United States Nuclear Regulatory Commission - Protecting People and the Environment

Methodology for Combining Dynamic Responses (NUREG-0484, Revision 1)

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Publication Information

Manuscript Completed: April 1980
Date Published:
May 1980

Prepared by:
R. K. Mattu

Division of Safety Technology
Office of Nuclear Reactor Regulation
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

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The NRC has historically required that the structural/mechanical responses due to various accident loads and loads caused by natural phenomena (such as earthquakes) be combined when analyzing structures, systems, and components important to safety. This requirement flows from lOCFR50, Appendix A, General Design Criterion 2, which calls for an appropriate combination of the effects of the above events to be reflected in the design bases of safety equipment. This requirement has been implemented in various ways both within the NRC and the Nuclear Industry. An NRR Working Group constituted to examine load combination methodologies developed recommendations which were published in September 1978 as NUREG 0484. NRC adopted the Working Group's recommendations which stated: "For the combination of the dynamic responses within the Reactor Coolant Pressure Boundary (RCPB) and its supports which result from the coincidence of an SSE and LOCA, the Square Root of the Sums of the Squares (SRSS) technique is acceptable contingent upon performance of a linear elastic dynamic analysis to meet the appropriate ASME Code, Section III, Service Limit." Revision 1 of NUREG-0484 extends the conclusions of the original NUREG-0484 on the use of SRSS methodology for the combination of SSE and LOCA responses beyond RCPB to any other ASME Section III, Class 1, 2, or 3 affected system, component or support, and provides criteria for the combination of dynamic responses other than SSE and LOCA.

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