• Nuclear Engineering and Technology
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• v.53 no.4
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• pp.1079-1087
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• 2021

NTP-ERSN is a package developed for solving the multigroup form of the discrete ordinates, characteristics and collision probability of the Boltzmann transport equation in one-dimensional cartesian geometry, by combining pin cells. In this work, C5G7 MOX benchmark is used to verify the accuracy and efficiency of NTP-ERSN package, by treating reactor core problems without spatial homogenization. This benchmark requires solutions in the form of normalized pin powers as well as the vectors and the eigenvalue. All NTP-ERSN simulations are carried out with appropriate spatial and angular approximations. A good agreement between NTP-ERSN results with those obtained with OpenMC calculation code for seven energy groups. In addition, our studies about angular and mesh refinements are carried out to produce better quality solution. Moreover, NTP-ERSN GUI has also been updated and adapted to python 3 programming language.

• Nuclear Engineering and Technology
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• v.53 no.7
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• pp.2151-2161
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• 2021

Nuclear data (ND) sensitivity and uncertainty (S/U) quantification in shielding applications is performed using deterministic and probabilistic approaches. In this paper the validation of the newly developed deterministic program package ASUSD (ADVANTG + SUSD3D) is presented. ASUSD was developed with the aim of automating the process of ND S/U while retaining the computational efficiency of the deterministic approach to ND S/U analysis. The paper includes a detailed description of each of the programs contained within ASUSD, the computational workflow and validation results. ASUSD was validated on two shielding benchmark experiments from the Shielding Integral Benchmark Archive and Database (SINBAD) - the fission relevant ASPIS Iron 88 experiment and the fusion relevant Frascati Neutron Generator (FNG) Helium Cooled Pebble Bed (HCPB) Test Blanket Module (TBM) mock-up experiment. The validation process was performed in two stages. Firstly, the Denovo discrete ordinates transport solver was validated as a standalone solver. Secondly, the ASUSD program package as a whole was validated as a ND S/U analysis tool. Both stages of the validation process yielded excellent results, with a maximum difference of 17% in final uncertainties due to ND between ASUSD and the stochastic ND S/U approach. Based on these results, ASUSD has proven to be a user friendly and computationally efficient tool for deterministic ND S/U analysis of shielding geometries.

• Nuclear Engineering and Technology
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• v.25 no.1
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• pp.51-62
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• 1993

A computational program ［TDET］ of the particle transport equation is developed on radiation shielding problem in two-dimensional cartesian geometry based on the discrete element method. Not like the ordinary discrete ordinates method, the quadrature set of angles is not fixed but steered by the spatially dependent angular fluxes. The angular dependence of the scattering source term in the particle transport equation is described by series expansion in spherical harmonics, and the energy dependence of the particles is considered as well. Three different benchmark tests are made for verification of TDET : For the ray effect analysis on a square absorber with a flat isotropic source, the results of TDET calculation are quite well conformed to those of MORSE-CG calculation while TDET ameliorates the ray effect more effectively than S$_{N}$ calculation. In the analysis of the streaming leakage through a narrow vacuum duct in a shield, TDET shows conspicuous and remarkable results of streaming leakage through the duct as well as MORSE-CG does, and quite better than S$_{N}$ calculation. In a realistic reactor shielding situation which treats in two cases of the isotropic scattering and of linearly anisotropic scattering with two groups of energy, TDET calculations show local ray effect between neighboring meshes compared with S$_{N}$ calculations in which the ray effect extends broadly over several meshes.eshes.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.2
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• pp.215-226
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• 2003

Experimental and numerical studies have been done to examine the effects of excess air ratio and tertiary air swirl number on the formation characteristics of NOx in a pilot scale combustor adopting a multi-air staged burner. In numerical calculation the mathematical models for turbulence, radiation and nitric oxide chemistry were taken into account. The radiative transfer equation was solved using the discrete ordinates method with the weighted sum of gray gases model. In the NOx chemistry model, the chemical reaction rates for thermal and prompt NOx were statistically averaged using a probability density function. The results were validated by comparison with measurements. For the experiment, a 0.2 MW pilot multi-staged air burner has been designed and fabricated. Using the numerical simulation developed here, a variation of thermal and prompt NOx formation was predicted by changing the excess air ratio and tertiary air swirl number. As the excess air ratio increased up to 1.9, the formation of the total as well as thermal NOx at exit increased while the prompt NOx decreased. The formation of thermal NOx was more affected by concentration of $O_2$ and $N_2$ than gas temperature. When the tertiary air swirl number increased, the formation of the total as well as the prompt NOx slightly decreased.

• Fire Science and Engineering
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• v.15 no.1
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• pp.7-15
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• 2001

This paper describes the smoke filling process of a fire field model based on a self-developed SMEP (Smoke Movement Estimating Program) codo to the simulation of fire induced flows in the atrium space (SIVANS atrium at Japan) containing smoke radiation effect. The SMEP using PISO algorithm solves conservation equations for mass, momentum, energy and species, together with those for the modified k-$\varepsilon$ turbulence model with buoyancy term. Also it solves the radiation equation using the discrete ordinates method. The result of the calculated smoke temperature containing radiation effect has shown a better prediction than the result calculated by only convection effect in comparison with the experimental data. This seems to come from the radiation effect of $H_2$O and $CO_2$ gas under smoke productions. Thus, the consideration of the radiation effect under smoke in fire should be necessary in order to get more realistic result. Also the numerical results indicated that the smoke layer is developing at a rate of about 0.1 m/s. It would take about 450 seconds after starting the ultra fast fire of 560 kW that the smoke layer move down to 1.5m above the escape level.

• Fire Science and Engineering
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• v.11 no.1
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• pp.21-35
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• 1997

The natural convection and combined heat transfer induced by fire in a rectangular enclosure is numerically studied. The model for this numerical analysis is partially opened right wall. The solution procedure includes the standard k-$\varepsilon$ model for turbulent flow and the discrete ordinates method (DOM) is used for the calculation of radiative heat transfer equation. In numerical study, SIMPLE algorithm is applied for fluid flow analysis, and the investigations of combustion gas induced by fire is performed by FAST model of HAZARD I program. In this study, numerical simulation on the combined naturnal convection and radiation is carried out in a partial enclosure filled with absorbed-emitted gray media, but is not considered scattering problem. The streamlines, isothermal lines, average radiation intensity and kinetic energy are compared the results of pure convection with those of the combined convection-radiation, the combined heat transfer. Comparing the results of pure convection with those of the combined convection-radiation, the combined heat transfer analysis shows the stronger circulation than those of the pure convection. Three different locations of heat source are considered to observe the effect of heat source location on the heat transfer phenomena. As the results, the circulation and the heat transfer in the left region from heating block are much more influenced than those in the right region. It is also founded that the radiation effect cannot be neglected in analyzing the building in fire. And as the results of combustion gas analysis from FAST model, it is found that O2 concentration is decreased according to time. While CO and CO2 concentration are rapidly increased in the beginning(about 100sec), but slowly decreased from that time on.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.11
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• pp.1594-1605
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• 2001

In this study, a numerical simulation was developed which was capable of predicting the characteristics of NO formation in pilot scale combustor adopting the air-staged burner flame. The numerical calculation was constructed by means of establishing the mathematical models fur turbulence, turbulent combustion, radiation and turbulent nitric oxide chemistry. Turbulence was solved with standard k-$\xi$ model and the turbulent combustion model was incorporated using a two step reaction scheme together with an eddy dissipation model. The radiative transfer equation was calculated by means of the discrete ordinates method with the weighted sum of gray gases model for CO$_2$and H$_2$O. In the NO chemistry model, the chemical reaction rates for thermal and prompt NO were statistically averaged using the $\beta$ probability density function. The results were validated by comparison with measurements. For the experiment, a 0.2 MW pilot multi-air staged burner has been designed and fabricated. Only when the radiation was taken into account, the predicted gas temperature was in good agreement with the experimental one, which meant that the inclusion of radiation was indispensable for modeling multi-air staged gas flame. This was also true of the prediction of the NO formation, since it heavily depended on temperature. Subsequently, it was found that the multi-air staged combustion technique might be used as a practical tool in reducing the NO formation by controlling the peak flame temperature.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.4
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• pp.600-609
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• 2001

WSGGM based low-resolution spectral model for calculating radiation transfer in combustion gases is applied to estimate self-absorption of radiation energy in one-dimensional opposed flow flames. Development of such a model is necessary in order to enable detailed chemistry-radiation interaction calculations including self-absorption. Database of band model parameters which can be applied to various one-dimensional opposed flow diffusion and partially premixed flames is created. For the validation of the model and database, low resolution spectral intensities at fuel exit side are calculated and compared with the results of a narrow band model with those based on the Curtis-Godson approximation. Good agreements have been found between them. The resulting radiation model is coupled to the OPPDIF code to calculate the self-absorption of radiant energy and compared with the results of an optically thin calculation and the results of a discrete ordinates method in conjunction with the statistical narrow band model. Significant self-absorption of radiation is found for the flames considered here particularly for the fuel side of the reacting zone. However, the self-absorption does not have significant effects on the flame structure in this case. Even in the case of the low velocity diffusion flame and the partially premixed flame of low equivalence ratio, the effects of self-absorption of radiation on the flame temperature and production of minor species are not significant.

• Fire Science and Engineering
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• v.14 no.3
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• pp.6-12
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• 2000

This paper describes the smoke movement of a fire field model based on a self-developed SMEP(Smoke Movement Estimating Program) code to the simulation of fire induced flows in the two types of compartment space containing the radiation effect under smoke movement in room fire. The SMEP using PISO algorithm solves conservation equations for mass, momentum, energy and species, together with those for the modified k-$\varepsilon $ turbulence model with buoyancy term. Also it solves the radiation equation using the discrete ordinates method. The result of the calculated smoke temperature containing radiation effect has shown reasonable agreement compared with the experimental data. On the other hand, a difference of a lot was found between the temperature predicted by the SMEP with only convection effect and obtained by the experimental result. This seems to come from the radiation effect of $H_2$O and $CO_2$ gas under smoke productions. Thus, the consideration of the radiation effect under smoke in fire may be necessary in order to produce more realistic result.

• Nuclear Engineering and Technology
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• v.14 no.4
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• pp.196-203
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• 1982

To transport the spent fuel assemblies of Korea Nuclear Unit 1, which is a Westinghouse type two loop pressurized water reactor, it has been found that steel is the most appropriate material for the design of a shipping cask in comparison with lead and depleted uranium. The proposed shipping cask will transport nine fuel assemblies at the same time and is well within the weight limit of transportation by unrestricted rail car. The cask requires 33cm thick steel shield and 27cm thick water region to satisfy the 3 feet apart dose rate limit set forth in 10 CFR 71, and 1.27cm thick steel boron fuel basket to hold the fuel elements inside the cask and control the effective multiplication factor. As a safety analysis, the fuel cladding and centerline temperatures were calculated under the accident condition of complete loss of water coolant, and it was found that the temperature was much lower than the limit of the melting point. k$_{eff}$ was calculated with fresh fuel assemblies, which was found to be well lower than 0.95. For shielding computation, the multipurpose Monte Carlo code MORSE-CG and one dimensional discrete ordinates transport code ANISN were used, and the Monte Carlo codes KENO and MORSE-CG were used for criticality calculation. The radiation source terms were calculated using ORIGEN-79.9.