ML20030D252
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Gentlemen:
The enclosed Information Notice No. 81-25, "Open Equalizing Valve of Differential Pressure Transmitter Causes Reactor Scram and Loss of Redundant Safety Signals",
is forwarded to you for information.
No written response is required.
If you desire additional information regarding this matter, please contact this office.
Sincerely, e
B H. Grier Director
Enclosure:
IE Information Notice No. 81-25, with 2 attachments CONTACT:
D. L. Caphton (215-337-5287) i S
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8109010070 010824 DR ADOCK 05000003
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Attachm;nt 1 August 24, 1981 IN 81-25 EXTRACT FROM NSSS INFORMATION LETTER The NSSS recommends that licensees consider for implementation the following various means for controlling critical dp sensor instrumentation equalizing valves:
1.
Installed dp instrumentation equalizing valves may be removed and the low and high side pipe stubs capped (see note below).
Such removal will prevent equalizing valving errors and also prevent sensor errors due to installed, leaky equalizing valves.
This is, however, not feasible where valve block assemblies are in use.
2.
Installed dp instrumentation equalizing valves may be closed in a positive manner by permanently locking the valves in the closed position or by closing the valves and removing the valve wheels and extended portions cf the valve stems, etc.
NOTE:
For Items 1 and 2 above any function of the equalizing valves can be performed by equalizing valves mounted on calibration systems or devices which are disconnected for normal operation.
3.
Root, vent, drain and equalizing valve handles may be painted different colors, and the color included in cali.bration and line up verification checks.
4.
After normal checklists are complete, an independent supervisory check may be performed and then valves may be wire and lead sealed in position.
5.
Procedures may include a supervisory comparison of the dp instrument reading taken just prior to surveillance testing / calibration and just after signoff and channel restoration.
The final reading should only differ from the initial reading due to calibration or a change in plant operating conditions.
6.
A periodic check may be made of dp instrumentation to detect wara instru-ment lines (for instruments connected to systems at high temperatures).
A warm instrument line would indicate significant leakage or an open equalizing valve.
Attachm:nt 2 IN 81-25 August 24, 1981 RECENTLY ISSUED IE INFORMATION NOTICES Information Subject Date Issued to Notice No.
Issued 81-24 Auxiliary Feed Pump 8/5/81 All holders of a Turbine Bearing power reactor Failures OL or CP 81-23 Fuel Asse:noly Damaged 8/4/81 All holders of a due to Improper power reactor Positioning of Handling OL or CP Equipment 81-22 Section 235 and 236 7/31/81 All power and research Amendments to the reactors holding an OL Atomic Energy Act or CP, all fuel fabrication of 1954 and reprocessing and spent fuel storage licensees and applicants 81-21 Potential Loss of 7/21/81 All holders of a Direct Access to power reactor Ultimate Heat Sink OL or CP 81-20 Test Failures of Elec-7/13/81 All holders of a trical Penetration power reactor Assemblies OL or CP 81-19 Lost Parts in Primary 7/6/81 All holders of a Coolant System power reactor OL or CP 81-18 Excessive Radiation 6/23/81 Specified licensees Exposures to the Fingers holding Byproduct l
of Three Individuals licenses Incurred During Cleaning and Wipe Testing of Radioactive Sealed Sources at a Sealed-Source Manufacturing Facility 81-16 Control Rod Drive 4/23/81 All holders of a BWR System Malfunctions power reactor OL or CP l
81-15 Degradation of Auto-4/22/81 All holders of a matic ECCS Actuation power reactor l
Capability by Isolation OL or CP l
of Instrument Lines i
LIST OF HOLDERS OF NUCLEAR POWER REACTOR OPERATING LICENSES AND CONSTRUCTION PERMITS RECEIVING IE INFORMATION NOTICE NO. 81-25 Baltimore Gas and Electric Company Docket Nos. 50-317 ATTN:
Mr. A. E. Lundvall, Jr.
50-318 i
Vice President, Supply i
P. O. Box 1475 Baltimore, Maryland 21203 Boston Edisor.
mpany M/C Nuclear Docket No. 50-293 ATTM:
Mr. A. V. Morisi Nuclear Operations Support Manager 800 Boylston Street Boston, Massachusetts 02199 4
Connecticut Yankee Atomic Power Company Docket No. 50-213 ATTN:
Mr. W. G. Counsil Vice President - Nuclear Engineering and Operations P. O. Box 270 Hartford, Connecticut 06101 Consolidated Edison Company of Docket Nos. 50-03 New York, Inc.
50-247 ATTN:
Mr. John D. O'Toole Vice President - Nuclear Engineering and Quality Assurance 4 Irving Place New York, New York 10003 Duquesne Light Company Docket No. 50-334 ATTN:
Mr. J. J. Carey Vice President i
Nuclear Division P. O. Box 4 Shippingport, Pennsylvania 15077 l
Jersey Central Power and Light Company Docket No. 50-219 i
ATTN:
Mr. Philip R. Clark I
Vice President - Nuclear GPU Nuclear 100 Interpace Parkway Parsippany, New Jersey 07054 i
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2 l
Maine Yankee Atomic Power Company Docket No. 50-309 ATTN: Mr. Robert H. Groce Senior Engineer-Licensing 1671 Worcester Road Framingham, Massachusetts 01701 Metropolitan Edison Company Docket No. 50-289 ATTN:
Mr. H. D. Hukill Vice President and Director of TMI-l i
P. O. Box 480 Middletown, Pennsylvania *17057 Metropolitan Edison Company Docket No. 50-320 ATTN:
Mr. G. K. Hovey Vice President and Director of TMI-2 P. O. Box 480 Middletown, Pennsylvania 17057 Niagara Mohawk Power Corporation Docket No. 50-220 ATTN:
Mr. T. E. Lempges Vice President Nuclear Generation 300 Erie Boulevard West Syracuse, New York 13202 Northeast Nuclear Energy Company Docket Nos. 50-336 ATTN: Mr. W. G. Counsil 50-245 Senior Vice President - Nuclear 50-423 Engineering and Operations Group P. O. Box 270 Hartford, Connecticut 06101 Philadelphia Electric Company Docket Nos. 50-277 ATTN:
Mr. S. L. Daltroff 50-278 Vice President Electric Production 2301 Market Street Philadelphia, Pennsylvania 19101 Power Authority of the State of New York Occket No. 50-286 Indian Point 3 Nuclear Power Plant ATTN:
Mr. J. C. Brons Resident Manager P. O. Box 215 Buchanan, New York 10511
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3 Power Authority of the State of New York Docket No. 50-333 James A. FitzPatrick Nuclear Power Plant ATTN: Mr. R. J. Pasternak Resident Manager P. C. Box 41 Lycoming, New York 13093 Public Service Elactric and Gas Company Docket Nos. 50-272 ATTN: Mr. F. W. Schneider 50-311 Vice President - Production 80 Park Plaza - 15A Newark, New Jersey 07101 Rochester Gas and Electric Corporation Docket No. 50-244 ATTN:
Mr. John E. Maier Vice President Electric and Steam Production 89 East Avenue Rochester, New York 14649 Vermont Yankee Nuclear Power Corporation Docket No. 50-271 ATTN: Mr. Robert 1. Smith Licensing Engineer 1671 Worcester Road Framingham, Massachusetts 01701 Yankee Atomic Electric Company Docket No. 50-29 ATTN:
Mr. James A. Kay Senior Engineer-Licensing 1671 Worcester Road Framingham, Massachusetts 01701 Duquesne Light Company Docket No. 50-412 ATTN:
Mr. E. J. Woolever Vice President 135 Sixth Avenue Pittsburgh, Pennsylvania 15219 Jersey Central Power & Light Company Docket No. 50-363 ATTN: Mr. J. T. Carroll Acting Director Oyster Creek Nuclear Generating Station P. O. Box 388 Forked River, New Jersey 08731 Long Island Lighting Company Docket No. 50-322 ATTN:
Mr. M. S. Pollock Vice President - Nuclear 175 East Old Country Road Hicksville, New York 11801 i
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4 Niagara Mohawk Power Corporation Docket No. 50-410 ATTN:
Mr. Gerald K. Rhode Vice President System Project Management c/o Miss Catherine R. Seibert 300 Erie Boulevard, West Syracuse, NY 13202 Pennsylvania Power & Light Company Docket Nos. 50-387 ATTN:
Mr. Norman W. Curtis 50-388 Vice President Engineering and Construction - Nuclear 2 North Ninth Street Allentown, Pennsylvania 18101 Philadelphia Electric Company Docket Nos. 50-352 ATTN:
Mr. John S. Kemper 50-353 Vice President Engineering and Research 2301 Market Street Philadelphia, Pennsylvania 19101 Public Service Electric & Gas Company Docket Nos. 50-354 ATTN: Mr. T. J. Martin 50-355 Vice President Engineering and Construction 80 Park Plaza - 17C Newark, New Jersey 07101 Public Service Company of New Hampshire Docket Nos. 50-443 ATTN:
Mr. W. C. Tallman 50-444 Chairman and Chief Executive Officer 1000 Elm Street Manchester, New Hampshire 03105
SSINS No.:
6835 Accession No.:
81033 0-IN M5
UNITED STATES f
p NUCLEAR REGULATORY COMMISSION 0FFICE OF INSPECTION AND ENFORCEMENT T
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August 24, 1981
.kJ IE INFORMATION NOTICE NO. 81-25:
OPEN EQUALIZING VALVE OF DIFr M SURE TRANSMITTER CAUSES REACTOR SCRAM S OF REDUNDANT SAFETY SIGNALS Descriotion of Circumstances:
On March 13, 1981, the Tennessee Valley Authority reported to the NRC that a scram occurred at the Browns Ferry Unit 2 facility as a result of an open equalizing valve used with the lower wide-range Yarway water level transmitter.
Equalizing valves, which are closed during normal plant operation, are used to conduct instrument calibrations and to prevent over-ranging the transt.itter during instrument isolation valve manipulations. With the plant operating at normal full recirculation flow conditions, there is no clear indication that this equalizing valve is open.
However, once recirculation i'ow is decreased, the reference leg will drain, causing erroneous delta pressure (dp) input signals to other transmitters connected to.the same reference water column.
This affects a large number of safety and control systems that use water level as an input. A review of the event showed that under reduced flow conditions the false high water level signals led to loss of redundancy in the logic for initiating safety functions, as well as initiation of a turbine trip which caused the reactor to scram.
Safety syster.: dp transmitters that could be affected by the drained reference leg provided water level input signals to the logic circuits for the following functions:
primary containment isolation, low water level scram protection, automatic depressurization system conf;rmatcry low rater level, and high water level trip signal for high pressure coolant injection and reactor core isolation cooling.
In addition, a large number of control functions can be affected, either directly or indirectly, by the drained reference leg.
Under normal operating conditions with full recirculation flow, the operator would be unaware of the abnormal position of the equalizing valve because the lower wide-range Yarway transmitter, which was byparsad by the open equalizing valve and the affected safety syM.em transmitters, wouid continue to provide signals to the control vocm instrumentation that appear normal.
The lower wide range Yarway tranimitter is designed to provide accurate water level o
signals only for accident conditions when there is no jet pump flow. With full recirculation flow, this transmitter reads full scale (high water level) whether or not the equalizer valve is open because the variable leg is g ;g conditions, the common reference las for the safety system dp transmitters t.a connected near the high pressure outlet section of the jet pump.
Under these,j 7
identified above will not drain.
Therefore, even if the equalizing valve is open, these trcnsmitters also provide normal signals when there is full recirculation flow.
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IN 81-25 August 24, 1981 Page 2 of 2 During the event at Browns Ferry Unit 2 on March 13, 1981, the abnormal condition became apparent to the operator when the recirculation flow rate was being reduced as part of a planned reactor shutdown.
Reactor power had been reduced from 100%
to 54% over the previous 45 minutes.
As the recirculation flow was reduced, the pressure across the jet pump diffuser changed so that at lower flow rates the driving force across the equalizing valve reversed, causing the reference leg to have a higher relative pressure.
Higher pressure on the reference leg, coupled with an open equalizing valve, caused the water in the reference leg to drain into the variable leg water column.
This caused all level transmitters connected to the affected reference leg to indicate higher-than-actual water level.
The false indication of high water level caused the feedwater control valve to close and caused a turbine trip.
The turbine trip caused the reactor to scram.
It is unknown when the lower wide-range transmitter equalizing valve was opened.
However, thirty-six hours prior to the scram, a surveillance test was performed on the unit.
Similiar problems have occurred previously and, in July 1980, the nuclear steam system supplier (NSSS) prepared an information letter that delineates similar safety concerns with respect to the control of differential pressure transmitter equalizing valves.
This information letter provides recommendations to alleviate :he chronic problem of open equalizing valves. An extract of the NSSS recommended actions is attached for information.
I This information notice is provided as notification of a possible significant matter.
It is expected that recipients will review the information for applicability to their facilities.
No specific action or response to this information is required at this time.
If you have questions regarding this matter, please contact the Director of the appropriate NRC Regional Office.
Attachments:
1.
Extract from NSSS Information Letter 2.
Recently issued IE Information Notices
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