ML19340E195
| ML19340E195 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point, Palisades File:Consumers Energy icon.png |
| Issue date: | 11/07/1980 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Dewitt R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| References | |
| NUDOCS 8101060628 | |
| Download: ML19340E195 (2) | |
Text
d(Secoq'o s
UZlTED STATES
, g,7-NUCLEAR REGULATORY COMMISSION 3k, I]g* 'f REGION 111 g
799 ROOSEVELT ROAD c'
CLEN ELLYN ILLINOIS 6o137
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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 requec'.ed 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,
., _ ~_ _ t 0 James G. Keppler v Director
Enclosure:
IE Information Notice No. 80-40 cc w/ enc 1:
Mr. D. W. Kane, Sargent & Lundy Mr. Gary N. Wright, Chief Division of Nuclear Safety Reproduction Unit NRC 20b 01000&&
RIII's CORPORATE ADDRESSES FOR OPERATING LICENSEES AND CONSTRUCTION PERMIT HOLDERS (BWR's and PWR's)
Docket No. 50-440 Docket No. 50-441 h5 The Cleveland Electric Illuminating r-Company C2 ATTN:
Mr. Dalwyn R. Davidson Vice President - Engineering L;. ]
- 71; P. O. Box 5000.
Cleveland, OH 44101 7
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.-i
^3 u
E cc w/ enc 1:
0; n3 Central Files Director, NRR/DPM Director, NRR/ DOR PDR Local PDR NSIC TIC Harold W. Kohn, Power Siting Commission Mr. Daniel D. Wilt, Attorney Helen Evans, State of Ohio Docket No. 50-155 Docket No. 50-255 Consumers Power Company ATTN:
Mr. R. B. DeWitt Vice President Nuclear Operations 212 West Michigan Avenue Jackson, MI 49201 cc w/ encl:
Mr. D. P. Hoffman, Nuclear Resident Inspectors, RIII Licensing Administrator PDR Mr. C. J. Hartman, Local PDR P1 at Superintendent NSIC Mr
. W. Montross, Manager TIC ral Files Ronald Callen, Michigan Director, NRR/DPM Public Service Commission Director, NRR/ DOR Myron M. Cherry, Chicago j
AEOD l
1
SSINS No.:
6835 Accession No..
UNITED STATES 8008220269 NUCLEAR REGULATORY COMMISSION IN 80 0FFICE OF IN:PECTION AND ENFORCEMENT WASHIhGTON, D.C. 20555 November 7, 1980 IE Information Notice No.: 80-40:
EXCESSIVE NIR0 GEN 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 I 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 ar.d 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 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 pneumatic operator of the safety-relief valve.
l 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 i
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 l
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 l
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 sf 7.........-_
The particular solenoid actuator valves use DUPLICATE DOCUMENT valves are manufactured by TRC. Their des-pressure tends to unseat the solenoid valva Entire document previously valves use either AVC0 (Automatic Valve Cor Company) solenoid valves according to infoi entered into system under:
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ANO $00cb7.2, c 2_(A No. of pages:
30