ML18100B239
| ML18100B239 | |
| Person / Time | |
|---|---|
| Site: | Salem  |
| Issue date: | 07/27/1994 |
| From: | Labruna S Public Service Enterprise Group |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NLR-N94122, NUDOCS 9408040402 | |
| Download: ML18100B239 (4) | |
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Public Service Electric and Gas Company I
Stanley LaBruna Public Service Electric and Gas' Company P.O. Box 236, Hancocks Bridge, NJ 08038 609-339-1700 Vice President - Nuclear Engineering JUL 2 '7 1994 NLR-N94122 United States Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 Gentlemen:
10CFR21 NOTIFICATION, HIGH STEAM LINE FLOW SI INSTRUMENTATION -
SIGNAL SUMMATORS PM-505B & 506B SALEM GENERATING STATION UNIT NOS. 1 AND 2 DOCKET NOS. 50-272 AND 50-311 Pursuant to the notification requirements of 10CFR21, Public Service Electric and Gas Co. {PSE&G) hereby provides the attacheq report concerning a deficiency in signal summators 505B & 506B which provide the setpoint signal to high steam line flow comparators that initiate Safety Injection on High Steam Line Flow coincident with Low-Low Tave. or Low Steam Line Pressure.
This deficiency was reported to the NRC Operations Center on June 30, 1994.
If there are any questions regarding the information provided in, please contact us.
Attachment
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9408040402 940727 PDR ADOCK 05000272 S
PDR Sincerely,
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Document Control Desk NLR-N94122 2
C Mr. T. T. Martin, Administrator - Region I
- u. s. Nuclear Regulatory Commission 475 Allendale Road King of Prussia, PA 19406 Mr.
~- c. Stone, Licensing Project Manager -
Salem U. S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Rockville, MD 20852 Mr. c. Marschall (S09)
USNRC Senior Resident Inspector Mr. K. Tosch, Manager, IV NJ Department of Environmental Protection Division of Environmental Quality Bureau of Nuclear Engineering CN 415 Trenton, NJ 08625 JUL 2 7 1994
NLR-N94122 ATTACHMENT 1 Introduction The following is a summary of the results of PSE&G'S evaluation in accordance with 10CFR21 concerning a deficiency in signal summators PM-505B and PM-506B.
These signal summators were found to saturate high when the summators lose power and are then reenergized.
These signal summators provide the setpoint signal to high steam line flow comparators that generate the high steam line flow Safety Injection (SI) signal to Reactor Protection System Trains A and B.
SI actuation occurs as a result of high steam line flow coincident with Low-Low Tave or Low Steam Line Pressure.
Background
Due to the recent spurious SI event on April 7, 1994, testing of signal summators PM-505B and 506B was initiated to determine if, on reactor trip, the signal summators setpoint would undershoot below the 40% steam flow setpoint. It was believed that the undershooting of the setpoint may have been a contributor to the inadvertent SI event on April 7 which was initiated on High Steam Line Flow coincident with Low-Low Tave.
During this testing, it was identified that should the signal summators lose power, upon reenergizing, the summators setpoint output would saturate high.
Technical Specifications define the High Steam Line Flow setpoint at 110%, and following a reactor trip, the setpoint is automatically reduced to 40%.
As a result of the setpoint output saturating to a setpoint significantly greater than the setpoint limit allowed by Technical Specifications, a high steam line flow SI signal would not be generated by the flow comparators.
The period of time that the summators would saturate high following a loss of power and subsequent reenergizing has not been estimated.
The summators are powered from independent vital instrument busses (uninterruptable power supplies) and inverters.
Safety Evaluation Each vital instrument bus and its inverter are required to be operable in accordance with Technical Specification 3.8.2.1 during Modes 1-4.
Upon a loss of normal AC power to a vital instrument bus (i.e., LOP), the inverter is designed to transfer to the vital DC power supply with no significant interruption in power to the bus loads.
Should an inverter failure occur such Page 1 of 2
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NLR-N94122 ATTACHMENT 1 (Cont'd) that power is lost and not restored, the affected protection channel fails in the safe position satisfying.the High Steam Flow coincidence logic.
However, shoulq an inverter failure or power transient occur to the summator power supply, with power subsequently restored, the signal summator would saturate which would render the summator inoperable.
Assuming that saturation of the signal summator pre-exists, in.the event of a design basis accident that would require the initi'ation of a SI signal on High Steam Flow coincident with either Low-Low Tave or Low Steam Line Pressure (e.g., Main Steam Line Break), this reactor protective function could be lost considering a single active failure in the remaining operable instrument channel.
Therefore, PSE&G has concluded that this deficiency is reportable in accordance with 10CFR21.
Corrective Actions
.Prior to restart of Salem Unit 1 following the April 7 event, design changes had been implemented to correct this deficiency.
Following identification of this deficiency, an Engineering Evaluation (EE) and supporting 10CFRS0.59 safety evaluation were completed to demonstrate that the High Steam Line Flow SI signal channels to the Reactor.Protection System were fully functional and operable.
The EE and safety evaluation concluded that Unit 2 could continue to operate safely until the next refueling outage or forced outage of sufficient duration to implement a design change similar to Unit 1.
While Unit 2 was shutdown recently to allow dredging at the Circulating Water Intake Structure, PSE&G corrected the saturation deficiency with a design change similar to that previously implemented on Unit 1.
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