Regional instability evaluation of Ringhals unit 1 based on extended frequency domain model

The frequency domain model has been extended for the regional instability evaluation while retaining its practicality and improving the reliability of major influential numerical models. The unified friction and local pressure loss model of the original LAPUR was modified considering the different dynamic characteristic of two pressure loss mechanisms. The detailed ex-core recirculation loop model was implemented and the neutron point kinetics model was also modified to reflect the inter-mode void reactivity interaction. The neutron flux modal analysis code, ACCORD-N, was developed based on the nonlinear iterative nodal method. Efficient schemes were proposed to give the higher mode initial flux guess. The modified code system was verified based on the Ringhals unit 1 stability test data. Extensive studies were performed to identify influential factors in the regional instability. A dependence of the decay ratio was investigated with regard to the sub-criticality of the first azimuthal mode, Nyquist plots and several power shape indices. It seemed reasonable to conclude that the regional instability was strongly influenced by the thermal hydraulic mechanism. Including the simulation results of other reactors, the distance weighted axial power momentum, named the AS-value, gave a good account of both core-wide and regional instability modes.     

Driving force controller considering lateral slip based on brush model for traction control of independent‐four‐wheel‐drive electric vehicle

As one of the motion control methods of electric vehicles (EVs), a driving force controller (DFC) with a slip ratio limiter has been proposed. The conventional controller has a slip ratio limiter for safety reasons, but it does not consider the lateral slip of the tire during cornering. To deal with this problem, this paper proposes a DFC with a variable slip ratio limiter based on brush model. The experimental results show that the proposed controller can work on both acceleration and deceleration cornering, by increasing the lateral force and lateral acceleration for smoother cornering.     

Investigation of interfacial reactions between metallic substrates and n-type bulk bismuth telluride thermoelectric material

Journal of Materials Science - In practical applications of bismuth telluride thermoelectric materials, the materials need to be connected with a metallic electrode before they can be used;...     

Shielding performance of newly developed boron-loaded concrete for DT neutrons

In order to enhance the neutron-shielding performance of concrete in neutron-generation facilities from the viewpoint of reduction of effective dose rates in operation and radioactive wastes in decommission, we developed concrete with boron of more than 10 wt%. We performed a neutron-shielding experiment using the mockup of the newly developed boron-loaded concrete and Deuterium Tritium (DT)neutrons at the Fusion Neutronics Source in the Japan Atomic Energy Agency, and measured the reaction rates of ⁹³Nb(n,2n)^92mNb and ¹⁹⁷Au(n,γ)¹⁹⁸Au reactions in the mockup. The calculations were conducted using MCNP-5.14 and FENDL-2.1. The calculation results agreed well with the measured ones, and we confirmed that the accuracy was very good on the atomic composition data of boron-loaded concrete and their nuclear data. In addition, we calculated the neutron and photon effective dose rates and reaction rates of ⁵⁹Co(n,γ)⁶⁰Co and ¹⁵¹Eu(n,γ)¹⁵²Eu reactions, which produce critical radioisotopes in decommission, in boron-loaded concrete and other concretes with DT neutrons, and the experimental condition presently used. The dose rates and reaction rates were drastically reduced by using boron-loaded concrete and it was concluded that boron-loaded concrete had very good shielding performance for DT neutrons.     

承受高压及轴向应变的高性能输气管线用钢管的开发和性能分析(中)

近50年来,天然气的消耗量大大增加,并且会继续增加以降低主要能源的CO2排放量。随着天然气供应量的增加,为保证其输送的经济性和安全性,开发了高强度大直径焊管,并已成功应用在全球多个地区（如北极地区、地震带和深海海域）。天然气需求的增加对长距离输送管线用钢管提出了新的要求,为此,研究了更为恶劣环境下承受高压和轴向应变的高性能钢管：分析了所开发的高压输气管线用高品质钢管的性能;探讨了承受轴向应变钢管的进一步开发。     

Numerical study on sodium–water reaction mechanism in the gas phase using counter-flow reaction region

Sodium water reaction (SWR) is a design basis accident of a sodium-cooled fast reactor (SFR). In a steam generator of the SFR, when a heat transfer tube fails, highly pressurized water and/or water vapor will leak into liquid sodium resulting in a chemical reaction between sodium and water or water vapor. In the previous works, mechanisms of the SWR have been researched on surface reaction and gas-phase reaction. The mechanisms, however, are complicated and have not been fully elucidated. The authors have developed a numerical code in which chemical reaction models of sodium and water vapor are coupled with thermal-hydraulics. Experiments of a counter-flow diffusion flame for the gas-phase reaction have also been carried out. In this article, the authors perform numerical simulations based on the experimental conditions to validate two chemical reaction models, the chemical equilibrium model and the Arrhenius model. With respect to the reaction products, the latter model gives more realistic results. In addition, sensitivity analyses are performed for various hydration numbers and main-flow velocities. It is founded that hydration reaction occurs somewhat in the gas-phase reaction and that influences of the main-flow velocity are not negligible mainly from the viewpoint of the reaction surface location.     

Sequencing of a 23 kb fragment from Saccharomyces cerevisiae chromosome VI

Plasmid clone gapB and lambda phage clone 4682, which contain fragments of Saccharomyces cerevisiae chromosome VI, were analysed. A 23 kb sequence was determined and ten open reading frames (ORFs) were revealed. Among them, five ORFs were identical to five yeast genes (SEC4, MSH4, SPB4, DEG1 and NIC96), two were identical to transposable elements (TYA and TYB), one (gapBorfF003) was highly homologous to a yeast expressed sequence tag, and another (4682orfF002) was predicted to be a nuclear protein. Sequence data have been submitted to DDBJ/EMBL/GenBank data library under Accession Number D44604 (clone gapB) and D44600 (clone 4682), respectively.     

不同长度粒料对玻璃纤维增强聚丙烯复合材料力学性能的影响

对采用玻璃纤维形成的不同长度粒料(3.00 mm的短纤维粒料1种,7.00、11.00、15.00 mm的长纤维粒料3种)所制备的4种玻璃纤维增强聚丙烯复合材料进行拉伸、弯曲、冲击试验,测量注塑成型后残留的玻璃纤维长度,采用X-ray CT扫描法观察复合材料内部的纤维排列,探讨不同长度玻璃纤维对复合材料力学性能的影响。结果表明:注塑成型后玻璃纤维断裂严重,4种粒料的玻璃纤维长度均下降50%以上。随着玻璃纤维的原始长度从1.50 mm增加到15.00 mm,残留纤维长度从0.68 mm增加到4.18 mm。在残留纤维长度从0.68 mm增加到3.02 mm范围内,复合材料的拉伸强度和弯曲强度明显提高;在残留纤维长度从3.02mm增加到4.18 mm范围内,复合材料的拉伸强度和弯曲强度保持稳定。复合材料的冲击强度随着玻璃纤维的原始长度增加而增加。以短纤维增强粒料制得的复合材料,虽然玻璃纤维的原始长度非常短,但纤维排列接近长度方向;以长纤维增强粒料制得的复合材料,其芯层有宽阔的纤维排列杂乱区,纤维取向趋向无序状态,且该现象随着玻璃纤维的原始长度增加而加剧,部分纤维发生相互缠绕。