UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555

June 25, 2003

NRC INFORMATION NOTICE 2003-08: POTENTIAL FLOODING THROUGH UNSEALED

CONCRETE FLOOR CRACKS

Addressees

All holders of operating licenses or construction permits for nuclear power reactors.

Purpose

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

addressees of observed flooding in a room containing safety-related panels and equipment as

a result of fire water seepage through unsealed concrete floor cracks. It is expected that

recipients will review the information for applicability to their facilities and consider actions as

appropriate to avoid similar problems. However, suggestions contained in this NRC information

notice are not NRC requirements; therefore, no specific action or written response is required. 

Description of Circumstances

On May 3, 2002, at Energy Northwest’s Columbia Generating Station, 15 to 20 gallons of water

spilled from a firewater drain line onto the floor of the radwaste building 484' elevation cable

spreading room. A small amount of this water leaked down into the remote shutdown room and

the Division II switchgear room, which is located below the cable spreading room floor. The

licensee determined that the pathway for the leakage was through cracks in the concrete floor. 

Discussion

During the performance of a fire protection system surveillance test, 15 to 20 gallons of water

spilled on the cable spreading room floor. The water leaked through the concrete floor through

a small crack and a spalled area of the concrete floor. The rooms below the cable spreading

room floor housed the remote shutdown panel and safety-related switchgear. It was estimated

that only a small amount of the 15-20 gallons actually passed through the floor. No damage

occurred to the switchgear or the remote shutdown panel. However, thousands of similar small

cracks were present on the cable spreading room floor. The room also housed a deluge fire

system. Actuation or inadvertent rupture of the deluge system would likely result in additional

floor leaks that could impact the Division I and II switchgear, Division I and II batteries, the

remote shutdown panel and the alternate remote shutdown panel.

10 CFR 50, Appendix A, Criterion 3 requires licensees to design fire protection systems so that

their rupture or inadvertent operation does not significantly impair safety systems.

NRC Branch Technical Position 9.5.1, Appendix A, “Guidelines for Fire Protection for Nuclear

Power Plants,” references guidance contained in National Fire Protection Association (NFPA)

92M for maintaining concrete floors. NFPA 92M states that, “Concrete floors should be 

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inspected frequently for cracks. Damaged floors may be repaired by use of special

compounds. Fine hairline cracks may, in most cases, be sealed with an application of floor

paint.” As corrective measures, the licensee performed additional inspections and sealed all

appropriate unsealed concrete floors with an approved flexible epoxy coating. 

The licensee determined that the cracks in the concrete floor resulted from flexing and

shrinkage of the floor. In the case of the spalled concrete around a penetration seal, the

material was degraded to the point that cracks provided a pathway for water to bypass the

penetration seal and enter the remote shutdown room. The degradation was caused by

cracking of the concrete during installation of the concrete anchors adjacent to the seal. The

cracking occurred due to insufficient distance between the concrete anchors which allowed the

formation of tensile shear cracks.

Neither the water that entered the remote shutdown room nor the water that entered the safetyrelated switchgear room caused safety-related equipment to become inoperable. In order for

the water entry to have become significant, the water would have had to collect in an area

where electrical contacts or terminals are located or enter into the cables. A related information

notice, IN 2002-12, “Submerged Safety-Related Electrical Cables” addresses cable failure

caused by water intrusion into the cable with subsequent drying and degradation of the

insulation.

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

questions about the information notice in this notice, please contact the technical contact listed

below or the appropriate project manager from the NRC’s Office of Nuclear Reactor Regulation.

/RA/

William D. Beckner, Program Director

Operating Reactor Improvements Program

Division of Regulatory Improvement Programs

Office of Nuclear Reactor Regulation

Technical contact: George Replogle, RIV

509-377-2627

E-mail: gdr@nrc.gov

Attachment: List of Recently Issued NRC Information Notices