Yoshitsugu Nekomoto

The development of a diagnostic and monitoring system for vibrating pipe branches

Abstract This paper deals with a diagnostic and monitoring system for assessing the integrity of pipe branches, during the operation of the nuclear power plant. This system have been developed under the concept of “easy to use without any sophisticated analysis” and “portable”. The accuracy of the diagnosis is based on the model optimization subsystem, which automatically modifies the numerical vibration model so as to fit its natural frequency to the actual natural frequency. The information obtained by this system may be reflected to a maintenance program of the plant to assure more reliable operation of the plant.

Experimental Study on Free Standing Rack Loading Full Fuel Assembly

The spent fuel storage rack of a nuclear plant stores the spent fuel temporarily before it can be moved to a reprocessing facility. Therefore, the spent fuel storage rack must have a high tolerance against large seismic loads. So, the free standing rack is developed in Japan as other countries. The free standing rack structure incorporates the effect of the friction force on the spent fuel pool floor, and the fluid effect.Under earthquake condition, the free standing rack sliding and rocking motions are induced and the spent fuels rattle in the cells.In this paper, sliding and rocking motions of full-scale rack model having full loading fuel assembly subjected to the seismic excitation are studied. To develop an analysis evaluation method for rack motions, we carried out seismic test of a full-scale rack model using a shaking table, and obtained the fundamental data about the free standing rack.Copyright

Experimental Parameter Study on Free Standing Rack

The spent fuel rack of a nuclear plant stores the spent fuel temporarily before it can be moved to a reprocessing facility. Therefore, the spent fuel rack must have a high tolerance against big seismic loads. Sliding and rocking motions of full-scale rack model having full loading fuel assembly subjected to the seismic excitation are studied [1]. We carried out the seismic test of the free standing rack under some conditions. The distribution of the fuel assembly affects the sliding and rocking motions of the rack, and the outer plate reduces the rack response level by fluid effect. We made sure of them by seismic experiment using a shaking table.In this paper, sliding and rocking motions of full-scale rack model under some conditions are studied. To develop an analysis evaluation method of the rack sliding and rocking motions, we obtained the fundamental data about the free standing rack by seismic test using a shaking table.© 2012 ASME

Experimental and Analysis Study of Free Standing Rack Under Seismic Excitation

For high earthquake resistance and ease of installation, free standing racks which are not anchored to the pool floor or walls has been adopted in many countries.Under the earthquake, the response of the free standing rack is highly nonlinear and involves a complex combination of motions (sliding, rocking, twisting, and turning) and impacts between the fuel assemblies and the fuel cell walls, rack-to-rack, and the pit floor and rack pedestals. To obtain an accurate simulation of the free standing rack, the seismic analysis requires careful considerations of these complex phenomena (sliding, rocking, twisting, and turning), fluid coupling effects and frictional effects.We carried out seismic experiments on the full-scale rack model in water and dry conditions to obtain the fundamental data about free standing rack (sliding, rocking and turning motions). We have developed the nonlinear dynamic analysis method to predict seismic response for the free standing rack utilizing the full-scale test result and verified the analysis evaluation method of the rack by comparison of test result.Copyright

Evaluation of the Sliding Behavior of the Rack Using CAV Concept

The spent fuel taken out of a nuclear plant reactor is temporarily stored in spent fuel racks. This fuel will often have to be stored in the long periods before it can be moved to a reprocessing facility. Therefore, the spent fuel rack must have a large capacity with a high tolerance against big seismic loads. So, the free standing rack is developed as the optimal equipment meeting these requirements. The free standing fuel rack is installed on the floor in the spent fuel pool and it can have the simple structure, as it needs no supports on the floor or the wall of the spent fuel pool. The free standing spent fuel rack structure actively incorporates the effects of the friction force generated on the spent fuel pool floor, and the fluid effect. So, seismic analysis is performed by nonlinear dynamic time history analysis. In this study, we applied CAV concept (CAV: Cumulative Absolute Velocity) to evaluate of nonlinear rack response. And it was confirmed that the CAV concept using the low-pass filter is useful to evaluate the sliding and rocking behavior of the rack by simulation analysis.Copyright

Development of on-line computer seismic test system using substructuring method.

The on-line computer test method is a new type of research technique to study the earthquake response bohavior of various types of structural elements, assemblages, and systems. It combines the experiment and numerical analysis and utilizes the benefits of both experimental and analytical research. In this study, we applied substructuring concepts to the on-line computer test method and developed a new algorithm which increases the accuracy of the substructuring method. By using this algorithm, we can simulate a more realistic elasto plastic seismic response of structures. For the purpose of development and verification of this algorithm, we prepared a small-scale on-line computer test system and simulated the high-level seismic response of a liquid tank which had seismic isolation devices.