ML20045D368

LER 93-009-00:on 930520,manual Reactor Trip from 100% Power Initiated When MSIV Closed During Quarterly Testing, Resulting in Feedwater & Two Emergency Feedwater Isolations. Caused by Debris in Valves.Valves Replaced

ML20045D368
Person / Time
Site:	Seabrook
Issue date:	06/18/1993
From:	Peschel J NORTH ATLANTIC ENERGY SERVICE CORP. (NAESCO)
To:
Shared Package
ML20045D366	List: ML20045D365 ML20045D368
References
LER-93-009, LER-93-9, NUDOCS 9306280289
Download: ML20045D368 (4)

Text

. _ _ m - _ _ _ _ _ _ _ ._- - _ - _ _ _ _ _ _ . _ ___ _ _.- _ _ _ _ _ _

t .

• n NRC FORM 366 U.S. NUCLEAR REGULATORY COPMISSIC3 APPROVED BY OMB NO. 3150-0104

($-92) EXPIRES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH NF OL 0 HR LICENSEE EVENT REPORT (LER) $ARD TION REgUEST THE INFORMATION AND RECORDS MANAGEMENT BRANCH l (MNBB7714),U.S.NUCLEARREGULATORYCOMMISSION, 1 (Seereverseforrequirednumberofdigits/charactersforeachblock) ggN, C 0555-0001 D TO TH RW0g MANAGEMENT AND BUDGET. WASHINGTON, DC 20503.

FACILITYNAME(1) DOCKET NUMBER (2) PAGE(3) l SEABROOK STATION 05000443 1 OF 4 l TITLE (4)

MANUAL REACTOR TRIP DUE TO INADVERTENT MSIV CLOSURE ~

EVENT DATE (5) LER NUMBER (6) REPORT DATE (7) OTHER FACILITIES INVOLVED (8)

SEQUENTIAL REVISION MONTH DAY YEAR YEAR MONTH DAY YEAR NUMBER NUMBER 05000 FAM NAME DOCKET "

05 20 93 93 --

09 --

00 06 18 93 0 000 OPERATING y THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR 6: (Check one or more) (11)

MODE (9) 20.402(b) 20.405(c) X 50.73(a)(2)(iv) 73.71(b)

POWER 20.405(a)(1)(1) 50.36(c)(1) 50.73(a)(2)(v) 73.71(c) 100 LEVEL (10) 20.405(a)(1)(ti) 50.36(c)(2) 50.73(a)(2)(vii) OTHER

- 20.405(a)(1)(iii) 50.73(a)(2)(1) 50.73(a)(2)(viii)(A) (Specify in trac low l iM g 20.405(a)(1)(iv) 50.73(a)(2)(ii) 50.73(a)(2)(viii)(B)

WP 20.405(a)(1)(v) 50.73(a)(2)(ill) 50.73(a)(2)(x) NRC Form 366A)

LICENSEE CONTACT FOR THIS LER (12)

NAME TELEPHONENUMBER(IncludeAreaCode)

Mr. James M. Peschel, Regulatory Compliance Manager (603)474-9521 ext.3772 COPFLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

CAUSE SYSTEM COMPONENT MANUFACTURER CAUSE SYSTEM COMPONENT MANUFACTURER R0 E 0 P X SB FSV E095 Y '

si!,

a SUPPLFK NTAL REPORT EXPECTED (14) EXPECTED MONTH DAY YEAR i Y  !

X (ESIf yes, complete EXPECTED SUBMISSION DATE). NO SUBMISSION 9 15 93 DATE(15)

ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) (16)

On May 20, 1993, at 0437 EDT, a manual reactor trip from 100 percent power was initiated when a main steam [SB] isolation valve (MSIV) closed during MSIV quarterly testing. The trip was followed by a Feedwater Isolation and two Emergency Feedwater actuations. This event was reported to the NRC at 0553 EDT as an immediate notification pursuant to 10CFR50.72(b)(2)(ii),actuationoftheReactorProtectionSystem(RPS)andEngineered SafetyFeature(ESF) System.

During MSIV quarterly testing, the MSIVs are alternately stroked to ten percent closed and then reopened. However, one MSIV failed to return to the open position when the ten )

percent limit was reached, and instead continued to close. The reactor was manually tripped when the narrow range level in the affected steam generator was twenty-two percent and decreasing. l There were no adverse safety consequences as a result of this event.

The cause of the MSIV malfunction was determi.ied to be debris lodged in a hydraulic solenoid valve that allowed the hydraulic pressure keeping the MSIV open to bleed off, resulting in the MSIV drifting closed.

NRC FORM 366 (5-921 9306280289 930618 PDR ADOCK 05000443 s PDR

.i O

~

FJC f0RM 366A U.s. NUCLEAR REGULATORY CO MISSION APPROVED BY O M NO. 3150-0104 (S.92) EXPIRES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH 50.0 HRS.

THis INFORMATION COLLECTION" REgEST:

LICENSEE EVENT REPORT (LER) NNFOM A ECORDs MANAGEM BRAN TEXT CONTINUATION gNkDN2'0555-0 1 AND T H $

REDUCTION PROJECT (31500104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME (1) DOCKET NUIEER (2) LER NUfEER (6: PAGE (3)

YEAR SEQUENTIAL REVISION SEABROOK STATION "

05000443 2 OF 4 93 -- 09 -- 00 TEXT (If more space is required, use additional copies of NRC form 366A) (17)

Description of Event On May 20, 1993, at 0437 EDT, plant operators initiated a manual reactor trip from 100 percent power when a main steam isolation valve (MSIV) closed during the performance of MSIV quarterly testing.

Seabrook Station is a four loop Westinghouse plant, with an MSIV in each of the four main steam lines. Each MSIV is controlled by a hydraulic / pneumatic actuator that uses nitrogen '

to maintain pressure on top of an operating piston (which tends to close the MSIV) and hydraulic pressure on the bottom of the operating piston to keep the valve open. There are two hydraulic solenoid operated valves that are used to vent the hydraulic pressure to a reservoir to close the valves. There are two trains of hydraulic control for each MSIV to increase reliability. MSIV operability is verified once per quarter during power operation by cycling each valve through ten percent of valve travel with both trains of hydraulic control using a test panel on the main control board. '

The train A test of the four MSIVs had been performed earlier on the shift with all MSIVs  !

cycling properly. Two minor discrepancies, low nitrogen pressure on MSIV A and loose i limit switches on MSIV B, were noted. The train B test of MSIV A and C were then l completed satisfactorily (MSIV B was not tested using train B due to the loose limit i switches). However, when MSIV D was tested, the Senior Control Room Operator noted that '

the valve failed to stop at ten percent closed. The MSIV's continued closure was verified by indications of steam generator level shrinkage, steam flow reduction from steam generator D, and a delta temperature deviation alarm in the affected reactor coolant loop.

Attempts to stop the valve from closing were unsuccessful. Approximately four minutes after the start of the MSIV D test, with steam generator D narrow range level at twenty-I two percent and decreasing, the Unit Shift Superintendent ordered a manual trip of the reactor.

The decision to trip the reactor, and the response to the reactor trip and the subsequent recovery actions by plant operators, were determined to be correct. Primary plant system response was normal with ex FeedwaterSystem(EFW)[BA]pectedEngineeredSafetyFeature(ESF)actuations(Emergency actuation on Steam Generator LO-LO level and Feedwater System

[SJ] Isolation in response to low Reactor Coolant System temperature). During the response to the reactor trip, the Unit Shift Supervisor (USS) ordered the Senior Control Room Operator (SCRO) to reopen the feedwater isolation valves, as required by the applicable Emergency Response Procedure (ES-0.1, Reactor Trip Response). However, the SCR0 did not hear this order, and the USS continued with ES-0.1, verifying the startup l feed pump was running with greater than 14 percent level in the steam generators, and then  !

securing the emergency feedwater pump. With feedwater secured, steam generator levels  !

decreased to the LO-L0 level setpoint and a second EFW actuation occurred.

At 0553 EDT on May 20, 1993 North Atlantic made a four-hour notification to the NRC l- pursuantto10CFR50.72(b)(2)(ii).

l l

6 NRC FORM $66A U.s. NUCLEAR REGULA10RY COPNISSION APPROVED Hf OMB NO. 3150-0104 l l

(5-92) ,

EXPIRES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH 50.0 HRS.

THIS INFORMATION COLLECTION REgEST:

LICENSEE EVENT REPORT (LER) $ F0 A ECORDS NAGE BRAN REGULAT R OMP TEXT CONTINUATION [M g g g . j.S. NUCLE REDUCTION PROJECT (3150-0104), OFFICE OF l MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME (1) DOCKET NUMBER (2) LER MUMBER (6? PAGE (3)

SEQUENTIAL REVISION YEAR SEABROOK STATION "" " " "

05000443 93 0 3 OF 4 ,

-- 09 -- l TEXT (If more space is required, use additional C.Tles of MRC forin 366A) (11)

Safety Conseauences There were no adverse safety consequences as a result of this event. Plant equipment functioned as designed and operator actions were determined to be correct. At no time during the event was there any impact on the health and safety of plant employees or the  ;

public.

1 Root Cause The root cause of this event was determined to be debris lodged in one of the hydraulic solenoid valves that align the hydraulic portion of the MSIV operating piston with the ,

hydraulic reservoir. This debris caused the solenoid valve to stay in mid position during '

the ten percent closure test, permitting the hydraulic fluid to drain from the bottom of the operating cylinder. As the hydraulic pressure in the operating piston fell below the nitrogen pressure on top of the operating cylinder, the MSIV closed. A supplement to this report will be provided when the mechanism for introducing the debris is determined.

The root cause of the second EFW actuation was detern ined to be incomplete communication between the Unit Shift Supervisor and the control board operator regarding the reopening i of the feedwater isolation valves.  ;

Corrective Actions j The hydraulic solenoid valves on MSIV D were replaced and the MSIV was tested satisfactorily. The minor discrepancies on MSIV A and MSIV B (low nitrogen pressure and loose limit switches, respectively) have been corrected. In addition, a Human Performance Evaluation was performed for the trip and for the events leading to the second EFW actuation.

The following additional actions are being taken:

1. The failed solenoids from MSIV D are being evaluated to determine what mechanism introduced the debris and produced their failure mode.

2. A logic change to the slow closure circuit is being developed so that the MSIV does not momentarily transfer from slow to fast closure before reopening during the partial closure test.

3. Emergency Response Procedure ES-0.1 will be revised to list the feedwater Isolaticn valve numbers.

4. Other Emergency Response Procedures will be reviewed for the use of specific valve numbers while performing evolutions. Precedure changes will be issued as applicable.

4 o

NRC.f0RM'366A U.S. NUCLEAR REGULATORY COP 9tlSS10N APPROVED BY OMB NO. 3150-0104 (3-92) EXPIRES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS.

LICENSEE EVENT REPORT (LER) h0!"Yrfr0N!$fi A EC PDS P NAGE i BRAN TEXT CONTINUATION [Fjjyg.th'S'05SS_9 D 2 NUCLE REGULAT R 0 REDUCTION PROJECT (3150-0104),

g OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.

FACILITY KAME (1) DOCKET NUMBER (2) LER NUMBER (6L PAGE (3)

YEAR SEQUENTIAL REVISION SEABROOK STATION """ " "

05000443 93 0 4 OF 4

-- 09 --

TEXT (if more space is required, use additional copfes of hRC Fonn 366A) (11)

5. The decibel level and frequency for control board alarms will be evaluated to determine if they have been set too high, thereby contributing unnecessarily to the environmental noise level in the control room.

6. The lessons learned from this event will be discussed with all operating crews.

Plant Conditions At the time of this event, the plant was in Mode 1, at 100 percent power, with a Reactor Coolant System temperature of 587 degrees Fahrenheit and a pressure of 2235 psig.

Related Events This is the first event at Seabrook Station where MSIV testing anomalies resulted in a reactor trip.

This is the third event at Seabrook Station where incomplete communication among the operations crew contributed to a Reactor Protection System / Engineered Safety Features actuation. The previous occurrences were reported in LER 92-017 and LER 93-01, 1

I l

.