ML20002C085
| ML20002C085 | |
| Person / Time | |
|---|---|
| Site: | Marble Hill |
| Issue date: | 11/07/1980 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Shields S PSI ENERGY, INC. A/K/A PUBLIC SERVICE CO. OF INDIANA |
| References | |
| NUDOCS 8101090090 | |
| Download: ML20002C085 (2) | |
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'o, UNITED STATES E".#
NUCLEAR REGULATORY COMMISSION REGION lil
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v November 7, 1980 Those on Attached Address Listing:
This IE Information Notice No. 80-40 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 this office.
Sincerely,
--- Q).
y m
y ames G. Keppler Director
Enclosure:
IE Information Notice No. 80-40 cc w/ encl:
Mr. D. W. Kane, Sargent & Lundy Mr. Gary N. Wright, Chief Division of Nuclear Safety Reproduction Unit NRC 20b i
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8101090090 Q
.e RIII's CORPORATE ADDRESSES FOR OPERATING LICENSEES AND CONSTRUCTION PERMIT HOLDERS (BWR's end PWR's)
Docket No. 50-263 Docket No. 50-282 Docket No. 50-306 L!
Northern States Power Company
.~i ATTN:
Mr. Dennis E. Gilberts Vice President
,'?.Il Power Production and System C'1 Operation
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414 Nicollet Mall 0;
n3 Minneapolis, MN 55401 28 cc w/ encl:
Mr. W. A. Shamla, Resident Inspectors, RIII Plant Manager PDR Mr. F. P. Tierney, Jr.,
Local PDR Plant Manager NSIC Central Files TIC Director, NRR/DPM John W. Ferman, Ph.D.,
Director, NRR/ DOR Nuclear Engineer, MPCA AEOD Docket No. 50-546 Docket No. 50-547 Public Service of Indiana ATTN:
Mr. S. W. Shields Senior Vice President Nuclear Division Post Office Box 190 New Washington, IN 47162 cc w/ enc 1:
Mr.
teve J. Brewer-Nuclear TIC fety and Licensing Supervisor LeBoeuf, Lamb, Leiby & MacRae tral Files Mr. Dave Martin, Office of the i
irector, NRR/DPM Attorney General Director, NRR/ DOR Mr. John R. Galloway, Staff l
PDR Director, Environment, Energy Local PDR and Natural Resources Subcommittee NSIC I
i
S!!NS No.:
6835 UNITED STATES Accession No.:
NUCLEAR REGULATORY COMMISSION 8008220269 o
IN 80 0FFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C. 20555 November 7, 1980 IE Information Notice No. : 80-40:
EXCESSIVE NIROGEN SUPPLY PRESSURE ACTUATE 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 nitrogen and not a failure of the TR safety relief valve to function as designed j
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 i
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.
time of the events the two pressure regulators were in service with the bypass At the closed.
Nitrogen pressure supplying the valves increased to This may have been caused by liquid nitrogen reaching the pressure regulators 160 - 165 psi.
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 pressur,e 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 s' The particular solenoid actuator valves ust valves are manufactured by TRC.
Their des-DUPLICATE DOCUMENT pressure tends to unseat the solenoid valve valves use either AVC0 (Automatic Valve Cor Entire document previously Company) solenoid valves according to info entered into system under:
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