ML18093B174

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LER 88-017-00:on 880831,reactor Trip Occurred After Turbine Trip as Result of Steam Generator hi-hi Level.Caused by Design/Equipment Problem Associated w/23BF19 Valve.Maint Requirements Will Be modified.W/880920 Ltr
ML18093B174
Person / Time
Site: Salem PSEG icon.png
Issue date: 09/20/1988
From: Miller L, Pollack M
Public Service Enterprise Group
To:
NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
LER-88-017-01, LER-88-17-1, NUDOCS 8809280052
Download: ML18093B174 (4)
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Text

NRC Form 3M 19-<!1)

  • LICENSEE EVENT REPORT (LER)
  • U.S. NUCLEAR REGULATORY COMMISSION Al"PROVED OMB N0. 31!§0--4104 EXPIRES: 8/311115 FACILITY NAME 111 DOCKET NUMaER 121 I P'AU~ 131 Salem Generatinq Station - Unit 2 TITLE 141

!o 1s I o I o I o 13 11 Il. 1IOFOl3 Hi-Hi S/G Turbine Trio/Rx. Trip Due To A Design/Equipment Problem (23BF19)

EVElllT DATE 181 LEA NUMBER 1111 REPORT DATE 171 OTHER FACILITIES INVOLVED Ill MONTH CAY YEAR YEAR E{:} SE~~~~~~AL tt ~~~~?;: MONTH DAY YEAR FACILITY NAMES DOCKET NUMBERISl 8 8 al a THll REl'ORT 11 IUIMITTED PURIUANT TO THE REQUIREMENTI OF 10 CFR §: IC-k OM or mon of th* following) 1111 OPERATING 1

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LICENSEE CONTACT FOR THIS LEll (121 NAME TELEPHONE NUMBER AREA CODE M. J. Pollack - LER Coordinator 61019 31319 I -1410 I 21 2 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DEICRllED IN THll PU!l'ORT 1131 MANUFAC* MANUFAC*

CAUSE SYSTEM COMPONENT TUR ER TUA ER B S IJ CIP IQ IS B 10 I 415 y I I I I I I I I I I I I I I I I I I I I I IUPl'LEMENT AL REPORT EXPECTED 1141 MONTH DAY Y~AR EXPECTED

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DATE 1151 I I I AISTRACT (Limlr ro 1400 -

  • i.*.* *pproximoN/y fiftHn 1/ngf..,poc* rypowrimn /inn) 11111 On 8/31/88 at 0553 hours0.0064 days <br />0.154 hours <br />9.143518e-4 weeks <br />2.104165e-4 months <br />,a Turbine Trip occurred as a result of No. 23 Steam* Generator (S/G) High-High Level (67%). Following the Turbine Trip a Reactor Trip occurred due to the plant being above 10% power (Permissive P-7). The unit was in the process of a power coast down as the start of the fourth refueling outage approached. Prior to the event, the Nuclear Control 0Rerator (NCO) received an alarm indicating that steam flow was significantly less than feed flow for No. 23 S/G.

Feed flow was at 100% with steam flow at 70%. The NCO attempted to manually close the 23BF19 valve (Feedwater Control Valve), however, the valve could not be closed resulting in the S/G level rising to the Turbine Trip setpoint. The apparent cause of this occurrence has been attributed to a design/equipment problem associated with the 23BF19 valve. Investigation of the 23BF19 valve revealed that its positioner linkage had disconnected due to vibration. The linkage had pulled itself away from the lower turn buckle as evidenced by the damaged rod threads. Since the Unit was very near the end of its fuel. cycle, the scheduled fourth refueling outage was initiated. The "star" type lockwasher will be replaced with an "overlap" type lockwasher for all BF19 and BF40 valves. Also, "locktight" will be applied to the rod threads. The preventive maintenance requirements for the BF19 valves will be modified to require inspection of the turnbuckles and tightness of the rod nuts every 18 months. ~y~?J~\

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LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 2 5000311 88-017-00 2 of 3 PLANT AND SYSTEM IDENTIFICATION:

Westinghouse - Pressurized Water Reactor Energy Industry Identification System (EIIS) codes are identified in the text as {xxl IDENTIFICATION OF OCCURRENCE:

Hi-Hi Steam.Generator Turbine Trip/Reactor Trip Due To A Design/Equipment Problem Associated With the 23BF19 Feedwater Valve Event Date: 8/31/88 Report Date: 9/20/88 This report was initiated by Incident Report No.88-383.

CONDITIONS PRIOR TO OCCURRENCE:

Mode 1 Reactor Power 72% - Unit Load 760 MWe DEStRIPTION OF OCCURRENCE:

On August 31, 1988 at 0553 hours0.0064 days <br />0.154 hours <br />9.143518e-4 weeks <br />2.104165e-4 months <br />,a Turbine Trip occurred as a result of No. 23 Steam Generator (S/G} High-High Level (67%). Following the Turbine Trip a Reactor Trip occurred due to the plant being above 10%

power (Permissive P-7). The unit was in the process of a power coast down as the start of the fourth refueling outage approached.

Prior to the event, the Nuclear Control Operator (NCO} received an alarm indicating that steam flow was significantly less than feed flow for No. 23 SIG fSB}. Feed flow was at 100% with steam flow at 70%.

The NCO attempted to manually close the 23BF19 valve (Feedwater Control Valve} fSJ}, however, the valve could not be closed resulting in the S/G level rising to the Turbine Trip setpoint.

The Unit was stabilized in Mode 3 (Hot Standby}. At 0616 hours0.00713 days <br />0.171 hours <br />0.00102 weeks <br />2.34388e-4 months <br /> the same day, in accordance with the requirements of the Code of Federal Regulations 10CFR 50.72(b} (2) (ii), the Nuclear Regulatory Commission was notified of the automatic actuation of the Reactor Protection System fJC}.

APPARENT CAUSE OF OCCURRENCE:

The apparent cause of this occurrence has been attributed to a design/equipment problem associated with the 23BF19 valve.

Investigation of the 23BF19 valve revealed that its positioner linkage had disconnected due to vibration. The linkage had pulled itself away from the lower turn buckle as evidenced by the damaged rod threads.

ANALYSIS OF OCCURRENCE:

The Turbine Trip on S/G high-high level is an anticipatory trip to

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 2 5000311 88-017-00~~~~-3~o_f_~3~~

ANALYSIS OF OCCURRENCE: (cont'd) prevent moisture carryover from the S/G and damage to the main turbine due to excessive moisture carryover. The purpose of the reactor trip is to reduce the primary plant transient resulting from the loss of the turbine above 10% power. A turbine trip above 10% power results in a direct reactor trip and a controlled short term release of steam to the condenser via the steam dump. This steam release removes sensible heat from the reactor coolant system and precludes S/G safety valve operation.

The Reactor Trip after a Turbine Trip with the Unit above 10% power is anticipatory and is included as part of good engineering practice and prudent design. No credit is taken in any of the safety analysis for this trip. For rapid temperature transients during power operation, protection of the reactor is provided by the Main Steam safety valves. For slower developing transients, protection of the reactor is provided by atmospheric relief valves, condenser steam dump, and overtemperature delta temperature bistables.

This occurrence involved no undue risk to the-health and safety of the public. However, because of the automatic actuation of the reactor protection system, the event is reportable in accordance with the Code of Federal Regulations 10CFR 50.73 (a} (2} (iv}.

Since the Unit was very near the end of its fuel cycle, the scheduled fourth refueling outage was initiated.

CORRECTIVE ACTION:

The "star" type lockwasher, used to prohibit loosening of the rod, will be replaced with an "overl~p" type lockwasher for all BF19 valves and all BF40 valves (Feedwater Control Bypass Valve). Additionally, "locktight" will be applied to the rod threads. These modifications should prevent recurrence of this event. The Salem Unit 1 BF19 and BF40 valve positioner linkages have been modified.

The preventive maintenance requirements for the BF19 valves will be modified to require inspection of the turnbuckles and tightness of the rod nuts every 18 months.

The replacement of the star type washer with overlap washers was originally scheduled to be performed during the Unit 2 fourth refueling outage and any Unit 1 outage of sufficient duration. The work was scheduled in response to a review of an INPO Network item

  • (reference OE 1846 FARLEY, 08-JAN-87, "Loss of a Valve Positioner Feedback Linkage"} addressing this issue.

/,[;~

General Manager -

Salem Operations MJP:pc SORC Mtg.88-078

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OPS~G

  • Public Service Electric and Gas Company P.O. Box E Hancocks Bridge, New Jersey 08038 Salem Generating Station September 20, 1988 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 88-017-00 This Licensee Event Report is being submitted pursuant to the requirements of the Code of Federal Regulations 10CFR 50.73(a) (2) (iv). This report is required within thirty days of discovery.

Sincerely yours, L. K. Miller General Manager-Salem Operations MJP:pc Distribution The Energy People 95-2! 89 'I'. Mi'. 2-8d

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