Radiation characteristics as a function of the gas flow rate emitted from argon torch plasma arc discharge

When a reduction of the waste and dissolution of the iron are carried out by means of an arc plasma, the radiant power of the arc should be suppressed. In those cases the radiant power from the plasmas has to be precisely controlled. Therefore, we tried to measure the radian power from the torch plasma using a power meter. The radiant power was measured to be about 620 to 950 W for an external plasma length of 2 cm at a current of 100 A, with gas flow rates of 4 to 20 l/min (Normal), and increases in proportion to the 0.25 to 0.37 power of the gas flow rate and with the increment of external plasma length and the plasma current. The total radiant efficiency is 32 to 40% in the condition mentioned above in the sphere model. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 139(3): 1–8, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10006     

Latest technical trend of arc plasma,electrical contacts,and their applications

Arc plasma generated by arc discharges is used in various fields because of its extraordinary characteristics such as very high temperature and high energy density. On the other hand, the principle of current interruption by extinguishing the arc discharge between electrical contacts is practical and useful in many types of circuit breakers. Arc discharge and electrical contacts have been well investigated, and numerous procedures have been developed. In this review paper, we introduce the recent technical trends in arc plasma treating wastes, synthesizing new materials, and the latest circuit breakers equipped with arc plasma and electrical contact techniques. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

锅炉受热面管子超音速活性镍基复合防护涂层的试验研究

针对电站锅炉受热面管的防护．应用超音速活性喷涂系统研制镍基复合活性功能涂层。通过金相组织分析、扫描电镜检测以及X射线衍射分析。证明该涂层具有良好的组织形貌。高温腐蚀试验也说明了涂层能够耐受高温腐蚀。     

Fundamental research on thermal plasma technology for treatment of low-level radioactive solid waste

The technology for treatment of low-level radioactive solid waste generated in nuclear power plants is expected to be established. The main problems are volume reduction and stabilization of radionuclides acceptable for final disposal. Thermal plasma technology offers advantages for such waste treatment because of the easy supply of heat at high temperature independent of chemical and physical properties of the waste. New, noncontaminated waste, such as metallic, inorganic and combustible materials, have been melted in a crucible furnace. A transferred-type of a dc plasma torch with a solid electrode was used as heat source and rated up to 50 kW. The main results obtained are as follows:

• 1 (1) Metallic and inorganic materials can be melted and vitrified. Combustible materials can be pyrolyzed. Consequently, high-volume reduction rates can be attained.
• 2 (2) Compressive strength of solidified products is more than twice as great as that of cement composites used for solidification of the liquid waste. Leaching rate of main components of the slag layer is in the same order of that of the high-level radioactive waste glass.
• 3 (3) To obtain a guiding principle for design of an off-gas treating system, compositions of the off-gas and properties of the dust entrained in the off-gas are clarified.

From these results, technical prospects so that plasma heating technology can be applied for treatment of low-level radioactive solid waste have been obtained.     

Investigation of plasma treatment for hazardous wastes such as fly ash and asbestos

Hazardous wastes such as fly ash and asbestos can be melted by plasma treatment to convert them into blocks of vitrified slag resulting in a volume reduction by 49 to 65%. Vitrified slag of fly ash containing such heavy metals as Zn, Cu, and Fe has an extremely high resistance to water. Electric conductivity of the elution of 18.8 g of slag in 700 ml of distilled water is nearly the same as that of pure distilled water, being only about 0.1% of the electric conductivity of the solution of fly ash in distilled water. The surface of the molten asbestos becomes a hard shell without needlelike fibers, thus rendering asbestos safe for human health. As a result, plasma waste treatment can become a powerful tool for environmental protection. © 1999 Scripta Technica, Electr Eng Jpn, 126(3): 73–82, 1999