excessive control pressure tends to unseat the solenoid valve disk.
The three-stage TR safety-relief valves use either AVCO (Automatic Valve Company) or ASCO (Automatic Switch Company) solenoid valves according to information from GE.
- The AVCO solenoid valve has been tested to 300 psi and found not to leak and the ASCO solenoid valve tends to seat with i.ncreasing supply pressure.
Therefore, the NRC believes that the tendency for solenoid leakage and hence safety-relief valve openi~g 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 anticipated 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 regarqing this
- matter, please contact the Director of the appropriate NRC Regional Office.
e IE Information Notice No. 80-40 November 7, 1980 Information Notice No. 80-39 80-38 80-37 80-36 80-35 80-34 80-33 80-32 80-31 RECENTLY ISSUED IE INFORMATION NOTICES Subject Date Issued Malfunctions of 10/31/80 Solenoid Valves Manufactured by Valcor Engineering Corporation Cracking in Charging 10/30/80 Pump Casing Cladding Containment Cooler 10/24/80 Leaks and Reactor Cavity Flooding at Indian Point Unit 2 Failure of Steam 10/10/80 Generator Support Bolting Leaking and Dislodged 10/10/80 Iodine-125 Implant Seeds Boron Dilution of 9/26/80 Reactor Coolant During Steam Generator Decontamination Determination of.
9/15/80 Teletherapy Timer At curacy Clarification of 9/12/80 Certain Requirements for Exclusive-use Shipments of Radioactive Materials Maloperation of Goulrl-8/27/80 Brown Boveri 480V-Type K-600S and K-Don 600S Circuit Breakers Issued to All holders of a power reactor OL or CP All holders of a PWR power reactor OL or CP All holders of a power reactor OL or CP All holders of a power reactor OL or CP All holders of a Category G or Gl Medical License All holders of a PWR Power Reactor OL All holders of a teletherapy license All holders of an NRC or Agreement State License All holders of a power reactor OL or CP