[en] The laminated rubber bearing consisting of rubber and steel plates has been widely used in base structures to absorb earthquake vibration. The function of this bearing is to support all the weight of the structure and protect the structures from shear vibration by earthquake. Due to the nearly incompressible property of hyperelasticity, the displacement-based finite-element solutions cause large errors in pressure solutions. In order to overcome this shortcoming, a mixed method has been proposed, where pressure and displacement fields are developed as independent unknown variables. Finite-element solutions depend upon shape function and the numerical integration technique; however, the suitable numerical condition for a laminated rubber bearing has not been fully discussed. The present paper will show the mixed finite-element formulation in rate type for hyperelasticity, and show numerical examples of the laminated rubber bearing system in shear deformation to clarify the advantage of the analysis method and the fundamental feature of mechanical response. (author)

[en] In this study, combustion character of thermal degraded electrical cable for the nuclear power plant was evaluated. To make aging degradation electrical cables, accelerated thermal ageing tests were carried. The electrical cable combustion tests on a simple cable tray were applied to evaluate combustion character of thermal degraded electrical cable. Temperature of the accelerated thermal ageing tests were 90degC. 80degC, 70degC and period of tests were 10, 20, 40 days respectively. Finally, combustion tests on the simple cable tray was analyzed by FDS (Fire Dynamics simulation). FDS analysis software apply two fire models (one model was based on heat released rate: HRR model, the other was based on chemical reaction: CR model). In this case, the HRR model was applied. Heat released rate calculated by the FDS analysis was similar to it by the electrical cable combustion tests. (author)

[en] In this study, a cable fire in nuclear power plant room was analyzed by FDS (Fire Dynamics Simulator). To evaluate combustion character of electrical cable was important in terms of safety assessment of nuclear power plant. However, experiment at evaluation was difficult due to scale and costs. FDS analysis software apply two fire model (one model was based on heat released rate: HRR model, the other was based on chemical reaction: CR model). HRR model and CR model were prepared by combustion tests by cone-calorie heater machine. FDS analysis of cable fire at switchgear room was conducted. The numerical result of FDS analysis showed reasonable fire spreading at CR model. It is because CR model could take oxygen concentration into consideration. (author)

[en] Thick rubber bearings as 3-dimensional base isolators have been developed to reduce both horizontal and vertical seismic loads especially for equipment in Fast Breeder Reactors. In this report, a design method of thick rubber bearings is presented. Rubber bearing tests are conducted with 1/3 scale models to evaluate mechanical properties of thick rubber bearings including ultimate limits. In the tests, horizontal and vertical characteristics of 1/3 scale model are compared with those of 1/6 scale model to discuss scale effect of test specimen. Ultimate limits such as failure shear strain of thick rubber bearings are obtained under various lading conditions. From the test results, we confirm that full scale thick rubber bearing to satisfy requirements is feasible. Furthermore, to consider nonlinearity of vertical stiffness affected by vertical stress in the design of thick rubber bearings, Lindley's evaluation method of vertical stiffness is modified as an explicit form of vertical stress. We confirm that the presented method is efficient for design of the thick rubber bearings from comparing between test results and predicted values. (author)

[en] The ordering of the one-dimensional Heisenberg spin glass interacting via the long-range power-law interaction is studied by Monte Carlo simulations. Particular attention is paid to the possible occurrence of 'spin-chirality decoupling' for appropriate values of the power-law exponent σ. Our result suggests that, for intermediate values of σ, the chiral-glass order occurs at finite temperatures while the standard spin-glass order occurs only at zero temperature

[en] In this study, design procedure on three-dimensional base isolation system is developed. Base isolation system proposed by CRIEPI uses thick rubber bearing and damper as isolation device. As for thick rubber bearings, design formula for evaluating vertical stiffness is proposed, and design conditions regarding size and vertical pressure are investigated. Figure-U type lead damper is proposed as three-dimensional damper and by loading tests its mechanical characteristics is evaluated. The concept of multi-layered interconnected rubber bearing, which is advantageous over large scale bearing in manufacturability, is proposed and its good performance is confirmed by the loading test. Through the response analyses, it is shown the rocking response of the proposed three-dimensional base isolation system is very small and not influential to the system, and the reduction of the vertical response is attained using the proposed isolation device. (author)

[en] Rubber bearings with thick rubber layers to be used for 3-dimensional base isolation system are developed. Design parameters of the rubber bearings are determined to effectively reduce both horizontal and vertical seismic loads especially for equipment in the system; horizontal natural period and vertical natural frequency of the system supported by the rubber bearings are 3 sec. and 3 Hz, respectively. Furthermore, primary and secondary shape factors and design vertical stress of the rubber bearings are determined to give stable mechanical properties. Using scale models of the rubber bearings, static, dynamic and failure tests were carried out to evaluate the mechanical characteristics and the performance of the rubber bearings. From these tests, it is shown that the developed rubber bearings are efficient as 3-dimensional base isolation device. (author)

[en] In this report, to evaluate creep properties and effects of creep deformation on mechanical properties of thick rubber bearings for three-dimensional isolation system, we show results of compression creep test for rubber bearings of various rubber materials and shapes and development of numerical simulation method. Creep properties of thick rubber bearings were obtained from compression creep tests. The creep strain shows steady creep that have logarithmic relationships between strain and time and accelerated creep that have linear relationships. We make numerical model of a rubber material with nonlinear viscoelastic constitutional equations. Mechanical properties after creep loading test are simulated with enough accuracy. (author)

[en] In order to reduce horizontal and vertical earthquake response of internal equipments in the nuclear power plants, we evaluated the performance of three dimensional base isolation system using laminated thick rubber bearings. From the loading test of scaled model of laminated thick rubber bearing, it was found that the natural rubber bearing was able to be extended to thick rubber bearings, and the difference of mechanical characteristics was only the dependency of the vertical stiffness on the horizontal displacement. Second, we carried out shaking table test for scaled model of base isolated structure. The results showed that horizontal characteristics of thick rubber bearing was almost the same as the thin one, and the vertical stiffness was able to be determined according to the resonance period of internal equipments. After the test, we carried out the numerical analysis on the shaking table test. Numerical results showed that the response of the model for earthquake input motion and its response spectra were in good agreement with the experiment, and the resonance peak of the floor response spectra can be reduced when the damping coefficient of the vertical damper increases. (author)

[en] In order to verify the long-term leak tightness of transport casks for MOX fresh fuel, aging tests of the sealing gasket were performed on the containment system of the casks under a predicted condition of five years at 70degC. The durability was verified by the accelerated tests by heating to simulate the aging effect using the Larson-Millar Parameter (LMP). Scale models (rate:1/5) of the containment system of the cask with two types of gaskets (Fluorocarbon rubber: FKM and Ethylene Propylene Diene Monomer: EPDM) were employed for the tests. There was no change in the leak rate before and after the heating. The compression set: Dp corresponding to 70degC for five years (LMP=5367) are less than 80% which is generally considered as a service limit Dp for leak tightness. Therefore, it can be concluded that the sealing gaskets will keep their containment integrity, at least, for five years at temperature of 70degC. (author)