U.S. 1997 Geological Survey Thorium Report

钍

由詹姆斯B. Hedrick

钍是一种柔软，非常韧性，银灰色，厚重，金属元素的神奇系列元素。它由化学符号TH或同位素符号TH232表示。钍金属具有非常高的熔点，而也称为梭坡的氧化物具有最高氧化物的熔点。Th232是钍的四种天然存在的同位素中最丰富的。TH232发出放射性α颗粒，并且具有1.405 x 1010年的长期半衰期。TH232崩解系列的女儿产品产生alpha，beta和伽玛排放。大多数崩解系列的产品具有相对较短的半衰期，范围从5.75秒到0.145秒。TH232系列的最终衰减产品是稳定的同位素PB208。Thorium的其他天然存在同位素，TH228，TH230和TH234，分别为1.9116岁，75,380岁和241天。

Thorium was discovered in 1828 by Swedish chemist and mineralogist Jons Jakob Berzelius. He named it thoria, after Thor, the ancient Norse god of thunder. Berzelius isolated the element from a black silicate mineral from the island of Lovo near Brevig, Norway. Subsequently, the black mineral from which thoria was derived was named thorite. Thorium’s radioactivity was discovered independently in 1898 by Madame Marie Curie and C.G. Schmidt.

Thorium is the 39th most abundant of the 78 common elements in the Earth’s crust, at 7.2 parts per million. It is about three times more abundant than uranium and is associated with uranium in igneous rock As the primary thorium minerals are more resistant to geochemical and physical weathering, the thorium/uranium ratio in sedimentary rock is typically higher than its igneous source rock. Thorium occurs in several minerals, the most common being monazite and thorite.

Domestic consumption of refined thorium products increased in 1997, according to the U.S. Geological Survey (USGS). The value of thorium metal and compounds used by the domestic industry was estimated to be about $300,000. Thorium production was primarily from the rare-earth-thorium-phosphate mineral, monazite, a byproduct of processing heavy-mineral sands for titanium and zirconium minerals or tin minerals. Thorium compounds were produced from monazite during processing for the rare earths. Only a small portion of the thorium produced was consumed; most was discarded as waste. The major monazite-producing countries were Brazil, China, India, Malaysia, and Sri Lanka. Essentially all of the thorium compounds, metal, and alloys used by the domestic industry were derived from imports, company stocks, or material sold from U.S. Government stocks.

相对于稀土的钍需求有限，继续在钍化合物和残留物的供过于求的全球范围内。大多数主要的稀土处理器对无钍中间体化合物切换了饲料材料。多余的钍，未指定用于商业用途，要么是放射性废物或储存的潜在用途作为核燃料或其他应用。主要的非能量使用从耐火材料应用转移到焊接电极和照明。

与钍的天然放射性相关的问题对参与其采矿，加工，制造和使用的公司表示重要成本。增加了遵守环境法规，潜在的法律负债以及购买储存和废物处理空间的成本的成本是其商业用途的主要威慑。据行业来源称，与钍的天然放射性相关的健康问题并不是切换到替代非偶极物质的重要因素。

Legislation and Government Programs

The calendar year 1997 included parts of the U.S. Government fiscal years (October 1 to September 30) 1997 and 1998. Public Law 104-201, the National Defense Authorization Act for Fiscal Year 1997, was enacted on September, 23, 1997. It did not change the previous authorization for the disposal of all stocks of thorium nitrate in excess of the National Defense Stockpile (NDS) goal of 272,155 kilograms (600,000 pounds). The National Defense Authorization Act for Fiscal Year 1998, Public Law 105-85, also known as the “Strategic and Critical Stock Piling Act,” was enacted on November 18,1997. The revised annual material plan proposed the disposal of up to 453,592 kilograms (1,000,000 pounds) of thorium nitrate in fiscal year 1998. It did not change previous authorizations for the disposal of 2,946,185 kilograms (6,495,225 pounds) of thorium nitrate classified as excess to goal.

Production

Domestic mine production data for thorium-bearing monazite were developed by the USGS from a voluntary survey of U. S. operations entitled “Thorium.” The one mine to which a survey form was sent responded. Thorium was not produced in the United States in 1997, however, the mine that had previously produced thorium-bearing monazite continued to operate and maintained capacity on standby. Monazite was last produced in the United States in 1994.

基本上，国内工业使用的所有钍合金和化合物都来自于从美国政府库存中销售的进口，公司股票或材料。国内公司处理或制作各种形式的钍，用于陶瓷，镁 - 合金，耐火材料和焊接电极。

Consumption

通过调查各种处理器和制造商，评估进出口数据，分析政府储存货物，开发了国内钍消费的统计数据。（见表1.）

Domestic thorium producers reported consumption of 13.0 metric tons of thorium oxide equivalent in 1997, an increase from the 1996 level of 4.92 tons. The increase was primarily the result of increased demand for thorium in a catalyst application. Nonenergy uses accounted for essentially all of the total consumption.

Thorium oxide (thoria) has the highest melting point of all the binary metal oxides at3,300°C. This property contributed to its use in several refractory applications. High-temperature uses were in ceramic parts, investment molds, and crucibles.

Thorium nitrate was used in the manufacture of mantles for incandescent “camping” lanterns, including natural gas lamps and oil lamps. Thorium mantles provide an intense white light that is adjusted towards the yellow region by a small addition of cerium. Thoriated mantles were not produced domestically due to the development of a suitable thorium-free substitute.
Thorium nitrate also was used to produce thoriated tungsten welding electrodes. Thoriated tungsten welding electrodes were used to join stainless steels, nickel alloys, and other alloys requiring a continuous and stable arc to achieve precision welds.

硝酸盐形式也用于生产用于磁控管管的负极的钍钨元件。使用钍是使用其在真空中加热时在相对低的温度下发射电子的能力。磁控管管用于在微波频率下发射电子，以在微波炉和用于跟踪飞机和天气条件的雷达系统中加热食物。

Thorium was used in other applications as catalysts, electron emitting-tubes, elements in special use light bulbs, fuel cell elements, high-refractivity glass, photo conductive films, radiation detectors, and target materials for X-ray tubes.

In metallurgical applications, thorium was alloyed primarily with magnesium. Thorium metal has a high melting temperature of 1,750°C and a boiling point of about 4,790°C. Magnesium-thorium alloys used by the aerospace industry are lightweight and have high strength and excellent creep resistance at elevated temperatures. Thorium-free magnesium alloys with similar properties have been developed and are expected to replace most of the thorium-magnesium alloys presently used. Small quantities of thorium were used in dispersion-hardened alloys for high-strength, high-temperature applications.

钍用作钍-232 /铀-233燃料循环中的核燃料。没有外国或国内商用反应堆采用这种燃油循环运行。由于低成本铀的可用性，预计钍作为核燃料的使用不会产生。

股票

Government stocks of thorium nitrate in the NDS were 3,216,828 kilograms (7,091,891 pounds) on December 31, 1997. The NDS shipped 1,724 kilograms (3,800 pounds) for waste disposal research in 1997. The NDS inventory included 273,181 kilograms (602,262 pounds) of thorium nitrate allocated to meet the NDS goal requirements and 2,943,646 kilograms (6,489,629 pounds) classified as excess to the goal. No stocks of thorium nitrate were sold during the year.

美国能源部（DOE）库存末期为535,000公斤金属和各种化合物中含有535,000千克氧化钍等效物。Fernald环境恢复管理公司（FERMCO）是Huor Daniel Fernald的子公司Fernald环境恢复管理公司（Fermco），1997年运送了14万公斤氧化钍，Fermco也运送到废物处理估计矿石含有4,200公斤的氧化钍等同物。

Prices

Monazite浓缩物的价格，通常以最少55％的稀土氧化物出售，包括在美国美元，并以美国进口数据所引用的洛尼亚，自由的（F.O.B.）。每吨400美元。1997年的Monazite价格从前几年的价格增加，澳大利亚美元（A $）转换为244美元（金属公告，1997）。1997年含有稀土氧化物的Monazite的价格以每公斤0.73美元出售。

Thorium oxide prices quoted by Rhone-Poulenc Basic Chemicals Co. (Rhodia as of January 1, 1998) decreased slightly or were unchanged in 1997. At yearend 1997, thorium oxide prices per kilogram f.o.b. Shelton, CT, were $82.50 for 99.9% purity and $107.25 per kilogram for 99.99% purity.

Thorium alloy prices, previously quoted by Reade Manufacturing Co., a division of Magnesium Elektron, Lakehurst, NJ, were no longer available because of depletion of the company’s stocks.

世界评论

钍需求继续保持低迷dustrial consumers expressed concerns with the potential liabilities, the costs of complying with environmental monitoring and regulations, and cost increases at approved waste disposal sites.

Outlook

Nonenergy uses for thorium in the United States have decreased substantially over the past 7 years. Domestic demand is forecast to remain at current depressed levels unless low-cost technology is developed to dispose of residues. Manufacturers have successfully developed acceptable substitutes for thorium-containing incandescent lamp mantles, paint and coating evaporation materials, magnesium alloys, ceramics, and investment molds. The traditionally small markets for thorium compounds, welding electrodes, and lighting, are expected to remain the leading consumers of thorium compounds through the end of the millennium. Thorium’s potential for growth in nonenergy applications is limited by its natural radioactivity. Its greatest potential exists in energy applications as a nuclear fuel or subatomic fuel in an industry that accepts radioactivity. In the long term, high disposal costs, increasingly stringent regulations, and public concerns related to thorium’s natural radioactivity are expected to continue to depress its future use.

Reference Cited

Metal Bulletin, 1996, Non-ferrous ores: Metal Bulletin [London] no,. 8141, December 31, p.25.

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