ML18100B129
| ML18100B129 | |
| Person / Time | |
|---|---|
| Site: | Salem  |
| Issue date: | 06/08/1994 |
| From: | Stone J Office of Nuclear Reactor Regulation |
| To: | Miltenberger S Public Service Enterprise Group |
| Shared Package | |
| ML18100B131 | List: |
| References | |
| NUDOCS 9406210114 | |
| Download: ML18100B129 (10) | |
Text
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- Docket No. 50-272 Mr. Steven E. Miltenberger Vice President and Chief Nuclear Officer Public Service Electric & Gas Company Post Office Box 236 Hancocks Bridge, New Jersey 08038
Dear Mr. Miltenberger:
June 8, 1994 e
SUBJECT:
INTERNATIONAL NUCLEAR EVENT SCALE EVENT REPORTING FORM The Nuclear Regulatory Commission (NRC) is forwarding the International Nuclear Event Scale (INES) Event Reporting Form that was disseminated regarding your recent declaration of an Alert at the Salem Nuclear Generating Station, Unit 1, on April 7, 1994.
The event involved a reactor trip and two safety injections, and was initiated by excessive marsh grass/debris causing some circulating water pumps to trip.
The NRC participates in the INES in a limited way, as was communicated to you through Generic Letter 92-09, issued on December 31, 1992.
As stated in the Generic Letter, the INES rating is not intended to affect emergency classifications, event reporting to the NRC, or communications with the public.
Because usage of the INES could lead to confusion with the existing four-level emergency response scale used in the United States, the NRC delays the INES rating for at least one week after the event is terminated.
The NRC evaluates every event classified as an Alert or higher on the U.S. emergency response scale for its INES applicability.
An INES Event Rating Form is then prepared utilizing available documentation pertaining to the event.
Not every Alert (or higher) will necessarily receive an INES classification, as some may be rated "out of scale".
In this case, the event was classified as "Level 1".
A copy of the rating form is enclosed.
The NRC does not request a review or concurrence with the INES classification nor is any response requested. If standard questions exist, please contact me at (301) 504-1419.
,i---.-94062-101-14-940608 - ----~
PDR ADOCK 05000272 p
- ... PDR. __
Enclosure:
Event Reporting Form cc w/enclosure:
See next pag1e DISTRIBUTION w/enclosure:
See Page OFFICE LA: PDI-PM:PDI-2 NAME DATE Sincerely,
/S/
James C. Stone, Senior Project Manager Project Directorate I-2 Division of Reactor Projects Office of Nuclear Reactor Regulation COPY D:PDI-2 CMILLER 94 I
pV1 ~ t/
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 June 8, 1994 Mr. Steven E. Miltenberger Vice President and Chief Nuclear Officer Public Service Electric & Gas Company Post Office Box 236 Hancocks Bridge, New Jersey 08038
Dear Mr. Miltenberger:
SUBJECT:
INTERNATIONAL NUCLEAR EVENT SCALE EVENT REPORTING FORM The Nuclear Regulatory Commission (NRC} is forwarding the International Nuclear Event Scale (INES} Event Reporting Form that was disseminated regarding your recent declaration of an Alert at the Salem Nuclear Generating Station, Unit 1, on April 7, 1994.
The event involved a reactor trip and two safety injections, and was initiated by excessive marsh grass/debris causing some circulating water pumps to trip.
The NRC participates in the INES in a limited way, as was communicated to you through Generic Letter 92-09, issued on December 31, 1992.
As stated in the Generic Letter, the INES rating is not intended to affect emergency classifications, event reporting to the NRC, or communications with the public. Because usage of the INES could lead to confusion with the existing four-level emergency response scale used in the United States, the NRC delays the INES rating for at least one week after the event is terminated.
The NRC evaluates every event classified as an Alert or higher on the U.S. emergency response scale for its INES applicability.
An INES Event Rating Form is then prepared utilizing available documentation pertaining to the event.
Not every Alert (or higher} will necessarily receive an INES classification, as some may be rated "out of scale".
In this case, the event was classified as "Level 1".
A copy of the rating form is enclosed.
The NRC does not request a review or concurrence with the INES classification nor is any response requested. If standard questions exist, please contact me at (301} 504-1419.
Enclosure:
Event Reporting Form cc w/enclosure:
See next page Sincerely,
~ck James C. Stone, Senior Project Managei Project Directorate 1-2 Division of Reactor Projects Office of Nuclear Reactor Regulation
J Mr. Steven E. Miltenberger Public Service Electric & Gas Company cc:
Mark J. Wetterhahn, Esquire Winston & Strawn 1400 L Street NW Washington, DC 20005-3502 Richard Fryling, Jr., Esquire Law Department - Tower SE 80 Park Place Newark, NJ 07101 Mr. Calvin A. Vondra General Manager - Salem Operations Salem Generating Station P.O. Box 236 Hancocks Bridge, NJ 08038 Mr. J. Hagan Vice President - Nuclear Operations Nuclear Department P.O. Box 236 Hancocks Bridge, New Jersey 08038 Mr. Charles S. Marschall, Senior Resident Inspector Salem Generating Station U.S. Nuclear Regulatory Conuniss_ion Drawer I Hancocks Bridge, NJ 08038 Dr. Jill Lipoti, Asst. Director Radiation Protection Programs NJ Department of Environmental Protection and Energy
- CN 415 Trenton, NJ 08625-0415 Maryland People's Counsel American Building, 9th Floor 231 East Baltimore Street Baltimore, Maryland 21202 Mr. J. T. Robb, Director Joint Owners Affairs PECO Energy Company 955 Chesterbrook Blvd., SlA-13 Wayne, PA 19087 Mr. S. LaBruna Vice President - Nuclear Engineering Nuclear Department P.O. Box 236 Hancocks Bridge, New Jersey 08038 Salem Nuclear Generating Station, Units 1 and 2 Richard Hartung Electric Service Evaluation Board of Regulatory Commissioners 2 Gateway Center, Tenth Floor Newark, NJ 07102 Regional Administrator, Region I U. S. Nuclear Regulatory Commission 475 Allendale Road King of Prussia, PA 19406 Lower Alloways Creek Township c/o Mary 0. Henderson, Clerk Municipal Building, P.O. Box 157 Hancocks Bridge, NJ 08038 Mr. Frank X. Thomson, Jr., Manager Licensing and Regulation Nuclear Department P.O. Box 236 Hancocks Bridge, NJ 08038 Mr. David Wersan Assistant Consumer Advocate Office of Consumer Advocate 1425 Strawberry Square Harrisburg, PA 17120 Ms. P. J. Curham MGR. Joint*Generation Department Atlantic Electric Company P.O. Box 1500 6801 Black Horse Pike Pleasantville, NJ 08232 Carl D. Schaefer External Operations - Nuclear Delmarva Power & Light Company P.O. Box 231 Wilmington, DE 19899 Public Service Commission of MD Engineering Division Chief Engineer 6 St. Paul Centre Baltimore, MD 21202-6806
e DISTRIBUTION w/enclosure:
Docket File NRC.& Local PDRs DCS AEOD R/F ELJordan DFRoss DOA R/F IRB R/F KBrockman JMacKinnon TMcGinty BHuf fman PDI-2 Rdg.
SVarga JCalvo CMil l er MO' Brien JStone OGC ACRS(IO)
EWenzinger, RGN-I JWhite, RGN-I
Mr. Bernard Thomas INES Coord;nator Division of Nuclear Safety Internat;onal Atomic Energy Agency Wagramerstrasse 5 P.O. Box 100 A-1400 v;enna Austr;a
Dear Mr. Thomas:
ENCLOSURE.
MAY 3 1 1994 Enclosed is a completed Event Rating Form for an event at Salem, Unit 1.
The event involved a plant trans;ent, which was ;nitiated by excess;ve marsh grass/debris in the Delaware river causing some circulating water pumps to trip off. The transient ;ncluded an automatic reactor tr;p and two safety injections, with some additional complications. The event was cons;dered to be a "Level l" based on the gu;dance contained in Part III of the INES User's Manual.
Enclosure:
INES Rating Form 940621oi23 940608 _____ \\
PDR ADOCK 05000272 P
... PDR Sincerely,
- ~~~i.,
Ken E. Brockman, Chief Incident Response Branch Division of Operational Assessment Office for Analysis and Evaluation of Operational Data
IN.fERN~flONAl NUCLEAR E'IE~rr SCJ.\\lE (l~IESl EVEN*r R~f J~IG FOR1'A To be-sent to: ~EA. Wagramerstrasse 5, P.O. Box U>O, A-1.400, Vlema, Austria TELEX: 1-12645, cable: INATOM Vienna. Facsimile: 43-1-2309723, Telephone: 43-1-2360-268!
EVENT PLANT TRANSIENT INITIALLY CAUSED BY THE LOSS OF CIRCULATING EVENT DATE TITLE WATER PUMPS DUE TO HIGH MARSH GRASS/DEBRIS CONCENTRATIONS 04/07/94 RATING IAl1N9 OUfO#
IBOW ONICMI DRllADAllON Of DEFENSE IH>B'lll x DAii ICA&I tcA&I ro SAlllY IPICJ\\90NAL C 112ri1,r11*r1 AnBUll x I I I I I I ON-SIE lloWCI' flNM ti 05/16/94 Olf-!llE MIA.Cl' COUNTRY FACIUTY FACIUTY 1106 Mw(e)
USA NAME
~AT.F.M 1 TYPE PWR ASPECTS OF SIGNIACANCE TO THE PUBLIC:
VES NO ACCIDENT 0 INCIDENT lTI DEVIATION D RADIOACTIVE RELEASES OFF-SITE D
[Kl RADIOACTIVE RElEASES ON-SITE D
[))
WORKERS INJURED BY RADIATION D
[Kl WORKERS INJURED PHYSICALLY D
m PlANT SAFETY IS UNDER CONTROL 00 D
THE EVENT REPORTED IS A DISCOVERY OF A DEFICIENCY D
111 BY ROUTINE SURVEILLANCE A PRESS RELEASE WAS MADE (IF YES, PLEASE ATTACH IT)
D 111 A SHORT DESCRIPTION OF THE EVENT:
Salem Unit 1 was operating at 73% power when excessive marsh grass/debris in the Delaware river caused some of the main condenser circulating water pumps to trip off due to high differential pressure.
Operators manually initiated a power reduction to 7% power which, upon going below 10%,
automaticall~
re-instated the low power trip setpoints of 25%.
The operator subsequently withdrew rods to restore RCS (reactor coolant system) temperature to its normal band.
This resulted in a power increase to 25% and an automatic reactor trip.
Immediately thereafter, an automatic safety injection occurred on a high steam flow coincident with low RCS temperature signal.
The steam line high steam flow bistables actuated on a short (continued on next oaael MAW Ken E. Brockman.r>lf. -: // J!.~~"___.---
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duration pressure pulse which was generated when the turbine stop valves closed in response to the reactor trip.
The pressure pulse was not of sufficient duration to actuate both trains of the safety injection logic.
As a result, several automatic actions associated with a full safety injection did not occur, including:
-two of the four main steam isolation valves failed to close
-the main feedwater isolation valves failed to close
-the main feed pumps failed to trip Operators manually completed these actions.
A second safety injection later occurred on low pressurizer pressure.
The pressure reduction was due to the cooldown of the RCS when two steam generator safety relief valves lifted.
The two safety injections resulted in the pressurizer filling, and discharging to the PRT (pressurizer relief tank) via the power operated relief valves.
The PRT rupture disc blew, as designed, to prevent overpressurization of the tank.
Essentially no water was discharged from the PRT due to the blown rupture disc.
Operators subsequently re-established the pressurizer bubble and performed an orderly cooldown of the plant to Cold Shutdown.
The unit has remained shutdown for repairs while the event was being investigated, and is preparing for restart.
Basis for INES Rating of the Salem Unit I Alert on 4/7/94 BACKGROUND:
Salem Unit I was operating at 73% power (power was reduced at both Units due to high concentrations of marsh grass/debris in the Delaware River) when some circulating water pumps were lost on high differential pressure.
Operators initiated a power reduction, eventually lowering reactor power to less than 10%.
This automatically re-instated the low power trip setpoints (25%).
Because reactor power was lowered at a faster rate than turbine power, operators then encountered a low RCS (reactor coolant system) temperature condition.
In response to RCS average temperature being below the program value, operators withdrew rods in order to restore RCS temperat~re.
Reactor power increased above the 251 1 ow power reactor trip setpoi nt, and an automatic reactor trip occurred. Innediately thereafter, an automatic safety injection signal on high steam flow coincident with low-low average temperature occurred. The steam line high steam flow bistables actuated on a short duration pressure pulse in the main steam lines, caused by the closure of the turbine stop valves in response to the reactor trip.
The pressure pulse was not of sufficient duration to actuate the "B" train safety injection logic and in fact, caused only a partial actuation of the "A" train safety injection logic.
Several automatic actions which normally occur as a result of a full safety injection signal did not complete due to differences in the response of the actuation circuitry to the short duration pressure pulse, including:
-2 of 4 MSIV's (main steam isolation valves) did not close
-the main feed pumps did not trip
-the main feedwater isolation valves did not close Operators took manual actions to complete these actions.
Upon resetting the safety injection signal per emergency procedures, decay heat and reactor coolant pump operation caused the RCS temperature to increase.
The increasing RCS temperature and safety injection charging flow resulted in the pressurizer filling to a solid condition. The pressurizer PORVs (power operated relief valves) cycled, as designed, to prevent overpressurization. The PORV's discharged to the PRT (pressurizer relief tank).
Continued discharge via the PORVs to the PRT caused the PRT rupture disc to blow.
The PRT reached a level of approximately 821, and only about a gallon of water was discharged (condensation) when the rupture disc ruptured.
Subsequently, two safety valves for the No. 11 steam generator lifted several times. The lifting of the steam generator safety valves caused RCS temperature and pressure to drop rapidly.
This resulted in a second automatic safety injection signal on low pressurizer pressure (due to the RCS cooldown associated with the lifting steam generator relief valves). Since the pressurizer was sol id at this time, The licensee declared a precautionary ALERT to ensure proper technical staff was available. Operators then re-established the pressurizer bubble, and initiated an orderly plant cooldown. The plant entered a cold shutdown condition about 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> after the initial event.
RATING BASIS:
The event is rated in accordance with the INES User's Manual under the defence in depth criteria. Per paragraph II I. 2. 2 of the Manua 1, the fo 11 owing potential initiators were identified:
- 1) The reactor trip at 25% power due to the lowered reactor protection system setpoints (startup protection) when the operator withdrew rods to restore RCS temperature.
- 2) The first safety injection (low Tavg with high steam flow)
- 3) The No. 11 steam generator safety valves cycling
- 4) The second safety injection (low pressurizer pressure caused by low Tavg, due to the steam generator safety valves that opened
- 5) The blowing of the PRT rupture disc on high pressure Utilizing the initiator frequency table (Appendix II I. a of the Manual), all of the initiators fall under the "expected" in the lifetime of the plant category. Considering the safety function availability, in accordance with paragraph III.2.3 of the Manual, there was full availability for each of the initiators at the time of the event. Thus, utilizing Table III.2 of the Manual, the event would be rated as a level 0.
Considering classification of the event without an actual initiator (Table III.I) also leads to a rating of level O.
While the "failure" of some of the components (MSIVs, main feed pump trips and feedwater isolation) to completely actuate is of concern, the reason for these "failures" is significant. The cause of the steam flow portion of the first safety injection signal was due to a pressure pulse generated by the turbine stop valves closing in response to the reactor trip. A "true" high steam flow condition due to a leak did not occur.
Also, the signal that was generated was of such a short duration that it was not picked up by both channels of the protection logic, resulting in a partial actuation. Subsequent testing showed that if a valid signal were to have been generated, it would have resulted in a complete actuation. Therefore, there was full safety function availability throughout the event, again yielding a rating of level 0.
Section III.5 of the User's Manual contains guidance for the consideration of additional factors. It provides for upgrading the rating by one level based on co11111on cause
- failures, procedural inadequacies and safety culture deficiencies.
As discussed above, some components did not complete their required actions for the first safety injection, although they would have functioned as designed had it been an actual high steam flow condition.
The operators have. since received guidance that if a partial safety injection (one channel) occurs, they are to complete the actuation by actuating the other channel.
The event is also being addressed from a procedural guidance standpoint. Clarification to provide better guidance under low power operating conditions is being provided. This is specifically related to the decision to withdraw rods to restore temperature, which ended up causing the automatic reactor trip because the high power setpoints had been lowered to reflect startup conditions.
Based on the combination of personnel errors and the contributing factors of equipment problems and inadequate procedural guidance, the event is upgraded one level to a "Level I" per Section 111.5 of the User's Manual.