Radiation resistance of high-density uranium—molybdenum dispersion fuel for nuclear research reactors

Abstract

The results of radiation tests are discussed and the character of the failure of fuel compositions and the operability of fuel elements is analyzed as a function of the type of fuel and the irradiation conditions. The intense interaction of the fuel with the matrix material is considered as the main factor limiting the operability of fuel elements in power-dense high-flux nuclear reasearch reactors. It is concluded that low-enrichment high-density uranium-molybdenym fuel can provide reliable operation of dispersion fuel elements in low-and medium-power research reactors. Such fuel can be used in power-dense high-flux research reactors if the fuel load is decreased below the maximum admissible amount, the compatibility of the uranium-molybdenum alloy with an aluminum matrix is radically improved, or fuel elements with a different construction, for example, monolithic, are used.A large number of radiation tests of new types of dispersion fuel have been conducted as part of the international program on decreasing the enrichment of fuel for research reactors (RERTR) and national programs [1][2][3][4][5]. Plate-shaped miniscale fuel elements with dispersion fuel based on various high-density alloys and uranium compounds have been tested at the first stage. Fuel based on uranium silicide U 3 Si 2 and uranium alloys with 7-10% molybdenum or zirconium and niobium with total content at least 10% exhibited the best radiation resistance. Consequently, mini-and full-scale fuel elements with fuel based on these alloys, primarily, uranium alloys with molybdenum (here and below, the mass fraction of the alloying element is given in %) were tested in further tests.The influence of the characteristics of the dispersion fuel and the conditions of irradiation on the radiation resistance of fuel elements were investigated in the experiments. The results obtained make it possible to draw conclusions about the regularities in the behavior of, the failure of fuel compositions of, and the operability of fuel elements as a function of the type of fuel and conditions of irradiation.Results of the First Stage of the Investigations. At the first stage of the investigations, the RERTR-1 and -2 computer programs were used to study the radiation resistance of plate-shaped miniscale fuel elements with fuel based on intermetallic compounds of uranium with iron, manganese, silicon, and aluminum and alloys of uranium with molybdenum, zirconium, and niobium. The uranium content in the composition was 4 g/cm 3 , the heat flux and temperature of the fuel-element cladding were 55 W/cm 2 and 65°C, respectively, and the burnup 40 and 70% 235 U.Some of the fuel elements successfully withstood the tests -they remain sealed, and the increase in the thickness of the plates was negligible. The microstructure of the fuel composition of such fuel elements after irradiation in the reactor was essentially identical to the initial microstructure (Fig. 1). The fuel particles retained their shape and size. The interaction of

Atomistic modeling of the self-diffusion in γ-U and γ-U-Mo

“…Alloys based on the disordered solid solution of molybdenum in γ U (containing from 7 to 12 wt % molybdenum, which corresponds to 15.1-21.6 at %) have high indices of density, thermal conductivity, and increased corrosion and radiation resistance [14][15][16]. However, to reliably evaluate the efficiency of using this alloy in nuclear power engineering, detailed information on a large set of mechanical and thermal properties is nec essary; in addition, we should know how these prop erties vary under intense thermal and radiation effects.…”

Quantum mechanical calculations of uranium phases and niobium defects in γ-uranium

“…The addition of small amount of Nb significantly improves its corrosion resistance, allowing the production of 'stainless' U. Together with Zr, the addition of Nb to U also stabilizes the c phase at low temperature [6] for applications as metallic fuel [7,8]. Due to the low solubility of Nb in a and b phases of U, Nb is introduced to the hightemperature c phase [9,10].…”

Microstructural development from interdiffusion and reaction between U Mo and AA6061 alloys annealed at 600° and 550 °C

“…U-Mo alloys in contact with Al undergo complex diffusional interactions that can produce various phases with undesirable growth kinetics [1,[38][39][40][41][42][43][44][45][46][47][48][49][50] and irradiation behavior [51][52][53][54][55][56][57][58][59][60][61]. In prior studies by the authors [1,2,39,44,62], U-Mo alloys, high purity Al (99.999%) and Al-Si alloys were used to assemble diffusion couples to investigate the fundamental interactions that take place in the ternary U-Mo-Al and quaternary U-Mo-Al-Si systems.…”