Andrew J. Murphy

Seismic responses and resistance of age degraded structures and components

Nuclear power plants, as with many other structures, can experience aging degradation on a continuing basis. In some cases, the environmental or operating conditions, which they are subjected to, may be more severe than those affecting non-nuclear structures. This degradation needs to be understood and adequately managed for the continued safe operation of nuclear power plants. To date a limited number of nuclear power plants in the US have specific monitoring and inspection programs for structures. The evaluation for seismic loading is particularly important because the degraded structures or components could be more vulnerable to the seismic loads. From a seismic analysis point of view, the aging or degradation may affect dynamic properties, structural response, resistance or capacity, failure modes, and locations of failure initiation. Further, the NRC license renewal rule requires in part that the current licensing basis (CLB) be maintained throughout the period of extended operation. To meet this requirement, an assessment and timely maintenance of the degraded structures and components becomes necessary. An international cooperative program is being considered to pull together resources to tackle the issue of seismic effects on aged/degraded structures and components, and to augment existing databases by using experience of nuclear power plants worldwide. Based on the insights and lessons learned from this program, technical bases could be established for each participating country, as needed, to develop guidelines to address the seismic capability of aged/degraded structures and components for continued and extended service. The extent of the program will depend on the results of a scoping or bounding study to be performed in the initial phase.

PROBABILISTIC SITE IDENTIFICATION ANALYSIS USING NUPEC RECORDED FREE FIELD MOTIONS.

THIS PAPER DESCRIBES A PROBABILISTIC SITE IDENTIFICATION ANALYSIS PERFORMED BY BNL, USING THE FREE FIELD EARTHQUAKE MOTIONS RECORDED AT THE NUPEC TEST SITE. THE BNL ANALYSIS WAS INTENDED TO PROVIDE ADEQUATE CHARACTERIZATION OF THE SOIL PROPERTIES FOR THE TEST SITE TO BE USED FOR SSI ANALYSES. THE FREE FIELD DATA WERE PROVIDED BY NUPEC. THE METHODOLOGY EMPLOYED IN THE BNL PROBABILISTIC ANALYSIS OF SITE IDENTIFICATION INCLUDES THE MONTE CARLO PR...

Recent assessments in USA of spent fuel packages exposed to severe thermal environments different from regulatory standards

Abstract The regulatory driven design of radioactive material transportation packages leads package vendors to perform analyses that demonstrate the ability of packages to meet the regulatory requirements. For risk assessment and communication, the analysis of package response to thermal environments that are more severe than those described in the regulations is required. In general, experimental and analytical assessments of casks exposed to thermal insults other than the regulatory environment are performed in the USA by the Department of Energy national laboratories. This paper provides a brief summary of some recent thermal analyses of spent fuel transportation packages exposed to thermal environments different from regulatory standards. The analyses were performed by Sandia National Laboratories under several different projects for multiple customers. These analyses examined the response of spent fuel packages exposed to severe thermal environments different from the regulatory hypothetical accident condition. One assessment determined the response of four generic casks to very long duration engulfing fires. The results from these analyses included fire durations necessary to reach critical temperatures of the fuel and seals. In another assessment, two certified spent fuel casks were analysed for exposure to 1 h pool fires. The height of the cask above the pool was varied to study the effect of the vapour dome on the heating of the casks. Another assessment investigated the effect of offset long duration fires on rail cask performance, which showed that casks can withstand offset fires of much longer duration than the regulatory fire. Other assessments examined the response of packages to thermal environments resulting from propane fires and realistic liquid hydrocarbon fires that included various positions of the transportation rail car in the simulation.