NRC Generic Letter 87-11, Relaxation in Arbitrary Intermediate Pipe Rupture Requirements

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June 19, 1987

TO ALL OPERATING LICENSEES, CONSTRUCTION PERMIT HOLDERS AND APPLICANTS FOR CONSTRUCTION PERMITS

SUBJECT: RELAXATION IN ARBITRARY INTERMEDIATE PIPE RUPTURE REQUIREMENTS (GENERIC LETTER 87-11)

The NRC has finalized a revision to Branch Technical Position MEB 3-1 of Standard Review Plan Section 3.6.2 in NUREG-0800 (Enclosure 1). The revision eliminates all dynamic effects (missile generation, pipe whipping, pipe break reaction forces, jet impingement forces, compartment, subcompartment and cavity pressurizations and decompression waves within the ruptured pipe)

and all environmental effects (pressure, temperature, humidity and flooding)

resulting from arbitrary intermediate pipe ruptures. This action allows the elimination of pipe whip restraints and jet impingement shields placed to mitigate the effects of arbitrary intermediate pipe ruptures, and other related changes. Licensees of operating plants desiring to eliminate previously required effects from arbitrary intermediate pipe ruptures may do so without prior NRC approval unless such changes conflict with the license or technical specifications. In the case of a conflict, a license amendment should be requested before any changes are made. In either cases the licensees' updated FSARs should reflect eliminated hardware associated with arbitrary intermediate pipe ruptures.

Arbitrary intermediate pipe ruptures, which previously were specified in B.1.c.(1)(d) of MEB 3-1 for ASME Code Class 1 piping and in B.1.c.(2)(b)(ii)

of MEB 3-1 for ASME Code Class 2 and 3 piping, are now no longer mentioned or defined in MEB 3-1. Besides the relaxation in requirements relating to arbitrary intermediate pipe ruptures, the revised Standard Review Plan Section 3.6.2 updates the citations to the ASME stress limits to achieve con-sistency with current practices, and introduces other minor changes. However, requirements for postulated terminal end pipe ruptures, postulated intermediate pipe ruptures at locations of high stress and high usage factor and for leakage cracks are retained in the revision to MEB 3-1.

Frank J. Miraglia, Jr. Associate Director for Projects Office of Nuclear Reactor Regulation

Enclosure: Revised MEB 3-1 of SRP 3.6.2.

8706230486

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