ML19345C068
| ML19345C068 | |
| Person / Time | |
|---|---|
| Site: | Grand Gulf  |
| Issue date: | 11/07/1980 |
| From: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | Stampley N MISSISSIPPI POWER & LIGHT CO. |
| References | |
| NUDOCS 8012030829 | |
| Download: ML19345C068 (1) | |
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UNITED STATES
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NUCLEAR REGULATORY COMMISSION b
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Q 101 MARIETTA ST., N.W., SUIT E 3100 ATLANTA, GEORGIA 30303 NOV MC M
In Reply Refer To:
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.E/;j Mississippi Power and Light Company y
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-S Vice President of Production 0
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P. O. Box 1640 4
Jackson, MS 39205 Gentlemen:
This Information Notice is provided 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,
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James P. O'Reilly Director
Enclosures:
1.
IE Information Notice No. 80-40 2.
List of Recently Issued IE Information Notices cc w/ encl:
C. K. McCoy, Plant Manager f
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UNITED STATES NUCLEAR REGULATORY cot 9 FISSION OFFICE OF INSPECTION AND ENFORCEffENT WASHINGTON, D.C. 20555 November 7, 1980 IE Information Notice No.: 80-40: EXCESSIVE NIROGEN SUPPLY PRESSURE ACTUAT 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 1 uses a GE BWR. The depressurizations 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 two events involved a failure in the pressure regulation of the supply 3
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 th'e 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 a:ay 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.
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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 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 simulteneous.
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 t
i valves use either AVC0 (Automatic Valve Company) or ASCO (Automatic Switch Co'spany) solenoid valves according to information from GE. The AVCo solenoid
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IN 80-40 Navrebar 7, 1980 i.4-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 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 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, particular1y'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.
O 1
IN 80-40 Nsve bar 7, 1980
'j RECENTLY ISSUED IE INFORMATION NOTICES Information Date of Notice No.
Subject Issue Issued to 80-40 Excessive Nitrogen Supply 11/07/80 All nuclear power reactor Pressure Actuates Safety-facilities with an OL Relief Valve Operation to or CP Cause Reactor Depressuri-zation 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 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 Indian Point power 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 OLs or cps 80-35 Leaking and dislodged 10/10/80 All categories G and Iodine-124 implant seeds G1 medical licensees 80-34 Boron dilution of reactor 9/26/80 All pressurized water coolant during steam reactor facilities generator decontamination holding power reactor OLs 80-33 Determination of teletherapy 9/15/80 All teletherapy timer accuracy (G3) licensees 80-32 Clarification of certain 8/12/80 All NRC and agreement requirements for Exclu-state licensees 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-DON 600S circuit breakers
- Operating Licenses or Construction Fermits S