[en] In order to investigate the release kinetics of Kr-85 fission gas during DUPIC fuel fabrication process using spent fuel materials, the test equipment and its procedure was developed. The purpose of this test involves the measurement of Kr-85 released during OREOX process in DUPIC fuel fabrication as well as the analysis of fission- gas release kinetics with the variation of fuel fabrication conditions. Gas monitoring system installed inside glove box was located at out-cell of DFDF(DUPIC Fuel Fabrication Facility) at which OREOX and tube furnaces have already installed inside hot cell. The use of glove box is aimed for preventing a gas release from sampling gas line under negative pressure. Based on the allowable discharge concentration of Kr-85 to environment and the preliminary analysis assuming total released amount a year, environmental impact according to Kr-85 measuring test would be minimal

[en] Key technologies highly applicable to the development of advanced nuclear fuel cycle for the spent fuel recycling were developed using spent fuel and simulated spent fuel (SIMFUEL). In the frame work of dry process oxide products fabrication and the property characteristics of dry process products, hot cell experimental data for decladding, powdering and oxide product fabrication from low and high burnup spent fuel have been produced, basic technology for fabrication of spent fuel standard material has been developed, and remotely modulated welding equipment has been designed and fabricated. Also, fabrication technology of simulated dry process products was established and property models were developed based on reproducible property measurement data. In the development of head-end technology for dry refabrication of spent nuclear fuel and key technologies for volume reduction of head-end process waste which are essential in back-end fuel cycle field including pyro-processing, advanced head-end unit process technology development includes the establishment of experimental conditions for synthesis of porous fuel particles using a granulating furnace and for preparation of UO2 pellets, and fabrication and performance demonstration of engineering scale equipment for off-gas treatment of semi-volatile nuclides, and development of phosphate ceramic technology for immobilization of used filters. Radioactivation characterization and treatment equipment design of metal wastes from pretreatment process was conducted, and preliminary experiments of chlorination/electrorefining techniques for the treatment of hull wastes were performed. Based on the verification of the key technologies for head-end process via the hot-cell tests using spent nuclear fuel, pre-conceptual design for the head-end equipments was performed

[en] • Evaluation of nuclear fuel cycle options: - Selection of nuclear fuel cycle option is mainly driven by county-specific circumstances that ultimately determine national strategies; - Comprehensive standard methodology for objective evaluation of various fuel cycle options would provide potential information. • Pyroprocessing: - KAERI has developed an environment-friendly and proliferation resistant pyroprocessing for spent fuel treatment; - To recover useful materials such as U, TRU, and reduce the volume and radiotoxicity of spent fuel. • Infrastructure: - Proving transparency and escalating technology improvement in terms of technical, economical and proliferation-resistance aspects

[en] Desorption characteristics of C-14 adsorbed on spent resin as H¹⁴CO₃ ion type by applying various stripping solutions were analyzed, and some experiments for gasification of C-14 to CO₂ gas with were also performed. Based on these results, the process concept for spent resin treatment was suggested. Real spent resin was prepared from sampling in storage tank in site 1 of Wolseung Nuclear Power Plant. Desorption characteristics of C-14 and cations of Cs, Co from spent IRN-150 resin was evaluated. Desorption efficiency of C-14 from spent resin by using H₃PO₄ desorption solution was over 96% regardless of C-14 amount on initial spent resin when comparing a activity of C-14 on initial spent resin. Also, desorption percent of cation of Cs, Co from anion ion-exchange resin (IRN-77) showed that Co-60 was below 1%, Cs-134, 137 was in a range of 2 ∼ 5%. Fundamental studies include an development of adsorbent manufacturing technology and its performance evaluation for C-14 gas trapping, the adsorption process by adopting gas circulation method was suggested for the design of ¹⁴CO₂ gas treatment system generated from spent resin treatment process. In order to predict adsorbent performance of CO₂ trapping, modelling was carried out to verify the breakthrough curves of CO₂ trapping by using soda lime adsorbent. The effect of humidity on CO₂ trapping by using soda lime adsorbent was modelled via chemical reaction in porous media. Assessment of the state-of-the-arts on the solidification of the used adsorbent showed that the cement matrix would be the best-available binder from the view points of the matrix compatibility, properties of the final waste form, simplicity of the process and relatively low cost

[en] Fabrication characteristics of the dry processed fuel with a variation of fuel burn-ups in a range of 27,300 to 65,000 MWD/tU were experimentally evaluated. Density comparison of powders which were fabricated from oxidation, OREOX and milling processes at same process conditions was performed with a function of fuel burn-ups respectively. The influence of fuel burn-ups on sintering characteristics of dry processed fuel was studied by comparing the density change of sintered pellet as well as green pellet. Weight gain by fuel oxidation to U₃O₈ showed semi-linear dependence with increasing fuel burn-ups. OREOX powder density increased up to 3.7 g/cm³ at high burn-up fuel, and the density of milled powder with fuel burn-ups represented almost similar value of 3.2±0.2 g/cm³. Also, the green pellet density compacted by 120 MPa decreased smoothly with increasing fuel burn-ups, and the density change of sintered pellet showed the similar trend as green pellet. The sintered density of pellet in a range of 27,000 to 40,000 MWD/tU was found to be more 95% of Theoretical Density(T.D.), but the sintered pellet density fabricated from high burn-up fuel showed a range of 92 % to 93% of T.D

[en] The manual of Manufacturing and Operating Procedure (MOP) for the fabrication of DUPIC fuel with high quality was developed based on quality assurance program with CAN3-Z299.2-85 to the extent as needed and appropriate. This manual describes a series of fabrication processes that can be applied to fabricate the DUPIC fuel and element, which cover the slitting process, powder fabrication with improved sinterability, milling and sintering processes conducted in DFDF. The qualification tests for establishing the optimal process conditions of DUPIC fuel fabrication were carried out with various process conditions such as pressing pressure. This MOP was revised twice with the support of qualification test results and a specified procedure

[en] The experiments on the fission products release behavior from spent fuel at high temperature assuming reactor accident conditions have been carried out at Oak Ridge Nation Laboratory of USA in HI/VI tests, CEA of France in HEVA/VERCOS tests, AEA of England and CRNL of Canada in HOX test. The VEGA program to study the fission product release behavior from LWR irradiated fuel was recently initiated at JAERI. The key parameter affecting the fission product(FP) release behavior is temperature. In addition, other parameters such as fuel oxidation, burnup, pre-transient conditions are found to affect the FP releases considerably in the earlier tests. The atmosphere conditions such as oxidizing atmosphere (steam or air) or reducing atmosphere (hydrogen) can cause significant change of FPs release and transport behavior due to chemical forms of the reactive FPs which is dependent on the oxidation potential. The effect of fuel burnup on the Kr-85 or Cs-137 release showed that the release rates of these radionuclides increased with the increase of burnup, meaning that release rates are dominated by the atomic diffusions in the grains and they are primarily a function of temperature. However, the data on FPs release behavior using higher burnups above 50,000 MWD/MTU are not so many reported up to now. This report summarizes the test results of FPs release behavior in reactor accident conditions produced from other countries mentioned above. This review and analysis on earlier studies would be useful for predicting the release characteristics of FPs from domestic spent fuel. The release rates of fission gas or FPs from spent fuel at high temperature conditions during fabrication process of dry recycling fuel were also analyzed using many data obtained from earlier tests

[en] Oxygen enriched combustion technology has recently been used in waste incineration. To apply the oxygen enrichment on alpha-bearing waste incineration, which is being developed, a state-of-an-art review has been performed. The use of oxygen or oxygen-enriched air instead of air in incineration would result in increase of combustion efficiency and capacity, and reduction of off-gas product. Especially, the off-gas could be reduced below a quarter, which might reduce off-gas treatment facilities, and also increase an efficiency of off-gas treatment. However, the use of oxygen might also lead to local overheating and high nitrogen oxides (NOx) formation. To overcome these problems, an application of low NOx oxy-fuel burner and recycling of a part of off-gas to combustion chamber have been suggested

[en] Highlights: • Pyroprocessing is a complicated batch-type operation. • Discrete event system modeling was used to create an integrated operation model. • Simulation showed that could be accomplished. • The dynamic material flow helps us understand the process operation. • We showed that complex material flow could be simulated in terms of mass balance. - Abstract: Pyroprocessing is a complicated batch-type operation, involving a highly complex material flow logic with a huge number of unit processes. Discrete event system modeling was used to create an integrated operation model for which simulation showed that dynamic material flow could be accomplished to provide considerable insight into the process operation. In the model simulation, the amount of material transported upstream and downstream in the process satisfies a mass balance equation while considering the hold-up incurred by every batch operation. This study also simulated, in detail, an oxide reduction group process embracing electrolytic reduction, cathode processing, and salt purification. Based on the default operation scenario, it showed that complex material flows could be precisely simulated in terms of the mass balance. Specifically, the amount of high-heat elements remaining in the molten salt bath is analyzed to evaluate the operation scenario.

[en] Remote welding system for endplate welding of multi-pin nuclear fuels was designed, fabricated. Welding specimens were fabricated for the performance test of remote welding system by resistance welding method. The torque of welding between endplug and endplate of welding specimens was measured, and analyzed on current, pressure of main electrode, pressure of branch electrode and time. It was confirmed that the torque between inner endplug-endplate and outer endplug-endplate can be controlled by welding factors. The torque of welding specimens was available for connection of requirement between endplug and endplate. Welding condition of welding specimens is current 4000A, pressure 4 bar of main electrode, pressure 2.5bar of branch electrode and time 2 cycles. Metallographic examination on weldment between endplug and endplate was performed and continuity of welding line, integrity of weldability were investigated. Upper jig and lower jig for 7 pin nuclear fuels and 3 pin nuclear fuels were fabricated. The welding of upper endplate and lower endplate of 7 pin nuclear fuels and 3 pin nuclear fuels was carried out. It was confirmed that endplate welding of multi-pin nuclear fuels can be performed by remote welding system