Showing papers in "Journal of Nuclear Science and Technology in 2006"

Advanced Doped UO2 Pellets in LWR Applications

Abstract: The nuclear industry strives to reduce the fuel cycle cost, enhance flexibility and improve the reliability of operation. This can be done by both increasing the fuel weight and optimizing rod internal properties that affect operational margins. Further, there is focus on reducing the consequences of fuel failures. To meet these demands Westinghouse has developed ADOPT (Advanced Doped Pellet Technology) UO2 fuel containing additions of chromium and aluminium oxides. This paper presents results from the extensive investigation program which covered examinations of doped and reference standard pellets both in the manufactured and irradiated states. The additives facilitate pellet densification during sintering and enlarge the pellet grain size. The final manufactured doped pellets reach about 0.5% higher density within a shorter sintering time and a five fold larger grain size compared with standard UO2 fuel pellets. The physical properties of the pellets, including heat capacity, thermal expansion coeffici...

Radial-hydride embrittlement of high-burnup zircaloy-4 fuel cladding

Abstract: Prestorage drying operations of high-burnup fuel may make Zircaloy-4 (Zry-4) fuel cladding more susceptible to failure, especially during fuel handling, transport, and post-storage retrieval. In particular, hydride precipitates may reorient from the circumferential to the radial direction of the cladding during drying operations if a threshold level of hoop stress at or above a corresponding threshold temperature is exceeded. This study indicates that the threshold stress is approximately 75–80 MPa for both nonirradiated and high-burnup stress-relieved Zry-4 fuel cladding cooled from 400°C and, under ring compression at both room temperature and 150°C, that radial-hydride precipitation embrittles Zry-4. Specifically, the plastic tensile hoop strain needed to initiate unstable crack propagation along radial hydrides decreases dramatically from >8% to lt;1% as radial-hydride fraction increases. Lower hydrogen contents (lr;300wppm) appear to be more susceptible to radial-hydride embrittlement compared to hig...

Development of a Fine and Ultra-Fine Group Cell Calculation Code SLAROM-UF for Fast Reactor Analyses

Abstract: A cell calculation code SLAROM-UF has been developed for fast reactor analyses to produce effective cross sections with high accuracy in practical computing time, taking full advantage of fine and ultra-fine group calculation schemes. The fine group calculation covers the whole energy range in a maximum of 900-group structure. The structure is finer above 52.5 keV with a minimum lethargy width of 0.008. The ultra-fine group calculation solves the slowing down equation below 52.5 keV to treat resonance structures directly and precisely including resonance interference effects. Effective cross sections obtained in the two calculations are combined to produce effective cross sections over the entire energy range. Calculation accuracy and improvements from conventional 70-group cell calculation results were investigated through comparisons with reference values obtained with continuous energy Monte Carlo calculations. It was confirmed that SLAROM-UF reduces the difference in k-infinity from 0.15 to 0.01% for ...

Evolution of Microstructure and Microchemistry in Cold-worked 316 Stainless Steels under PWR Irradiation

Abstract: The evolution of microstructures and microchemistry was examined by transmission electron microscopy in cold-worked SUS 316 stainless steel components irradiated in a pressurized water reactor to 1...

Effects of hydrogen peroxide on corrosion of stainless steel, (V) : Characterization of oxide film with multilateral surface analyses

Abstract: In order to understand corrosion behavior of stainless steel in BWR reactor water conditions, characteristics of oxide films on stainless steel specimens exposed to H2O2 and O2 in high temperature water were determined by multilateral surface analyses, i.e., SEM (scanning electron microscope), LRS (laser Raman spectroscope), SIMS (secondary ion mass spectroscope) and STEM-EDX (scanning transmission electron microscope). The following points were experimentally confirmed. 1. Oxide layers were divided into inner and outer layers: Outer layers of the specimen exposed to 100ppb H2O2 consisted of larger corundum type hematite (α-Fe2O3) particles, while inner layers consisted of very fine Ni rich magnetite (Fe3O4). Outer layers of the specimen exposed to 200 ppb O2 consisted of larger magnetite mixture particles, while inner layers consisted of fine Cr rich magnetite. 2. Outer oxide layers consisted of oxide particles. The oxide particles depositing on the specimens exposed to 100ppb H2O2 were divided into two ...

Characteristics of Oxidation Reaction of Rare-earth Chlorides for Precipitation in LiCl-KCl Molten Salt by Oxygen Sparging

Abstract: The precipitation reaction of some rare earth chlorides (La/Ce/Nd/GdCl3) in a LiCl-KCl molten salt has been carried out by using the oxygen sparging method. In this study, regardless of the oxygen sparging time and the molten salt temperature, oxychlorides (REOCl) for LaCl3, NdCl3 and GdCl3, and an oxide (REO2) for CeCl3 are formed as a precipitate. The conversion of rare-earth chlorides into insoluble precipitates was described by using a conversion ratio. The conversion ratio increased exponentially with the oxygen sparging time and finally showed asymptotic value at 1,023 K of the molten salt temperature condition. The conversion ratios of LaCl3, NdCl3 and GdCl3 were increased with the molten salt temperature, however, even though the conversion ratio was increased from 0.660 to 0.995 with increasing molten salt temperature from 823 to 923 K at 60 min of a sparging time, the values of the conversion ratio of CeCl3 were nearly constant (over 0.999) with the molten salt temperature. As a result of the th...

Phenomenological Nuclear Level Densities using the KTUY05 Nuclear Mass Formula for Applications Off-Stability

Abstract: A new parametrization for the phenomenological nuclear level density taking account of the shell and pairing energies of the recent nuclear mass formula of Koura, Tachibana, Uno, and Yamada (KTUY05) a is proposed. Such a level density formula is often required to calculate nuclear reaction cross sections for nuclei off-stability, especially for fission systems and astrophysical applications. With the phenomenological level density formula of Gilbert-Cameron with the energy dependent level density parameter of Ignatyuk, a smooth dependence of the asymptotic level density parameter a* on the mass number is obtained. At low energies, systematics for the constant temperature model are also derived by connecting the Fermi gas level density and the discrete level information available for more than 1,000 nuclei. Some comparisons with the discrete level data and the microscopic model are made to validate our approach, and it is concluded that the parametrization obtained can be used for nuclear reaction calculat...

Out-of-pile and In-pile Perfomance of Advanded Zirconium Alloys (HANA) for High Burn-up Fuel

Abstract: The performance of the advanced Zr alloys (HANA) for a high bum-up fuel has been evaluated in the out-of-pile and in-pile conditions. The corrosion resistance of the HANA claddings was superior to Zicaloy-4 in a PWR-simulating loop condition. The improved corrosion resistance of the HANA claddings was attributed to the fine distribution of the precipitate. HANA claddings showed a higher creep resistance as compared to Zircaloy-4 from the thermal creep test. The deformation behavior of HANA in a LOCA condition was similar to Zircaloy-4. Threshold ECR value of HANA was higher than the conventional value of 17% in Zircaloy-4, which is mainly due to the fact that the Nb decreases the oxidation rate as well as the hydrogen pickup. Fretting wear test revealed that HANA claddings have a similar wear resistance to Zircaloy-4. From the irradiation test up to burn-up of about 12 GWd/MtU, HANA claddings showed a better corrosion resistance as well as a better creep resistance than Zircaloy-4. The in-pile corrosion resistance of the HANA claddings was improved by 40-50% as compared to Zircaloy-4 on the basis of the oxide thickness measurements.

Modeling Radon Flux Density from the Earth's Surface

Abstract: In order to make the idealized model for predicting soil radon flux more practically and accurately, two central variables (radon emanation power and soil water content) controlling the amount of radon transportation in soil were formulated. The reformulated model for predicting radon flux density was verified by the field measurements carried out in 10 different sites. The result indicates that the reformulated model is useful for improving the prediction feasibility and accuracy of radon flux density from the earth's surface.

Evaluation of Dancoff Factors in Complicated Geometry using the Method of Characteristics

Abstract: A simple and efficient method to estimate the Dancoff factor in a complicated geometry, named “the Neutron current method,” is presented in this paper. In this method, Dancoff factors are evaluated from the flux values obtained by the method of characteristics (MOC). By setting appropriate neutron sources in the non-fuel regions of target geometry and then executing fixed source calculation by MOC, the neutron current method can evaluate Dancoff factors for complicated geometry. It was demonstrated that the neutron current method can easily be adopted for complicated geometries, such as a PWR fuel assembly or large-scale geometry that is difficult to handle by the traditional collision probability method. By utilizing the neutron current method instead of a traditional collision probability method, the calculation time of Dancoff factors in complicated large geometry is drastically reduced.

Corrosion of Steels in Lead–Bismuth Flow

Abstract: For the development of lead-bismuth (Pb-Bi) cooled fast breeder reactors, the corrosion characteristics of various steels in a flowing Pb-Bi were investigated by means of steel corrosion test performed in the flowing Pb-Bi for 1,000 h. It was found that liquid metal corrosion was inhibited by single or multiple oxide layers formed on the steel surfaces. The oxide layers can be classified to an inner layer and an outer one. The existence of the inner oxide layer might be more important for the corrosion resistance since the inner one was compact and stuck to the steel surface while the outer one was easily broken into small pieces with cracks and peeled from the substrate. The effect of Cr content in steels on corrosion resistance was investigated. Stable Cr rich oxide layers were easily formed on the high Cr steels. The weight losses were lower in the steels with higher Cr contents. The content of Cr in the steel was effective to form the thin and compact Cr-rich oxide layer and suppressed the corrosion. ...

Grain Boundary Phosphorus Segregation in Thermally Aged Low Alloy Steels

Abstract: Intergranular embrittlement due to grain boundary segregation of phosphorus is recognized as one of the potential degradation factors in irradiated reactor low alloy steels at high neutron fluence. In this study, low alloy steels thermally aged at 400-500°C were investigated to evaluate the correlation between phosphorus segregation and intergranular embrittlement. Phosphorus segregation determined using Auger electron spectroscopy increased after thermal aging above 450°C and was in good agreement with the calculated value based on McLean's model. No influence of thermal aging on tensile properties or hardness was observed. The ductile brittle transition temperature determined using a one-third size Charpy impact test increased at a P/Fe peak ratio of 0.14. These results indicated that there is a threshold level of phosphorus segregation for non-hardening embrittlement. The ductile to brittle transition temperature (DBTT) increased with the proportion of intergranular fracture, so this result shows that ...

Electrochemical Study on the Reduction Mechanism of Uranium Oxide in a LiCl-Li2O Molten Salt

Abstract: By means of a linear sweep voltammetry, a cyclic voltammetry and a chronopotentiometry, the electrolytic reduction of uranium oxide has been studied to establish the reduction mechanisms, which are based on a simultaneous uranium oxide reduction and a Li2O electrowinning, and the formation and electrolysis of lithium uranate. From the voltammograms, the reduction potentials of the uranium oxide and Li2O were obtained. From the chronopotentiometries based on the results of the voltammograms, the uranium oxide was reduced to uranium metal through the reduction mechanisms showing a more than 99% conversion. For a verification of the reduction mechanisms feasibility, basic data on the electrolytic reduction of the uranium oxide was obtained from the experiments and the characteristics of the closed recycle of Li2O were discussed.

Fuel and Core Design of Super Light Water Reactor with Low Leakage Fuel Loading Pattern

Abstract: An equilibrium core for the High Temperature Supercritical-pressure Light Water Reactor, now called the Super Light Water Reactor (Super LWR), has been designed. The fuel assemblies loaded in the peripheral region of the core are cooled with descending flow to achieve a high average coolant core outlet temperature. This flow scheme is compatible with a low leakage fuel loading pattern (LLLP) in which 3rd cycle fuel assemblies are loaded in the core peripheral region. Stainless steel is used for fuel rod claddings and for structural materials. Watts correlations are used for predicting heat transfer in the core. They take into account the improved heat transfer for downward flow. It is found that the water rods with their downward flow need to be thermally insulated with thin ZrO2 layer to keep the moderator temperature below the pseudo critical temperature and to reduce the thermal stress in water rod walls. An average coolant core outlet temperature of 500°C is achieved. The effects of various heat trans...

Temperature Dependence of Isotope Effects in Uranium Chemical Exchange Reactions

Abstract: Temperature dependence of isotope effects in U(IV)-U(VI) exchange reaction was experimentally studied by means of redox chromatography using columns packed with anion exchange resin in the temperature range 87- 160°C (360–433 K). The experimentally observed isotopic separation coefficient, e, was converted to the isotopic equilibrium constant, 1n K-eo, of the U(IV)-U(VI) exchange reaction with the aid of the experimentally measured ionic mole fractions of U(IV) and U(VI) in the resin phase and the aqueous solution phase. The plots of eo vs. 1/T led to the temperature dependence of eo=0.69/T-82/T2 , where the first term is due to the nuclear field effect (nuclear-electron interaction effect) and the second term is due to the molecular-vibration mass effect. The discussion is extended to the temperature dependence of the previously reported isotope effects in the U(III)-U(IV) electron exchange reaction, and the U(VI)-malate-complex ligand exchange reaction.

Novel Syntheses Method of Phenol Type Benzo-15-Crown-5 Ether Resin and its Application for Lithium Isotope Separation

Abstract: The novel synthesis method of phenol type benzo-15-crown-5 ether resin was proposed. The chemical bonding of benzo-crown ether and phenol was succeeded by using hexamethylenetetramine and trichloroacetic acid as the condensing agent and solvent, respectively. The control of the diameter and shape of resin was also succeeded by using the high porous silica beads support. The isotope fractionation by chromatography using the synthesized resin was confirmed. The lighter isotope was disproportionately located in the crown ether resin. The separation coefficient, ϵ, in the present system was 0.033.

Fission Gas Release Behavior from High Burnup UO2 Fuels under Rapid Heating Conditions

Abstract: Fission gas release (FGR) behavior under rapid heating conditions of high burnup UO2 fuels with developed rim structure has been examined using two different out-of-pile heating techniques with no restraint pressure. The burnups of the fuel specimens were 36–86 GWd/tU. The bare fuel specimens were heated up to 600-1,800°C at heating rates of 1.7 to 4,600°C/s. The FGR process strongly depended on fuel burnup (extent of rim structure formation) and heating conditions (heating rate, terminal temperature). At lower heating rates below about 10°C/s, growth and interlinkage of fission gas bubbles controlled FGR only at higher temperatures above the threshold temperatures of 1,250--1,450°C, depending on fuel burnup. At higher heating rates above at least 90°C/s, instantaneous FGRs, which originated from the occurrence of microcracks and fuel fragmentation induced by the overpressurization of rim bubbles, arose at higher temperatures above 700°C, only for the high burnup fuels of 74 and 86 GWd/tU with developed r...

Measurement of response functions of a liquid organic scintillator for neutrons up to 800 MeV

Abstract: Response functions of a BC501A liquid organic scintillator for neutrons up to 800 MeV have been measured at the heavy-ion accelerator of the National Institute of Radiological Sciences, Japan. A thick graphite target was bombarded with 400-MeV/u C ions and 800-MeV/u Si ions to produce high-energy neutrons whose kinetic energy was determined by the time-of-flight method. The measured response functions were compared with the results obtained using SCINFUL-QMD code, and the accuracy of the code was experimentally verified up to 800 MeV. This work will contribute to extending the energies measurable with our new radiation dose-monitoring system (DARWIN), which is based on the BC501A scintillator.

Development of TOF-PET using Cherenkov Radiation

Abstract: We proposed a new concept of TOF-PET (Time-of-Flight Positron Emission Tomography) using Cherenkov radiation. Basic experiments revealed a timing resolution of 170ps, but the detection efficiency was less than those of the conventional BaF2 scintillators. Through simulation studies, we confirmed that the spatial resolution and the S/N ratio of the images reconstructed with TOF information were 1.5 and 3 times better, respectively, than they were without TOF information, when we adopted the FP (Forward Projection) method combined with the ML-EM (Maximum Likelihood Expectation Maximization) algorithm as an image reconstruction algorithm. Consequently, we concluded that TOF-PET using Cherenkov radiation is a promising candidate for next-generation PET. We concluded that PWO (PbWO4) is the best Cherenkov radiator from the viewpoint of detection efficiency. Additionally, we found that the Monte Carlo algorithm was able to generate images having error bars and thus to make quantitative diagnoses possible.

Fracture Behavior of Irradiated Zircaloy-4 Cladding under Simulated LOCA Conditions

Abstract: Laboratory-scale experiments were performed with Zircaloy-4 fuel cladding, irradiated to 39 and 44 GWd/t at a PWR, for evaluating high burn-up fuel rod behavior in a loss-of-coolant accident. Short test rods, fabricated with the cladding were heated, isothermally oxidized at 1,303 to 1,451 K in steam flow, and quenched with water flooding. Two cladding specimens, oxidized to about 26 to 29% ECR, were fractured during the quench, while four cladding specimens, oxidized to about 16 to 22% ECR, survived the quench. Threshold of fracture is comparable with that of unirradiated cladding specimens which are hydrided to the same level. Accordingly, in the burnup level of the present study, differences were not significant between irradiated and unirradiated cladding specimens in terms of threshold of fracture during quenching, though the threshold is reduced as initial hydrogen concentration increases.

Characterization of High Burnup Fuel for Safety Related Fuel Testing

Abstract: Fuel Assemblies designed and fabricated by Westinghouse Electric Sweden (WSE) to reach high burnup have been operated in the Leibstadt nuclear power plant (KKL) for seven cycles attaining an assembly average burnup above 60 MWd/kgU. The irradiation conditions in KKL featured linear heat generation rates ranging from 250 W/cm early in life down to 100W/cm in the last cycle and normal water chemistry with zinc injection. Selected rods have been extracted at both intermediate and final irradiation stages and hot cell examinations have been carried out. The results show that the fuel is well suited for high burnup applications and rod segments have been provided to the OECD Halden Reactor Program, the OECD Studsvik Cladding Integrity Program and the Japanese ALPS program for dedicated high burnup tests with regard to fission as release and cladding lift-off as well as behavior under power transient, RIA and LOCA.

Transient-Diffusion Measurement of Radon in Japanese Soils from a Mathematical Viewpoint

Abstract: A transient-diffusion measurement method for radon diffusion coefficients in porous materials was first developed in the U.S.A. To get a correct interpretation of measured data by the transient-diffusion method, more attention needs to be put on mathematical treatment which has been somewhat neglected perhaps because of the inherent mathematical difficulty. Strictly speaking, the measured radon concentrations have to be interpreted mathematically as a two-region problem. But, solving diffusion equations is quite difficult analytically because of time-dependent boundary conditions for the two-region problem. On the other hand, the advent of high performance computers has made it possible to easily solve diffusion equations numerically. However, without good knowledge of the diffusion phenomena in the actual measuring system, there is a possibility that the wrong boundary conditions are set. To prevent this, prior consideration by mathematical interpretation leading to visual understanding of the diffusion ...

Electrodeposition characteristics of uranium in molten LiCl-KCl eutectic and its salt distillation behavior

Abstract: Electrorefining experiments with a crucial anode containing U, elemental rare earths; Gd, Nd and Ce or Nd2O3 were carried out in KCL-LiCL eutectic melt at 500°C. Partitioning behavior of the components according to the applied voltage or current was investigated at various initial U concentrations in a molten salt. Elemental REs concentrations in the cathode deposits increased as the applied voltage decreased at a low initial UCl3 concentration, while they were maintained at a very low level at a higher concentration than ∽6 wt%. Nd2O3 also shows a similar electrochemical behavior with the elemental REs. This means that rare earth oxides which are inherently incorporated in a U ingot can be partitioned during an electrorefining. The dependency of the applied current on the microstructure of the deposit was also discussed. From a variation of the cell resistance according to the rotation speed of the anode, a concentration polarization was detected below 3 wt% of UCl3 in the molten salt, but not above 6 wt...

Fuel R & D to Improve Fuel Reliability

Abstract: Light water reactor fuel is operating in an increasingly challenging environment. Fuel burnup extension and cycle length increase both can increase the local duty. Reactor water chemistry modifications for the purpose of protection the plant system materials have the potential of increasing fuel surface deposition and cladding corrosion and hydriding. The status of fuel performance in US reactors is summarized and an update of the “Fuel Reliability Program” established by the utility industry to ensure reliability is provided.

Effects of Fuel and Coolant Temperatures and Neutron Fluence on CANDLE Burnup Calculation

Abstract: A new method is developed to analyze CANDLE (Constant Axial shape of Neutron flux, nuclide densities and power shape During Life of Energy producing reactor) burnup, where the microscopic group cross-sections are evaluated at every space mesh by TLLI (Table Look-up and Linear Interpolation) method, and used to analyze a fast reactor with natural uranium as a fresh fuel. The results are compared with the conventional method, where only one set of the microscopic group cross-sections is employed, to investigate the effects of space-dependency of the microscopic group cross-sections and feasibility of the old method. The differences of the effective neutron multiplication factor, burning region moving speed, spent fuel burnup and spatial distributions of nuclide densities, neutron fluence and power density may be considerable from the reactor designer point. However, they are small enough when we study about the characteristics of CANDLE burnup for different designs.

Stress Reorientation of Hydrides in Recrystallized Zircaloy-2 Sheet

Abstract: A series of measurements was performed to examine the effects of texture, hydrogen concentration, thermal cycling and morphology of hydrides on stress reorientation of hydrides using unirradiated recrystallized Zircaloy-2 sheet materials. It was found that the threshold stress for reorientation of hydrides is approximately 80 MPa, and the threshold stress is not affected by hydrogen concentration, thermal cycling or hydride morphology before the hydride reorientation test. Over the threshold stress, texture, thermal cycling and morphology of hydrides affect the stress reorientation. The modified Ells' equation was proposed for expressing the effect of the texture of Zircaloy-2.

Behavior of 60 to 78MWd/kgU PWR Fuels under Reactivity-Initiated Accident Conditions

Abstract: To provide a data base for the regulatory guide of light water reactors, behavior of reactor fuels during off-normal and postulated accident conditions such as reactivity-initiated accident (RIA) is being studied in the Nuclear Safety Research Reactor (NSRR) program of the Japan Atomic Energy Agency (JAEA). The paper presents recent results obtained from the NSRR power burst experiments with high burnup fuels, and discusses effects of pellet expansion as PCMI (Pellet-Cladding Mechanical Interaction) loading and cladding embrittlement primarily due to hydrogen absorption. Results from the recent four experiments on high burnup (about 60 to 78 MWd/kgU) PWR UO2 rods with advanced cladding alloys showed that the fuel rods with improved corrosion resistance have larger safety margin against the PCMI failure than conventional Zircaloy-4 rods. The tests also suggested that the smaller inventory of inter-granular gas in the pellets with the large grain could reduce the fission gas release during the RIA transient...

Pressure Drop Experiments using Tight-Lattice 37-Rod Bundles

Abstract: In order to design a Reduced-Moderation Water Reactor (RMWR) core from a thermal-hydraulic point of view, an evaluation method on the pressure drop in a tight-lattice rod bundle is required. In this study, axial pressure drops in tight-lattice 37-rod bundles were measured under conditions of 2-9 MPa in exit pressure and 200-1,000 kg/(m2·s) in mass velocity. The measured pressure drops were compared with calculated ones by the evaluation method with the Martinelli-Nelson's correlation. The comparison shows that a single-phase friction factor can be applied not only to a circular tube but also to a tight-lattice bundle except for an extremely small gap width. Then two-phase friction loss is a dominant component and accounts for about 60% of the pressure drop under an RMWR nominal operating condition. The evaluation method can evaluate effects of the flow area configuration (rod number, rod diameter, gap width) and axial power distribution under a wide range of flow conditions, and it can yield a good predic...

Measurement of the Induced Radionuclides in Production of Radiopharmaceuticals for Positron Emission Tomography (PET)

Abstract: The radioactive by-products contained in an entire series of target foil, [18O]H2O and synthesis apparatus were identified and quantified. From the perspective of waste management, 60Co induced in Havar foil should be taken into consideration. Because the exempt activity of 60Co in BSS is 0.1 MBq, the used Havar foil should be managed more than for 20 years. The radionuclides in the [18F]-FDG synthesis apparatus are negligible. Equivalent doses at skin and to tissues were estimated assuming a point source at a distance of 30 cm in air. The annual equivalent doses at skin and equivalent dose at deep tissues of such an operating staff will be 56 and 8.3 μSv, respectively, as two times the remove of the target foil and five hundreds times the synthesis of the [18F]-FDG. When proper radiation protection is provided, the exposure from the cyclotron management and the [18F]-FDG synthesis process will not cause meaningful radiological risk to the operating staff. The activity concentration of 3H, 180kBq-cm−3, de...

Development of a Multi-functional Reprocessing Process based on Ion-exchange Method by using Tertiary Pyridine-type Resin

Abstract: A series of separation experiment was performed in order to study a multi-functional spent fuel reprocessing process based on ion-exchange technique. The tertiary pyridine-type anion-exchange resin was used in this experiment and the mixed oxide fuel highly irradiated in the experimental fast reactor “JOYO” was used as a reference spent fuel. As the result, 106Ru+125Sb, 137Cs+155Eu+144Ce, plutonium, americium and curium could be separated from the irradiated fuel by only three steps of ion-exchange. The decontamination factor of 137Cs and trivalent lanthanides (155Eu, 144Ce) in the final americium product exceeded 3.9x104 and 1.0x105, respectively. The decontamination factor for the mutual separation of 243Cm and 241Am was larger than 2.2x103 for the americium product and, moreover, the content of 137Cs, trivalent lanthanides and 243Cm included in 241Am product did not exceed 2 ppm. These results prove that the proposed simplified separation process has a reality as a candidate for future reprocessing pro...