ICONE14-89378 EXPERIMENTAL STUDY ON STRUCTUAL INTEGRITY OF A CORE SHROUD SUPPORT WITH A CRACK UNDER SEISMIC LOAD

ABSTRACT This study was performed to experimentally confirm the conservatism of the integrity assessment procedure for a cracked core shroud support of the boiling water reactor (BWR) under seismic load. From the comparison of the experimental and analytical results, it is shown that finite element method (FEM) is accurate and collapse load estimated by twice-elastic slope method is conservative

Characteristics of Cu stabilized Nb3Al strands with low Cu ratio

Characteristics of recently developed F4-Nb{sub 3}Al strand with low Cu ratio are described. The overall J{sub c} of the Nb{sub 3}Al strand could be easily increased by decreasing of the Cu ratio. Although the quench of a pulse-like voltage generation is usually observed in superconducting unstable conductor, the F4 strand with a low Cu ratio of 0.61 exhibited an ordinary critical transition of gradual voltage generation. The F4 strand does not have magnetic instabilities at 4.2 K because of the tantalum interfilament matrix. The overall J{sub c} of the F4 strand achieved was 80-85% of the RRP strand. In the large mechanical stress above 100 MPa, the overall J{sub c} of the F4 strand might be comparable to that of high J{sub c} RRP-Nb{sub 3}Sn strands. The Rutherford cable with a high packing factor of 86.5% has been fabricated using F4 strands. The small racetrack magnet, SR07, was also fabricated by a 14 m F4 cable. The quench current, I{sub q}, of SR07 were obtained 22.4 kA at 4.5 K and 25.2 kA at 2.2 K. The tantalum matrix Nb{sub 3}Al strands are promising for the application of super-cooled high-field magnets as well as 4.2 K operation magnets

METHOD TO EVALUATE FATIGUE LIFE OF CARBON STEEL UNDER SIMULATED SYNCHRONOUSLY CHANGING BWR CONDITION-asme/terms-of-use ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ( ) ( )

ABSTRACT V : Water flow rate (m/s) The environmental fatigue life of carbon steel is influenced by BWR conditions such as water temperature, dissolved oxygen concentration, water flow rate and so on. These parameters change inconstantly during operation of BWR plants and strain rate changes in the structural components due to the temperature change. In general, fatigue life evaluation equations have been formulated based on the fatigue data obtained under constant conditions. To apply these equations to evaluate the fatigue life of actual components, a study is necessary to confirm the applicability of the proposed equations to the changing conditions. In this study, fatigue tests were performed under changing conditions of strain amplitude, strain rate, temperature, dissolved oxygen concentration and water flow rate. It was confirmed that the proposed fatigue life equation could predict the fatigue life under changing conditions. INTRODUCTION Ferritic steels are used for the primary structures of Light Water Reactor (LWR) plants. The corrosion fatigue behavior of these types of steels must be considered because these structures contain high-temperature oxygenated water, which is known to influence the fatigue life of these types of steels Although these fatigue life evaluation methods have been applied to the fatigue life evaluation of LWR plants, the data to construct these fatigue life evaluation equations have been obtained under constant testing conditions. In an actual plant, however, the mechanical and environmental parameters are changing during the plant operation. Therefore, the effects of such mechanical and environmental parameter changes on fatigue life evaluation have to be studied. A modified rate approach method has been proposed as a technique for estimating the fatigue life under mechanical and environmental parameter change conditions [7][8][9][10][11][12]. The applicability of the modified rate approach method has been studied under simulated PWR conditions including the changing conditions of temperature and strain rate [13, 14]. In the BWR conditions, however, dissolved oxygen concentration is know as one of the controlling parameters of fatigue life changes during the plant operation. And a recent study indicated that water flow rate has an effect on the fatigue life of ferritic steels under BWR conditions [15] and the water flow rate also changes during plant operation. Therefore, the applicability of the modified rate approach method under DO and flow rate change conditions must be studied. The method has been tried to the conditions in LWR plants [16]. In this study, the applicability of the modified rate approach under strain rate, strain amplitude, temperature, DO and flow rate was studied. EXPERIMENTAL PROCEDURE Materials The material used in this study was a carbon steel commonly used in piping for high-pressure service conditions (JIS G3455 STS410). The chemical composition and mechanical properties of this material are listed in Specimens Hollow cylindrical specimens, with an inner diameter of 10 mm and an outer diameter of 16 mm at the test section, were used for the fatigue tests. The shape and dimensions of the specimens are shown in Testing Apparatus A schematic illustration of the testing system is shown in The water was stored in a reservoir tank after being purified by a filter and an ion-exchanger. Nitrogen and oxygen gases were supplied to the tank to control the dissolved oxygen concentration (DO) of the stored water. A high-pressure pump forced water to flow from the tank to a pre-heater at rates between 0.01 and 0.03 m 3 /h. Three air-operated valves were used. While fatigue testing was being performed, air-operated valves No. 1 and 2 were open, and No. 3 was closed. The water was heated mainly by the pre-heater, while a micro-heater coiled around the pipe leading to the specimen was used for fine control of the water temperature. And also, an induction heating system set around the specimen can compensate the heat which is necessary to control the temperature change in some testing condition. The water flowed into the specimen from the bottom. The tip of a thermocouple was percussion-welded to the surface of the cylindrical core at a location corresponding to the longitudinal center of the gage length of the specimen. The fatigue testing was performed under high-flow-rate conditions over 0.3 m/s, induced by a high-flow-rate pump. This pump could recirculate the high-temperature water at up to 1 m3/h. The total volume of water flowing into the specimen was the sum of the volume from the high-pressure pump and the volume from the high-flow-rate pump. The water flowing out of the specimen was divided into two lines: one went back into the high-flow-rate pump, and the other to a cooler. After flowing through the cooler, the moderate-temperature water, which was slightly above room temperature, flowed through a pressure-regulating valve, a flow meter, and an ion-exchanger, then back to the tank. A by-pass line connected to the high-flow-rate pump included a valve, which could be used to control the flow rate of water to the pre-heater. The flow from the high-flow-rate pump was measured by a flow meter. The water flow rate through the specimen could be calculated by Eq. A load cell, which was fixed between the crosshead of the fatigue testing machine and the specimen chucking jig, measured the load applied to the specimen during fatigue testing. The longitudinal strain generated over the gage length of the specimen was calculated from the output of the displacement gage, the legs of which were touch-set on the specimen surface at a distance equal to the gage length. When the deepest crack penetrated the wall thickness of the specimen, high-temperature water normally leaked out as vapor. This decreased the pressure in the high-temperature water recirculation loop. A pressure gage, which was placed between valve No. 2 and the cooler, detected the pressure drop and caused valve No. 3 to open and valves No. 1 and 2 to close. Recirculation water then no longer flowed into the specimen. An acrylic resin cover was fixed around the specimen to ensure that the experiment could be performed safely. (2) Evaluation of Fen under changing conditions F en under the changing conditions was evaluated by the modified rate approach with the equation below. Fatigue testing The test conditions are listed in Here, F en,k is F en at the kth incremental segment in a strain increase cycle, ∆ε k is the strain range at the kth incremental segment in a strain increasing cycle and m is the number of segmentation in a strain increasing cycle. In the testing condition in which each strain wave synchronizes with the same environmental parameter fluctuation, F en can be evaluated from one stain wave. Then fatigue life in water can be predicted from F en and the fatigue life in air. On the other hand, in the testing condition in which the environmental parameters change for every strain wave, F en for each strain wave need to be evaluated such as F en,1 , F en,2 , F en,3 ,･･･F en,n . Then the fatigue life prediction is performed for every Fen such Method to Incorporate Flow Rate Effect Effects of water flow rate on fatigue life of carbon steel is shown in If F en,n ' becomes less than 1.0, the F en,n ' is set to 1.0. For test conditions with a flow rate changing condition, fatigue life was predicted with and without the flow effect incorporation expressed by equation RESULTS AND DISCUSSION The predicted fatigue life and test results are shown in CONCLUSIONS The applicability of the modified rate approach method to the fatigue evaluation of the BWR plant conditions was evaluated based on the tests under strain rate, strain amplitude, temperature, DO and flow rate changes. It was confirmed that fatigue life can be well predicted by the modified rate approach method within the factor of 3. ACKNOWLEDGEMENT The present research was conducted by the Japan Nuclear Energy Safety Organization（JNES） after being taken over from the Japan Power Engineering and Inspection Corporation (JAPEIC). The authors express their appreciation to the members of the EFT Project in JNES for their valuable comments and discussions

GT2011-45450 A NUMERICAL METHOD FOR TURBULENT FLOWS IN HIGHLY STAGGERED AND LOW SOLIDITY SUPERSONIC TURBINE CASCADES

ABSTRACT Two main problems are associated with conventional numerical methods for simulating turbulent flows in highreaction-type supersonic turbine cascades near the tip of the last stage blade in a steam turbine: the large skewness of computational grids and treatments of boundary conditions when the shock waves hit boundaries. This paper presents a numerical method to deal with these issues. A grid generation technique which uses five-block structured grids has been developed. The orthogonality of the grid is good even for highly staggered and low solidity cascades. In addition, the grids are completely continuous at the boundary between the blocks and at the periodic boundaries. Both the gradient of the grid lines and the change rate of the grid widths connected smoothly. As a result, shock waves can be captured accurately and stably. The inflow and outflow boundary conditions based on the two-dimensional characteristic theory have been applied and diminished the spurious reflections and fluctuations of shock waves at both the inlet and outlet boundaries. Therefore the non-physical reflection does not affect the flow in the cascades. A low Reynolds number k-ε turbulent model has been proposed. Distance from a wall is not used as the characteristic length of turbulent flows so that the turbulent model can be applied to a wake and a separation flow. The validity of the numerical method was verified by comparisons of the pressure distributions on the blade, the loss coefficients, and flow angles with linear cascade experiments of transonic compressor cascades

ICONE18-29214 FAST BREEDER REACTOR CORE CONCEPT TO IMPROVE NUCLEAR PROLIFERATION RESISTANCE

S