Information Notice No. 92-52: Barriers and Seals Between Mild and Harsh Environments

                                 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



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                                                            IN 92-52
                                                            July 15, 1992
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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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