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NRC Revises Its Regulations for Fire Barrier Penetration Seals

The Nuclear Regulatory Commission is revising its regulations to modify the requirement for fire barrier penetration seal material for nuclear power plants because the present requirement makes a negligible contribution to safety.

As part of the NRC's defense-in-depth philosophy for protecting nuclear power plants through the use of multiple safety features, the plants are divided into separate areas by fire-rated barriers designed to contain a fire and prevent its spread to other areas. Various kinds of materials, some silicone-based, are used to seal openings between fire barriers. The seals provide reasonable assurance that a fire will be confined to the area in which it starts.

NRC has determined that if fire barrier penetration seals are properly designed, tested, configured, installed, inspected and maintained, they are capable of preventing the spread of fire for one, two or three hours, providing sufficient time for automatic systems or firefighters to control and extinguish the fire. Therefore, the NRC's technical staff and Advisory Committee on Reactor Safeguards -- an independent body of technical experts that provides guidance to the Commission -- agreed that the non-combustibility requirement in Title 10 of the Code of Federal Regulations, Part 50, Appendix R, be eliminated because it has a negligible contribution to safety.

The proposed rule was published in the August 18 edition of the Federal Register for public comment. Eight letters were received and the NRC staff reflected some of the suggestions in the final rule.

The new rule will become effective 90 days following publication in an upcoming edition of the Federal Register. A copy of the rule will be posted at: http://ruleforum.llnl.gov on the NRC homepage.

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