Relaxation in Arbitrary Intermediate Pipe Rupture Requirements (Generic Letter No. 87-11)
NUCLEAR REGULATORY COMMISSION
WASHINGTON, D.C. 20555
June 19, 1987
TO ALL OPERATING LICENSEES, CONSTRUCTION PERMIT HOLDERS AND APPLICANTS FOR
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.
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