U.S. NUCLEAR REGULATORY COMMISSION

Region III Office of Public Affairs

801 Warrenville Road, Lisle IL 60532-4351

NEWS ANNOUNCEMENT: RIII-96-44 August 7, 1996

CONTACT: Jan Strasma 708/829-9663

Angela Dauginas 708/829-9662

E-mail: opa3@nrc.gov

NRC INSPECTION TEAM ISSUES REPORT ON FOAM SEALANT MATERIAL FOUND

IN EQUIPMENT COOLING SYSTEM AT LASALLE NUCLEAR POWER STATION

A Nuclear Regulatory Commission Augmented Inspection Team

has issued its report on the foam sealant material found in the

equipment cooling water system, resulting in the shutdown in late

June of both units at the LaSalle Nuclear Power Station.

The LaSalle Station, which has two reactors, is operated by

Commonwealth Edison Co. near Seneca, Illinois.

The NRC inspection was conducted July 1-17, and the team's

preliminary findings were discussed in a July 17 meeting, which

was open to the public.

In May and June, a utility contractor repairing cracks in

concrete at the plant's water intake building injected a foam

sealant material in the cracks. Some of this material entered a

large water-filled tunnel beneath the floor of the building and,

in two instances, reduced the water flow into systems which cool

various plant components.

Initially, the utility believed that the foreign material

would not affect any plant safety systems because it would float

at the top of the tunnel. Subsequently, the sealant material was

found in the lower part of the tunnel where it could affect the

cooling system for safety-related components.

When it was discovered that safety systems might be

affected, the utility shut both reactors down on June 28-29. The

units resumed operation after the foreign material was removed

and plant systems were thoroughly inspected and tested.

The NRC team found that the cause of the foreign material

entering the cooling system was poor control of the concrete

crack repairs. The contractor was permitted to perform the work

with no knowledge of the potential impact of the work, no

approved procedures, and inadequate oversight.

In addition, once water flow in the equipment cooling system

was affected, the utility failed to rigorously pursue the cause

of the problem and to appreciate its significance.

The NRC team's function was to gather information about the
problem, its causes, and the utility's corrective actions.

Further NRC reviews will determine what violations of NRC

requirements occurred, if any, and what enforcement action is

appropriate.

The executive summary of the inspection report is attached.

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(NOTE: The full report may be obtained from the NRC Region III

Office of Public Affairs. It is also available on the NRC's

internet web site at the following address:

<http://www.nrc.gov/OPA/reports>.

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NRC AUGMENTED INSPECTION TEAM REPORT EXECUTIVE SUMMARY

On June 19, 1996, with both units [at the LaSalle Nuclear Power

Station] operating at 100% reactor power, non-essential service

water discharge pressures began to decrease due to high

differential pressures across the in-line strainers. Actions

were successfully taken by the operators to backwash the

strainers and restore normal discharge pressures. On June 24,

1996, the same problem recurred and a diesel fire pump

concurrently experienced high coolant temperatures during routine

surveillance testing.

The licensee's root cause determination following the initial

event on June 19 was inadequate and focussed on sandblasting

material that the licensee believed had become entrained in the

non-essential service water system and fouled the strainers.

Subsequent to the June 24 event, the licensee determined that the

cause of both events was injectable sealant being used to repair

cracks in the structure of the safety-related service water

intake tunnel. The intake tunnel provides a common water source

for both Unit 1 and Unit 2 non-essential and emergency service

water systems. The crack repair activities resulted in a large

amount of the sealant getting into the tunnel and a portion of it

being drawn into the non-essential service water strainers.

Following the June 19 and 24 events, the licensee incorrectly

concluded that the material that fouled the non-essential service

water system could not affect the emergency service water

systems. On June 28, during service water intake tunnel cleaning

operations, divers found sealant in the tunnel that could

compromise operability of the emergency service water systems.

After some delay, the licensee then declared the emergency

service water systems inoperable and shut down both units.

Subsequent to the events the licensee developed and effectively

implemented a plan to clean the sealant from the intake tunnel
and inspect selected system components. After discussion with

licensee management regarding NRC concerns on the scope and

direction of the licensee's actions, additional plans were

developed by the licensee which included the inspection and

cleaning of all emergency service water strainers and performance

of additional testing to ensure that all emergency systems

functioned and to demonstrate emergency system strainer backwash

capability. These additional inspections and tests were

satisfactorily performed and resulted in the discovery of several

significant issues.

The AIT concluded that the root cause of the strainer fouling was

poor control of work on a safety-related structure. The staff

responsible for assigning and controlling this work lacked

sufficient facility knowledge to appreciate the potential

consequences of this work. As a result, a contractor was

permitted to seal cracks in the safety-related service water

intake tunnel structure with no knowledge of the potential impact

of the work, no approved procedures, and inadequate oversight.

Control room operator performance and command and control in the

control room during event response were good. However, operators

responding to the Lake Screen House lacked appropriate knowledge

regarding non-essential service water strainer operation.

The AIT also concluded that an inadequate assessment of the root

cause of the June 19 and 24 events, as well as the failure to

develop a comprehensive and thorough inspection and recovery

plan, permitted repeated challenges to key safety systems and the

availability of the ultimate heat sink. Loss of the function of

those safety systems, and the resultant loss of the ultimate heat

sink, would have significantly impacted the licensee's ability to

respond to analyzed accidents. Had the root cause evaluation for

the initial event been thorough, the event of June 24 could have

been avoided, reducing the time that the emergency service water

systems for both units were threatened.