Thorium manufacture

Articles manufactured from natural or depleted uranium or natural thorium Manufactured articles in which the sole radioactive material is unirradiated natural uranium, unirradiated depleted uranium or unirradiated natural thorium may be transported as an excepted package, provided that the outer surface of the uranium or thorium is enclosed in an inactive sheath made of metal or some other substantial material. ICAO 2-1.9 A... 

Cerium is a component of misch metal, which is extensively used in the manufacture of pyrophoric alloys for cigarette lighters. While cerium is not radioactive, the impure commercial grade may contain traces of thorium, which is radioactive. The oxide is an important constituent of incandescent gas mantles and is emerging as a hydrocarbon catalyst in self cleaning ovens. In this application it can be incorporated into oven walls to prevent the collection of cooking residues. 

Thu umalai Chemicals Ltd., 176 Thomas Register of American Manufacturers, 309 Thomas Register of European Manufacturers, 309 Thomas Swan Co. Ltd., 213 Thorium and Thorium Compomids, 128 3M Coi poration, See Minnesota Mrnriig and Manufacturing Company (US), 250... 

Alkoxide gels, 23 60 Alkoxide gels, in optical fiber manufacturing, 11 145 Alkoxide initiators, 14 259 Alkoxide ligands, thorium, 24 770 Alkoxides, 12 190 25 72-86 controlled hydrolysis of, 23 56 iron, 14 533 mixed-metal, 25 100 titanium, 25 82 uranium complexation with,... 

Hydrocarbon sulfonates, 23 531 Hydrocarbon surfactants, 24 133 Hydrocarbon waxes, 26 220 Hydrocarbyl complexes of thorium, 24 773 of uranium, 25 441-442 Hydrochloric acid, 13 808-809, 821-822. See also Hydrogen chloride in ascorbic acid manufacture, 25 757 chlorine from, 6 172-175 constant boiling, 13 814t density and concentration of, 13 808t end use of chlorine, 6 135t for fermentation, 11 38... 

The first actinide metals to be prepared were those of the three members of the actinide series present in nature in macro amounts, namely, thorium (Th), protactinium (Pa), and uranium (U). Until the discovery of neptunium (Np) and plutonium (Pu) and the subsequent manufacture of milligram amounts of these metals during the hectic World War II years (i.e., the early 1940s), no other actinide element was known. The demand for Pu metal for military purposes resulted in rapid development of preparative methods and considerable study of the chemical and physical properties of the other actinide metals in order to obtain basic knowledge of these unusual metallic elements. 

The physical and chemical properties of elemental thorium and a few representative water soluble and insoluble thorium compounds are presented in Table 3-2. Water soluble thorium compounds include the chloride, fluoride, nitrate, and sulfate salts (Weast 1983). These compounds dissolve fairly readily in water. Soluble thorium compounds, as a class, have greater bioavailability than the insoluble thorium compounds. Water insoluble thorium compounds include the dioxide, carbonate, hydroxide, oxalate, and phosphate salts. Thorium carbonate is soluble in concentrated sodium carbonate (Weast 1983). Thorium metal and several of its compounds are commercially available. No general specifications for commercially prepared thorium metal or compounds have been established. Manufacturers prepare thorium products according to contractual specifications (Hedrick 1985). 

Davis MW. 1985. Radiological significance of thorium processing in manufacturing. Report. INFO-0150. 

One method of preparation consists in a modification of the Goldschmidt process. Niobium pentoxide is mixed with an alloy of the rare earths, called mixed metal, obtained in the manufacture of thorium nitrate, and consisting roughly of 45 per cent, of cerium, 20 per cent, of lanthanum, 15 per cent, of didymium, and about 20 per cent, of other rare-earth metals. The reaction is carried out in a magnesia-lined crucible, and is started with a firing mixture of barium peroxide, potassium chlorate, and aluminium powder. Considerable evolution of heat takes place and the reduction is extremely rapid a button of niobium is obtained 4 which, however, is not pure. 

Analytical data of samples of ore utilised on the commercial scale are set out on p. 119. By-products produced during the working-up of the rare earths for cerium and thorium compounds for use in the manufacture of incandescent mantles, as well as by-products from oertain tin and tungsten ores, are also available as sources of tantalum. 

The main source of the alpha particles is trace quantities of uranium and thorium in the silica filler. Because silica fillers that did not contain these radioactive elements were not available, other methods for preventing alpha particles from reaching the active DRAM cells were devised. These early methods consisted of cov-vering the active cells with either a silicone or polyimide chip coat or with Rapton tape. These methods added extra steps to the manufacturing process which were cumbersome and labor intensive and, if not done precisely, had a negative reliability impact. These processes were not widely used once "low alpha fillers" became commercially available in 1982/1983. Initially, these "low alpha fillers", which contain <1 ppb uranium, were only available from one or two natural sources. Now, however, there are additional natural and synthetic sources of silica, all of which contain <1 ppb of uranium and have an alpha particle emission rate of less than. 001 alpha particles/hr-cm. Figure 9 shows where the industry was in 1980 and where it stands today. An improvement by a factor of 30-50 has been achieved with "lower alpha" filler and compound manufacturing. 

Having now determined to total amount of nuclear electricity required, the thorium fuel input to the energy amplifiers can be calculated from the design data of Rubbia and Rubio (1996). The thermal output from the prototype design reactor is 1500 MW, with a fuel amount of 27.6 t in the reactor (Fig. 5.42). The fuel will sit in the reactor heat-generating unit for 5 years, after which the "spent" fuel will be reprocessed to allow for manufacture of a new fuel load with only 2.9 t of fresh thorium oxide supply. This means that 2.6/5 t y of thorium fuel is required for delivery of 5 x 1500 MWy of thermal power over 5 years, or 675 MWy of electric power, of which the 75 MWy is used for powering the accelerator and other in-plant loads. The bottom line is that 1 kg of thorium fuel produces very close to 1 MWy of electric power, and 1 kt thorium produces close to 1 TWh. ... 

Phosphate rock deposits contain uranium (U), radium (Ra), thorium (Th), and other radionuclides as contaminants. Uranium in phosphate rock deposits throughout the world range from 3 to 400 mg kg (Guimond, 1978). It has been estimated that 1000 kg of Florida phosphate rock contains about 100 pCi each of" U and Ra and 4 pCi of °Th (Menzel, 1968). Some of these elements are retained in the HjPO and the remainder are transferred to the by-products during fertilizer manufacture. For instance it is estimated that 60% of the radioactivity in mined Florida phosphate rock remains with slime and sand tailings during beneficiation (Guimond and Windham, 1975). 

Thorium fluoride is used in the manufacture of propane lantern mantles and high-intensity searchlights. 

Applications The most important application sectors for metallic sodium in the USA are in the production of sodium borohydride (ca. 38%), which is used as a reducing agent, and in the manufacture of herbicides (ca. 25%). A further important sector accounting for 20% of the consumption of sodium, is the production of metals which are difficult to reduce such as uranium, thorium, zirconium, tantalum and titanium. Its utilization in the production of titanium has, however, declined of late. Tetramethyl- and tetraethyl lead... 

Calcium is utilized in the manufacture of special metals such as zirconium, thorium, uranium and the rare earths, as a refining agent in metallurgy (steel, copper, magnesium, tantalum, lead) and in the manufacture of calcium hydride (hydrogen source). 

A scheme has been proposed for using the neutrons from the fusion reaction to convert uranium 238 to plutonium 239 or thorium 232 to uranium 233 for the manufacture of bombs. While in theory this may be possible, it does not appear to offer an easier route to the produetion of bombs than the current methods of separation of uranium 235, or the production of plutonium in a conventional reactor. As a result of these factors, use of a fusion energy system will in no way add to the potential for further nuclear weapons or provide a source for the unauthorized procurement of materials that might be used to produce weapons. 

Uses. — Pure metallic cerium has no commercial uses, but its alloys are both interesting and capable of wide application. The most important of these is the alloy called misch metal, mixed metal, commercial cerium, or simply cerium, It is essentially a mixture of cerium, lanthanum, neodymium, and praseodymium, but as usually prepared it contains from 1-5 per cent iron and very small amounts of other elements. The most abundant constituent is cerium, which sometimes runs as high as 70 per cent or more, though generally it is about half of the mixture. The alloy is produced from the rare earth residues of monazite sand. This mineral is used in large quantities for the manufacture of incandescent gas mantles (see Thorium Uses), which usually contain 99 per cent thoria and 1 per cent ceria. The composition of various monazites is shown in Table XXVI. 

The only important commercial use of thorium, however, is in the manufacture of incandescent gas mantles. This industry had a very modest beginning in 1884 when Welsbach patented the use of a fibrous network of rare earth oxides which were to be heated by an ordinary gas flame of the Bunsen type. The first mantles were composed of a mixture of zirconia, lanthana,... 

The manufacture 2 of incandescent mantles is based upon the impregnation of a combustible fabric with the nitrates of thorium and cerium and the ignition of this material by which the fabric is consumed and the nitrates converted to the oxides. The fabric selected was first long fiber cotton, which is still extensively used in the United States. Better grades of mantles are produced by the use of ramie, which before the war was used for the production of 90 per cent of the mantles made in Europe. Artificial silk has been used with very satisfactory results, as. it gives a mantle which is strong and elastic, and... 

The. number of mantles manufactured from a pound of thorium nitrate varies widely with the size and quality of the mantles. In the United States about 325 is the average number produced from a pound of thorium nitrate, while in England the number varies from 225 to 450. As many as 500 of the cheaper German mantles are said to be prepared from a pound of the nitrate. 

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