[en] It was in 1970 when the first commercial light-water reactor (LWR) was operated in Japan. Since then, the number of LWRs in operation in Japan has totaled 35 units by the end of March, 1989. One unit more is put into commercial operation and the total generating capacity will be 29.1 GW during 1989. Construction of LWRs in Japan was initiated mainly by the introduction of the U.S. technology. Since then, strenuous efforts have been made by the cooperation of government, electric power companies and manufactures in Japan to improve technology in the design, construction, operation, maintenance and quality assurance (QA) activities of LWRs. As a result, today, Japan stands in the top rank in the world in respect of the operating performance of LWRs. This report is to present the background, characteristics and processes through which QA activities in Japan have evolved, simultaneously introducing the latest example of QA activities developed by a comprehensive nuclear plant manufacturer

No abstract available

[en] A three-dimensional CAD system for plant layout of nuclear power plants has been developed, adopting the latest technologies of knowledge engineering, CAD/CAM, and interactive computer graphics. With this system, Hitachi is now able to plan plant layout more effectively, reduce design time and cost, and detect defective designs before actual construction problems occur. Hitachi is planning to enhance this three-dimensional CAD system to a plant total life computer-aided engineering (CAE) system. This system will include a construction CAE system, a test operation and in-service inspection control system, and a plant maintenance system. After completion of this system, Hitachi will be able to plan, monitor, and control all major aspects in the life of a nuclear power plant from the very first stage of the planning to its decommissioning

[en] A magnetohydrodynamic relaxation process of spheromak merging is studied by means of an axi-symmetric numerical simulation. As a result of counter-helicity merging, a field-reversed configuration is obtained in the final state, while a larger spheromak is formed after co-helicity merging. In the counter-helicity case, a clear pressure profile of which iso-surfaces coincide with flux surfaces is generated by thermal transport of a poloidal flow that is induced by driven reconnection. It is also found that a sharp pressure gradient formed at the edge of a current sheet causes a bouncing motion of spheromaks. According to the bounce motion, the reconnection rate changes repeatedly. As is shown by the TS-3 experiments, furthermore, strong acceleration of a toroidal flow and reversal of a toroidal field are observed in the counter-helicity merging. (author)

[en] The diversion properties of the magnetic field outside the last closed magnetic surface of a Helias stellarator configuration are investigated for finite β-equilibria. The results support a divertor concept which has been developed from the diversion properties of the corresponding vacuum field. Cross-field transport is simulated by a simplified scrape-off layer (SOL) model. (author)

[en] Several new types of photodetector have been developed for use in severe environmental conditions; four types of phototube are especially designed to be operated in high magnetic fields of several kilogauss or more. A photomultiplier which is designed for use under pressures as high as 600 atm has stable gain and energy resolution under such high pressures. And a 15 inch diameter spherical photocathode photomultiplier has also been developed for high pressure use when packed in a special strong glass housing. There is another photomultiplier which can be operated in temperatures over 175⁰C, such as in oil well logging works. (orig.)

[en] Fluidity of the flower membranes of cut chrysanthemums (Dendranthema grandiflorum Kitamura) decreased soon after gamma-irradiation at 750Gy and continued to decrease during storage following irradiation. Holding chrysanthemum cut inflorescence in 2% sucrose suppressed the decrease. The results suggest that sugars reduce radiation-induced physiological deterioration of chrysanthemum flower membranes

[en] Spheromak tilting instability was studied. A numerical technique to create a rather arbitrarily-shaped spheromak like the one with a flux hole was investigated. The dynamics governing the tilting instability, namely, the influence of the magnetic index, the toroidal current (q-profile) and the resistivity upon the tilting growth rate, and the roles of magnetc reconnection upon the nonlinear development were studied. The best way to control the tilting instability was invented. The stabilizing effects of the vertical wall, the isolated conducting cylindrical belt, and the horizontal wall were studied. Central pole stabilization was also investigated. The influence of the wall condition, namely, whether the wall acted as a flux conserver in the spheromak creation stage or not is discussed. The present study has shown that the three- dimensional simulation is indeed useful and practical in not only studying the underlying physics but also finding a stabilization technique of spheromaks. (Kato, T.)

[en] Direct numerical simulations of fully three-dimensional, compressible and nonlinear magnetohydrodynamic equations are conducted to investigate nonlinear evolution of MHD instability in LHD. A series of DNS under a condition of inward-shifted vacuum magnetic axis position show that MHD instability can be suppressed by combinations of compressibility, parallel flow and parallel heat conduction. It is also shown that a plasma recovers a well-confined state as a consequence of composite stabilization effects by the compressibility, parallel flow and parallel heat conductivity. (Author)

[en] Magnetic island formation in three-dimensional finite-β equilibria in the H-1 Heliac is studied by using the HINT code. It is found that the size of a dangerous island should increase with β but that a destruction of the equilibrium at low β is avoided because the rotational transform evolves to exclude the rational surface concerned. At higher β there is evidence of near-resonant flux surface deformations which may lead to an equilibrium limit. A reconnected equilibrium at still higher β exhibits a double island structure which is similar to homoclinic phase portraits which have been observed after separatrix reconnection in Hamiltonian systems. Physical mechanism of the island formation in finite-β helical equilibria is investigated to confirm there are cases where the global effect of the Pfirsch-Schlueter currents is important. The earlier theory is extended to elucidate the occurence of the complete self-healing of island when the resistive interchange criterion satisfied. (author)