• Title, Summary, Keyword: Source-term

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An Approach to Estimation of Radiological Source Term for a Severe Nuclear Accident using MELCOR code (MELCOR 코드를 이용한 원자력발전소 중대사고 방사선원항 평가 방법)

  • Han, Seok-Jung;Kim, Tae-Woon;Ahn, Kwang-Il
    • Journal of the Korean Society of Safety
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    • v.27 no.6
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    • pp.192-204
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    • 2012
  • For a severe accident of nuclear power plant, an approach to estimation of the radiological source term using a severe accident code(MELCOR) has been proposed. Although the MELCOR code has a capability to estimate the radiological source term, it has been hardly utilized for the radiological consequence analysis mainly due to a lack of understanding on the relevant function employed in MELCOR and severe accident phenomena. In order to estimate the severe accident source term to be linked with the radiological consequence analysis, this study proposes 4-step procedure: (1) selection of plant condition leading to a severe accident(i.e., accident sequence), (2) analysis of the relevant severe accident code, (3) investigation of the code analysis results and post-processing, and (4) generation of radiological source term information for the consequence analysis. The feasibility study of the present approach to an early containment failure sequence caused by a fast station blackout(SBO) of a reference plant (OPR-1000), showed that while the MELCOR code has an integrated capability for severe accident and source term analysis, it has a large degree of uncertainty in quantifying the radiological source term. Key insights obtained from the present study were: (1) key parameters employed in a typical code for the consequence analysis(i.e., MACCS) could be generated by MELCOR code; (2) the MELOCR code simulation for an assessment of the selected accident sequence has a large degree of uncertainty in determining the accident scenario and severe accident phenomena; and (3) the generation of source term information for the consequence analysis relies on an expert opinion in both areas of severe accident analysis and consequence analysis. Nevertheless, the MELCOR code had a great advantage in estimating the radiological source term such as reflection of the current state of art in the area of severe accident and radiological source term.

NUMERICAL METHODS FOR RECONSTRUCTION OF THE SOURCE TERM OF HEAT EQUATIONS FROM THE FINAL OVERDETERMINATION

  • DENG, YOUJUN;FANG, XIAOPING;LI, JING
    • Bulletin of the Korean Mathematical Society
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    • v.52 no.5
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    • pp.1495-1515
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    • 2015
  • This paper deals with the numerical methods for the reconstruction of the source term in a linear parabolic equation from final overdetermination. We assume that the source term has the form f(x)h(t) and h(t) is given, which guarantees the uniqueness of the inverse problem of determining the source term f(x) from final overdetermination. We present the regularization methods for reconstruction of the source term in the whole real line and with Neumann boundary conditions. Moreover, we show the connection of the solutions between the problem with Neumann boundary conditions and the problem with no boundary conditions (on the whole real line) by using the extension method. Numerical experiments are done for the inverse problem with the boundary conditions.

Mathematical Modeling for Leaching and dissolution of Solidified Radioactive Waste in a Geologic Reposiory (지하 처분장에서의 방사성폐기물 고화체의 용출 및 용해에 대한 수학적 모형 분석)

  • Kim, Chang-Lak;Park, Kwang-Sub;Cho, Chan-Hee;Kim, Jhinwung;Suh, In-Suk
    • Nuclear Engineering and Technology
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    • v.20 no.2
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    • pp.120-131
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    • 1988
  • A souce term model describes mathematically the source of radionuclides as they begin slow migration and decay in deep groundwater. Various source term models based on mass-transfer analysis and measurement-based source term models are reviewed. Ganerally, two processes are involved in leaching or dissolution: (1) chemical reactions and (2) mass transfer by diffusion. The chemical reaction controls the dissolution rates only during the early stage of exposure to groundwater. The exterior-field mass transfer may control the long term dissolution rates from the waste solid in a geologic repository. Mass-transfer analyses re3y on detailed and careful application of the governing equations that describe the mechanistic processes of transport of material between and within phases. If used correctly, source term models based on mass-transfer theory are valuable and necessary tools for developing reliable predictions.

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NUMERICAL DIFFUSION DECREASE OF FREE-SURFACE FLOW ANALYSIS USING SOURCE TERM IN VOLUME FRACTION TRANSPORT EQUATION (볼륨비 이송방정식의 소스항을 이용한 자유수면 유동 해석의 해 확산 감소)

  • Park, Sunho;Rhee, Shin Hyung
    • Journal of computational fluids engineering
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    • v.19 no.1
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    • pp.15-20
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    • 2014
  • Accurate simulation of free-surface wave flows around a ship is very important for better hull-form design. In this paper, a computational fluid dynamics (CFD) code, termed SNUFOAM, which is based on the open source libraries, OpenFOAM, was developed to predict the wave patterns around a ship. Additional anti-diffusion source term for minimizing a numerical diffusion, which was caused by convection differencing scheme, was considered in the volume-fraction transport equation. The influence of the anti-diffusion source term was tested by applying it to free-surface wave flow around the Wigley model ship. In results, the band width of the volume fraction contours between 0.1 to 0.9 at the hull surface was narrowed by considering the anti-diffusion term.

An Improvement of Estimation Method of Source Term to the Environment for Interfacing System LOCA for Typical PWR Using MELCOR code

  • Han, Seok-Jung;Kim, Tae-Woon;Ahn, Kwang-Il
    • Journal of Radiation Protection and Research
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    • v.42 no.2
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    • pp.106-113
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    • 2017
  • Background: Interfacing-system loss-of-coolant-accident (ISLOCA) has been identified as the most hazardous accident scenario in the typical PWR plants. The present study as an effort to improve the knowledge of the source term to the environment during ISLOCA focuses on an improvement of the estimation method. Materials and Methods: The improvement was performed to take into account an effect of broken pipeline and auxiliary building structures relevant to ISLOCA. An estimation of the source term to the environment was for the OPR-1000 plants by MELOCR code version 1.8.6. Results and Discussion: The key features of the source term showed that the massive amount of fission products departed from the beginning of core degradation to the vessel breach. Conclusion: The release amount of fission products may be affected by the broken pipeline and the auxiliary building structure associated with release pathway.

Use of MAAP in Generating Accident Source Term Parameters

  • Kim, Jong-Wok;Yun, Joeng-Ik;Kang, Chang-Sun
    • Nuclear Engineering and Technology
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    • v.30 no.3
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    • pp.235-244
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    • 1998
  • The parametric model method determines the accident source term which is Presented by a set of source term parameters. In this method, the cumulative distribution of each source term parameter should be derived for its uncertainty analysis. This paper introduces a method of generating the parameters in the form of cumulative distribution using MAAP version 4.0. In MAAP, there are model parameters which could incorporate uncertain physical and/or chemical phenomena. In general, the model parameters do not have a point value but a range. In this paper, considering that, the input values of model parameters influencing each parameter are sampled using LHS. Then, the computation results are shown in cumulative distribution form. For a case study, the CDFs of FCOR and WES of Kori Unit 1 are derived. The target scenarios for the computation are the ones whose initial events are large LOCA, small LOCA and transient, respectively. It is found that the computed CDF's in this study are consistent to those of NUREG-1150 and the use of MAAP is proven to be adequate in assessing the parameters of the severe accident source term.

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Numerical Investigation of Anti-Diffusion Source Term for Free-Surface Wave Flow

  • Park, Sunho;Lee, Heebum;Rhee, Shin Hyung
    • Journal of Advanced Research in Ocean Engineering
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    • v.2 no.2
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    • pp.48-60
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    • 2016
  • Accurate simulation of free-surface wave flows around a ship is very important for better hull-form design. In this paper, a computational fluid dynamics (CFD) code which is based on the open source libraries, OpenFOAM, was developed to predict the wave patterns around a ship. Additional anti-diffusion source term for minimizing a numerical diffusion, which was caused by convection differencing scheme, was considered in the volume-fraction transport equation. The influence of the anti-diffusion source term was tested by applying it to free-surface wave flow around the Wigley and KCS model ships. In results, the wave patterns and hull wave profiles of the Wigley and KCS model ships for various anti-diffusion coefficients showed quite close patterns. While, the band width of the water volume-fraction values between 0.1 to 0.9 at the Wigley and KCS model hull surfaces was narrowed by considering the anti-diffusion term. From the results, anti-diffusion source term decreased free-surface smearing.

Verification of a tree canopy model and an example of its application in wind environment optimization

  • Yang, Yi;Xie, Zhuangning;Tse, Tim K.T.;Jin, Xinyang;Gu, Ming
    • Wind and Structures
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    • v.15 no.5
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    • pp.409-421
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    • 2012
  • In this paper, the method of introducing additional source/sink terms in the turbulence and momentum transport equations was applied to appropriately model the effect of the tree canopy. At first, the new additional source term for the turbulence frequency ${\omega}$ equation in the SST k-${\omega}$ model was proposed through theoretical analogy. Then the new source/sink term model for the SST k-${\omega}$ model was numerically verified. At last, the proposed source term model was adopted in the wind environment optimal design of the twin high-rise buildings of CABR (China Academy of Building Research). Based on the numerical simulations, the technical measure to ameliorate the wind environment was proposed. Using the new inflow boundary conditions developed in the previous studies, it was concluded that the theoretically reasonable source term model of the SST k-${\omega}$ model was applicable for modeling the tree canopy flow and accurate numerical results are obtained.

Review on the divergence form for bed slope source term and correction of the volume/free-surface relationship (발산형 바닥 경사 생성항의 재검토와 체적-수위 관계의 수정)

  • Hwang, Seung-Yong
    • Journal of Korea Water Resources Association
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    • v.50 no.5
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    • pp.289-302
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    • 2017
  • DFB (Divergence Form for Bed slope source term) was rigorously derived and the error of mDFB using mean water depth at the cell face in DFB was clearly demonstrated. In addition, DFB technique turned out to be an exact method to the bed slope source term. The existing volume/free-surface relationship to the PSC (Partially Submerged Cell) has been corrected. It was discussed that treatment for the partially submerged edge is required to satisfy the C-property in PSC. It is expected that this study will provides a more accurate means in analyzing the shallow water equations with the approximate Riemann solver.

Radiation Activity of Safety-Related Fission Products of DUPIC Fuel

  • Ryu, Ho-Jin;Park, Chang-Je;Park, Hangbok;Song, Kee-Chan
    • Proceedings of the Korean Radioactive Waste Society Conference
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    • pp.397-398
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    • 2004
  • It is important to estimate the radiation activity of the nuclear fuel which is a source term of the loss of coolant accident. The purpose of this study is to identify the most important parameters of the source term calculation based on three fuel types: typical natural uranium CANDU fuel, slightly enriched uranium and DUPIC fuel. The characteristics of the radiation source term were analyzed through sensitivity calculations of the linear power, fuel turnup, and the power shape.(omitted)

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