China
Africa
Explore chapters and articles related to this topic
Surface Treatments
Published in Thomas E. Carleson, Nathan A. Chipman, Chien M. Wai, Separation Techniques in Nuclear Waste Management, 2017
The use of fluoride volatility to process and separate plutonium and uranium from spent reactor fuels was examined in the 1960s by Jonke.7 Fluoride volatility is based on the fact that the higher fluorides of uranium and plutonium (UF6 and PuF6) have very high vapor pressures at near-ambient temperatures. Thus, reacting surface contaminants with fluorine gas can result in removal of the actinides from the surface. However, elevated temperatures are required in order for the reaction to proceed at a reasonable rate. Although applicable as a possible surface treatment, the highly corrosive nature of hot fluorine gas has not made this technique very attractive. A modification to this technique uses dioxygen difuoride as the fluorination agent.
Nuclear Fuel Materials
Published in C. K. Gupta, Materials in Nuclear Energy Applications, 1989
Many pyro processes are known. None to date has found favor in commercial reprocessing. Several advantages can be cited for pyro processes. They can, in the first place, be simple and compact. Because the inorganic materials used in the pyro processes are less sensitive to radiation, pyro processes are better adapted to short cooling times. Solid waste generation is relatively less in pyro processes. The disadvantages of pyro processes include high temperature of operation, making maintenance difficult, corrosion problems, and failure to yield low contamination of fission products from uranium and plutonium. Typical illustrations of the pyro processes are fluoride volatility and pyrozine processes. Figure 6 shows the essential steps involved in the two pyro processes. The fluoride volatility process takes advantage of the high volitility of fluorides or uranium and plutonium relative to most of the fission products. The process is an example of a fractional distillation separation technique. The pyrozine process is an example of a fractional crystallization separation technique and is based on the solubility difference of uranium and fission products in zinc. The fuel elements are dissolved in zinc at about 700°C. Since solubility of uranium in zinc decreases from about 13 wt% at 900°C to almost nil at 500°C, the uranium crystallizes out as the temperature of molten zinc with dissolved uranium is brought down slowly to about 500°C. The uranium values are filtered away, leaving the fission products still in the liquid. Recovery of uranium from zinc is accomplished by distillation.
Molybdenum-99 from Molten Salt Reactor as a Source of Technetium-99m for Nuclear Medicine: Past, Current, and Future of Molybdenum-99
Published in Nuclear Technology, 2023
Jisue Moon, Kristian Myhre, Hunter Andrews, Joanna McFarlane
Molybdenum is a multivalent metal with several oxidation states from 0 to +VI, and the stability of each species in molten salt solution varies with the operation condition. Generally, molybdenum speciation in both molten chloride and fluoride salts has shown similar patterns. Mo(0) precipitates as a solid or colloidal species, but Mo(I) and Mo(II) are not stable in solution.51 Mo(III) and Mo(IV) have both been observed to remain stable in salt. Mo(IV), Mo(V), and Mo(VI) species have been observed at high temperatures as vapor in the form of MoF4, MoF5, and MoF6. Because of these volatile high-valency molybdenum species, there is a high possibility that molybdenum can be separated through volatilization in a MSR. Fortunately, fluoride volatility studies have been conducted to answer these questions, and important details are discussed in the following section.
Application of fluoride volatility method to the spent fuel reprocessing
Published in Journal of Nuclear Science and Technology, 2020
Tetsuo Fukasawa, Kuniyoshi Hoshino, Daisuke Watanabe, Akira Sasahira
The authors have conducted various experiments in order to confirm the feasibility and the effectiveness of each FLUOREX process: fluorination of pulverized simulated SF, UF6 purification, oxide conversion of fluorination residue and its dissolution. Pulverization and solvent extraction processes are also needed before fluorination and after dissolution, respectively. There are many works carried out for pulverization and solvent extraction processes [9,10], which will be applied to the FLUOREX system. In this section, the experimental apparatus and procedure for fluoride volatility (fluorination and UF6 purification) processes are explained.
Flexible fuel cycle system for the effective management of plutonium
Published in Journal of Nuclear Science and Technology, 2020
Tetsuo Fukasawa, Kuniyoshi Hoshino, Junichi Yamashita, Masahide Takano
The uranium separation processes in the developed and developing reprocessing methods can be applied for the uranium removal technology in the FFCI system. Various reprocessing methods are picked up in Table 2[9] and investigated with laying emphasis on the U removal technologies. Table 2 shows the reprocessing type and abbreviation, developed or developing institution, U removal order in the reprocessing processes, media number used, removed U product purity and form, and the U removal residue (RM) form. Reprocessing has several separation processes after SF dissolution. For example, PUREX has U+ Pu extraction, their back extraction and U extraction processes, then the U removal order is 3 and the media number is 2 (extraction solvent and nitric acid solution). Suitable characteristics for the application to the FFCI system are lower U removal order for minimizing the processes, lower media number for reducing their regeneration systems, high removed U purity for its utilization, easy to be converted to re-enrichment form for removed U for its reuse in LWR, and easy to be dissolved form for RM for the recovery of actinides from the RM. The high U purity means the decontamination factor (DF) of around 106 and low about <103. The recovered U has higher U-235 content than natural U and is beneficial to be recycled to LWR after re-enrichment. The U removal order and the media number are relatively more important than others and 1 is the best for these characteristics. It is concluded from these points that the co-crystallization and fluoride volatility technologies are most suitable for the FFCI system among wet and dry methods, respectively. Fluoride volatility technology has been developed as the advanced reprocessing method [10].