초록 ▼

본 과제는 사용후핵연료의 양 및 독성 저감화를 통한 고준위폐기물 안전관리의 실현과 GEN-IV 원자로시스템에 적용 가능한 핵확산 저항성을 갖는 환경친화성의 핵연료주기 기술 개발을 추진하며 세부연구 결과는 다음과 같음.
- 전해환원 : PWR SF의 금속전환과 고방열 핵종 분리를 위한 고온 용융염 전해환원기술을 개발하였으며, 공학규모 PRIDE 전해환원 시스템의 설계, 제작하였음.
- 전해정련 : PWR SF의 금속전환 체로부터 93 % 이상 차지하고 있는 우라늄 금속을 고순도로 회수할 수 있는 전해정련 기술을 개발하였으며

본 과제는 사용후핵연료의 양 및 독성 저감화를 통한 고준위폐기물 안전관리의 실현과 GEN-IV 원자로시스템에 적용 가능한 핵확산 저항성을 갖는 환경친화성의 핵연료주기 기술 개발을 추진하며 세부연구 결과는 다음과 같음.
- 전해환원 : PWR SF의 금속전환과 고방열 핵종 분리를 위한 고온 용융염 전해환원기술을 개발하였으며, 공학규모 PRIDE 전해환원 시스템의 설계, 제작하였음.
- 전해정련 : PWR SF의 금속전환 체로부터 93 % 이상 차지하고 있는 우라늄 금속을 고순도로 회수할 수 있는 전해정련 기술을 개발하였으며, 공학규모 전해정련 시스템의 설계 자료를 확보하였음.
- 전해제련 : 전해정련 조업 후 용융염의 U/TRU를 액체음극에 공회수 할 수 있는 전해 제련 기술을 개발하였으며, PRIDE 공학규모 전해제련 시스템을 구축하였음.
- 염폐기물 재생·고화 : 염폐기물로부 터 고방열성 핵종 및 기타 핵분열 생성물 제거를 통한 염 재생 및 재활용, 그리고 처분대상 폐기물의 고건전성 고화체 제조기술을 개발하였으며， 공학규모 염폐기물 시스템의 설계 자료를 확보하였음.
- 파이로공정 계통평가 : 세부 과제간 연계/조정 업무를 원활히 수행하여 파이로 일관 공정 물질수지 효름도 를 확립하였으며 WFO 표로그램의 계약에 의해 미국 ANL과의 공도연구를 통하여 실시간 모니터링 시스템을 개발하였음.
(출처: 보고서 요약서 6p)

Abstract ▼

IV. Research results
IV-1. Development of Electrolytic Reduction System for PWR Spent Fuel
The perfonnance of the lab-scale electrolytic reducer has been tested to evaluate the electrolytic reduction system. For the modification and optimization of the process, the tests on the mechanical and

IV. Research results
IV-1. Development of Electrolytic Reduction System for PWR Spent Fuel
The perfonnance of the lab-scale electrolytic reducer has been tested to evaluate the electrolytic reduction system. For the modification and optimization of the process, the tests on the mechanical and thermal stability of the porous magnesia membrane in a LiCl-Li2O molten salt, the molding and sintering of the ceramic anodes, the applicability of carbon anodes, the elucidation of the local corrosion of the Pt anodes and metal materials have been carried out. For the production of the kinetic and physicochemical data with the aim of the process interpretation, the evaluation of the effects of lithium compounds and complex oxides on the electrolytic reduction has been conducted. Also, for the enhancing the interconnection of the electrolytic reduction process with the electrorefining process, a cathode process has been developed. Finally, the design and construction of PRIDE electrolytic reduction system was completed.

1. Test of a Lab-scale (20 kgHM/batch) Electrolytic Reduction System
The design and construction of 20 kgUO2/batch electrolytic reducer which is very large compared to the systems of USA (~1 kgUO2/batch) and Japan(-5 kgUO2/batch in 2011) was finished showing the excellency of KAERI technology There has been big progress on the performance of the electrolytic reduction system in the SIMFUEL tests considering the current density, current efficiency, corrosion resistance of the reactor, and process safety. Especially, the development of the metal cathode basket based electrolytic reducer should be notable because it has improved mass transfer and mechanical stability compared to the previous ceramic cathode basket. More than 99% of the reduction yield was achieved and the current density on the anode amounted to the 0.5 - 1 A/cm2 depending on the size of the electrolytic reducer. According to the systematic procedure, the design of the reaction system was conducted after the calculation of the potential distribution on the anode/cathode/molten salt by modeling and optimization of the shape of the anodes. The results led to the deduction of the optimized electrolytic reduction conditions which can prevent the dissolution of Pt anodes and minimize the current losses. Feed form (powder, pellet, granule, plate) effects were also evaluated suggesting porous pellets as the best form for the electrolytic reduction process. 99.6% reduction of uranium oxides and more than 50% reduction of rare earth oxides were observed in the experiments using Simfuel.

2. Improvement and optimization of the system
As a part of the commercialization study, the material requirements of magnesia were established. The mechanical and chemical stability of the magnesia was improved by the addition of the Al2O3 and Y2O3, respectively. The fracture strength of the porous magnesia samples manufactured by pressing and casting were measured as a function of the porosity and time.
The stability of the Pt anodes mainly depends on the concentration of Li2O in the molten salt (Li20 < 0.6 wt% → local corrosion, Li2O < 0.3 wt% → uniform corrosion). Pt dissolution occurred in the condition of > 3.0 V vs Li/Pb and 1 wt% Li2O in LiCI.
For the development of the ceramic anodes, ratio of the SrRuO3 and CaSiO3 (binder), molding condition (1,800-2,000 kgf/cm2), and sintering condition ( - 1,400℃, -25 시간) was optimized. The possibility of electrolytic reduction by using carbon anode was realized in a bench-scale tests. Anode shroud system made of MgO or Ta was applied to prevent the corrosion by oxygen gas.
The formation of corrosion products and their growth from the construction materials in the electrolytic reduction conditions were elucidated. For Inconel 600 having 74Ni-16Cr-8Fe composition, the corrosion products were NiO, F~03 at the initial stage, NiO, Cr2O3, NiFe2O4, and NiCr2O4 at the propagation stage, and transformation of NiFe2O4 to NiCr2O4 at the growth and formation stages. The quantitative and long term corrosion data were obtained. The local corrosion was suppressed by the prevention of the internal diffusion of oxygen ion by Ni-rich oxygen active oxides. The corrosion rates were measured by Tafel plots.
The new electrolytic reducer characterized by metal shroud, passive cooling, bus bar was developed and tested showing improved results.

3. Production of kinetic and physicochemical data
For the process operation condition optimization of an electrolytic reduction which has been developed from 2000, the metallization of complex oxides and their distribution were studied. The solubility of rare earth oxides as a function of Li2O concentraion was found about several ppm except Eu (603 ppm in the condition of l.83 wt% of Li2O)
Cations (I, Br, Se) do not have significant effects on the electrolytic reduction reaction. However, Se2- damaged the Pt anodes with the formation of PtSe2. Br2 formation from Br- is reversible reaction and the oxidation product of r reacts with I2 to form I3-.
The kinectic model was developed and utilized for the estimation of reduction time considering diffusion, chemical reaction, and applied currents.
The on line- monitoring system of Li2O concentration based on the square wave voltammetry was developed by joint study with Argonne National Laboratory. Accordingly, on-line monitoring system was applied to Lab-scale apparatus and tested.

4. Design and Construction of PRIDE Electrolytic Reduction System
The engineering scale electrolytic reduction system (PRIDE) was designed and constructed based on the operation experiences of lab-scale electrolytic reducer.
The remote operation tests at the mock- up facility were successfully completed.
- Characteristics of PRIDE Electrolytic Reducer
. 50 kg UO2/batch (2.5 times of Lab scale)
. Maximum current 3000 A → high speed reduction
. Modulation, simple
. Separable cathode, anode shroud, passive cooling, bus bar connection
. Short inter electrode distance (Lab-scale: 11 cm, PRIDE: 8 cm)
- Characteristics of PRIDE Chathode Processor
. 20 kg residual salts treatment/batch
. Modulation, simple
. Salt recovery as a solid powder form

IV-2. Development of High- Throughput(HT) Electrorefining System
1. Development of high-throughput (HT) electrorefining
To recover U only from the spent nuclear fuel (93% of total spent nuclear fuel), the electrorefiner with a capacity of 20 kg-U/day was developed. And, structural design of anode/cathode for giving high- throughput to the electrorefiner was carried out using commercial simulátion code, ANSYS CFX code, which performed an electric field analysis, deposition behavior of U and molten salt fluid analysis for the five arrays of cathode electrodes according to the operational conditions.
By adaption of a graphite cathode and a bucket- type transfer system, the continuous electrorefining concept was successfully introduced the high-throughput electrorefiner. This work was selected to the MEST 2008 best research results 50s.
For development and performance evaluation of the graphite cathode, the deposition of uranium and the mechanism of self- scraping was investigated and the performance of the anode dissolution and current- potential behavior was carried out. The mechanism of the spontaneous falling of uranium deposits from the graphite cathode was verified due to the intercalation of uranium into the carbon.
In order to enhance the throughput of electrorefiner, we modified the deposit transfer system. At the first and second modification, the deposit transfer system was modified by introducing the shaftless screw to solve embedding U deposit between screw shaft and b1ade. Next, the deposit transfer system was further modified by introducing bucket transfer system to solve grinding U deposit by screw. From the modification of the deposit transfer system at three times, we can collect the U deposit simultaneously during the electrochemical reaction, hence the throughput of electrorefiner was greatly enhanced. In addition, we can continuously collect the produced U deposit more than 70% with a salt content lower than 20%.
The performance test of the HT electrorefiner was. carried out using simulated reduced spent fuel (SIMFUEL). The current- potential curves were measured and the performance of the deposition of uranium was evaluated. From the results, 80% of the current efficiency was achieved, and the contents of the RE and NM were fewer than l0ppm at LiCl-KCl-5wt%UCl3 salt. The uranium deposits were highly recovered by self- scraping of the graphite cathodes. The throughput of this electrorefiner is 10 times higher than those of Mark- V electrorefiner developed in INL (8 kg-U/month·L).
The optimum condition of electrorefining was confirmed from the theoretical and experiment results. From the calculation of the limiting current density, the minimum concentration of UCl3 at the constant current of 150 mA cm-2 was determined to 3.18wt%. From the variation of the concentrations of U, TRU and RE in a molten salt, it was concluded that the electrorefiner should be operated the condition where the UCl3 concentration is between 3.18 and 9wt%. In this condition, the final weigh ratio of PU to U in a molten salt after 20 batch operation will be 3.
The durability of the graphite cathode was tested over 720 h. After long time electrorefining test, the microstructure and loss of the weight of the cathode was analysed. From the results, we concluded that the graphite cathode can be durable during electrorefining over 720 h.
For effective development of the HT electrorefiner, the computational simulation was applied to the electrorefiner. By using the commercial COMSOL electrodeposition modules, the optimum electric field model for electrorefiner was developed. Using the electric field model, electrorefining behavior of the electrorefiner such as cell potential, current density, the array of the cathode and the strring rate of the anode basket was analysed in consideration of fluid dynamics and electrochemical model. The analyzed results were applied to the production of the design data for the sca1e-up of the electrorefiner.

2. Development of UCl3 preparation and transfer system
In order to stabilize cell potential during electrorefining and chlorinate unreduced metals, we have developed a process to fabricate UCl3 and pelletize the produced UCl3. And, we have achieved the purpose with producing the eutectic sal in LiCI- KCl-30 mol% UCl3.
To characterize the preparation for LiCI- KCI-UCl3 eutectic salt, the preparation apparatus for LiCI-KCI-UCl3 eutectic salt was designed and manufactured. we have found that the 30 mol% UCl3 produced in LiCl-KCl eutectic salt contained Cd in the concentration ranging from 600~30,000ppm at 600 ℃ of operating temperature. We have also confirmed that the melting temperature of LiCI-KCI-UCl3 eutectic salt was 540 ℃ by means of TG-DTA analysis. As a result of reaction test of uranium and distillation in vacuum for purifying the fabricated UCl3, we successfully reduced the concentration of contained Cd below 200ppm. The results were obtained in the operating condition at 600 ℃ and 60 torr maintained for 2 hr,
In this apparatus, the temperature of all components of transfer line and contact point with LiCl-KCl-UCl3 salt is maintained higher than me1ting temperature with a aid of heater and heat- transfer. In addition, the pelletizer for LiCI-KCI-UCl3 eutectic salt was designed and manufactured to make LiCI-KCI-UCl3 eutectic salt pellet using STS materials. The transport system was designed to heat the 1/4- inch STS up to 500 ℃ and pressurize up to 3 atm, and it is confirmed that the apparatus transport the UCl3 smoothly. The salt was easily separated from mold when the salt was injected into the mold after heating of the pelletizer to 90-120 ℃.
We have fabricated blocks for the heating and insulation of salt transfer equipment as well as simplify kit of the heating equipment, in order to improve durability of the UCl3 making equipment. At the same time, we have established pressure control system to prohibit from a blockage of the chloride transportation line by installation of the constant pressure regulator and the flowmeter.

3. Development of residual salt distillation
The basic study on the cathode processer was carried out for the structural design of salt distiller to treat the U deposit. The salt distillation condition for removing the residual salt at 99%, i.e., 0.05 Torr, 700 ℃, was analyzed using the Hertz-Langmuir equation and the experimental result. It was found that the LiCI-KCl eutectic salt and the rare-earth were distilled together in the distillation experiment of the uranium deposit.
Kiln type salt distiller, of which throughput corresponds to that of the continuous electrorefiner, was manufactured and installed. The temperature and pressure, which are the key conditions in salt distillation, was confirmed with the design requirement in the blank test. The transfer system to the Kiln type salt distiller works well, and the bulk of the U deposit was found at the storage tank. However, the jamming of deposits in the screw was occurred sometimes during the distillation operation and the maintenance of the distiller in the hot cell seems to be difficult.
It was proposed to increase the throughput of the salt removal process by the separation of the liquid salt prior to the distillation of the LiCl-KCl eutectic salt from the uranium deposits. The feasibility of liquid salt separation was examined by salt separation experiments on a stainless steel sieve. The amount of salt to be distilled could be reduced by the liquid salt separation prior to the salt distillation in case of the uranium deposits with high salt content. The residual salt remained in the deposits after the liquid salt separation was successfully removed further by the vacuum distillation.
Recovered salt block should be divided and returned to the electrorefiner after distillation of the salt. In this study, the salt dividing method was developed by dipping the cross in the recovered salt vessel. The salt block was easily separated from the vessel and divided into four pieces after pulling out the cross form the condensed salt.
The salt content after the distillation in the uranium deposits was about 0.2 - 0.65 wt% at the temperature range of 900 - 800 ℃, which is a much lower than the requirement of 1 wt% in the ingot preparation process.

4. Development of the uranium ingot casting system
In order to increase the productivity of an ingot casting equipment, we have adopted continuously feeding raw materials, melting, and injecting melt into multiple molds. Also for preventing chamber from corrosion by salts in uranium deposits produced from electrorefiner, a glove box was attached to the furnace. The fabricated Lab- scale ingot casting equipment comprises with a vacuum chamber, a glove box, a feeding cup of uranium deposits, a heating coil and crucible, a mold heating apparatus, and a control panel. For the preliminary test with Cu powder, feeding cup after charging raw materials could be transferred above a crucible, and by tilting it, the Cu powder could be charged into a crucible. Tilting stile of melting crucible tapping has solved problems on a leakage of molten metal and scattering of the melt. After melting the Cu powder, it was injected into a preheated graphite mold. The preliminary test showed promising results of producing a Cu ingot. For the safety check of fabricated equipment, thermocouples was installed at 6 places inside the chamber. The temperatures of thermocouples was not reached above 220 ℃ during melting 5 kg Cu, whose temperature is a limitation of safe operations. In this equipment, DU raw material was charged in a yittria plasma coated graphite crucible, and melt at 1300 ℃, injected into a preheated yittria plasma coated graphite mold at 300 ℃ by tilting the crucible. We could get a good ingot with no big shrinkage cavity whose dimension was a diameter of 68 mm, height of 70 mm, and weight of 4.8 kg.
On the basis of the Lab-scale ingot casting experiment, we could design an engineering scale ingot casting equipment dealing with quantity of 50 kg U/day. The size of crucible was determined 3.5 times as large as the size of Lab-scale crucible, and the feeding system was changed from cup feeder to vibrational feeder whose quantity was about 50 liters. The multiple 8 molds was designed to be rotated for producing ingots. This approach significantly reduces the amount of waste that has produced in a batch operation of graphite crucibles.
In industry, they generally use a water-cooling induction coil, because there is considerable heat generated during heating of the coil. In this research, we have introduced non-water cooling coil to improve safety in ingot casting equipment for uranium deposits, since a leakage of water-cooling induction coil could occur a troublesome accident in the hot-cell operation. And, we have successfully melt 20 kg of Cu using our non-water cooling induction coil. During the melting of the Cu, the temperature of coil was reached to 530 ℃, confirming the high possibility of non-water cooling induction coil systems.

A new method to melt uranium dendrite in a particle shape was established by melting test, i.e., additional uranium dendrite was charged into molten uranium. As a result, ingot was successfully cast with an addition of 0.35 kg of uranium dendrite to 4.8 kg of molten DU.
An optimum condition to cast ingot in high-quality was derived by controlling tilting rates of the melting crucible. An optimum tilting rate was 40 second, showing minimal gravitational shrikage cavity in the produced ingot.
In order to supply SIMFUEL which could be used as a substitute of spent fuel, we had alloyed DU with Zr, Mo, Ce, Nd, Gd, Ru and Dy using induction furnace. After melting it, the molten alloy was poured into a mold (10 mm in diameter, 300 mm in length). The 300 mm rods produced were cut into 10 mm in length, and ,therefore, totally 30kg of SIMFUEL was fabricated.

5. Development of molten salt transport system
A high-temperature molten salt transport is essential to KAERI pyroprocess since a molten salt should be transported from the electrorefiner to electrowinner after the electrorefining process.
Three different transport technologies (the gravity, the suction pump, and the centrifugal pump) were reviewed. Among those methods, the molten salt transport by suction was selected due to the flexibility of flow control by the pressure control of vacuum chamber. A suction transport system was designed and installed, and the performance test was carried out. For salt transport experiment, LiCI-KCl eutectic salt was prepared by mixing of commercial grade LiCl and KCl, and drying, since the high cost of original LiCl-KCl eutectic salt. In this study, the drying condition was determined by the TGA analysis of prepared LiCl-KCl eutectic salt.
The molten salt transport by suction was carried out with 2kg LiCI-KCl eutectic salt at 500 ℃ From the result, almost 99% molten salt was transported. For a transfer from the collected uranium deposits at the bottom of the electrorefiner to the salt distiller, the interface apparatus such as air-tightened vessel is being designed, and the performance test of this apparatus was carried out.

IV-3. Development of the Electrowinning System for TRU Recovery
1. LCC electrowinning technology
In the simulated LCC electrolytic system which recovers HM 50 g, Zn and Ga were used as a simulated material for U and Cd, respectively and ZnSO4 solution was used as an electrolyte. Since all the systems were designed to be visually observed, the deposition characteristics of the metal dendrite were effectively examined. Various types of LCC assemblies were prepared using pounder and rotating stirrers such as paddle, tilt, and harrow to inhibit the growth of U dendrite and the performances of each assemblies were evaluated. By comparing the LCC assemblies, the harrow- type stirrer was found to be effectively prevent the formation and growth of dendrite.
Electrolysis experiments in a bench-scale system were carried out to observe the TRU recovery characteristics using uranium and simulated TRU elements with a various concentration ratios of U/TRU and current densities. The order of metal deposition on Cd from molten salt was following U, Nd, Cd, La, and Y. The diffusion coefficient of U was identified as l.2±0.4×10-5 cm2/s in l.45 wt% UCl3-LiCI-KCl system at 500 ℃. It was confirmed that the difference of standard fonnal potential of RE (Nd, Cd) between solid and liquid electrode was due to the formation of intermetallic compound between RE and Cd. Based on the redox potentials of U, Nd, and Ce at the liquid Cd electrode obtained by CV, the effects of current density, electrolysis method (e.g., constant current, constant potential), and concentration ratio of U/RE on the recovered amount of U/RE were investigated.
Lab-scale LCC electrolytic system was designed and prepared to develop a LCC assembly which can be easily dissembled from the system. Molten salt of 2.5 kg was contained in an electrolytic bath (ID 15 cm) and U-loaded anode basket and LCC (liquid Cd cathode) crucible (ID =5 cm) were setup in the bath. Based on the previous results, the LCC assemblies were developed to apply in the lab- scale LCC system. It was found that both of paddle and harrow stirrers did not prevent the growth of U dendrite effectively, because the rotating stirrers may help the migration of U deposits on the wall surface of cathode crucible, resulting in the growth of U dendrite along the crucible wall. In order to solve those problems, automatically operated mesh- type LCC assembly was developed. It enabled to sink the U deposits into the bulk of liquid Cd directly by its vertical movement as well as by rotation, thus no U dendrite formed on the Cd surface. Using the developed mesh-type LCC assembly, the electrolysis experiments were conducted. The maximum amount of U deposition was obtained to be 10 wt% U/Cd without the growth of U dendrite out of the alumina crucible. This outstanding result of U recovery can be compared with 8 wt% U/Cd in Japan and 9 wt% HM/Cd in US.
The inert anode material used in the LCC electrolytic system was selected as a pyrographite in terms of the electrical and mechanical stabilities. More detail, tube-type of pyrographite was loaded in a porous SiC basket to increase the surface area of anode. The SiC basket was embedded in a SUS tube to prevent the loss of anode materials. Also, the developed anode structure consisted to SUS tube and SiC basket where tube-type graphite was loaded has a vent system which allows to collect and emit the Cl2 gas generated during the operation of the LCC electrolytic process effectively.

2. Distillation technology of TRU deposits on LCC
Thermodynamic data such as vapor pressures, melting points, phase diagrams were collected and analysed for metals and intermetallic compounds. A lab-scale cadmium distiller was setup and tested. The distiller is composed of an evaporator, a condenser, a control unit, and an off gas treatment system. The loading capacity is 1 kg-Cd/batch.
The cadmium evaporation rate- temperature-vacuum pressure relations for the design and operation mode decision of a cadmium distiller were examined in this study. An attempt was made to control vacuum pressure by using a throttle valve, a pressure sensor and a controller. The vacuum pressure can be controlled very precisely. Therefore, the apparent evaporation rate of cadmium can be measured at a constant vacuum pressure.
The apparent evaporation rate of cadmium increased with an increasing temperature, whereas the apparent evaporation rate decreased with an increasing vacuum pressure. The evaporation rate of cadmium varied within 9.7 ~ 40 g/cm2/h in the temperature range of 500~650 ℃ and pressure range of 0.5 ~ 10 TOIT. Evaporation rates of cadmium were calculated by the Hertz-Langmuir relation based on the kinetic theory of gases. The theoretical values calculated by the Hertz-Langmuir relation were much higher than experimental values. The deviation was compensated for by an evaporation coefficient (a) obtained empirically and the evaporation coefficient was a function of the temperature. The evaporation coefficients of cadmium distillation varied from 0.0100 to 0.00304 in the temperature range of 500 to 650 ℃. About 0. 02~0.20 wt % of residue was left in the crucible after distillation and found to be CdO by XRD.
Further improvement of experimental distillation process was carried out based on the remote operability, leak tightness and crucibles installation. The distillation experiments with pure Cd metal were conducted in 100 g scale. Cadmium was heated and evaporated in vacuum at various temperature gradient conditions. In the distillation at a temperature profile range of 900 ~ 500 ℃, ~ 99% of the initial Cd amount evaporated was collected in the condensing crucible. A Ce-Cd alloy was prepared and the distillation behavior of the alloy was investigated. Cadmium was effectively distilled and separated from cerium. The evaporation rate of cadmium in the alloy was lower than that of cadmium metal.
In addition, a CD-Salt(LiCl-KCl) mixture was also effectively evaporated and collected up to 98% of the initial amount at the temperature profile range of 900~500 ℃.
An engineering-scale PRIDE cadmium distiller with a capacity of 15 kg-Cd-salt/batch was designed based on the experiences of the lab-scale distillation experiments.

3. Residual actinides recovery technology
Composition and characteristics of the salt waste generating from an LCC electrowinning process recovering TRU were evaluated based on the flow sheet and material balance of the pyroprocess. Technical applicability of oxidation, electrolysis and reductive extraction methods recovering residual actinides was reviewed and analyzed in order to select one efficient method which is the most feasible among four methods such as using O2 in a salt or an LCC, using CdO or CdCl2 in an LCC from the viewpoint of the thermodynamic property of the formation of metal chloride. It was confirmed that a method using CdCl2 in an LCC is the most feasible. Basic experiments to examine selectivity of an oxidation using CdClz were performed. As a result, KAERI has developed a hybrid residual actinides recovery(RAR) method which has new concept combining LCC electrolysis and oxidation using CdCl2 oxidant. Also, a lab-scale RAR equipment that has functions to test an LCC electrolysis and an oxidation of RE metals in series was manufactured according to a RAR process concept. The equipment was consist of a reaction vessel which has a capacity of processing 2 kg salt in one batch operation and an LCC assembly to be inserted into or removed from the salt.
In order to evaluate recovery characteristics of LCC electrolysis and oxidation methods a series of experiments was carried out using U, La, Nd, Ce, Gd, Y elements. A RAR process was established based on the (0.01 wt%), on-line monitoring by CV measurement for a diagnosis of process, equipment construction and operation method. A target residual actinide concentration, 0.01wt%(l00 ppm) in the waste salt can be achieved in an LCC electrolysis step at a condition of 50 rpm stirring, current density 30 mA/cm2, using glassy carbon anode. If the amount of CdCl2 oxidant added into a salt can be controlled at a condition of oxidizing about 75 % of RE metals codeposited with An in an LCC the residual concentration of U can be maintained at less than 100 ppm in a oxidation step.
A RAR operation method applying an LCC electrolysis for recovering An metals and CdCl2 oxidant addition for oxidizing RE metals codeposited in LCC was established. The developed RAR process was completed the domestic patent registration in July 2011. Also, the U.S. patent is under application. Same electrowinning equipment using an LCC for a recovery of the fuel material such as uranium and transuranic elements can be used for a RAR operation. The RAR process has promising merits such as compact equipment and a simple operation compared to the multi staged counter-current reductive extraction process which is under development at CRIEPI in Japan. These features are very good benefits considering a special situation that a RAR equipment will be used by remote devices in a hot cell.
According to the reaction rate of UCl3 forrnation by using a Cd-U alloy prepared in an LCC electrolysis step of the RAR test selective recovery feature of actinide metals in an LCC structure used in the RAR system was investigated. As a result of the reaction of uranium metal in an LCC with CdCl2 oxidant, UCl2 could be generated in the LiCI-KCl salt phase by stirring. However, the rate of UCl2 formation is very slow compared to that of direct reaction of uranium metal with CdCl2. Most rare earth metals exist at the interface between salt and cadmium due to their lower densities than cadmium, but actinide meta1s such as uranium and TRU can be precipitated in the form of uranium metal particles or TRU metal- cadmium intermetallic compounds below the liquid cadmium metal due to a heavier density than cadmium. So, selective oxidation behavior of the rare earths by a CdCl2 oxidant dissolved in salt could be preferred because of cadmium pool as a barrier role to prevent contacting of a CdCl2 oxidant with actinide metals.
To practically use the recovered actinides as a SFR fuel, it is necessary to protect the co- deposition of lanthanide elements. For lanthanide-contaminated fuel, the neutron f1ux of the transmutation of the actinides is significantly decreased due to certain lanthanide elements with large neutron capture cross sections. Therefore, it is necessary to understand the chemical behavior of lanthanide in molten salt in order to efficiently avoid the co- deposition of lanthanide elements and to further improve the efficiency of the electrowinning process. For this purpose, an effective analytical technique for lanthanides and actinides in the molten salt is desired.
Some properties such as the standard potential, diffusion coefficient, and activity coefficient have been investigated by electrochemical technique. A general methodology to characterize CV data, which includes non-linear curve fittings of multiple CV curves obtained at many different scan rates over a side range of timescales. The standard rate constant(K0), transfer coefficient(a), and formal potential(E0') for the electrode reaction of RE3 /RE2 in LiCI-KCl eutectic melts at 773K were simultaneously determined using nonlinear curve fittings applied to six CV curves taken at a scan rate of 500-10000 m V/s.
Absorption spectrophotometry, which provides information about the change of the chemical status of complexes through the change in electronic absorption spectrum, is an adequate technique. The absorption spectrum of lanthanide are measured. Each spectrum was obtained by subtracting the blank spectrum from the raw spectrum of each concentration.
An on-line monitoring method for prompt determination the actinide and lanthanide concentrations in the molten salt is required for process control. Voltammetric methods are well- suited for on - line monitoring of actinide and lanthanide elements in pyrochemical processes because they are rapid in situ measrument techniques which produce no sample waste.
Before the experiments with actinide elements, the effect of the potential waveform for the NPV(Normal Pulse Voltammetry), DPV(Differential Pulse Voltammetry) and SWV(Square Wave Voltammety) measurements were examined with lanthanide elements(La, Ce, Gd).
In order to confirm the applicability of NPV, DPV and SWV for on-line monitoring of pyroprocesses, the concentration dependence and performance of these methods in a multi-component system were specially studied.
The PRIDE eng-scale RAR equipment which has a capacity of handling 50 kg salt and 10 kg LCC in a batch and will be operated by MSM in remote was designed using these experimental results, operation method, function and structure of a RAR process based on the operational experiences of a lab-scale RAR equipment.

4. Computational simulation for the electrowinning process
Equilibrium behavior and electrotransport of the actinide and rare-earth elements in a molten salt electrowinning system with liquid cadmium cathode(LiCl-KCVCd) has been numerically simulated with an simplified approach of the thermochemical and diffusion controlled model.
Electrochemical equilibrium distributions of the actinide and rare-earth elements between the molten salt and liquid cadmium phase have been estimated for an infinite potentiostatic electrolysis from the thermodynamic data and material balance. It was simulated that the liquid cadmium cathode would be possible to recover all of the actinide together among the elements while the solid cathodes is the suitable for the separation of pure uranium. At liquid cadmium cathode, the reduction potential of actinides are close together because of larger activity coefficient than that of rare-earth elements. However, the rare-earths could accompany the recovered actinide elements.
In addition, a simple dynamic modeling of this process was performed by taking into account the material balances and diffusion- controlled electrochemical reactions in a diffusion boundary layer at an electrode interface between the molten salt electrolyte and liquid cadmium cathode. The proposed modeling approach was based on the half- cell reduction reactions of metal chloride occurring on the cathode. This model demonstrated a capability for the prediction of the concentration behaviors, a faradic current of each element and an electrochemical potential as function of the time up to the corresponding electrotransport satisfying a given applied current based on a galvanostatic electrolysis. The results of selected case studies including five elements (U, Pu, Am, La, Nd) system are shown, and a preliminary simulation is carried out to show how the model can be used to understand the electrochemical characteristics and provide better information for developing an advanced electrowinner.
Based on an output of the ORIGEN Code 2.1 using the reference composition of the spent nuclear fuel, a case of electrowinning for ten elements (U, Np, Pu, Am, La, Ce, Pr, Nd, Gd, Y) is computed to find a simulation capability in the same computational platform. 1n this demonstration simulation, the results show that a large amount of rare- earths accompanies the recovered actinide elements at a given current density condition(100mA/cm2) and assumed kinetic parameters for electrochemical polarization (exchange current density).
Multiphysics electrochemical modeling in a framework of Computational Fluid Dynamics (CFD) code has been proposed and dealt with in detail to simulate the electro-transport behavior that appears in a molten-salt electrowinning system. The modeling approach in this study is focused on the mass transport and current arising due to the concentration and the surface over potential based on a cell configuration and molten-salt electrolyte turbulence. The electrowinning cell model simulated here has a structure arranged concentrically with the anode annulus surrounding an LCC crucible inside it. This implementation with unique feature of the potential-to-current algorithm could provide the useful information for more realistic spatial variation of the electrochemical characteristics.
This approach was applied to the design of PRIDE scale electrowinning system. The cell potential simulated as a function of the applied curent density (20-200 A/cm2) is expected to be in a range of 0.6-1.8V based on the assumption that anode is grounded as 0 V. These cell potential drops are considered to be a resonable polarization performance for the design of the engineering scale electrowinning system.

5. Design & Construction of PRIDE Electrowinning System
The engineering scale electrowinning system (PRIDE) was designed and constructed based on the operation experiences of lab-scale LCC electrowinner, Cd distiller and RAR equipment. The remote operation tests at the mock-up facility were successfully completed. An engineering-scale LCC electrowinner which can recover 1 kg HM/batch was designed and constructed based on not only the operation experiences of lab-scale LCC electrowinner but also the computational simulation results of heat transfer and current distribution depending on the electrode positions in a electrolytic salt. It has a dimension of electrolytic cell of 40 cm (ID) where 20 kg of Cd and 50 kg of salt was used.
Capacity of the Cd distiller is 10 kg of cadmium per batch. The Cd distiller consists of frame assembly, furnace assembly, distiller vessel assembly, crucible support assembly, utility assembly and control box assembly. Furnace assembly is used for heating the distiller vessel and controlling the temperature of the vessel. In order to make different temperature profiles in the vessel, it is divided into five zones where a heater and a thermocouple are equipped separately. Cadmium in LCC electrodeposit is evaporated and condensed in the distiller vessel, whose internal diameter is 200 mm and height is 800 mm. Crucible support assembly can placed a crucible with LCC electrodeposit at upper part, a set of insulation plate at middle part and a crucible with condensed cadmium at lower part of the distiller vessel.
Capacity of the RAR equipment is 50 kg of salt and 10 kg of cadmium per batch. The RAR equipment consists of frame assembly, furnace assembly, electrolytic vessel assembly, LCC crucible assembly, upper flange assembly, LM guide assembly and control panel. Furnace assembly can heat the electrolytic vessel with a given constant heating rate and keep its temperature constant. Its electric capacity is 20 kW with STS material. Two inert anodes with tube-type of pyrographite loaded in a porous SiC basket, two stirrers, two reference electrodes and LCC crucible assembly are placed in the vessel. The LCC crucible assembly including frame, a LCC crucible and its support and a LCC stirrer can move up and down by a driving motor.

IV-4. Development of Waste Salt Regeneration and Solidification System
1. Development of reuse technology for LiCl waste salt
Experiments to evaluate the removal performance of zeolite-4A in a molten LiCl was conducted and the chemical state of metal ions in molten salt was infered from the transformation of zeolite-4A, depending on the mole fraction of metal ions. Zeolite-4A was transformed into useless compound for removal of radionuclides. 1n order to clean the dirty salt, a new material, not decomposed in molten salt, is required. So, a new inorganic material for the removal of radionuclide from a molten LiCl was synthesized by using a sol-gel process. The material with Si/Al=4 ratio had O.3meq/g, two times higher than zeolite-4A capaclty.
Various chemical addition methods, which include carbonate, sulfate and phosphate addition methods were tested. Carbonate reaction of some alkaline-earth chlorides was investigated by using a carbonate agent injection method in LiCl molten salts containing SrCI2. The effects of the injected molar ratio of the carbonate agent(Li2CO3) and the temperature on the conversion efficiency of the strontium and barium chloride to their carbonates were determined. The form of strontium and barium carbonate resulting from the carbonate reaction with carbonate agents was identified via XRD and SEM-EDS analysis. 1n these experiments, the carbonate agent injection method can carbonate strontium and barium chlorides effectively at over 99% in LiCl molten salt conditions, where strontium was carbonated in the form of SrCO3 by an injection of Li2CO3. For sulfate reaction of Cs and Sr, Li2SO4 was used as sulfate. Cs was converted to CS2S2O6 and Sr was SrSO4 by reaction with LizSO4. The maximum sulfate reaction efficiency, in case of Cs, was about 78.9%. But the conversion efficiency of Sr was nearly over 95% at over 700℃ molten LiCl temperature and over 1 sulfate addition ratio. As an alternative to conventional Group 1 and II separation methods (such as a chemical agent addition and ion- exchange), melt crystallization processes, zone freezing and layer melt crystallization, were tested for the separation (or concentration) of cesium and strontium fission products in a LiCl waste salt generated from an electrolytic reduction process of a spent oxide fuel.
Among the many possible melt crystallization processes, based on the results of the screening-tests and an analysis on operationability, layer crystallization process was chosen for lab-scale Group I and Ⅱ fission products separation method to form LiCl waste salts. The lab-scale layer crystallization apparatus of which the maximum batch size is 4kg - LiCl/batch. As shown it consisted of four parts: crystallization furnace, melting furnace, crystallizer moving device and cooling air injection system. All the parts are located in a glove box maintained in Ar and a moisture- free atmosphere. The crystallizer, which had a cooling surface for the crystal layer growth, was a rectangular type. In the crystallizer, a uniform temperature distribution was very important to attain even crystal growth. To provide a uniform temperature distribution as soon as possible, cooling air was injected at the bottom of the crystallizer and there were several baffles in the axial direction inside the crystallizer to make a cooling air stream line. Compressed dry air was used as the cooling agent the cooling rate, and therefore the crystal growth rate were controlled by changing the air flow rate. During layer crystallization process, the crystal formation characteristic was monitored using the temperature change of the cooling air. The separation efficiency decreases with an increasing crystal growth rate. This is because at a high crystal growth rate, many impurities are entrapped in the crystal layer.

2. Development of reuse technology for LiCI- KCI eutectic waste salt
For the reuse of a waste salt from an electrorefining process of a spent oxide fuel, a separation of rare earth elements by an oxidative precipitation in a LiCI- KCl molten salt was tested without using precipitate agent. In the oxygen sparging method, oxygen is sparged into the molten salt bed to react with the free rare earth elements and then the resultant oxides or oxychlorides which are insoluble in the molten salt are precipitated. In this study, regardless of the sparging time(max. 420 min) and the molten salt temperature(400 ~ 650 ℃), oxychlorides(EuOCl, NdOCl, PrOCI) and oxides(CeO2, PrO2)were formed as a precipitates by a reaction with oxygen. The conversion efficiency of the rare earth elements to the insoluble precipitates increases with the sparging time and the molten salt temperature. In the conditions of 650 ℃ of a molten salt temperature and 420min of a sparging time, the values of the conversion efficiency of the used rare earth chlorides were over 99.9%. The oxygen sparging method is effective for a precipitation of rare earth chlorides in eutectic molten salts without changing the eutectic composition of the salts and there is no formation of byproducts. Lab-scale lanthanide precipitation equipment which has a 4kg/batch size was installed and tested.. Using this apparatus, precipitation experiments were carried out for a multiple-RE system. This system contains 8 rare-earth elements (Y, La, Ce, Pr, Nd, Sm, Eu and Gd). Via reaction with oxygen gas, Y, La, Pr, Nd, Sm, Eu and Gd were converted to their oxychloride forms (REOCl), while Ce and Pr to their oxide forms (CeO2, PrOCl). Since these rare-earth oxychlorides or oxides are not soluble in the molten salt, they were all precipitated by free settling. About 7 h of precipitation time was required. It was found that in the conditions of 700℃ salt temperature and 12 hours of oxygen sparging with a flow rate of 5L/min, 99.5% of the rare-earth elements were oxidized. In the case of 800℃ salt temperature, the oxidation efficiency was around 99% after only 6hours of operation. Of these two salt temperature conditions, when considering the possibility of salt entrainment and material corrosion, 800℃ salt temperature seems to be more favorable condition. Simplicity of distillation chamber (two adjacent chambers of vaporization and condensation, no vapor transport pipe or connecting flange). The closed chamber type of distillation system is subjected to the force a temperature gradient at a reduced pressure, in order to minimize loss of vaporized salt. The distillation system consists of four electric heaters, distillation chamber, samp1e boat, valve, vacuum pump, controller and cooling water circulator, and it has a capacity of 2kg/batch and a heating capacity up to 1100℃. After a distillation operation, 0.1 wt% of eutectic salts was residual in the rare earth precipitates and the rests were separated from them. Over 99% of the vaporized salts was recovered at the bottom of the condensation chamber through the closed chamber tests and it is thought that it is possible to recover all of the vaporized salts according to an appropriate condition. The stabilization of the salt distillation system was verified through a long-term (24 h) test. About 70 wt% of salts in the eutectic salt wastes was separated in the oxidation/precipitation process and about 29 wt% of the salts was recovered through the salt distillation system. About 99 wt% of the salts in the eutectic salt wastes recovered by using the oxidation/precipitation system link to the salt distillation system, and it was verified that the salts can be completely separated from the rare earth nuclides through the system. Reduction of the high-temperature operation time by the development of the online monitoring technology of the lab-scale vacuum distillation/condensation apparatus and the control of temperature gradients in the apparatus.
The improvement designs on the precipitated phase separation, the gas sparger control and the recovery crucible control for a remote control of the integrated lab-scale LiCl-KCl eutectic salt regeneration apparatus were verified to apply to the PRIDE apparatus by a 3D simulation test. Total performance objectives (total salt recovery > 95%) was realized by the continuously integrated operation of the lab- scale LiCI-KCl eutectic salt regeneration apparatus.

3. Development of waste solidification technology for residual waste
An inorganic composite for the immobilization of waste salt was designed and prepared. By using this material, the dechlorination reaction, thermal stability and durability of reaction products was investigated. From these experiments, solidification method for waste salt was set-up. The optimum composition of SAP was Si/Al/P=1/1/1.25 and it was prepared via sol-gel process which consists of gelation, aging, drying and heat-treatment step. By using this SAP, the metal chlorides were converted into aluminosilicate, aluminophosphate and orthophosphate compounds which is thermally stable compounds. At the SAP/Salt ratio=2, SAP125 shows the thermal weight loss was about below 1 wt% upto 1200℃. The reaction products were mixed with glass powder to fabricate a wasteform at 1150 ℃ for 4hrs. The wasteform prepared by this method has high durability; Cs/Sr leach rate were about 10-3g/m2·d by PCT- A method. From these method, the final waste volume could be reduced about 1/4 of the final volume by the other solidification method for final disposal of waste salt.
The wasteform containing LiCl waste was successfully fabricated as a monolithic form. The morphology, physical properties and chemical durability was investigated to confirm the performance of wasteform. A monolithic wasteform was fabricated with glass powder (21-36wt%) at 1100-1200℃ and there were no phase separation and defect under given conditions. The wasteform has two kinds of phases, Su-rich phase and P-rich phase, which constructed a domain-matrix structure in a size, about 1-2μm. The components of domain and matrix were dependent on the mixing ratio of glass. The physical properties such as density, thermal expansion coefficient, glass transition temperature, thermal capacity, thermal conductivity and micro-hardness was measured and the measured was reasonable as a radioactive waste. In order to confirm the chemical durability, a series of leaching test methods (PCT-A and B, ISO and MCC-1) was carried out and leaching behavior, leach rate and long-term leaching mechanism were evaluated. The test results showed that the wasteform prepared by SAP method has good properties and its durability is comparable to other radioactive wasteforms.
Different from two- step method, the one step method using zinc titanate-based composite can fabricated a highly dense and monolithic wasteform at relativley lower temperature. This wasteform has also the same host phase as the two- step method, monazite. With this wasteform, its properties was investigated by using various experiments. Zinc titanate- based composite composed of zinc titanate, CaHPO4, SiO2, B2O3 and it could be prepared by simply Mixing with each other at 600 - 900℃. This composite was mixed with rare earth oxides as a residual waste and heat- treated below1100.C for 4 hrs. The prepared wasteform has high density and durability (d=-4.3g/cm3 and leach rate). Also, the thermal properties such as thermal capacity and conductivity was measured
The equipments for crushing and pulverizing salt ingot was chosen to obtain an effective particle size and to effectively prohibit the particle below 20μm from being dispersed into the air. Jaw crusher and ro11 mill has an impact crusher operating in a left and right motion and slow rotating pulverizer. The capability of screw- impeller mixer was confirmed by mixing 10μm particles for 12hrs, where the effective mixing range was about 50-125μm. This means that the effective particle size for the dechlorination reaction, 100μm, is successfully mixed by using the mixer. In order to prevent the reactor from being oxidative corrosion, The vessel surface controlled-reaction was adapted to dechlorinate the salt, where the optimum surface temperature was about 610 - 650℃ and gas phase temperature was about 420-470℃. Based on the experimental results, the reaction rate was 0.7-14g/m2/min and the reaction yield was above 99% under a condition (650℃, 24hrs). The Lab-size of wasteforms were fabricated as 40g at 2007, 1.2kg at 2008 and 20kg at 2011 and their characteristics were evaluated. (ten times higher leach - resistance and three times lower final volume than zeolite- using method). Also, the inorganic composite gradually modified to enhance the reactivity and simplify the solidification process from SAP to M-SAP and U-SAP. As a universal composite was developed to stabilize and solidify waste salt by using just one material. For rare earth wastes, Zinc-titanate composite(ZIT) was developed to obtain a monolithic form at milder processing condition. By using ZIT, the waste loading increased from 20wt% to about 50wt% while the leach- resistance was comparable to other wasteforms immobilizing rare earth elements. 1n order to realize the developed solidification method, a unique mixer/reactor system with a screw-impeller was developed. With this equipment, Lab-scale solidification system composed of 4 steps, (1) pulverization of waste, (2) mixing waste and composite, (3) reaction and (4) consolidation of mixture. Each unit equipment in this lab-scale solidification system was modified to improve the acceptability for the Eng-scale solidification. After the evaluation of each unit process, the results was used to design the PRIDE solidification equipments.

4. Design of Eng-scale(PRIDE) salt waste treatment process system
Design of Eng-scale(PRIDE) salt waste treatment process system based on the operation results of the lab-scale apparatuses and operation schedules of the PRIDE process system
• LiCl -KCl eutectic salt waste regeneration process
- Organization Oxidation/Precipitation, Condensed eutectic salt separation, Precipitation phase separation and Vacuum distillation apparatus Capacity : 20 kg/batch (rare earth nuclide precipitation/separation), 7 kg/batch (vacuum distillation)
- Size : 1400(L)×l900(W)×l961(H)mm(Oxidation/Precipitation), 1400(L)×l900(W)×l900(H)mm(Condensed eutectic salt separation), 1200(L)×1900(W)×1900H)mm(Precipitation phase separation), 2300(L)×1300(W)×2600(H)mm(Vacuum distillation)
- Characteristics
. Rare earth nuclide precipitation/separation
: Working table was applied to make it easy to operate the linked apparatuses (Oxidation/Precipitation, Condensed eutectic salt separation, Precipitation phase separation apparatus)
. Vacuum distillation
: Glove boxes were designed in the upper and lower parts of the PRIDE apparatus to seal the crucible feeding parts
• LiCl salt waste regeneration process
- Organization Ⅰ/II group nuclide crystallization/melting and Condensed LiCl
salt separation apparatus
- Capacity : 20 kg/batch
- Size : 1600(L)×900(W)×1950(H)mm(Ⅰ/II group nuclide crystallization/melting), 1400(L)×l900(W)×l900(H)mm(Condensed LiCl salt separation)
- Distinctiveness The shifter of the crystallization plate was designed to be controlled automatically or passively
• Design of Eng-scale solidification system(PRIDE)
- Unit operation sector: Pulverization, Mixing/Reaction, Consolidation, Transportation and Off-gas treatment
- Capacity: 80-100kg wasteform for 1 cyc1e of solidification system
- Size: 5895(L)×3315(W)×2650(H), large chamber controlling atmosphere
- Distinctiveness: Full automation of each operation in the large chamber containing small size of window

IV-5. Development of System Evaluation Technology for Pyroprocessing
1. Development of an on- line monitoring system for pyroprocessing
Voltammetric methods such as NPV (normal pulse voltammetry) and SWV (square wave voltammetry) as well as LIBS (laser induced breakdown spectroscopy) system were studied to develop an on-line monitoring system of actinide and rare earth elements in molten salt at high temperature. The feasibility of those analysis methods to apply in real process was demonstrated.
NPV had a higher linearity between concentration and current response than SWV at high concentration range, but it needed a longer detection time and several repeated measurements for the peak separation in the presence of multi - species in molten salt. In case of SWV, it had good linearity at low concentration range with a short detection time and was good at separating the peaks corresponding to multi - species. Thus, it was concluded that SWV is preferred for the monitoring of pyrochemical process.
LIBS is a recently developed analytical technique that is based upon the measurement of emission lines generated by atomic species close to the surface of the sample, thus allowing their chemical detection, identification and quantification. With powerful advantages of LIBS compared to the conventional analytical methodology, this technique can be applied in the detection of heavy metals in the field and it allows the rapid analysis by avoiding laborious chemical steps. In order to be applied in the monitoring of actinides, we studied the laser properties and the various factors affecting on the analytical signal of LIBS. Also, it was investigated that the feasibility of LIBS application in quantitative analysis of spent fuel by considering the basic idea to enhance the data quality of LIBS including the calibration method for the various effects on the analytical signal of LIBS.

2. Development of a mass balance flow sheet for the integrated pyroprocessing
The preliminary mass balance data was obtained and the mass balance flow sheet for the integrated pyroprocessing was derived from the experimental results of the unit process and the interconnection system. Accordingly, the validity and applicability of the interconnection system were determined. Voloxidation process is for the recovery of oxidized nuclear fuel and transfer to electrolytic reduction process by removing the nuclear fuel rod and off - gas product from the spent nuclear fuel. The recovery rate of UO2 was 99.9% and the removal rate of off-gas was 1. The oxidized spent nuclear fuel was converted to the metal form through the electrolytic reduction process. The capability of the electrolytic reduction process was 50 kgHM/batch and the conversion rate of HM was 99.5%. Electrorefining process, where pure uraniums are recovered from the metal form in electrolytic reduction, has the capability of 50 kgHM/batch and the recovery efficiency of uranium was 99.675 %. The process operation is stopped when Pu/U > 3.0. The primary function of electrowinning is to recover the TRUs in molten salt using liquid cadmium cathode after electrorefining process. The capability of electrowinning is 1 kgHM/batch and the revoery ratio of TRU/RE is > 4. The LiCl molten salt used in electrolytic reduction is reused by removing the group 1 and II elements through a waste salt regeneration process with the removal efficiency of 90 %. Also, the eutectic molten salt (LiCI- KCD is reused by removing rare earth elements through the process with the removal efficiency of 100 %.
A study on the interconnection systems between unit processes was performed such as the mass transfer of unreduced material from electrolytic reduction process to electrorefining process, the treatment of solid waste generated from anode residuals in electrorefining process, the salt transfer from electrorefining to electrowinning, the characteristic analysis of salt waste used in electrolytic reduction and electrowinning process, etc. From the results, the mass balance flow sheet of the integrated pyroprocessing was established.
(출처: Summary 37p)

목차 Contents

• 표지 ... 1
• 제출문 ... 5
• 보고서 요약서 ... 6
• 요약문 ... 7
• SUMMARY ... 33
• CONTENTS ... 61
• 목차 ... 63
• 제1장 서론 ... 65
• 제2장 국내외 기술개발 현황 ... 67
• 제1절 국외 파이로 기술개발 현황 ... 67
• 1. 미국의 연구개발 현황 ... 67
• 2. 일본의 연구개발 현황 ... 67
• 3. 러시아의 연구개발 현황 ... 68
• 제2절 국내 파이로 공정 기술개발 현황 ... 68
• 제3장 연구개발 목표 달성도 및 관련 분야에 의기여도 ... 71
• 제1절 연구개발 목표달성도 ... 71
• 1. 고온 용융염 전해환원시스템 개발 ... 71
• 2. HT 전해정련 시스템 개발 ... 71
• 3. TRU 회수 전혜채련 시스템 개발 ... 72
• 4. 염폐기물 재생·고화 시스템 개발 ... 73
• 5. 파이로계통 평가 기술 개발 ... 74
• 제2절 관련분야에의 기여도 ... 76
• 제4장 연구개발결과의 활용계획 ... 78
• 제5장 연구개발과정에서 수집한 해외과학 기술정보 ... 80
• 제6장 참고문헌 ... 83
• 고온 용융염 전해환원시스템 개발 ... 85
• 제출문 ... 87
• 보고서 요약서 ... 88
• 요약문 ... 89
• SUMMARY ... 95
• CONTENTS ... 101
• 목차 ... 102
• 표목차 ... 103
• 그림목차 ... 106
• 제 1 장 고온 용융염 전해환원시스템 개발 과제 개요 ... 129
• 제 2 장 국 내외 기술개발 현황 ... 131
• 제 1 절 산화물 사용후핵연료 금속 전환 기술 ... 131
• 제 2 절 Cathode Processing 기술 ... 140
• 제 3 절 세라믹 양극 제조기술 ... 146
• 제 4 절 LiCI-Li2O 용융염계에서 주요 핵종의 전기화학적 거동평가 기술 ... 148
• 제 3.1 장 고온 용융염 전해환원 시스템개발 수행내용 및 결과-1 단계 (‘07 -’09) 연구내용 및 결과 ... 151
• 제 1 절. Lab-scale 전해환원시스템 성능평가 ... 151
• 제 2 절. 전해환원 시스템 공정개선 및 최적화 기술 개발 ... 232
• 제 3 절 . 공정해석용 반응공학 및 물리·화학적 자료 생산 ... 307
• 제 4 절. PRIDE 전해환원 공정시스템 설계 ... 349
• 제 3.2 장 연구개발 수행 내용 및 결과-2 단계 (‘ 10 - ’ 11) 연구내용 및 결과 ... 380
• 제 5 절. 산화물 사용후핵연료 전해환원 기술개발 ... 380
• 제 6 절. 전해환원 금속전환체 Cathode Processing 기술개발 ... 437
• 제 7 절. 환원-정련 연계운전기술 개발 ... 452
• 제 8 절. 대용량 전해환원장치 재료 건전성 평가 ... 480
• 제 4 장 목표 달성도 및 관련 분야에의 기여도 ... 508
• 제 5 장 연구개 발 결과의 활용계획 ... 510
• 제 6 장 연구개발과정에서 수집한 해외과학기술 정보 ... 512
• 제 7 장 연구시설·장비현황 ... 515
• 제 8 장 참고문헌 ... 517
• High- Throughput (HT) 전해정련 시스템 개발 ... 525
• 제출문 ... 527
• 보고서 요약서 ... 528
• 요약문 ... 529
• SUMMARY ... 533
• CONTENTS ... 538
• 목차 ... 540
• 표목차 ... 542
• 그림목차 ... 545
• 제 1 장 서론 ... 565
• 제 2 장 국내외 기술개발 현황 ... 568
• 제 1 절 전해정련공정 기술개발 ... 568
• 제 2 절 삼염화우라늄 (UCI3) 제조 기술 ... 579
• 1. 국외 UCI3 제조공정 ... 579
• 2 국내 UCI3 제조공정 ... 581
• 제 3 장 전해정련 시스템 개발 수행내용 및 결과 ... 592
• 제 1 절 1 단계(‘ 07~ ’09) 연구수행 내용 ... 592
• 1. Lab-scale HT 전해 정련 공정 장치 설계 ... 592
• 2. HT 전해정련 핵심기술 구축 (I), (II) ... 630
• 3. Lab- scale HT 전해정련 시스템 제작,설치 및 Blank Test ... 717
• 4. Lab-scale HT 전해정련 시스템 성능평가 (I), (II) ... 744
• 5. PRIDE 전해정련 공정장치 설계 ... 778
• 제 2 절 2 단계(‘ 10~ '11) 연구수행 내용 ... 793
• 1 전해정련장치 개량 및 성능 시험 (Lab- scale) ... 793
• 2. CP (염증류 및 잉곳주조) 장치 운전효율 평가 ... 854
• 3. 정련-제련 연계운전기술 (I) (II) ... 917
• 4. 공학규모전해정련기의 전기 수력학적 해석 (위탁과제) ... 942
• 제 3 절 참고문헌 ... 962
• 제 4 장 목표달성도 및 관련분야에의 기여도 ... 964
• 제 1 절 연구개발 목표 달성도 ... 964
• 제 2 절 관련분야에의 기여도 ... 964
• 제 5 장 연구개발결과의 활용계획 ... 969
• 제 6 장 연구개발과정에서 수집한 해외 과학기술정보 ... 972
• 제 7 장 연구시설·장비현황 ... 977
• 제 8 장 참고문헌 ... 979
• 끝페이지 ... 982