[en] The increasing use of microprocessor-based digital technology in safety related system has introduced concerns with respect to electrical noise in the nuclear power plant. Digital technology has been performance advancements but on the other hand, has an adverse impact on the operation of digital system in connection with EMI/RFI and power surge. Therefore, digital equipment is needed to minimize an electrical noise from the first design stage and to ensure EMC design in the final design stage. The purpose of this study is to assist the engineer/designer in minimizing the EMI problem and establishing equipment qualification for EMI/RFI by presenting a discussion of technical sound alternative for EMI and analysis of related requirements, Mil-Std-461D and EPRI TR-102323. (author)

[en] In this work, Cu(50 nm)/Ta(10 nm, or no Ta)/TaN(50 nm)/Ta(10 nm) metallization layers were deposited onto Si or SiO₂/Si substrates by magnetron sputtering. Samples were subsequently annealed at various temperatures ranging from 400 to 800 deg. C in vacuum. The sheet resistance, crystalline microstructure, and surface morphology were investigated by four-point probe, θ-2θ X-ray diffraction, and scanning electron microscopy. Experimental results reveal that Cu films exhibit (111) preferred orientation on Ta but show both (111) and (200) textures on TaN. After annealing, copper films agglomerate on TaN but remain continuous on Ta. However, the Ta layer interposed between Cu and TaN dilutes the nitrogen concentration of the barrier so that reaction between Cu and Si occurs in the Cu/Ta/TaN/Ta/Si system after annealing at 800 deg. C and Cu₃Si forms. In contrast, the Cu/TaN/Ta/Si system shows agglomeration but no reaction up to 800 deg. C. Upon annealing, Cu/TaN/Ta and Cu/Ta/TaN/Ta stacks on a SiO₂/Si substrate exhibit similar crystal structural and morphological evolution to their parallel samples on a Si substrate, except that no Cu-Si reaction is observed for the Cu/Ta/TaN/Ta/SiO₂/Si system after annealing at 800 deg. C. Grain growth behavior of Cu films deposited on different multilayer structures is also discussed

[en] Reactivity in thermal and epithermal reactors may be increased by inserting into these reactors at least one rod of a heavy element having high inelastic cross-section for high energy neutrons with energys above 1 MeV and low caputre cross-sections. The heavy element may be lead, bismuth, or compounds and mixtures of lead and bismuth. Such incrases may be used, for example, to reduce heavy water needs in the case of heavy water moderated reactors and enrichment needs in the case of light water reactors. (auth)

[en] This invention concerns nuclear reactors in general and thermal and epithermal reactors in particular. Its object is to use heavy elements, such as Pb or Bi, to replace or add to the moderator at specific places in the reactor in order to obtain reactivity increases. These increases in reactivity can be achieved because the heavy elements can, in certain energy areas, have cross sections which are more advantageous from the nuclear angle for thermal and epithermal reactors than those of the moderators generally used. In particular, in the very high energy areas (above 1MeV) heavy elements have much greater elastic and non-elastic scattering cross sections, with a much greater energy thindown of the neutrons and have very much lower capture cross sections

[en] A development of RELAP5/CANDU+ code for regulatory audits of accident analysis of CANDU nuclear power plants is on progress. This paper is undertaken in a procedure of a verification and validation for RELAP5/CANDU+ code by analyzing main steam line break accidents of WS 2/3/4. Following the ECC injection in sequence of the steam line breaks, the mismatch in heat transfer between the primary and the secondary systems makes pressure of the primary system instantly peaked to the open setpoint of liquid relief valves. The event sequence follows the result of WS 2/3/4 FSAR, but there is a difference in pressure transient after ECC injection. Sensitivity analysis for main factors dependent on the peak pressure such as control logics of liquid relief valves. ECC flow path and feedwater flow is performed. Because the pressure increase is continued for a long time and its peaking is high, open and close of the liquid relief valves are repeated several times, which is obviously different from those of WS 2/3/4 FSAR. As a result, it is evaluated that conservative modeling for the above variables is required in the analysis

[en] We study the nonthermal emission from SNR RX J0852.0-4622 based on a self-consistent kinetic method that describes the nonlinear shock acceleration of cosmic rays in supernova remnants (SNRs). In this method, the spectrum of accelerated protons in the SNR can be self-consistently calculated, where a proton's maximum momentum is determined by equating the SNR's age with the acceleration time of the proton. At the same time, the spectrum of accelerated electrons is similar to the proton's spectrum if the electron's momentum is much less than the electron's maximum momentum (p_e,max), which is estimated by equating the synchrotron loss time to the acceleration time of the electrons, but the cutoff shapes around p_e,max are assumed to be exponential. Using the accelerated particle's spectra, we calculate nonthermal photon spectra for different values of some main model parameters such as the SNR's age, an injection parameter, and a background magnetic field. Moreover, we study possible (hadronic or leptonic) origins of very high energy (VHE) γ-ray emission from SNR RX J0852.0-4622. Our results indicate that a hadronic origin of VHE γ-rays from SNR RX J0852.0-4622 seems to be more reasonable although a leptonic origin cannot be ruled out. We suggest that the observations of Fermi LAT for this remnant will help us find the evidence to determine the main emission mechanism.

[en] As preparations for the improvement of economical efficiency of the nuclear power plant and the reinforcement of the high burnup fuel damage criteria, 3-dimensional core neutronics codes and the system thermal hydraulics codes and coupled accident analysis methodologies are widely under developing. While on the regulatory and licensing side, we had better be ready in case of the licensing audit calculations. Therefore Korea Institute of Nuclear Safety (KINS) should be capable of 3-dimensional core neutronics calculations through the preliminary study of the related field. In the present study, PARCS code installation and its execution are settled as basic condition to obtain the 3-dimensional core neutronics evaluation capability and in terms of technical matters obtained during introduction and execution of PARCS code, technical state about 3-dimensional neutronics code and its coupled system thermal-hydraulic code are studied. And in order to verify that PARCS code is installed at computer system successfully, OECD/NEA benchmark A1 and A2 problems are targeted for verification

[en] The sensitivities for the reactor parameters and variables to the 3-dimensional kinetics analysis of the rod ejection accident are examined. PARCS code is used for their analyses on the calculations of fuel enthalpy rise which is being currently used as one of the fuel failure criteria. The sensitivities are evaluated as the maximum enthalpy rise for the variation of 'ρ_rod(ejected rod worth)-β(delayed neutron fraction)'. The results show that most of the parameters and variables in the 3-dimensional models are highly sensitive to the maximum fuel enthalpy and thus their trend should be verified for the application

[en] This study provides the working items and licensing issues required for the applications of multi-dimensional reactor kinetics methodology to accident analysis. The multi-dimensional reactor kinetics model takes further more uncertain parameters and kinetics parameters compared with the point kinetics model, and thus more various and systematic uncertainty analysis and sensitivity analysis can be required. It needs that input parameters used in a accident code be simplified and validated by quantifying their effects through theses analyses

[en] From different mechanical properties in highly irradiated state of high-burnup fuels, it was finalized that the regulatory fuel failure criteria for reactivity-induced accident and loss-of-coolant accident should be re-evaluated. Since it is supposed in the near future that these criteria will be set far below the current ones, one of the ways to examine the issues of the high-burnup fuels is to apply best-estimate methodology for licensing design. However, there are still many problems in the application of the methodology for licensing. This study finds out the general regulatory issues and problems in the application of the multi-dimensional approach of the core, by using RELAP5/PARCS, which is a coupled 3-dimensional core neutronics and system thermal-hydraulics code. The RELAP5/PARCS input deck was developed for a core configuration of cycle 19 with EOC of Kori unit 1. The most important process for a PARCS input deck was the way to generate macroscopic cross sections. CASMO-3 code was used for their generation. The process that macroscopic cross sections of a PARCS input are produced from a CASMO-3 output was computerized. The RELAP5/PARCS input deck developed was updated and improved by comparing the results of RELAP5 stand-alone calculation for steam line break accidents. Various sensitivity studies were carried out for break areas, safety injection setpoints, fuel classifications, and etc. It is important to understand the uncertainty of the fuel storage energy calculated from best-estimate methods. The uncertainty is clarified through the sensitivity studies. The systematic procedure to produce RELAP5/PARCS input deck would be help performing the sensitivity analysis