Papers by Keyword: Control Rod

Abstract: Metal hydrides have high hydrogen atom density, which is equivalent to that of liquid water. An application of the hafnium hydride has been investigated as a neutron absorber in the Fast Breeder Reactors (FBRs). Fast neutrons are efficiently moderated by hydrogen in Hf hydrides and are absorbed by Hf. Since three isotopes of Hf have large cross sections, increase in the life of control rod is considered by Hf hydride. Results of design study of the core with Hf hydride control rods shows that the long lived hafnium hydride control rod is feasible in the large sodium-cooled FBR. Results of irradiation test conducted in BOR-60 has demonstrated the integrity of the capsules during irradiation. Na bonded capsule has an advantage in confinement effect of hydrogen compared with He bonded one. An application of hydride technique to transmutation target of MA was also discussed. MA hydride target is able to enhance the transmutation rate in FBR.

Abstract: The distribution of neutron flux is simulated by MCNP code from reactor start-up to criticality when the control rods are drawn different length from reactor core on ex-core detector area of the WWER reactor of TianWan. Because physical model built is very large, in order to save calculation time, the moving process of control rod is simplified. The results of calculation show that The neutron mainly distributed in the range of 0-400cm outside the pressure vessel. The value of the relative neutron flux ex-core is maximum in the range of 110cm to 180cm, so detection effect is better when the detector is set in this region.

Abstract: Neutron energy spectrum has a high correlation with all kinds of nuclear processes in nuclear reactor. Neutron energy spectrums of the TMSR in some conditions were simulated using MCNP5.The distributions of thermal neutrons, epithermal and resonance neutrons, and fast neutrons in axial and radial were simulated, respectively. The simulation results indicate that thermal neutrons have a high ratio and control rods inserting the nuclear reactor have a serious effect on neutron distribution. The study of neutron energy spectrum is theoretical basis for measurement in the TMSR.

Abstract: Because the metallic hafnium has good combination properties, that makes it the preferred material for control rods of nuclear reactors. To prevent the irradiation deformation and the mechanical property decrease of hafnium plates, and to increase the service life of the control rods, a new type of square-tube control rod is developed. The elemental composition, mechanical property, the corrosion resistance and the physical characteristics of hafnium are researched. Several tests are carried out after the product manufactured, which prove that the design and manufacture of the control rod meet the requirement of the technical conditions.

Abstract: Metal hydrides have high hydrogen atom density, which is equivalent to that of liquid water. Fast neutrons are efficiently moderated by hydrogen in metal hydrides. Metal hydrides have been studied for their potential application as nuclear materials in fast reactors (FRs). Two types of the utilizations of metal hydride in FRs are discussed in this paper. One is the utilization for transmutation target of long-lived nuclear wastes. Hydride fuel containing 237Np, 241Am and 243Am has been studied as a candidate transmutation target to reduce the radioactivity of long-lived nuclides included in reprocessed nuclear wastes. An application of the hafnium hydride has been investigated as neutron absorber in FRs. The core design has been performed to examine its characteristics and to evaluate the cost reduction effect. Demonstration of fabrication of hydride pin has been done with hydride pellets and stainless steel cladding. Coating technique of inner cladding surface has been also developed to reduce the permeation of hydrogen through stainless steel cladding. Physical and chemical properties of the pellet have been measured for designing the hydride pin. The integrity of the pellets at high temperature has been tested and their compatibility with sodium has also been tested. Irradiation test of hydrides has been performed in the fast experimental reactor, JOYO, at Japan Atomic Energy Association (JAEA).