IR 05000443/1993001

Insp Rept 50-443/93-01 on 930103-20.Licensee Assessment of Event Thorough & Well Documented.Major Areas Inspected: Events Leading Up to Loss of Both Main Feedwater Pumps & Subsequent Manual Trip of Reactor

ML20128A186
Person / Time
Site:	Seabrook
Issue date:	01/25/1993
From:	Rogge J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
To:
Shared Package
ML20128A175	List: IR 05000443/1993001 ML20128A170
References
50-443-93-01, 50-443-93-1, NUDOCS 9302020150
Preceding documents:	ML20034E961 (23 February 1993)
Download: ML20128A186 (21)

Text

{{#Wiki_filter:l . . U. S. NUCl, EAR REGULATORY COMMISSION '

REGION I

. Report Number: 93-01 Docket No.: 50 443 License No.: NPF 86 Licensee: North Atlantic Energy Service Corporation Post Office llox 300 Scabrook, New llampshire 03874 Facility: Seabrook Station Dates: January 3-20, 1993 Inspector: Noel Dudley, Senior itesident inspector Richard 12ura, Resident inspector Fred Paulitz, Electrical lingineer Approved liy: / . c.

/$ ' & ohn F. Rogge, iicf ) ate Reactor Projects Section 411 OVERVIEW The operators manually isolated a feedwater heater to repair the bellows on a leaking tube side relief valve. A subsequent feedwater system transient isolated a string of feedwater heaters. Incorrect operator actions during restoration of the feedwater heaters resulted in completely isolating feedwater to the stea n generators. The control room operators mitnually tripped the reactor and stabilized plant conditions. The station staff completed a post-trip review prior to starting up the reactor and conducted an event evaluation.

Operators performed well in manually isolating the leaking relief valve. Operator errors made while restoring the feedwater heaters caused a loss of feedwater flow, improper verbal communications, the lack of written guidance for abnormal feedwater transients, weaknesses in operator training, and mor human factors at a turbine building control panel contributed to i the operator errors. Operator response to the loss of feedwater conservatively demonstrated . an appropriate safety attitude.

Plant staff fully understood the secondary plant transient for a single heater isolation.

110 wever, the staff misunderstood the effects of multiple feedwater heater isolations on plant operations, since they believed that loss of two E-21/22 heater strings would result in a reactor trip.

The licensce's assessment of the event was thorough and well documented. The recommended corrective actions in the station information report addressed the causes of the event.

9302020150 930127 . .PDR ADOCK 05000443

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. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ - _ _ _ _ _ _ ._ __ - __ _-. _- ' i ' . . .. TAllLE OF SUMMARY Repetitive operator errors resulted in a loss of normal feedwater floiv requiring a manual reactor trip. The operators responded well to the loss of feedwater and stabil_ized plant conditions. The North Atlantic event evaluation team reviewed the event and management approved reactor startup pending completion of identified short term corrective actionsc The inspectors concluded the cause of the event was _ operator error. (Secondary causes-included operator training on feedwater heater system detiils and indications; poor huma'n factors at CP-66; improper verbal communications; and the lack of _ written guidance for- , abnormal operation of the feedwater heaters. Proper action by the opera' tors could have restored the heaters and p= vented the thermal transient and the reactor. trip. The decision of - the control room operators to manually trip the reactor was'conservati_ve and demonstrated an appropriate safety attitude.

The inspectors concluded that the North Atlantic assessment of the event was thorough and well documented. The inspectors determined that the recommended corrective actions in the; o SIR addressed the identified root causes.

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, 7.0 MEETINGS (30702) - The scope and findings of the inspection were discussed periodically throughout the inspection. An oral summary of the inspection findings was provided to the station manager and his staff at the conclusion of the inspection period on January 21,1993.

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. '4 - 4 , A'ITACllMENT I - _' SEQUENCE OF EVENTS January 2,1993 5:15 p.m.

Auxiliary operator (AO) reports a steam leak from the relief valve on the tube - side of feedwater (FW) heater E-25 A.

5:35 p.m.

AOs isolate FW heater Il-25A. The AOs direct the heater drains off FW heater E-26A directly to the heater drain tank through the high level spill valve.

5:36 p.m.

A 111 HI water level in FW heater E-26A shuts the steam extraction valve, EX-VI, to the heater. The third condensate pump automatically sti.rts.

5:37 p.m.

A lit 111 water level in FW heater li-21C isolates the E-21/22C heater string by shutting the inlet and outlet isolation valves, and opening the bypass valve, CO-V-75.

5:45 p.m.

AOs open the high level dump valves on the three E-22 feedwater heaters.

' AOs restore the E-21/22C heater string by opening the inlet and outlet valves, and closing CO-V-75.

6:32 p.m.

Operators secured condensate pump CO-P-308. The E-26A heat exchanger water level oscillations cause continuous HI HI level alarms.

9:17 p.m.

AOs adjust the setpoint for FW heater E-26A level control to prevent HI III level alarms. The AOs open the breaker to EX-VI, manually open the valve, and shut the breaker.

January 3,1993 0:25 a.m.

The AOs shut the high level dump valves on the three E-22 feedwater heaters and returned the valves to automatic.

3:30 a.m.

The AOs change the air removal pump line up which causes a minor fluctuation in condenser vacuum.

3:36 a.m.

A Hi H1 water level in FW heater II-26A isolates steam extraction valve, EX-VI. The 'A' heater drain pump discharge valve closes.

3:37 a.m.

The secondary AO begins to_open EX-V1.

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.. . .,4 ' ' i -. L, 3:39 a.m.

Low main feed pump suction prersure starts the third condensate pump, CO-P-308. A HI H1 water level in FW heater E-21C isolates the E-21/22C heater-string by shutting' the inlet and outlet isolation valves, and opening the bypass valve, CO-V-75.

3:40 a.m.

Reactor thermal power exceeds license 100% rated conditions. Operators reduce power which adds additional perturbations to the feedwater heaters.

3:41 a.m.

The secondary AO opens the high level dump valves on the three E-22 feedwater heaters. The AO attempts to restore the E-21/22C heater string by opening the inlet valve and closing CO-V-75, but fails to open the outlet valve.

j The AO returns to EX-V1.

3:44 a.m A HI HI water level in FW heater E-21 A isolates the E 21/22A heater string by shutting the inlet and outlet isolation valves, and opening the bypass valveCO-V-75.

3:44 a.m.

Thermal power decreased below 100% rated conditions.

3:45 a.m.

The secondary AO attempts to restore the E-21/22A heater string by opening the inlet valve and closing CO-V-75, but fails to open the outlet valve. The - AO returns to FGVI.

3:48 a.m A Hi H1 water level in FW heater E-21B isolates the fi-21/22B heater string by shutting the inlet and outlet isolation valves, and opening the bypass valve,' CO-V.75.

3:49 a.m.

The secondary AO attempts to restore the E-21/22B heater string by opening the inlet valve and closing CO-V-75, but fails to open the outlet valve, eliminating all condensate flow. ; The AO returns to EX-V1.

. 3:49 a.m.

The ' A' main feedwater pump trips and initiates a turbine setback; 3:50 a.m.

The 'B' main feeduter pump trips. The operators' manually trip the reactor.

4:00 p.m.

North Atlantic conducts a post trip review meeting and authorizes plant'startup pending completion of required work items.

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Operators take the reactor critical.

- 10:40 a.m.

Operators place the turbine generator on the electrical grid, 11:05 a.m.

A HI H1 water level in FW heater E-21C isolates the E-21/22C heater string-by shutting the inlet and outlet isolation valves, and ' opening the bypass valve, CO-V-75.

11:35 a.m.

Two AOs correctly restore the E-21/22C heater string to the normal lineup.

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