Information Notice 2002-05, Foreign Material in Standby Liquid Control Storage Tanks

Foreign Material in Standby Liquid Control Storage Tanks
	ML013530020
Person / Time
Site:	River Bend
Issue date:	01/17/2002
From:	Beckner W; Division of Regulatory Improvement Programs
To:	;
	Fields E N 301-415-1173
References
	TAC MB0371 IN-02-005
	Download: ML013530020 (5)
	v • d • e

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D. C. 20555-0001

January 17, 2002

NRC INFORMATION NOTICE 2002-05:

FOREIGN MATERIAL IN STANDBY LIQUID

CONTROL STORAGE TANKS

Addressees

All holders of licenses for nuclear power reactors.

Purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to inform

addressees of equipment and design issues identified recently at the River Bend Nuclear

Power Plant concerning debris found in the standby liquid control system storage tank. It is

expected that recipients will review the information for applicability to their facilities and consider

actions, as appropriate, to avoid similar problems. The aspect of this event considered of

particular interest is the evident potential for systems initially filled with a combination of dry

chemicals and water to have the wrapper material for the chemicals left in the system and to

remain there undetected for an extended period. However, suggestions contained in this

information notice are not NRC requirements; therefore, no specific actions or written response

is required.

Description of Circumstances

During monthly sampling of the standby liquid control (SLC) system storage tank in September

2000, part of a plastic bag was found in the SLC tank. Both trains of SLC were declared

inoperable while the licensee inspected the tank, removed several pieces of plastic, and

performed an evaluation. This event was discussed in NRC Inspection Report 50-458/00-14, ADAMS Accession No. ML003774888 and Licensee Event Report 50-458/00-013-00, ADAMS

Accession No. ML003769869.

Discussion

On September 14, 2000, while drawing a routine monthly sample from the SLC tank at River

Bend, Unit 1, chemistry personnel retrieved a 10-inch square piece of plastic along with the

sampling equipment. The SLC tank manway cover was removed and several additional pieces

of plastic were observed floating on the surface. Approximately 20 pieces of plastic which

ranged in size from 2 square feet to one-half square inch were identified and removed. Further

inspection of the tank with an underwater camera identified additional pieces of plastic on the

sparger supports and the mixing heater located at the bottom of the SLC tank.

Because of the potential for the plastic to be sucked into the SLC pump suction piping, both

SLC subsystems were declared inoperable. The plastic material was removed and further

inspections of the SLC tank were performed with an underwater camera. No additional foreign

material was identified. Additionally, a boroscope inspection of the horizontal suction piping

from the tank outlet to the downward elbow was performed. No material was identified during

the inspection. Based on the inspection and the buoyancy of the plastic material, the licensee

concluded that the remaining SLC pump suction piping would not contain any significant

amount of plastic material.

The licensee evaluated the effect that 1 square inch pieces of plastic would have on system

performance. The evaluation determined that pieces of plastic less than 1 square inch which

might be introduced into the SLC pump suction would not preclude the system from injecting

sodium pentaborate into the reactor. The licensee believed that any remaining plastic material

would be less than 1 square inch. At 8:59 p.m. that same day, both SLC subsystems were

declared operable due to the inspections of the SLC system, the removal of the plastic material, and the engineering evaluation.

The licensee established a significant event review team to investigate the event and evaluate

the safety significance of the plastic material in the SLC tank. The licensee determined that the

incremental risk from this event, assuming that the SLC system was out of service for a one

year time frame, was 3.0E-8. Since the upper limit for non risk-significant changes in

conditional core damage probability was 1.0E-6, the licensee concluded the event was not risk

significant.

Due to low flow velocities and the buoyancy of the plastic, the licensee believed that the SLC

system would have been able to perform its function even with the plastic in the tank, provided

the SLC storage tank was in a steady state condition. The only time the licensee believed that

the SLC systems behavior could not be predicted and operability demonstrated was during the

10-minute air agitation before the monthly chemistry sampling of the SLC tank contents. During

and immediately following the air sparger, the location of the plastic material in the SLC tank

could not be predicted. Therefore, the licensee concluded that the SLC system may not have

been able to provide its intended safety function during periods in which the tank was being

agitated with air.

On September 25, 2000, NRC inspectors conducted a walkdown of the alternate SLC injection

emergency operating procedure. They determined that the sodium borate and boric acid

chemicals to be used were not available in the warehouse or onsite for alternate SLC. The

inspectors notified the licensee and replacement chemicals were shipped from the Grand Gulf

Nuclear Station and arrived onsite at approximately 4 a.m., on September 26, 2000.

Further investigation by the licensee revealed that the alternate SLC injection chemicals had

been removed from the site. On March 3, 1999, a quality assurance chemistry audit had

identified chemical storage discrepancies (i.e., deteriorated packaging) with chemicals stored in

the onsite warehouse. On July 14, 1999, warehouse personnel removed the identified

chemicals from inventory as a corrective action for the deteriorated packaging problems

identified during the quality assurance audit. On July 28, 1999, the chemicals that had been

removed from inventory were transported to the environmental storage yard and subsequently shipped offsite. Warehouse personnel had not recognized that these chemicals were required

for an emergency operating procedure and adequate controls were not in place to identify them

as such. As a result, the chemicals were never replaced.

The licensees guidance document on procedural control, Authors Guide/Control and Use of

Emergency Operating and Severe Accident Procedures, required that operations personnel

perform yearly walkdowns of each emergency operating procedure enclosure. On October 2,

2000, in response to the inspectors identification of the missing chemicals, operations

personnel completed a review of their documentation of emergency operating procedure

enclosure audits and yearly walkdowns. The review determined that the yearly walkdowns of

each emergency operating procedure enclosure had not been performed since November 26,

1996.

As a result of this event, the Cooper Nuclear Station, also identified plastic material in their SLC

storage tank in the fall of 2001. Because of the small quantity of plastic found, the system was

not considered to be rendered inoperable.

This event points out the importance of effective foreign material exclusion controls to prevent

the introduction into the SLC storage tank or other similar systems of wrapper material which

could impair the system's operability. In this instance, the buoyancy of the plastic material

reduced the potential consequences. The event also pointed out the need for effective

periodic walkdowns of emergency operating procedure attachments to ensure that all required

equipment and materials are available to perform the emergency procedures.

This information notice requires no specific action or written response. If you have any

questions about the information in this notice, please contact one of the technical contacts

listed below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.

/RA/

William D. Beckner, Program Director

Operating Reactor Improvements Program

Division of Regulatory Improvement Programs

Office of Nuclear Reactor Regulation

Technical contacts: Stephen Max Schneider, Region IV

Ron Kopriva, Region IV

225-635-3193

817-860-8104 E-mail: sms2@nrc.gov

E-mail: rak1@nrc.gov

Attachment: List of Recently Issued NRC Information Notices shipped offsite. Warehouse personnel had not recognized that these chemicals were required