Uranium conversion

Generation of liquid waste from the uranium conversion process (see Table 5-1) is generally small and is handled by placing liquid effluent in lined ponds with sealed bottoms. The pond effluent is chemically neutralized to precipitate out uranium and uranium progeny in pond sludge. Water in the ponds is permitted to evaporate and sludge is disposed of as waste under controlled conditions (AEC 1974). 

Exxon Nuclear Company has conducted various development programs to support the design and licensing of a commercial nuclear fuel reprocessing plant. The uranium conversion portion of the reprocessing plant will use fluidized-bed processes for conversion of uranyl nitrate hexahydrate (UNH) to uranium hexafluoride (UF ). This paper describes the laboratory and pilot plant studies conducted at Oak Ridge National Laboratory (1) for Exxon Nuclear Company on the conversion of UNH to UF, and on the purification of UF. ... 

Traumer, W. E. Uranium Conversion at Eldorado Nuclear Limited, Atomic... 

C26.08 C1188-91(1997)el Standard Guide for Establishing a Quality Assurance Program for Uranium Conversion Facilities... 

Reconstruction of pilot scale reprocessed uranium conversion facility was completed in June, 1994. 

Although the uranium concentration has been raised substantially in the milling operation, the relative abundance of the fissile isotope, is too low. Natural uranium contains about 0.7% by weight To sustain a nuclear reaction in most commercial power reactors, the fuel must be enriched to about 3.5%. Enrichment is often with gaseous feedstock achieved by converting UsOg to the gaseous UFg. Uranium conversion plants that produce UFg as a feedstock for enrichment processes are currently in operation in both Europe and North America. 

In Chapter 2, we take a more detailed look at the analytical chemistry pertaining to key commercial activities, that is, uranium mining and its utilization in the nuclear fuel cycle (NFC) first, in the milling process, uranium-containing deposits are processed to form uranium ore concentrates (UOC) that are then shipped to uranium conversion facilities (UCF), where the uranium is transformed into high-purity nuclear grade compounds. These can serve as fuel for nuclear power plants or as feed material for isotope enrichment. Then we discuss the analytical aspects of compliance with the strict specifications of the materials used in enrichment plants and in fuel fabrication facilities. Finally, we deal with the analytical procedures to characterize irradiated fuel and waste disposal of spent fuel. 

The following section presents an overview of a generic uranium NFC (Figure 1.9) (IAEA 1613 2009) and a generic flow sheet of the chemical processes in a uranium conversion facility (UCF) where UOC is converted to UO2 (for nuclear fuel), U metal (for fuel or other metallurgical applications), or UFg (feed for enrichment plants) is shown in Eigure 1.10. 

FRAME 2.3 WHAT HAPPENS WHEN THINGS GO WRONG AT A URANIUM CONVERSION FACILITY ... 

Highlights Before shipping UOCs from the mill to the uranium conversion facility (UCF), an extensive series of tests is necessary, starting from proper sampling, continuing with dissolution procedures, and finally a suite of chemical, isotopic, and physical analyses must be carried out in order to produce the certificate that will... 

The main methods used for reprocessing of SNF flowsheet were reviewed in a 120 pages report by the Nuclear Energy Agency (NEA 2012). The three main processes are the so-called hydrometallurgy processes (PUREX and UREX), pyromet-allurgy processes and its variations, and the fluoride volatility process (quite like the method used at the uranium conversion facilities discussed in Chapter 1). The report reviewed in detail several of these processes that are deployed in different facilities for various types of spent fuel (NEA 2012). In this section, we shall try to briefly present an overview of the main points and the analytical aspects. 

Reactor physical characteristics have also drawn much attention. The control rod worth, including the differential worth and integral worth, were calculated by the Monte Carlo code for neutron and photon transport (MCNP) for the 2 MW TMSR-SE (Zhou and Liu, 2013). The measurement of the neutron energy spectrum was also theoretically and experimentally studied (Zhou, 2013). Parametric study of the thorium-uranium conversion rate was conducted to optimize the core structure for the improvement of the economics of the TMSR using the standardized computer analyses for licensing evaluation (SCALE) code (Wang and Cai, 2013). 

In 1999, a serious accident happened at the JCO uranium conversion facility in Tokai-mura, Japan, resulting in a large release of uranium isotopes into the local environment. Yoshida et al. collected soil samples just after this accident from around the JCO factory and determined both the concentration of U and the 235 jy238 j j otope ratio in these samples. They reported that the isotope ratio in the soil around the JCO factory was elevated compared to the... 

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