United States Nuclear Regulatory Commission - Protecting People and the Environment

Relaxation in Arbitrary Intermediate Pipe Rupture Requirements (Generic Letter No. 87-11)



                                UNITED STATES
                        NUCLEAR REGULATORY COMMISSION
                           WASHINGTON, D.C. 20555

                                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.


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