• Nuclear Engineering and Technology
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• v.32 no.3
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• pp.214-226
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• 2000

In an effort to assess the performance of KAERI's coupled 3D kinetics - system T/H code, MARS/MASTER, Exercise III of the OECD main steam line break benchmark is solved. The analysis model of the reference plant, TMI-1 - a 2772 MWth B&W plant, consists of three major components: a core neutronics model involving 241$\times$28 neutronic nodes, a vessel 3D T/H model consisting of 374 hydrodynamic volumes, and a 1D system T/H model containing 157 hydrodynamic volumes. The results show that there is a significant amount of flow mixing occurring in the upper and lower plenum regions and the core power distribution evolves to a highly localized shape due to the presence of a stuck rod, as well as the asymmetric flow distribution. It is judged that MARS/MASTER properly captures these drastic 3-dimensional effects. Comparisons with other results submitted to OECD confirm the accuracy of the MARS/MASTER solution.

• Nuclear Engineering and Technology
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• v.40 no.7
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• pp.593-606
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• 2008

In this study, data on radionuclide migration and retardation processes in the engineered and natural barriers of High-Level Radioactive Waste (HLW) repository have been reviewed and compiled for use in the performance assessment of a HLW disposal system in Korea. The status of the database on radionuclide migration and retardation that is being developed in Korea is investigated and summarized in this study. The solubilities of major actinides such as D, Th, Am, Np, and Pu both in Korean bentonite porewater and in deep Korean groundwater are calculated by using the geochemical code PHREEQC (Ver. 2.0) based on the KAERI-TDB(Korea Atomic Energy Research Institute-Thermochemical Database), which is under development. Databases for the diffusion coefficients ($D^b_e$ values) and distribution coefficients ($K^b_d$ values) of some radionuclides in the compacted Korean Ca-bentonite are developed based upon domestic experimental results. Databases for the rock matrix diffusion coefficients ($D^r_e$ values) and distribution coefficients ($K^r_d$ values) of some radionuclides for Korean granite rock and deep groundwater are also developed based upon domestic experimental results. Finally, data related to colloids such as the characteristics of natural groundwater colloids and the pseudo-colloid formation constants ($K_{pc}$ values) are provided for the consideration of colloid effects in the performance assessment.

• Current Optics and Photonics
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• v.3 no.3
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• pp.236-242
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• 2019

An Nd:YAG slab structure was designed for a high-power zigzag slab laser amplifier based on computational simulation of the wavefront distortion. For the simulation, the temperature distribution in the slab was calculated at first by thermal analysis. Then, the optical path length (OPL) was obtained by a ray tracing method for the corresponding refractive index variation inside the slab. After that, the OPL distribution of the double-pass amplified beam was calculated by summing the results obtained for the first and second passes. The amount of wavefront distortion was finally obtained as the peak-to-valley value of the OPL distribution. As a result of this study, the length and position of the gain medium were optimized by minimizing the transverse wavefront distortion. Under the optimized conditions, the transverse wavefront distortion of the double-pass amplified beam was less than $0.2{\mu}m$ for pump power of 14 kW.

• Journal of Radiation Industry
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• v.4 no.1
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• pp.85-89
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• 2010

The radioactive experiments are carried out for diagnosis of a variety of industrial processes in terms of the operation condition and the efficiency by measuring the residence time distribution. However, it is not easy to interpret the residence time distribution using the conventional methods when the flow rate is not constant and a number of processes are coupled in a complicated manner. In these cases, they can be analyzed by describing the system with mathematical models that can be defined with the state-space equations. In this paper, the residence time distribution of sludge was measured with a radiotracer, $^{46}Sc-EDTA$, in the digester of which the flow rate varies with time. The digester was assumed as a linear time variant system since the flow rate changed during the experiment and the operation efficiency of the digester was calculated by applying the state-spae equations.

• Journal of the Korean Society of Safety
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• v.39 no.1
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• pp.96-103
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• 2024

The demand for mass calculation of offsite consequence analysis to conduct exhaustive single-unit or multi-unit Level 3 PSA is increasing. In order to perform efficient offsite consequence analyses, the Korea Atomic Energy Research Institute is conducting model optimization studies to minimize the analysis time while maintaining the accuracy of the results. A previous study developed a model optimization method using efficient plume segmentation and verified its effectiveness. In this study, we investigated the possibility of optimizing the model through particle size distribution setting by checking the reduction in analysis time and deviation of the results. Our findings indicate that particle size distribution setting affects the results, but its effect on analysis time is insignificant. Therefore, it is advantageous to set the particle size distribution as fine as possible. Furthermore, we evaluated the effect of multithreading and confirmed its efficiency. Future optimization studies should be conducted on various input factors of offsite consequence analysis, such as spatial grid settings.

• Proceedings of the Korean Nuclear Society Conference
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• 2004.10a
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• pp.913-914
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• 2004

• Proceedings of the Korean Nuclear Society Conference
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• 2005.05a
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• pp.399-400
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• 2005

• Proceedings of the Korean Nuclear Society Conference
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• 1997.05b
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• pp.566-570
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• 1997

The effect of average gamma energy on the external radiation dose has been analyzed. Cloud- and groundshine have been calculated according to the average gamma energy. Monte Carlo integration method was used for the calculation of cloudshine and Romberg quadrature method was adopted for groundshine. The analysis shows that the external gamma exposure is strong]y dependent on the gamma energy and the distribution of radiation sources.

• Polymer(Korea)
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• v.33 no.3
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• pp.268-271
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• 2009

In this study, the distribution behaviors of the polystyrene sulfonic acid (PSSA) grafting polymer across the FEP-g-PSSA membranes prepared by a simultaneous irradiation method, were investigated by analyzing the cross-section of the membranes with a SEM-EDX instrument. The effects of irradiation conditions such as the degree of grafting, FEP film thickness, and grafting solvent on the distribution of the grafting polymer were mainly studied in this experiment. The results indicate that to obtain the evenly grafted FEP-g-PSSA membranes, the higher degree of grafting is required as the film thickness increases, and the lower dose rate are more effective than the higher dose rate at the given dose.

• Nuclear Engineering and Technology
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• v.35 no.1
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• pp.55-63
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• 2003

Threshold porosity above which fission gas release channels would be formed in the rim egion of high burnup UO$_2$ fuel was estimated by the Monte Carlo method and Hoshen-Kopelman algorithm. With the assumption that both rim pore and rim grain can be represented by cube, pore distribution in the rim was simulated 3-dimensionally by the Monte Carlo method according to porosity and pore size distribution. Then, using the Hoshen-Kopelman algorithm, the fraction of open rim pores interlinked to the outer surface of a fuel pellet was derived as a function of rim porosity. The simulation showed that porosity of 24-25% is the threshold above which the number of rim pores forming release channels increases very rapidly. On the other hand, channels would not be formed if the porosity is less than about 23.5%. This is consistent with the observation that, for porosity less than 23.5%, almost no fission gas is released in the rim. However, once the rim porosity reaches beyond 25%, extensive open paths would be developed and considerable fission gas release would start in the rim.