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[en] A molten salt technology using Li2O-LiCl has been extensively investigated to recover uranium metal from spent fuels in the field of nuclear energy. In the reduction process, it is an important point to maintain the concentration of Li2O. ZrO2 is inevitably contained in the spent fuels because Zr is one of the main components of fuel rod hulls. Therefore, the fate of ZrO2in Li2O-LiCl molten salt has been investigated. It was found that Li2ZrO3and Li4ZrO4 were formed chemically and electrochemically and they were not reduced to Zr. The recycling of Li2O is the key mechanism ruling the total reaction in the electrolytic reduction process. However, ZrO2will have a role as a Li2O sink.
[en] The annual operation time and thermal output of Research Reactor No. 1 were 207 hours and 874 kWh in 1994, and the bulk of operation was for reactor training for university students. Research Reactor No. 2 was used for sample irradiation for radioisotope production, activation analysis, etc., having 2,593 hours of annual operation time and 3,266 MHh of gross thermal output in this year. Number of samples irradiated was 1,118; 371 samples for radioisotope production, 648 samples for activation analysis and 99 for other purpose. It was planned Research Reactor No. 1 and No. 2 to be stopped sometime during next year, then a new reactor (HANARO) will take all missions of these two reactors. According to this policy, the reactor training course using reactor No. 1 was decide to be called off from 1995, and all spent fuels will be transported to the storage pool of (HANARO). Currently, preliminary arrangements for fuel transporting and discuss reporting for these two reactors are under operation, and reactor operation project will place the focus on this matter. 15 tabs., 21 figs. (Author) .new
[en] A boron doped diamond thin film electrode was employed as an inert anode to replace a platinum electrode in a conventional electrolytic reduction process for UO2 reduction in Li2O–LiCl molten salt at 650 °C. The molten salt was changed into Li2O–LiCl–KCl to decrease the operation temperature to 550 °C at which the boron doped diamond was chemically stable. The potential for oxygen evolution on the boron doped diamond electrode was determined to be approximately 2.2 V vs. a Li–Pb reference electrode whereas that for Li deposition was around −0.58 V. The density of the anodic current was low compared to that of the cathodic current. Thus the potential of the cathode might not reach the potential for Li deposition if the surface area of the cathode is too wide compared to that of the anode. Therefore, the ratio of the surface areas of the cathode and anode should be precisely controlled. Because the reduction of UO2 is dependent on the reaction with Li, the deposition of Li is a prerequisite in the reduction process. In a consecutive reduction run, it was proved that the boron doped diamond could be employed as an inert anode.
[en] Electrochemical reductions of various UO2 forms were investigated in a molten LiCl–Li2O electrolyte. The study focused on the influence of their sizes and densities on the reduction rate by running experiments with eight UO2 forms. They can be classified into porous and dense forms. The porous forms are one granule and four porous pellets with different densities (55%, 60%, 70% and 80%), all of which were fabricated in our laboratory. The dense forms were prepared by crushing dense pellets, and these were similar in size to the porous pellets and the granules. Systematic comparisons of the reduction rate among the tested UO2 forms revealed that a lower density and smaller size of UO2 led to a faster reduction rate. Particularly, attention was focused on the observation that the size of the UO2 provides more dominant effect on the reduction rate than the density
[en] Radioisotope facilities were operated to support research, development and production of radioisotopes. Irradiation facilities were operated to offer irradiation service to the clients. Even though intensive periodical checks and some essential maintenance had been carried out the results of RI facility maintenance seemed to be not much satisfactory due mainly to the shortage of skilled manpower and maintenance expenses. High intensity γ irradiator was normally operated 165 times for overall 2,670 hrs, and the low intensity γ irradiator was operated 89 times for overall 367 hrs, respectively. The reactor shutdown report of TRIGA Mark-II and Mark-III were submitted to MOST and the spent fuels from the core were transferred to storage racks in reactor pool for decommissioning which will be started in 1997. (author). 5 tabs., 3 figs