Full Description

The appropriateness of seismic design requirements and methods for nuclear power plant piping has been of increasing concern in the industry. Modern designs are characterized by a large number of seismic supports and many snubbers. Costs for design, installation, and maintenance for piping systems are extreme. In addition, the high level of congestion in the plant, from the structure for these supports, has an adverse impact on installation, maintenance, inservice inspection, and testing of all equipment. To improve this condition, it is important to investigate the root causes. Two aspect of the problem are evaluated in this report the nuclear piping code requirements for seismic loading, and the analytical methods used to predict the loads. The evolution and development of the ASME Boiler and Pressure Vessel Code requirements for seismic design of piping are documented. Included is the technical basis for the 3 Sm limit for piping primary stresses under Level D (or faulted) conditions. Primary stress limits in the code are based on static loading considerations. These limits are unnecessarily conservative for dynamic seismic loads and should be revised. Equally important to seismic design are the prediction of the seismic input to the piping and the response of the piping to that input. The development of analytical methods and regulatory requirements for seismic design are reviewed. Based on this information, it is the author's opinion that linear elastic dynamic analysis techniques-as presently implemented-are not realistic and are not effective for piping system seismic design. The design process should take advantage of the ductility of piping and the resulting inelastic energy absorption capability.

Product Details

Published: 1991 Number of Pages: 52 File Size: 1 file , 7 MB