Text

Final ASP Analysis - ANO 1 (LER 313-80-015)
	ML20147A330
Person / Time
Site:	Arkansas Nuclear
Issue date:	07/17/1980
From:	Christopher Hunter; NRC/RES/DRA/PRB
To:	;
	Littlejohn J (301) 415-0428
References
	LER 1980-015-01
	Download: ML20147A330 (5)
	v • d • e

PRECURSOR DESCRIPTION AND DATA NSIC Accession Number:

163499 Date:

July 17, 1980

Title:

Reactor Coolant Pump Seal Failure at Arkansas Nuclear I

The failure sequence was:

1. With the reactor at 86% power, reactor coolant pump (RCP)

"C" seal

failed, resulting in excessive RCS leakage to the containment.

2.

A controlled power reduction was begun, and approximately one-half hour later letdown was secured to reduce RCS inventory loss.

RCS leak was estimated to be 10-20 gpm.

3.

RCS leak rate increased during the power reduction and the plant was subsequently rapidly taken off line.

RCP "C" was tripped after the turbine was taken off line but with the reactor critical.

4.

RCS leak rate increased substantially when RCP "C" was tripped, and the RCP "C" lift pumps were started and stopped four times in succession in an attempt to reduce the leak rate.

On the fourth attempt a reduction in leak rate was noticed.

RCS leak rate had increased to a maximum of approximately 350 gpm.

5.

The reactor was manually tripped and HPI pumps B and C started and all HPI valves opened to provide RCS makeup.

The RCP "C" seal return line was isolated to prevent inventory loss through that line and RCP seal flow increased to quench the steam/water leaking by the failed seal.

6.

A one-half psi increase in containment pressure occurred and the reactor building emergency coolers were put in service to minimize the pressure increase.

7.

One HPI pump was secured and the HPI valves closed 1.3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> after the seal failure.

Two HPI pumps were used to provide continued RCS makeup from the BWST.

8.

Individual SLBIC trains were inadvertently initiated twice during the cooldown, resulting in start of the turbine-driven EFW pump.

This pump was subsequently stopped and the auxiliary feedwater pump lined up to feed the steam generators.

9.

During the RCS cooldown, containment entry was required to isolate the two core flood tanks to prevent their discharging into the RCS below 600 psig.

A decrease in core flood tank level of 18 in.

and 12 in.

occurred prior to effecting isolation.

10.

Throughout the incident a greater than 100'F margin to saturation existed.

Approximately 60,000 gallons of water collected in con-tainment.

Corrective action:

1.

The failed seal was examined and extensive damage observed.

The cause of the damage could not be identified with certainty.

2.

All remaining RCP seals were inspected and evidence of high temperature operation observed.

All seals were replaced.

3.

The CFT isolation valve controls were relocated outside containment to facilitate access.

Design purpose of failed system or component:

The RCP seals provide a pressure boundary against RC system pressure at the rotating shaft of the pump.

Reactor at Leakage rate RCP leak rate ReaCtor trip One HPI pump Core flood 86% power increases increases to and manual secured and isolation and RCP during power 350 gpm.

RCP HPI initiation HPI valves valves closed "C" seal reduction -

"C" lift pumps to provide closed.

Two to prevent failure plant taken operated, re-RCS makeup HPI pumps CFT discharge (10-20 gpm off line and sulting in provide at RCS pres-initial leak RCP "C" some reduction makeup sure of rate) tripped in leak rate 600 psig Potential Severe Core Damage No No No No No No No - operating makeup pump sufficient for makeup NSIC 163499 - Actual Occurrence for Reactor Coolant Pump Seal Failure at Arkansas Nuclear 1

Small Reactor Auxiliary High Low Pressure LOCA Trip Feedwater and Pressure Recirculation Secondary Injection and LPR/HPI Heat Removal Cross-Connect Potential Severe Core Damage Sequence No.

No Yes Yes 1

2 3

4 No Yes Yes Yes 5

6 7

NSIC 163499 -

Sequence of Interest for Reactor Coolant Pump Seal Failure at Arkansas Nuclear 1

CATEGORIZATION OF ACCIDENT SEQUENCE PRECURSORS NSIC ACCESSION NUMBER:

163499 LER NO.:

80-015 Rev.

I DATE OF LER:

July 17, 1980 DATE OF EVENT:

May 10, 1980 SYSTEM INVOLVED:

Reactor coolant system COMPONENT INVOLVED:

Reactor coolant pump seals CAUSE:

Seal failure SEQUENCE OF INTEREST:

Small break LOCA ACTUAL OCCURRENCE:

RCP "C" seal failure REACTOR NAME:

Arkansas Nuclear 1 DOCKET NUMBER:

50-313 REACTOR TYPE:

PWR DESIGN ELECTRICAL RATING:

850 MWe REACTOR AGE:

5.8 years VENDOR:

Babcock & Wilcox ARCHITECT-ENGINEERS:

Bechtel OPERATORS:

Arkansas Power & Light LOCATION:

6 miles NW of Russellville, Arkansas DURATION:

N/A PLANT OPERATING CONDITION:

86% power TYPE OF FAILURE:

Inadequate performance DISCOVERY METHOD:

Operational event COMMENT:

ML20147A330

Text

Title:

Navigation menu

Search