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UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF NUCLEAR REACTOR REGULATION WASHINGTON, D.C. 20555 July 15, 1992 NRC INFORMATION NOTICE 92-52: BARRIERS AND SEALS BETWEEN MILD AND HARSH ENVIRONMENTS Addressees All holders of operating licenses or construction permits for nuclear power reactors. Purpose The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to alert addressees to problems that could result from missing or deteriorated barriers or seals that protect equipment designed to operate in a mild environment from areas that could have a harsh environment following a design basis accident (DBA). 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 information notice are not NRC requirements; therefore, no specific action or written response is required. Description of Circumstances On April 1, 1992, with the Millstone Nuclear Power Station, Unit 1, in cold shutdown, the Northeast Nuclear Energy Company (the licensee) performed a walkdown inspection of the environmental qualification barriers in the switchgear area. The licensee found a number of postulated steam paths into the switchgear area, including gaps between floor hatch covers and the surrounding floors, openings around doors where gasket material was missing, and miscellaneous small gaps and openings. The licensee had previously performed evaluations for its environmental qualification (EQ) program but did not adequately document determinations of the acceptability of barriers or unsealed openings. The licensee's EQ program also did not establish procedures to periodically check and replace, as necessary, some of the gaskets and seals used in the plant to protect equipment from a harsh environment. Discussion In Section 50.49 of Title 10 of the Code of Federal Regulations, the NRC established requirements for the environmental qualification of electrical 9207090264. IN 92-52 July 15, 1992 Page 2 of 2 equipment important to safety. Equipment that operates in a "mild" environment was not included within the scope of the regulation; inherent is the presumption that "mild" environments do not change into "harsh" environments. The circumstances described above indicate that some licensees may not have maintenance procedures to ensure the integrity of seals or barriers between "harsh" and "mild" environment areas. If safety-related equipment intended for "mild" environments were operated at more demanding conditions, it could cause safety concerns. 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. Charles E. Rossi, Director Division of Operational Events Assessment Office of Nuclear Reactor Regulation Technical contacts: H. Walker, NRR (301) 504-2827 J. Carter, NRR (301) 504-1153 Attachment: List of Recently Issued NRC Information Notices .
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