ML19345C140
| ML19345C140 | |
| Person / Time | |
|---|---|
| Site: | Trojan File:Portland General Electric icon.png |
| Issue date: | 11/07/1980 |
| From: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Withers B PORTLAND GENERAL ELECTRIC CO. |
| References | |
| NUDOCS 8012030935 | |
| Download: ML19345C140 (1) | |
Text
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- o UNITED STATES
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8 h.n(J,g NUCLEAR REGULATORY COMMISSION t.('
c REGION V O, M '
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1990 N. CALIFORNIA BOULEVARD
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SUITE 202 WALNUT CREEK PLAZA
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,,,5 WALNUT CREE K. CALIFORNIA 94596 November 7, 1980
,3 [c/ io i..! 3 11EME3 Docket f!o. 50-3a4 Portland General Electric Company 121 S. W. Salmon Street Portland, Oregon 97204 Attention: Mr. Bart D. 'elithers '/ ice President Nuclear Gentiemen: This Infom.ation Notice is provided as an early notification of a possibly significant tratter. It is expectec Inat reclotents will review the information for possible applicability to trieir racilities. No specific acticn or response is recuested at this time. If further liRC evaluations so inoicate, an IE Circular or Bulletin will be issueo to recomreno or request spec 1fic licensee actions. If you have questions regaroing tnis matter, please contact the Director of the appropriate i1RC Regionai Office. Sincarely, ~7hih/l.$W/, ' R. H. ingelken 7oV Director
Enclosures:
1. IE Information flotice No. 80-40 2. List of P.ecently Issued IE Information flotices cc w/ enclosures: C. P. Yundt, PGE J. W. Durham, Esq., PGE 80120s0 W Q
o mf h 3w m$ & o' w b Js SSIUS No.: 5835 Accession f!o.: UNITED STATES 8008220269 f;UCLEAR REGULATORY COMMISSION IN 80 0FFICE OF INSPECTION AND ENFORCEMENT 'lASHINGTON, D.C.10555 November 7, 1980 IE Information Notice No.: 80-40: EXCESSIVE NIROGEN SUPPLY PRESSURE ACTUATES SAFETY-RELIEF VALVE OPERATION TO CAUSE REACTOR DEPRESSURIZATION -Description of Circumstances: On 0ctober 7 and 31, 1980, the-reactor coolant system was spuriously depres-surized at Boston Edison Comoany's Pilgrim Nuclear Power Station Unit No.1. The Pilgrim Staticn Unit i uses a GE BWR. The depressurizations resulted when excessive pressure.in the nitrecen suoply system caused the "A" Target Rock (TR) sefety-relief valve to open and remain open until the excessive supply pressure could be isolateo, pneumatic operator pressure ventec and the main steam system depressurizea sufficiently to allow tne 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 atnosphere control system (CACS). The CACS uses nitrogen for containment inerting. The succiy for the safety-relief valves is provided from the CACS through an ambient air vaporiter and then througn one of two parallel pressure regulators or a parallal bypass line. Shortly before the time of each event a new supply of liquid nitregen had been added to the storage tanks. At the time of the events the two pressure regulators were in service with the bypass closed. Nitregen cressure 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 pressura of the compressed air or nitrogen systems supplying the safety-relief valves is 90-110 psi. At a-pressure of 145 psi the solenoid valve may begin to leak since excessive pressure acts to unseat the disk. The suoply 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 increases, less instrument pressure is necessary to initiate-the pneumatic operator. Approximately 3 to 5 psi at the pneumatic operator is sufficient to initiate the safety-relief valve opening. 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 ocen 'as result of supply overpressure. It would
- appear that under such conditions of overpressure tht safety-relief valve openings would be sequential rather than simultaneous.
The particular solenoid actuator valves used with these two-stage safetyrelief valves are manufactured by TRC..Their design is such that excessive control pressure tends to unseat the solenoid. valve disk. The three-stage TR safety-relief or ASCO (Automatic-Switch Company).soiencid valves according to informatic)n frem GE. valves 'use either AVC0 (Automatic Valve Company The AVCc seleccid
-o Ifl 80 40 flovember 7, 1980 Page 2 of 2 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 leakace 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 t!RC 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 i terim, we expect that recipients will review the information for oossible applicability to their facilities, carticularly those with installations of the TR two-stage safety-relief valves. If you have cuestions regardino this ma'.ter.< please contact the Director of the acpropriate flRC Regional Office. O = --rr-17
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.1 m Ifl 80-40 flovember 7,1980 RECEilTLY ISSUED IE II:FORMATI0!! fl0TICES Information Cate of !!otice !!o. Subject Issue issued to 80-39 l'alfunctions Of Solenoid 10/31/30 All light water reactor Valves Manufactured Bv facilities holding Valcor Engineering Corporation power reactor OLs or cps 80-38 Cracking In Charging Pump 10/30/80 All PWR facilities Casing Cladding with an OL or CP 80-37 Containment cooler leaks 10/24/80 All nuclear power and reactor cavity -facilities holding flooding at Incian Point pcwer reactor OLs Unit 2 or cps 80-36 Failure of Steam 10/10/80 All nuclear power Generator Support Bolting reactor facilities holding power reactor e Ols or cps 80-35 Leaking and disloeged 10/10/80 All categories G and Icdine-124 implant seeds G1 mecical licensees 80-3a Coron dilution of reacter 9/26/80 All pressurized water ccolant during staam reactor facilities generator decontamination holding power reactor OLs 80-33 Cetermination of teletherapy 9/15/S0 All teletherapy timer accuracy (G3) licensees 80-32 Clarification of certain ~'12/G0 All flRC and agreement requirements for Exclu-state itcensees sive-use shipments of radioactive materials 80-31 Maloperation of Gould-8/27/80 All light water reactor Brown Boveri Type 480 facilities holding OLs volt type K-600s and or cps K-00!! 6005 circuit breakers
- Operating Licenses or Construction Permits
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