In a previous paper, it was shown that circumferential in-plane stresses in the pontoon shell are caused by the circumferential bending deformation of the pontoon of a floating roof due to nonlinearity of sloshing. In this paper, the validity of the present nonlinear sloshing analysis is confirmed by comparing the theoretical results with results of a sinusoidal excitation test using a floating roof of a cylindrical storage tank with capacity of 15, 000kl and diameter of 38m.Numerical results for the sinusoidal excitation with the radial first mode frequency show that large vibration mode at the pontoon with circumferential wave number 2, (that is cos 2φ)is caused. This behavior is also observed in the sinusoidal excitation test of floating roof of storage tank with liquid depth of 10m. Furthermore, the validity of the present nonlinear sloshing analysis is confirmed by comparing the calculated and measured circumferential in-plane stresses on pontoon outer rim.
Next, influence of the liquid depth on the stresses of pontoon is investigated. Numerical results show that the stresses become large due to the internal resonance when the liquid depth increases to 20m.This is due to the fact that the internal resonance occurs because the natural frequency of a mode with circumferential wave number 2 is twice the natural frequency of the radial first mode with circumferential wave number 1.

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The important factors of future nuclear reactors are efficiency of nuclear fuel, minimization of nuclear wastes, advancement of nuclear safety and high nuclear proliferation resistance. We investigate one of these innovative water reactors; Fast Spectrum Light Water Reactor (FLWR) . It has unique construction for the reactor core but the fuel cladding material will be exposed in high internal pressure, axial load and complex temperature distribution. Therefore, we conducted a specially designed fatigue-creep test that simulated several parameters (thermal distribution, temperature variation, internal pressure variation and binding stress) to evaluate an applicability of fuel cladding material for FLWR. Zircalloy-2 which is common cladding material was used for the test. Test result was confirmed to compare the deformation value between tested and calculated. The result showed the evaluation method could control several parameters simultaneously and the deformation value after the test coincided to the calculated value. This method is sufficient to evaluate thermal deformation characteristics for FLWR.

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The 2003 Tokachi-Oki earthquake caused severe damage to oil storage tanks due to liquid sloshing. Seven single-deck floating roofs had experienced structural problems as evidenced by sinking failure in large diameter tanks at the refinery in Tomakomai, Japan. The pontoons of the floating roofs might be buckled due to bending load during the sloshing. The initial geometrical imperfection may diminish the buckling load of the pontoon. This paper presents the lower bound buckling load of the pontoons based on the reduced stiffness method proposed by Croll and Yamada. The axisymmetric shell finite element method is used in the linear elastic bifurcation buckling analysis.

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Experimental leakage tests on a flexible box-shaped flange connection with a non-asbestos compressed sheet gasket subjected to internal pressure is carried out under several conditions using Helium gas. The amount of the gas leakage is measured by changing the initial clamping force, the cover material in the connection. The stress analyses are also performed using Finite Element Method (FEM) to simulate the leakage tests considering the hysteresis in the stress-strain curve of the gasket and it calculates the reduced contact gasket stress distributions in the connection due to the application of internal pressure, which dominates the leak tightness of the connection. Using the reduced contact gasket stress distributions and the measured amount of the gas leakage, the new gasket constants that can describe the sealing performance of the box-shaped flange connection are identified and the sealing performance is evaluated. In addition, the method estimating the amount of gas leakage using the new gasket constants is proposed. The sealing performance of the connection with the raised face is also examined by FEM and compared with the results with the flat face. Discussion is made on the effects of the initial clamping force, the cover material and the type of gasket facing on the sealing performance in the connection. It has been found the effect of the facing type becomes large. The sealing performance of the connection with the raised face gasket will be worse than that with the flat face gasket in case that the same average gasket stress is given. It has been also found that the effect of the cover material, the difference between aluminum alloy and carbon steel, is small on the sealing performance. The estimated amount of gas leakage is in a fairly good agreement with the measured one.

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A large-scale leakage happened from the discharge flange of water supply pump located at the Sasage pump station of Yokohama Waterworks bureau on July 10 in 2007. The motors in the pump station were submerged by water and inevitably stopped. Suspension of water supply or low pressure water supply reached to 22000 houses due to this accident. It took about six hours until the water supply was recovered by using another water supply routes. The investigation committee (headed by Professor Sekine of Yokohama National University) was formed. The investigation committee charged High Pressure Institute of Japan (in shorten HPI) to determine the root cause of the accident. HPI has formed the special group headed by Professor Sawa of Hiroshima University and the members described above. The group immediately started to investigate and take necessary measurements of the bolted flange joints in the facility. Then, the group interviewed the foreman engaged in the maintenance work, analyzed the operation data, carried out the experiment to measure the gasket behavior and examined the root cause. The group found that the main accident cause was due to the lower gasket stress caused by inadequate tightening of the bolts when the pump was overhauled in March 2007. The group summarized a written report of the whole activity of the special group to elucidate the accident cause and to propose the methods for preventing the leakage accident from bolted flange joints with gaskets.

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