Abstract: An apparatus of material surface observation related to the present invention is a scanning electron microscope which is combined with an accelerator of charged particles. The material surface is activated by irradiation of the charged particles and a surface reaction is induced. Secondary electron in generated by irradiation of the scanning electron beam depending on a shape of the material surface. The secondary electron generated by the irradiation of the scanning electron beam is discriminated from the secondary electrode generated by the irradiation of the charged particles, and only a signal of the secondary electron generated by the irradiation of the scanning electron beam is visualized. Consequently, a reaction process of the material surface which is activated or is reaction-induced by the irradiation of the charged particles can be observed in atomic level with less noise.

Abstract: In a light water moderation type nuclear reactor with the once-through method, the reactor core is divided into a central area and a peripheral area by a partition member, a first fuel assembly is arranged in the central area (high conversion area) and a second fuel assembly is arranged in the peripheral area. The ratio (r.sub.H/U) of the number of hydrogen atoms to that of uranium atoms in the central area is smaller than that of the ratio in the peripheral area and the second fuel assembly in the peripheral area is formed of fuel rods of the first fuel assembly having been previously burned in the central area and moved into the peripheral area. The plutonium production increases and uranium consumption is reduced during the first half of the lifetime of the fuel rods in the high conversion area with the take-up burn up increasing during the second half of the lifetime of the fuel rods in the burner area.

Abstract: Provided is a fuel assembly for a boiling water reactor. The fuel assembly comprises fuel rod arranged in an 8-lines/8-columns square lattice, water rod and a channel box surrounding these fuel rods and water rods. A central portion corresponds to 80% of the fuel rod comprises fuel pellet having an outer diameter of 10.31 mm and inner diameter of 5.95 mm.

Abstract: A core construction for a nuclear reactor having a multiplicity of fuel cells forming a core in which each fuel cell includes four fuel assemblies arranged in adjacent relationship and one control rod insertable into a position surrounded by the four fuel assemblies. The fuel cells includes first fuel cells each having a relatively high cell mean infinite neutron multiplication factor and including one fuel assembly containing a burnable poison, and second fuel cells each having a relatively low cell mean infinite neutron multiplication factor and including no fuel assembly containing a burnable poison. The first fuel cells are arranged both in a central zone of the core disposed within about one-half the core radius from the center of the core and in a circumferential zone of the core outside the central zone. The second fuel cells are arranged only in the central zone and no second fuel cells are arranged in the circumferential zone.