• Nuclear Engineering and Technology
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• v.54 no.7
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• pp.2690-2701
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• 2022

In this paper, we select important fission products for the estimation of the source term during a severe accident of a PWR. The selection is based on the numerical results obtained from depletion calculations for the typical PWR fuel via the in-house code named DEGETION (Depletion, Generation, and Transmutation of Isotopes on Nuclear Application), release fractions of the fission products derived from NUREG-1465, and effective dose conversion coefficients from ICRP 119. Then, for the selected fission products, we obtain the adjoint solutions of the Bateman equations for radioactive decay in order to determine the importance of precursors producing the aforementioned fission products via radioactive decay, which would provide insights into the assumption used in MACCS 2 for a level 3 PSA analysis in which up to six precursors are considered in the calculations of radioactive decays for the fission product after release from the reactor.

• Nuclear Engineering and Technology
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• v.56 no.8
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• pp.2990-2998
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• 2024

In ITER, the evaluation of the activated water radiation source and its impact on the radiological levels is necessary to demonstrate compliance with the safety requirements. The use of simplified or conservative approaches often results in the application of expensive constraints on the installation that impact its economics, operations, and construction schedule. In this work, we propose a novel methodology to calculate the activated water source term with a higher degree of realism. The methodology is based on the coupling of a system-level code with a Computational Fluid Dynamics (CFD) code in an explicit, one-way approach. We apply this methodology to the evaluation of the16N radioisotope within the ITER Vacuum Vessel Primary Heat Transfer System (VV-PHTS) cooling circuit in a steady-state and transient scenarios. We chose this system since previous analyses of the VV-PHTS were done with simple, ad-hoc calculations that yielded results that differed by up to a factor of five, underscoring a higher level of uncertainty. As a result, we generate a computational model of the source term that can be used to evaluate the radiological condition surrounding the cooling systems during the operations.

• Proceedings of the Korean Nuclear Society Conference
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• 2002.05a
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• pp.172-172
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• 2002

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2012.10a
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• pp.127-128
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• 2012

• Nuclear Engineering and Technology
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• v.43 no.6
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• pp.583-592
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• 2011

The radiological characteristics for waste classification were assessed for neutron-activated decommissioning wastes from a CANDU reactor. The MCNP/ORIGEN2 code system was used for the source term analysis. The neutron flux and activation cross-section library for each structural component generated by MCNP simulation were used in the radionuclide buildup calculation in ORIGEN2. The specific activities of the relevant radionuclides in the activated metal waste were compared with the specified limits of the specific activities listed in the Korean standard and 10 CFR 61. The time-average full-core model of Wolsong Unit 1 was used as the neutron source for activation of in-core and ex-core structural components. The approximated levels of the neutron flux and cross-section, irradiated fuel composition, and a geometry simplification revealing good reliability in a previous study were used in the source term calculation as well. The results revealed the radioactivity, decay heat, hazard index, mass, and solid volume for the activated decommissioning waste to be $1.04{\times}10^{16}$ Bq, $2.09{\times}10^3$ W, $5.31{\times}10^{14}\;m^3$-water, $4.69{\times}10^5$ kg, and $7.38{\times}10^1\;m^3$, respectively. According to both Korean and US standards, the activated waste of the pressure tubes, calandria tubes, reactivity devices, and reactivity device supporters was greater than Class C, which should be disposed of in a deep geological disposal repository, whereas the side structural components were classified as low- and intermediate-level waste, which can be disposed of in a land disposal repository. Finally, this study confirmed that, regardless of the cooling time of the waste, 15% of the decommissioning waste cannot be disposed of in a land disposal repository. It is expected that the source terms and waste classification evaluated through this study can be widely used to establish a decommissioning/disposal strategy and fuel cycle analysis for CANDU reactors.

• Journal of Environmental Science International
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• v.9 no.1
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• pp.57-64
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• 2000

The sensitivity analysis of two short-term models (ISCST3, INPUFF2.5) is performed to improve the model accuracy. It appears that the sensitivities on the changes of wind speed, stack height and stack inner diameter in the near distance from source, stability and mixing height in the remote distance form source, are significant. Also the gas exit velocity, stack inner diameter, gas temperature and air temperature which affect the plume rise have some effects on the concentration values of each model within the downwind distance where final plume rise is determined. And in modeling for the atmospheric dispersion of point pollutant source INPUFF2.5 can calculate amount, trajectory of puff and concentration versus time at each receptors. So, it is compatible to analyze distribution of point pollutants concentration at modeling area.

• Journal of Microbiology
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• v.45 no.3
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• pp.205-212
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• 2007

Anoxygenic photosynthesis, performed primarily by anoxygenic photosynthetic bacteria (APB), has been supposed to arise on Earth more than 3 billion years ago. The long established APB are distributed in almost every corner where light can reach. However, the relationship between APB phylogeny and source environments has been largely unexplored. Here we retrieved the pufM sequences and related source information of 89 pufM containing species from the public database. Phylogenetic analysis revealed that horizontal gene transfer (HGT) most likely occurred within 11 out of a total 21 pufM subgroups, not only among species within the same class but also among species of different phyla or subphyla. A clear source environment feature related phylogenetic distribution pattern was observed, with all species from oxic habitats and those from anoxic habitats clustering into independent subgroups, respectively. HGT among ancient APB and subsequent long term evolution and adaptation to separated niches may have contributed to the coupling of environment and pufM phylogeny.

• Journal of applied mathematics & informatics
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• v.26 no.1_2
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• pp.1-14
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• 2008

In this paper, A Riesz fractional diffusion equation with a nonlinear source term (RFDE-NST) is considered. This equation is commonly used to model the growth and spreading of biological species. According to the equivalent of the Riemann-Liouville(R-L) and $Gr\ddot{u}nwald$-Letnikov(G-L) fractional derivative definitions, an implicit difference approximation (IFDA) for the RFDE-NST is derived. We prove the IFDA is unconditionally stable and convergent. In order to evaluate the efficiency of the IFDA, a comparison with a fractional method of lines (FMOL) is used. Finally, two numerical examples are presented to show that the numerical results are in good agreement with our theoretical analysis.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.5 no.3
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• pp.173-181
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• 1993

An improved two-dimensional Eulerian-Lagrangian convection-dispersion model was established after comparing several models. To simulate long term release of discontinuous suspended solid source from coastal dike construction, source was represented by Fourier transformation. It was concluded that this model can effectively simulate long term coastal dispersion problems.

• Journal of the Korean Operations Research and Management Science Society
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• v.33 no.4
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• pp.13-30
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• 2008

We explore the determinants of long-term relationship between the buyer and the supplier to help suppliers develope a strategy to build long-term relationship with their buyers. Based upon an extensive literature review, we propose three droops of independent variables which may affect long-term relationship, including (a) environmental factors (product complexity, product importance, source dependence, price sensitivity), (b) relational factors(trust, commitment, satisfaction, intention of expansion), (c) operational performance(quality, delivery, cost capability, technical knowhow). The buyer's actual period of relationship with its main supplier is used as a dependent variable. Using hierarchical multiple regression analysis, we empirically test hypotheses, analysing a sample of 290 manufacturing firms in the U.S. The statistical results indicate that the buyer's source dependence, price sensitivity and the supplier's commitment play a significant role in establishing long-term relationship between the buyer and the supplier. However, the supplier's cost capability and technical knowhow in operational performance negatively affect long-term relationship in contrast with our hypotheses. Due to this controversial result, we divide the sample group Into dual sourcing and multiple sourcing environments and reconduct regression analysis in a post hoc manner. The findings show that the supplier's cost capability and technical knowhow are negatively associated with the length of relationship only in the multiple sourcing environment. The results may confirm that both parties' opportunistic behavior is more salient in the multiple sourcing environment than in the single sourcing environment.