Thorium thermal properties

Mitchell and 0 nfe(1971 and 1972) studied the thermal properties of various fluorinated /3-d>ketonates of the rare earths, uranium, and thorium and found the volatility and thermal stability of the chelates were improved when an adduct was formed with some neutral donor. Butts m wl6(1970) and later Sieck inLBatiHi (1972) demonstrated that the separation of the lanthanides as ternary complexes with a fluorinated /8-diketone and TBP or di-n-butylsulfoxide by gas-liquid chromatography was possible. Although this method is reasonably sensitive it has not been demonstrated to be reliable at trace levels of the rare earths. y O Laughlin et al. (l966a,b), reported the rare earths and a number of... 

The only large-scale use of deuterium in industry is as a moderator, in the form of D2O, for nuclear reactors. Because of its favorable slowing-down properties and its small capture cross section for neutrons, deuterium moderation permits the use of uranium containing the natural abundance of uranium-235, thus avoiding an isotope enrichment step in the preparation of reactor fuel. Heavy water-moderated thermal neutron reactors fueled with uranium-233 and surrounded with a natural thorium blanket offer the prospect of successful fuel breeding, ie, production of greater amounts of (by neutron capture in thorium) than are consumed by nuclear fission in the operation of the reactor. The advantages of heavy water-moderated reactors are difficult to assess. 

Thermal equilibrium, 56 Thermite reaction, 122 Thermometers, 56 Thiosulfate ion, 362 Third-row elements, 101 compounds, 102 physical properties, 102 properties, table, 101 Third row of the periodic table, 364 Thomson, J. J., 244 Thomson model of atom, 244 Thorium... 

The high-temperature gas-cooled reactor (HTGR) is a thermal reactor that produces desired steam conditions. Helium is used as the coolam. Graphite, with its superior high temperature properties, is used as the moderator and structural material. The fuel is a mixture of enriched uranium and thorium in the form of carbide particles clad with ceramic coatings. 

A molecular dynamics calculation was performed for thorium mononitride ThN(cr) in the temperature range from 300 to 2800 K to evaluate the thermophysical properties, viz. the lattice parameter, linear thermal expansion coefficient, compressibility, heat capacity (C° ), and thermal conductivity. A Morse-type function added to the Busing-Ida type potential was employed as the potential function for interatomic interactions. The interatomic potential parameters were semi-empirically determined by fitting to the experimental variation of the lattice parameter with temperature. 

The sole reason for using thorium in nuclear reactors is the fact that thorium ( Th) is not fissile, but can be converted to uranium-233 (fissile) via neutron capture. Uranium-233 is an isotope of uranium that does not occur in nature. When a thermal neutron is absorbed by this isotope, the number of neutrons produced is sufficiently larger than two, which permits breeding in a thermal nuclear reactor. No other fuel can be used for thermal breeding applications. It has the superior nuclear properties of the thorium fuel cycle when applied in thermal reactors that motivated the development of thorium-based fuels. The development of the uranium fuel cycle preceded that of thorium because of the natural occurrence of a fissile isotope in natural uranium, uranium-235, which was capable of sustaining a nuclear chain reaction. Once the utilization of uranium dioxide nuclear fuels had been established, development of the compound thorium dioxide logically followed. 

K for the compounds and aqueous species of thorium. There is also a "reaction catalog" which gives values of AG , AH , and S for individual processes or substances and upon which the tabulated formation properties are based. This report also contains thermal functions and includes references to the primary literature. 

A Thorium-Uranium Exponential Experltnenti C. If. Skeen and W. W. Broum(AI). Because of uncertainties in the knowledge of t nuclear properties of thorium fuel and lattices containing this fuel, an experimental study was made of a thorium based fuel that is to be loaded into the Sodium Reactor Experiment (8RB) in the near future. An exponential experiment was performed with a square-celled lattice of 7-rod elements (l-in. diameter rods) spaced 9.5 in. apart in praphite. The fuel Is a Th-U-23S alloy containing 7.6% uranium by weight which is 93.13 atomic per cent U-235. The feel elements were 5 ft. long. The subcrltical lattice was placed On thd thermal column of a water boiler reactor which served as the source of neutrons for the assembly. 

ThN is the compound with the lowest N Th ratio. In addition to its (former) nuclear interest due to its thermal and radiation stability, it has many very interesting physicochemical properties. Thorium nitrate, the other well-investigated compound, is of importance because it is (in the form of an adduct with tri-n-butylphosphate) the extracted compound when burnt-up thorium fuels are reprocessed. 

The acidic and basic properties are dependent upon the preparation and activation methods. Thorium oxide is usually prepared from aqueous solution of thorium nitrate or chloride by precipitation with aqueous ammonia followed by washing, and calcining. In some cases, Th02 is prepared by thermal decomposition of thorium nitrate or thorium oxalate. The acidic and basic properties of the Th02 prepared from ThCU are distinctly different from the other Th02. The catalytic activities of Th02 prepared by different methods for 1-butene isomerizaton and 2-butanol dehydration are summarized in Table 3.5.The ThOz prepared from cholride completely lacks the measur-... 

Considering chemical structures of ceramic fuels, these fuels can be categorized as oxide fuels, carbide fuels, and nitride fuels. Oxide fuels such as UO2, mixed oxide (MOX), and thorium dioxide (Th02) have low thermal conductivities compared to carbide and nitride fuels. Hence, from the heat transfer point of view, oxide fuels can also be identified as low thermal conductivity fuels. On the other hand, carbide (eg, UC and UC2) and nitride (eg, UN) fuels are identified as high thermal conductivity fuels. Table 18.3 lists basic properties of these fuels at 0.1 MPa and 25°C. 

The use of thorium-based fuels in nuclear reactors requires information on the thermophysical properties of these fuels. Jain et al. (2006) have conducted experiments on thorium and the solid solutions of Th02 and lanthanum oxide (LaOi 5). As a result of their experiments, Jain et al. (2006) have determined the density, thermal diffusivity, and specihc heat for several compositions of Th02 and LaOi 5 ranging from pure thorium tolO mol% LaOi 5. These properties were measured for temperatures between 100 and 1500°C (Jain et al., 2006). 

Preparation of thorium oxide. The principal method of preparing thorium oxide for use in aqueous slurries has been the thermal decomposition of the oxalate. Thorium oxalate, precipitated from thorium nitrate solution, is crystalline, easy to wash and filter, and the oxide product is readily dispersed as a slurry. In addition, the oxide particle resulting from oxalate thermal decomposition retains the relic structure of the oxalate, and hence the particulate properties are determined by the precipitation conditions. The mechanism by which the thermal decomposition takes place has been quite widely investigated [24-26]. The following is proposed by D Eye and Sellman [26] for the thermal decomposition ... 

Properties of thorium oxide prepared by the thermal decomposition of oxalate are discussed in detail in Articles 4-3.3 and 4-3.4. 

Characteristic Properties of Thorium Oxide from Oxalate Thermal Decomposition... 

Oxides from the hydrothermal decomposition of thorium oxalate. Oxides prepared by the hydrothermal decomposition of the oxalate [27] at 300°C in a closed autoclave were found to be markedly different in their characteristic properties from the thermally prepared materials. The precipitation temperature of the oxalate had no effect on the final shape or size, and all evidence of the original oxalate structure had disappeared. Sedimentation particle-size analyses indicated particle sizes between 0.5 and 1 micron. 

Suspensions of thorium oxide and thorium oxide containing 0.5 mole % of either natural or highly enriched UO3 were irradiated in the Low Intensity Test Reactor (LITR) at a thermal-neutron flux of 2.7 X 10 neutrons/(enri)(sec). Although more than 40 irradiations were carried out, no significant changes in the properties studied were noted [151]. 

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