Fuels nuclear, chemical process steps

The conversion of uranium concentrate or UFg to nuclear grade UO2 involves various chemical process steps such as dissolution of uranium ore concentrate in nitric acid to dissolve uranium for the PHWR fuel or hydrolysis of LEU UFg, in case of BWR fuel production stream. 

Isotope dilution analysis (IDA) involves mixing an aliquant of the sample with an aliquant of an artificially enriched isotope of the element to be analyzed. The content of the latter in the original sample is derived from the results of the isotopic analysis of the mixture compared to the isotopic compositions of the sample and of the enriched isotope. The term spiking is often used to refer to the mixing step. The aliquant of enriched isotope added to the sample is also commonly called a spike. IDA is used in particular for the determination of uranium, plutonium, or thorium in solutions of irradiated nuclear fuels. It has also been used for an independent measurement of the total volume or mass of solution in accountability tanks of chemical processing plants. 

Steps in PUREX waste processing and acid recovery. (From Benedict M., Nuclear Chemical Engineering, Pigford T.H., H.W. Levi, Eds, Second Eds., Chap 10—Fuel Reprocessing. McGraw-Hill, 1981. With permission.)... 

In each step of nuclear fuel reprocessing, the solvent is exposed to various radioactive sources and consequently prone to more degradation than solvents in other industrial fields. The resulting damage can be either chemical or physical. Numerous experimental studies have been carried out most of them were applied research and therefore restricted to studying the impact of degradation on process performance in order to develop an adequate cleanup treatment. 

The scraps which arise during the fabrication of plutonium-containing nuclear fuels are collected and stored for some time before they are processed to recover the plutonium. Due to the decay of Pu-241, considerable amounts of Am-241 may build up in the stored material. At the Alkem company, plutonium is recovered from the scrap by anion exchange the americium which is not sorbed on the resin is collected in the combined effluents from the loading and wash steps. The effluents are concentrated by evaporation besides americium, the concentrated effluents contain major amounts of uranium, plutonium, corrosion products, and residues from chemical reagents. A typical composition is given below ... 

After these steps, the power is transferred to storage drums for transfer to pelletization. At each step in the process, careful attention is paid to the physical, chemical, and nuclear properties of the powder. The quality assurance process ensures that the final material will provide for safe operation of the reactor in which the fuel is used. 

Understanding fundamental uranyl polyoxometalate chemistry in solution and the SS is the 1st step to defining its future role in the development of new actinide materials and separation processes that are vital to every step of the nuclear fuel cycle. Many SS geometries of uranyl polyoxometalates were described, but the authors are only beginning to understand their chemical behavior, which thus far includes the role of templates in their self-assembly, and the dynamics of encapsulated species in solution This study provides unprecedented detail into the exchange dynamics of the encapsulated species in the SS through MAS NMR spectroscopy. ... 

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