[en] This study described the treatment proposal of lagoon sludge in uranium conversion plant. Lagoon sludge consisted mainly of nitrate, ammonia, sodium, and calcium. Uranium was contained about 2 wt% in lagoon 1 sludge and 100 ppm in lagoon 2. Lagoon sludge should be treated by following methods. Firstly, water, ammonia, and nitrate in sludge should be removed by thermal denitration. And then, metal oxides such as sodium oxide in residual solid should be removed by leaching with water. After dissolving the residue by acid, uranium should be separated from by adsorption or precipitation

[en] This research investigates the optimal enrichment value thorium ratio that can prolong the operating cycle period, improve fuel burnup and achieve optimal thorium conversion ratio. The analysis was performed using variety of U-235 enrichment values and Th:U ratios to determine the optimal enrichment value and thorium ratio that can prolong the operating cycle period, improve fuel burnup and achieve optimal thorium conversion ratio. The study was performed using simulation of isotropic Tristructural fuel compact (TRISO) for Gas Turbine Modular Helium Reactor (GT-MHR) reactor using MCNPX version 2.7. The results showed that the increasing of U-235 enrichment will result in a higher kinf initial value and be able to maintain criticality until the end of the burning period. The thorium conversion ratio decreased with increasing U-235 enrichment and decreased from 1.0 for U-235 enrichment 10 % and above. The increased enrichment of U-235 has slowing down the rate of neutron capture by U-238 and Th-232 lead to the decrease formation of Pu- 239, Pu-241 and U-233. In addition to that, the increased enrichment of U-235 will reduce radioactivity from actinides waste. In conclusion, the increase in fuel burnup was not affected by U-235 enrichment and Th:U ratio. Thus, the most practical fuel composition proposed is U-235 20 %, Th: U 70:30 as it can maintain criticality throughout burnup, achieve long operating cycle duration and high thorium conversion ratio value. (author)

No abstract available

No abstract available

[en] Tests were carried out in the 1960s on two types of converter reactor using the uranium 235-plutonium and the uranium 233-thorium cycles. Framatome are re-evaluating this concept to make use of available plutonium. Since this type of reactor cannot replace Fast Breeder Reactors (FBRs) by using plutonium, it should be considered more as a transition reactor during the current period when plutonium is available and uranium is reasonably priced until the moment when FBRs are introduced on an industrial scale. Looked at in this way, a high conversion ratio is not necessary; it must, however, be sufficient for the reactor to recycle plutonium efficiently. In order to rely as much as possible on existing technology, it was decided to conduct a feasibility study using standard Zircaloy-clad fuel with a looser lattice to limit the consequences of cladding swelling in the event of a loss of coolant accident. The use of a mixed-oxide fuel significantly increases manufacturing costs. In addition, in order for the reactor to operate under economic conditions similar to those of the current PWRs, solutions had to be found that would permit increasing the burnup fraction while maintaining enrichments to prevent the voidage coefficient from causing any problems. For this reason it was decided to equip the reactor with a spectral shift system using fertile rod clusters. (author)

[en] Short communication

No abstract available

[en] The Philippine Research Reactor (PRR-1) is undergoing conversion from an MTR-type to a TRIGA-type reactor. Conversion mainly involves the replacement of all the old-plate type fuel assemblies with TRIGA-LEU fuel rod clusters, replacement of the reactor cooling systems allow operation up to 3 MW steady state power, and replacement of the central and instrumentation system. Time delays experienced were caused mostly by non-technical problems. The converted reactor should be ready for operation in mid-1987. (Author)

[en] The good neutron economy and the use of on-power refueling allow the CANDU reactor a wide variety of fuels and fuel cycles to be adapted to with no need of major alterations in the standard core design. A wide variety of thorium fuel cycles can be implemented in the CANDU reactor. These may be classified as (a) cycles without reprocessing, using separate fissile and fertile channels or separate fissile and fertile bundles, and (b) cycles with reprocessing or thorium conventional cycles, based on U-233 recycle and concurrently requiring an external fissile source such as enriched uranium or plutonium. Just on the line stands the self sustaining thorium cycle which, once the equilibrium is reached, no longer requires fissile addition from outside. With regard to the SSET (Self Sustaining Equilibrium Thorium) cycle the main problems reside in obtaining appropriate discharge burnup from the economic point of view and conversion rates to account for the through-cycle losses at the foreseeable technological performance of the reprocessing facilities. Three possible solutions of using thorium fuel in the CANDU reactor are examined in the paper: the use of different enrichment fueling zones, the use of a thorium blanket instead of the D20 reflector, and the use of metallic thorium fuel. The above solutions emerged from the need of obtaining high conversion rates and from that of keeping the main core parameters within the operational limits of the standard CANDU reactor. (author). 10 refs, tabs

[en] A reduction test of UF4 with Mg was carried out in order to stabilize the operating conditions under which a reduction reaction is run and in order to define the virtues and defects of the method selected as well as of the equipment and materials used. The material used was dehydrated UF⁴ prepared by electrolytic reduction. The Mg used was commercial grade. The reaction occurred in a cylindrical reactor, made of low alloy steel. The inside was lined with a one inch thick layer of CaF-2. The reaction began with external heating. The furnace heated by means of a program specifically written for this purpose. The test ran as planned and under conditions stipulated. The reaction began at 620^oC. The final product of this reaction was a cylinder of metallic U and MgF-2 slag, which was cut transversally to see the inside. The texture was smooth and homogenous without any pores, bubbles or incrusted slag. The efficiency of the reaction was about 75% of the weighted theoretical value. The test's final objective was achieved, because now the operating conditions under which the reaction can run are now known. The materials, operating conditions and behavior of the designed equipment were tested. All results agree with what was anticipated as they was previously determined by differential thermal analysis (DTA)