ML18100A380

LER 93-006-00:on 930415,unexpected Train a SI Sys Signal Occurred Due to Steam Line Differential Pressure.Caused by Operating Characteristics of Error Inhibit Switch.Procedures Re Manipulation of Switches reviewed.W/930514 Ltr

ML18100A380
Person / Time
Site:	Salem
Issue date:	05/13/1993
From:	Pastva M, Vondra C Public Service Enterprise Group
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-93-006-01, LER-93-6-1, NUDOCS 9305210251
Download: ML18100A380 (5)

Text

e Public Service Electric and Gas Company P.O. Box 236 Hancocks Bridge, New Jersey 08038 Salem Generating Station u. s. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555

Dear Sir:

SALEM GENERATING STATION LICENSE NO. DPR-75 DOCKET NO. 50-311 UNIT NO. 2 LICENSEE EVENT REPORT 93-006-00 May 14, 1993 This Licensee Event Report is being submitted pursuant to the requirements of the Code of Federal Regulations lOCFR 50.73(a) (2) (iv). This report is required to be issued within thirty (30). days of event discovery.

MJPJ:pc Distribution 9305210251 930513 PDR ADOCK 05000311 S PDR l he rower is in your hands. Sincerely yours, c. A. Vondra General Manager -Salem Operations 95-2189 REV 7-92 NRC FORM 366 (6-89) U.S. NUCLEAR REGULATORY COMMISSION APPROVED OMB NO. 3150*0104 LICENSEE EVENT REPORT ILER) EXPIRES: 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT BRANCH (P-530), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TO" THE PAPERWORK REDUCTION PROJECT (3150-0104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503 .. FACILITY NAME.(1) I DOCKET NUMBER (2) I PAGE Ill **Salem Genera tin£ Station -Unit 2

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,____ -60.731*ll2lliil 1---50.731oll2Hiiil LICENSEE CONTACT FOR THIS LER 112) NAME TELEPHONE NUMBER AREA CODE M. J. Pastva. Jr. -LER Coordinator COMPLETE ONE LINE FOR EACH FAILURE DESCRIBED IN THIS REPORT 113) CAUSE SYSTEM COMPONENT I I I I I I I I TURER I I I I I I *.:,:.::,[

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SUPPLEMENTAL REPORT EXPECTED 114) j YES (If yos. compl*t* EXPECTED SUBMISSl.ON DA TEI bi NO ABSTRACT (Limit to 1400 spaces, i.t1., approximtJttJly fiftesn singlt1-spsct1 typewritten lines) (16) SYSTEM I I COMPONENT MANUFAC* TUR ER I I I I I I I I I I I I EXPECTED SUBMISSIO.N DATE 1151 MONTH DAY YEAR. I I I At 1002 on 4/15/93, an unexpected Train "A" Safety Injection System (SI} signal occurred due to STEAM LINE DIFFERENTIAL PRESSURE when the Solid State Protection System (SSPS} Train "A" Input Error Inhibit Switch was positioned to "INHIBIT", as required by Step 8.6 of Procedure 2IC-18.4.004, "RESPONSE TIME OF SSPS LOGIC -SAFETY INJECTION, TRAIN B". The Reactor was defueled and the Safety Injection (SI} Pumps were cleared and tagged. Steam pressure transmitters were being replaced and the STEAM LINE DIFFERENTIAL PRESSURE bistables were tripped. Plant components, not cleared and tagged, functioned properly.

Prior to performing 2IC-18.4-004, the status of the tripped bistables was discussed.

This event resulted from the particular operating characteristics of the subject switch. Positioning the switch slowly, which occurred during this event, caused a c;telay between removing the signal block and disabling the inputs, which allowed the logic to initiate the SI signal. The switch is operating within acceptable tolerances.

2IC-18.4.004 will be revised, by 6/18/93, to require the SSPS train Mode Selector switch be positioned to "TEST" prior to positioning the corresponding Input Error Inhibit Switch to "INHIBIT" and will include a caution that under certain conditions a Reactor trip signal may be initiated whenever the Input Error Inhibit.switch is positioned to "INHIBIT".

In addition, other similar SSPS procedures on both units will be revised prior to their next use. Station procedures for manipulating SSPS switches will be reviewed and appropriately revised. NRC Form 366 (6-89)

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station Unit 2 DOCKET NUMBER 5000311 PLANT AND SYSTEM IDENTIFICATION Westinghouse

-Pressurized Water Reactor LER NUMBER 93-006-00 PAGE 2 of 4 Energy Industry Identification System (EIIS) codes are identified in the text as {xx} IDENTIFICATION OF OCCURRENCE Train "A" Safety Injection System Signal During Response Time Testing* Of Train "B" Safety. Injection Solid State Protection System Logic Event Daie: 4/15/93 Report Date: 5/13/93 This report was initiated by Incident Report No.93-222 . . CONDITIONS PRIOR TO OCCURRENCE Unit 2 -Defueled in its seventh refueling outage. DESCRIPTION OF OCCURRENCE

-At 1002 on April 15, 1993, an unexpected Train "A" Safety Injection System (SI) signal occurred due to STEAM LINE DIFFERENTIAL PRESSURE when the. Solid state :Protection System (SSPS) Train "A" Input Error Inhibit switch was repositioned to "INHIBIT", as required by Step 8.6 of Procedure 2IC-18.4.004, "RESPONSE TIME OF SSPS LOGIC -SAFETY INJECTION, TRAIN B". Plant components, not cleared and tagged out as a result of ongoing maintenance activities, functioned properly.

Due to actuation of the SI logic {BQ}, the Nuclear Regulatory*

Commission (NRC) was notified of this occurrence in accordance with Code of Federal Regulations lOCFR50.72(b) (ii). *ANALYSIS OF OCCURRENCE The Reactor Protection System (RPS) encompasses all instrumentation, and equipment that serve to protect the reactor core. The most vital component of the RPS is the SSPS. The SSPS combines into one system the initiation of reactor trips, safeguards actuation and certain non-protective permissives, interlocks and control functions.

It receives inputs from various process parameters such as pressure, temperature, level, and power, and initiates appropriate automatic action when the proper number of channels in the monitored parameter exceed a preset value. The SSPS consists of two identical, independent trains to provide complete redundancy.

Both trains receive identical inputs and either train is capable of generating all required outputs (Reactor Trip and/or Engineered Safety Feature (ESF) actuation)

• e LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station Unit 2 DOCKET NUMBER 5000311 ANALYSIS OF OCCURRENCE (cont'd) LER NUMBER *93-006-00 3 of 4 On April 15, 1993, response time testing of the Unit SSPS Train "B" logic was in progress in accordance with Instrumentation and Controls (I&C) Procedure 2IC-18.4.004.

Due to ongoing outage-related activities, the following safety-related equipment was cleared and tagged: "B" Emergency Diesel Generator (DG), Chemical Volume Control System, SI Pumps, Residual Heat Removal System, Component Cooling Water System, and the Emergency Air Compressors.

In addition, steam pressure transmitters were being replaced.

To support this, the STEAM LINE DIF-FERENTIAL PRESSURE bistables were tripped; however I -an automatic SI* signal was blocked since the Unit Reactor Trip Breakers -were open. Prior to performing the pre-existing condition involving the tripped bistables was discussed between the involved Technicians and Operations.

-At 1002 hours0.0116 days <br />0.278 hours <br />0.00166 weeks <br />3.81261e-4 months <br />, when the SSPSTrain "A" Input Error Inhibit switch was repositioned to "INHIBIT" as required by step 8.6 of the procedure, an unexpected Train "A" Safety Injection (SI) signal occurred.

Plant components, not cleared and tagged out as a result of the ongoing outage-related maintenance activities, functioned including automatic startingof "A" and "C" DGs.

• This event resulted from the particular operating characteristics of the subject switch, Grayhill Incorporated, Part No. 5004-2. When the switch was positioned to "INHIBIT", the SI block was removed before the existing coincident input logic cleared, which allowed the logic to initiate the SI signal. Testing showed that positioning the switch quickly causes the SI logic inputs to be disabled approximately five (5) milli-seconds after the SI block is removed thereby preventing an SI signal. Slower positioning of the switch, which occurred during this event, causes a delay of approximately fifty (50) milli-seconds between removing the block and disabling the inputs, which allows the logic to initiate an SI signal. An assessment determined the switch is operating within acceptable tolerances.

APPARENT CAUSE OF OCCURRENCE:

Based upon the switch characteristics as described in the above paragraph, the root cause of this event is "Other", -as defined by NUREG-1022, Licensee Event Report System. PREVIOUS OCCURRENCES LER 311/92-005-00 reported the unplanned opening of "B" Reactor Trip Breaker (RTB) during SSPS testing on March 16, 1992, due to procedural inadequacy.

This event occurred due to failure to recognize that unusual plant conditions (i.e., all high steam flow bistables tripped), concurrent with removal of the SI block during the procedure would cause the RTBs to open. This event occurred-when the SSPS Train "B" Mode Selector Switch was positioned to "TEST", in LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating station Unit 2 PREVIOUS OCCURRENCES (cont'd) DOCKET NUMBER 5000311 LER NUMBER 93-006-00 PAGE 4 of 4 accordance with Operations Procedure "Manual Safety Injection".

The April 15, 1993 event differs in that it occurred as a result of manipulating the Input Error Inhibit Switch. This switch has a different function from the switch manipulated in the 1992 event. SAFETY SIGNIFICANCE This event did not affect the health and safety of the public since plant conditions remained unaffected by the SSPS actuation.

• Plant equipment not cleared and tagged functioned properly.

This included automatic starting of "A" and 11 c 11 DGs. Although the SSPS is not required to be operable while defueled, the Engineered Safety Feature actuation of the system is reportable to the NRC, in accordance with (2) (iv). CORRECTIVE ACTION 1. To help prevent future similar occurrences, 2IC-18.4.004 is undergoing revision by the Procedure Upgrade Project, to require that the SSPS train Mode Selector Switch be positioned to "TEST" prior to positioning the affected train Input Error Inhibit Switch to "INHIBIT".

This revision has an expected completion by June 18, 1993 and will include a caution to notifiy the Operator that a Reactor trip signal may be initiated under abnormal conditions (i.e. tripped bistables during maintenance activities) whenever the. Input Error Inhibit switch is positioned to "INHIBIT".

In addition, other similar SSPS procedures (on both units) will be revised prior to their next use. 2. Station procedures involving manipulation of SSPS switches on the logic test panel will be reviewed and appropriately revised. MJPJ:pc SORC Mtg.93-043 General Manager -Salem