[en] The mechanical fretting endurance test of total 3000 hour was performed for the verification of the CANFLEX-NU fuel bundle. This bundle has been developed by KAERI/AECL joint design program. The CANDU Hot Test Loop facility in KAERI was used for the test. The test conditions of the temperature and pressure were the same as the normal operating conditions of CANDU-6 reactor and the flow rate was chosen in a conservative way by considering the creeping effect on the aged pressure tube. From the analysis of the fretting wear measurement results on bearing pads and spacers of the test bundles along the test, the fretting rate was steep at the beginning of the test ie, 500∼1500 hour and after that, it was relieved to the constant value. Based on the results of these historical trends on fretting wear, it was revealed that the final fretting wears on the fuel bundles which were evaluated by extrapolation did not exceed the ones in CANDU-37 bundle test for a cycle

[en] Synroc (Synthetic Rock), a titanate-based ceramic originally proposed by Prof. A. Ringwood (ANU) and designed for the immobilization of high level nuclear waste (HLW), consists of three principal phases such as hollandite, zirconolite and perovskite. Nearly all the fission products and actinides in HLW can be incorporated as solid-solution in at least one of these phase. The preferred form of Synroc can be obtained up to 20 % of high level waste calcine to form dilute solid solution. The constituent minerals, or close structural analogues, have survived in a wide range of geochemical environments for periods of 20-2000 Myr while immobilizing the same elements present in nuclear waste. A dense, compact, and mechanically strong form of Synroc can be formed by hot pressing reactive precursor powders at about 1200 dg C and 20 MPa. In this state-of-the-art report, formulation method and characterization of Syroc with respect to the crystal structure, the consisting substances, types, etc. were reviewed. Additionally, a new promising powder process, ^Combustion Process^, was proposed and the properties of the combustion-synthesized powder were described. An international cooperative program between JAERI and ANSTO, and US patents for early Synroc research in Australia were also introduced. From the literatures review, Synroc is expected to have advantages in using as an immobilizer of HLW. Therefore, a systematic research to develop the Synroc is needed. (author). 53 refs., 2 tabs., 16 figs

[en] The following were studied through the project entitled 'IAEA/CRP for decommissioning techniques for research reactors 1. Decontamination technology development for TRIGA radioactive soil waste - Electrokinetic soil decontamination experimental results and its mathematical simulation 2. The 2nd IAEA/CRP for decommissioning techniques for research reactors - Meeting results and program 3. Hosting the 2001 IAEA/RCA D and D training course for research reactors and small nuclear facilities

[en] A chemical decontamination process using nitric acid solution was selected as in-situ technology for recycle or release with authorization of a large amount of metallic waste including process system components such as tanks, piping, etc., which is generated by dismantling a retired uranium conversion plant at Korea Atomic Energy Research Institute (KAERI). The applicability of nitric acid solution for surface decontamination of metallic wastes contaminated with uranium compounds was evaluated through the basic research on the dissolution of UO2 and ammonium uranyl carbonate (AUC) powder. Decontamination performance was verified by using the specimens contaminated with such uranium compounds as UO2 and AUC taken from the uranium conversion plant. Dissolution rate of UO2 powder is notably enhanced by the addition of H2O2 as an oxidant even in the condition of a low concentration of nitric acid and low temperature compared with those in a nitric acid solution without H2O2. AUC powders dissolve easily in nitric acid solutions until the solution pH attains about 2.5 ∼ 3. Above that solution pH, however, the uranium concentration in the solution is lowered drastically by precipitation as a form of U3(NH3)4O9 . 5H2O. Decontamination performance tests for the specimens contaminated with UO2 and AUC were quite successful with the application of decontamination conditions obtained through the basic studies on the dissolution of UO2 and AUC powders

[en] As the increase of the operation age of the domestic high radiation facilities such as IMEF, PIEF and DFDF, the necessity of decontamination and refurbishment of hot cells in these facilities is also increased. In the near future, the possibilities of refurbishment of hot cells in compliance with the new regulations, the reuse of hot cells for the other purposes and the decommissioning of the facilities also exist. To prepare against the decontamination and refurbishment of hot cells, the reports on the refurbishment, decommissioning and decontamination experiences of hot cells in USA, Japan, France, Belgium and Great Britain were investigated. ANL of USA performed the project on the decontamination of hot cells. The purpose of the project was to practically eliminate the radioactive emissions of Rn-220 to the environment and to restore the hot cells to an empty restricted use condition. The five hot cells were emptied and decontaminated for restricted use. Chemical processing facility in JAEA of Japan was used for the reprocessing study of spent fuels, hot cells in CPF were refurbished from 1995 for the tests of the newly developed reprocessing process. In a first stage, decommissioning and decontamination were fully performed by the remote operation Then, decommissioning and decontamination were performed manually. By the newly developed process, they reported that the radiation exposure of workers were satisfactorily reduced. In the other countries, they also make an effort for the refurbishment and decontamination of hot cells and it is inferred that they accumulate experiences in these fields

[en] The originative CO₂ pellet blasting equipment was developed by improving additional components such as feed screw, idle roller and air-lock feeder to clear up the problems of freezing and discontinuity of blasting and by adopting pneumatically operated vacuum suction head and vacuum cup to prevent recontamination by collecting contaminant particulates simultaneously with the decontamination. The optimum decontamination process was established according to the kind of materials such as metal, concrete and plastic and the type of contaminants such as particulate, fixed chemical compound and oil. An excellent decontamination performances were verified by means of the lab-scale hot test with radioactive specimen and the technology demonstration in IMEF hot cell. The PFC dry decontamination equipment applicable to the surface contaminated with high radioactive particulate was developed. This equipment consists of the unit processes such as spray, collection, filtration and dry distillation designed originatively applicable to inside of dry hot cell. Through the demonstration of PFC spray decontamination process in IMEF hot cell, we secured on-site applicability and the decontamination efficiency more than 90 %. We investigated the characteristics of dismantled metal waste melting and the radionuclide(Co, Cs, U) distribution into ingot and slag by melting decontamination experiments using electric arc melter. We obtained the decontamination factors greater than 100 for Cs and of 10∼100 for uranium. The pilot scale(200 kg/batch) demonstration for melting decontamination was carried out successfully using high temperature melting facility at KAERI. The volume reduction factor of 1/7 and the economical feasibility of the melting decontamination were verified.

[en] In order to investigate the stability of xenon spatial oscillation in PWR, a model has been developed, which is based on the one group delayed equation with iodine-xenon dynamic equation. The system equation are perturbed and linearized for frequency domain stability analysis. Also in order to obtain the closed loop transfer function, the model expansion is adopted. The spatial stability will be finally determined by the generalized Nyquist Criterion for the multi-input/multi-output system. The axial stability analysis using this model has been performed for the Yonggwang-1 core. The core physical parameter for parametric study are power level, control rod position, and core average burnup. And the order of modal expansion is also the subject of the study to determined the effect of modal interaction

[en] Lithium titanate (Li₂TiO₃) is known to be a low-activation ceramics for use in tritium breeding. A new approach has been developed to produce the high purity, fine-grained lithium titanate (Li₂TiO₃). This technique is based on a combustion synthesis process in which the components are mixed in aqueous solution, simultaneously auto-ignited, and finally synthesized to the desired fine-grained particles. The combustion synthesis using glycine as a fuel was studied in order to prepare a fine, active and high purity powder that could be cold compacted without binder or lubricant and sintered to a high density (>80% theoretical density) at relatively low temperature (<1,000 .deg. C) and short sintering time (< 4 hours). Systematic studies and the microstructure and surface morphology of the powder and sintered pellet were carried out to optimize various parameters such as sintering temperature and time

[en] A. Decontamination Technology Development of Uranium Conversion Facility. Understanding of uranium conversion facility and related decontamination technologies, and analysis of current status of decontamination technologies. Establishment of the objective and research items of the middle and long term R and D project. Discussion of the erformance plan and about the methodology for connection with the project of environmental restoration of uranium conversion facility B. Treatment Technology Development of Uranium Sludge Analysis of the domestic and overseas research development status. Suggestion of treatment methodology of uranium slurry and cooperative R and D among industries, universities and research institute. Establishment of the objective and research items of the middle and long term R and D project. Discussion about the performance plan and about the methodology for connection with the project of environmental restoration of uranium conversion facility C. Decommissioning Technology Development Analysis of the domestic and overseas research development status and the overview of decommissioning technologies. Establishment of the objective and research items of the middle and long term R and D project. Discussion about the performance plan and about the methodology for connection with the project of TRIGA decommissioning D. Evaluation of KAERI Soil Decontamination Technology. Evaluation of soil decontamination process and the liquid decontamination waste treatment technology. Performance of soil decontamination test using solvent flushing test equipment for evaluation of residual radioactivity after decontami- nation and modeling of the results

[en] The usage of programmable logic component, i.e., Complex Programmable Logic Device (PDL) or Field- Programmable Gate Array(FPGA), has been becoming popular in a commercial application because of its flexibility. As a part of this trend, the up-to-date component adopted in a nuclear facility is gradually increasing. Therefore, it is important to verify functions of the programmable logic component. The objective of this study is provide a verification plan of programmable logic design appropriate to the nuclear Instrument and Control (I and C) system. To achieve our goal, we focus on the verification of safety-critical programmable logic design, i.e. avionics, and the guideline for nuclear safety system. This paper represents the first phase result of the project to develop a verification and validation (V and V) method for the programmable logic components. Next section depicts a relationship between a formal development process and a verification process. And the conclusion and the future work is represented in the final section