Ion exchange resins are widely used in the field of nuclear industry. The present work aimed at the development of a method
for complete decomposition of cation exchange resins with H2O2 in the presence of Fe3+ ion. The decomposition reaction proceeded at ambient temperature and decomposition time was greatly shortened with increasing
concentration of Fe3+ ion rather than that of H2O2. The catalytic action of Fe3+ ion was suppressed with increase of HNO3 concentration. As much as 4 g of the air-dried resin could be decomposed with 8 ml of 30% H2O2, and the use of about 60 ml of 30% H2O2 resulted in the complete decomposition of organic carbon to CO2. Absence of any orgnaic carbon in the residual solution will simplify the final disposal.
Establishment of a generalized method of separating and analyzing trace impurities of high-purity rare earth oxides was attempted
by neutron irradiation. The amount of the target materials and the size of the ion-exchange columns used for the analysis
were made uniform. The element with atomic number lower by one was added to the irradiated target solution, prior to the cation-exchange
separation, in an amount comparable to that of the carrier. α-Hydroxyisobutyrate solutions of various concentrations were
used as eluent, the pH value always being kept constant at 3. 77. By this method, impurities of Gd, Dy, Ho and Er in Tb4O7, Dy, Er and Yb in Ho2O3, and Sc, Eu, Tb and Tm in Yb2O3 were determined.
In determining the trace impurities existing in high-purity rare earth samples by the neutron activation analysis, there are
much interference due to nuclides induced from neutron induced second order nuclear reaction. This paper presents the degree
of interference calculated over the ranges of irradiation time from 105 to 107 sec and of thermal-neutron flux from 1·1012 to 1·1015 n·cm−2·sec−1. According to the results of these calculations, degree of interference under the neutron irradiation condition for 288 hrs
in the thermal-neutron flux of 3·1013n·cm−2·sec−1 is concluded to be 6.4·106 ppm Gd in Eu, 2.2·104 ppm Sm in Eu, 1.9·104 ppm Ho in Dy, 1.1·103 ppm Eu in Sm, 1.1·102 ppm Ce in La and 1.1·10 ppm Tb in Gd, respectively. Especially, the Gd determination in the Eu target is extremely affected
by153Gd formed from the151Eu (n, γ)
Oxalic acid or oxalate is widely used as a precipitant and a detergent in the field of nuclear energy. The present work aimed
at developing a method of decomposing oxalic acid with HNO3 in the presence of Mn2+ ion. The use of Mn2+ ion as low as 10−3 mol/l facilitated the complete decomposition of oxalic acid, and the acidity of the resulting solution became as low as 0.1
eq/1 under the optimum conditions. The decomposition of oxalic acid is a first order reaction and proceeds at temperatures
above 80°C; the activation energy of the reaction is 18.6 kcal/mol. This decomposition method is applicable to the dissolution
of an oxalate precipitate.
Adsorption and desorption of95Zr−95Nb,99Mo,103Ru,132Te and239Np in a HCl-alumina system were studied in order to purify99Mo and132Te obtained by the cation-exchange separation of fission products and to prepare highly pure99mTc and132I generators.99Mo and132Te, of which radionuclidic purity was over 99.99% and 99.999%, respectively, could be obtained by passing the cation-exchange
separated Mo and Te fractions through alumina columns, by washing with HCl and finally by eluting99Mo with 1M NH4OH and132Te with 3M NaOH. In order to raise the recovery of99Mo and132Te from the alumina columns, they should be eluted as quickly as possible after the adsorption. The direct use of the alumina
column containing99Mo or132Te as the generator allowed milking of99mTc or132I, of which radionuclidic purity was over 99.999%. Milking yields of99mTc with 0.1M HCl and132I with 0.01M NH4OH were 77% and 90%, respectively. The latter value was much higher than that in usual performance of the generator.
The solids formation behavior in a simulated high level liquid waste (HLLW) was experimentally examined, when the simulated HLLW was treated in the ordinary way of actual HLLW treatment process. Solids formation conditions and mechanism were closely discussed. The solids formation during a concentration step can be explained by considering the formation of zirconium phosphate, phosphomolybdic acid and precipitation of strontium and barium nitrates and their solubilities. For the solids formation during the denitration step, at least four courses were observed; formation of an undissolved material by a chemical reaction with each other of solute elements (zirconium, molybdenum, tellurium) precipitation by reduction (platinum group metals) formation of hydroxide or carbonate compounds (chromium, neodymium, iron nickel, strontium, barium) and a physical adsorption to stable solid such as zirconium molybdate (nickel, strontium, barium).
The filtration characteristics of solids generated in a simulated high level liquid waste (HLLW) were experimentally examined, when the simulated HLLW was processed according to the ordinary way of actual HLLW treatment process. The filtration characteristics of solids depended on the particle size. The phosphomolybdic acid, which was very fine particle with about 0.1 m diameter, made slurry a difficult-to-filter slurry, if the phosphomolybdic acid content (wt%) to the whole solids in a slurry exceeded 50 wt%. On the contrary, the zirconium compounds (zirconium molybdate and zirconium telluride) had positive effect on filtration characteristics because of their relatively large particle size of about 3 to 5 m. When the zirconium compounds content was above 50 wt%, slurry became a easy-to-filter slurry. A centrifugal sedimentation was discussed as a solid/liquid separation technique for very fine particles such as phosphomolybdic acid. The theoretical feed flow rate corresponded to 0.1 m diameter particles was about 20 l/h at the centrifugal acceleration of about 8000 G.
Solid formation in a simulated high level liquid waste (HLLW) was experimentally examined at 2M and 0.5M nitric acid concentrations. The precipitation studies were conducted by refluxing the simulated HLLW around 100°C. Zr, Mo, Te and Ru were major precipitation elements in both 2M and 0.5M HNO3 solutions. The amount of precipitate in 2M HNO3 solution decreased with decreasing Zr concentration and no precipitation was found in the solution without Zr. Only about 10% of Zr, Mo and Te were precipitated, if the Mo/Zr ratio in the 0.5M HNO3 solution was kept below 0.5. Complete removal of Zr and Mo was the most effective way to prevent solid formation in the solution with 2M and 0.5M HNO3 concentrations.
The acidity change and solid formation in a simulated high level liquid waste (HLLW) containing precipitate were experimentally examined, when the acidity was reduced from 2M to 0.5M by denitration or simple dilution. The acidity of the simulated HLLW containing precipitate could be adjusted from 2M to around 0.5M by means of denitration or dilution, as well as the case of simulated HLLW without precipitate. The precipitation fractions of Zr, Mo and Te during denitration decreased with increasing amount of the precipitate already contained in the simulated HLLW. The amount of solid formed in the dilute simulated HLLW also decreased with increasing amount of precipitate in the simulated HLLW. Two process flow sheets for preparing HLLW for transuranic elements extraction were developed. One was a denitration process and the other a dilution process.
This study was performed mainly from the viewpoint of consumption of diisodecylphosphoric acid (DIDPA) by the extracted Mo and Zr to estimate extraction capacities. The number of DIDPA molecules consumed per one extracted Mo atom was four when the concentration of Mo in the aqueous phase was less than 10–3M and it decreased with increasing Mo concentration. Two molecules of DIDPA were consumed per one extracted Zr atom when the Zr concentration was high. Dependencies of the distribution ratio of Mo on the concentrations of Mo, DIDPA and HNO3 are also described.