[en] A description is given for the program on PIE services and the related R and D works which have been undertaken to date, is currently underway and will be carried out in the future

[en] Exact analytical solutions for free vibration of steam generator U-tubes have been already known, however the computations are not straightforward because of the complexities of the solutions. In this study, a computer program, UTVA, for calculating natural frequencies and mode shapes of the U-tubes has been developed utilizing the existing exact solutions. As illustrations of calculations using the program, the typical results for steam generator U-tubes with various support conditions and dimension are provided

[en] Complex formation of radionuclides with chelating agents found in ground water significantly influence the migration behavior of the radionuclides. In this study, the effects of the presence of chelating agents on the adsorption capacity of geologic media such as minerals and soils are examined by using the developed adsorption model. This adsorption model includes the thermal degradation and formation of chelates. The calculated results are compared with the experimental results obtained by other authors. The suggested adsorption model does not correspond nicely to the experimental results. However this adsorption model is a significant progress for the evaluation of the transport phenomena of the radionuclide ions in the presence of chelating agents

[en] This proceedings contains articles of 1991 spring meeting of the Korean Nuclear Society. It was held on May 24-25, 1991 in Taejon, Korea. This proceedings is comprised of 6 sessions. The main subject titles of session are as follows: nuclear reactor design, nuclear reactor thermal-hydraulics, safety analysis, structure and materials, radiation and chemistry and nuclear reactor control. (Yi, J. H.)

[en] The neutron diffusion equation in reactor physics is solved on the transputer, an MIMD parallel computer. Schwarz alternating procedure for overlapping subdomains is used in domain decomposition. The results of parallel computation for two benchmark problems (one-dimensional and two-dimensional) are reported and compared with those of serial computation

[en] A loss of feedwater accident with multiple failure has been studied in order to identify the potential severity of the accident when compared with the design basis accident in PWR. The PCS heatup and recovery mode in a LOFA with multiple failure was evaluated using the LOFT L9-1/L3-3 experiment. From experimental result, 4 separable subphase were identified and the associated phenomena were also addressed

[en] For the safety analyses and for the evaluation of long term health effects of the actinides, KIGEN[4] is improved in this study and the exact decay-chain-path file is found for the actinides on the basis of the ENDF/B-IV decay library. Using this decay chain path file KIGEN2 that is an updated version of KIGEN can consider both forward and backward decay reactions simultaneously, thus removing the major limitation in KIGEN. KIGEN2 developed in this study allows us to obtain accurate concentrations of the fission products and actinides and other important related quantities, using approximately half of the computer time required by ORIGEN2

[en] The Back-propagation Neural Network (BPN) algorithm is applied to connectionist expert system for the identification of BWR transients. Several powerful features of neural network-based expert systems over traditional rule-based expert systems are described. The general mapping capability of the neural networks enables to identify transients easily. A number of case studies were performed with emphasis on the applicability of the neural networks to the diagnostic domain. It is revealed that the BPN algorithm can identify transients properly, even when incomplete or untrained symptoms are given. It is also shown that multiple transients are easily identified

[en] A defect model explaining the oxygen potential of gadolinia doped urania based on the defect structure of pure urania has been developed. In the hyperstoichiometric region, dopant exists mainly as an isolated form; and in the hypostoichiometric region, as a vacancy-dopant cluster. Gd-dopants are assumed to push away nearby oxygen interstitials reducing the number of interstitial sites. This model explains the discontinuous change of the oxygen potential at O/M=2 as well as the increase of the potential with the dopant concentration

[en] A three-phase optimization method for determining an optimal loading pattern for pressurized water reactors has been developed. This method is composed of three phases. In the first phase, only the fast group diffusion equation is solved to get an ideal fuel region. In the second phase, using the result of the first phase, a heuristic algorithm, what is called the even-odd rule, is newly introduced to obtain the optimal fuel assembly distribution which has maximum soluble boron concentration at the EOC. Finally, a suitable control poison distribution which maintains an optimal power shape throughout the cycle is determined. To validate the feasibility of the method, it is applied to the cycle 4 of Kori Unit 4. The critical soluble boron concentration of the optimal loading pattern at the EOC is about 20 ppm higher than that of the standard loading pattern