• Nuclear Engineering and Technology
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• 제51권7호
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• pp.1729-1737
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• 2019

This paper presents neutronics design of VVER-1000 fuel assembly using burnable poison particles (BPPs) for controlling excess reactivity and pin-wise power distribution. The advantage of using BPPs is that the thermal conductivity of BPP-dispersed fuel pin could be improved. Numerical calculations have been conducted for optimizing the BPP parameters using the MVP code and the JENDL-3.3 data library. The results show that by using $Gd_2O_3$ particles with the diameter of $60{\mu}m$ and the packing fraction of 5%, the burnup reactivity curve and pin-wise power distribution are obtained approximately that of the reference design. To minimize power peaking factor (PPF), total BP amount has been distributed in a larger number of fuel rods. Optimization has been conducted for the number of BPP-dispersed rods, their distribution, BPP diameter and packing fraction. Two models of assembly consisting of 18 BPP-dispersed rods have been selected. The diameter of $300{\mu}m$ and the packing fraction of 3.33% were determined so that the burnup reactivity curve is approximate that of the reference one, while the PPF can be decreased from 1.167 to 1.105 and 1.113, respectively. Application of BPPs for compensating the reduction of soluble boron content to 50% and 0% is also investigated.

• 방사성폐기물학회지
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• 제18권4호
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• pp.481-496
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• 2020

After nuclear power plants are permanently shut down and decommissioned, the remaining irradiated metal components such as stainless steel, carbon steel, and Inconel can be used as neutron absorber. This study investigates the possibility of reusing these metal components as neutron absorber materials, that is burnable poison. The absorption cross section of the irradiated metals did not lose their chemical properties and performance even if they were irradiated over 40-50 years in the NPPs. To examine the absorption capability of the waste metals, the lattice calculations of WH 17×17 fuel assembly were analyzed. From the results, Inconel-718 significantly hold-down fuel assembly excess reactivity compared to stainless steel 304 and carbon steel because Inconel-718 contains a small amount of boron nuclide. From the results, a 20wt% impurity of boron in irradiated Inconel-718 enhances the excess reactivity suppression. The application of irradiated Inconel-718 as a burnable absorber for SMR core was investigated. The irradiated Inconel-718 impurity with 20wt% of boron content can maintain and suppress the whole core reactivity. We emphasize that the irradiated metal components can be used as burnable absorber materials to control the reactivity of commercial reactor power and small modular reactors.

• 한국수소및신에너지학회논문집
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• 제26권2호
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• pp.96-104
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• 2015

Reactivity of commercial WGS catalyst and four new catalysts(RMC-3, PC-73, PC-67SU, PC-59) manufactured with various compositions by Korea Electric Power Research Institute(KEPCO RI) were compared to select suitable WGS catalyst for SEWGS system. Steam/CO ratio, gas velocity, flow rates of syngas, and temperature were considered as operating variables. As a result, commercial catalyst showed the highest CO conversion and RMC-3 catalyst showed also high CO conversion. Therefore, commercial and RMC-3 catalysts were selected as applicable catalysts. However, PC-73 catalyst showed low CO conversion at low temperature($200^{\circ}C$) but showed good reactivity at high temperature($225{\sim}250^{\circ}C$), and therefore, PC-73 catalyst was selected as applicable catalyst for high temperature operation. Continuous operations up to 24 hours for those three catalysts(commercial, RMC-3, PC-73) were conducted to check reactivity decay of catalysts. All three catalysts maintained their original reactivity.

• 한국환경과학회지
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• 제29권12호
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• pp.1205-1211
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• 2020

In this study, the applicability of reduction-oxidation-linked treatment was evaluated for nitrobenzene and a by-product by analyzing the reaction kinetics. Nitrobenzene showed very low reactivity to persulfate that was activated using various methods. Nitrobenzene effectively reacted through the reduction process using Zero-Valent Iron (ZVI). However, aniline, a toxic substance, was produced as a by-product. Reduction-oxidation-linked treatment is a method that can allow the oxidative degradation of aniline after reducing nitrobenzene to aniline. The experimental results show improved reactivity and complete decomposition of the by-product. Improved reactivity and decomposition of the by-product were observed even under conditions in which the reduction-oxidation reaction was induced simultaneously. No activator was injected for persulfate activation in the process of reducing oxidant linkage, and the activation reaction was induced by ferrous iron eluted from the ZVI. This indicates that this method can be implemented relatively simply.

• Nuclear Engineering and Technology
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• 제54권4호
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• pp.1526-1533
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• 2022

Small modular reactors have garnered considerable attention in the recent years. Plate fuel elements exhibit a good application prospect in small modular pressurized water reactors for marine applications. Further, improved economic benefits can be achieved by extending the core lifetime of small modular reactors. However, it is necessary to realize a large initial residual reactivity for achieving a relatively long burnup depth finally. Thus, the selection of a suitable burnable poison (BP) is a crucial factor that should be considered in the design of small modular reactors. In this study, some candidate BPs are selected to realize the effective control of reactivity. The results show that ²³¹Pa₂O₃, ²⁴⁰Pu₂O₃, ¹⁶⁷Er₂O₃, PACS-J, and PACS-L are ideal candidates of BP, and since the characteristics of BP can increase the final burnup depth of assembly, the economic benefits are gained. Additionally, an optimal combination scheme of BPs is established. Specifically, it is proved that through a reasonable combination of BPs, a low reactivity fluctuation during the lifetime can be achieved, leading to a large final burnup depth.

• 시스템엔지니어링학술지
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• 제19권2호
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• pp.46-58
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• 2023

Deterministic safety analysis is a crucial part of safety assessment, particularly when it comes to demonstrating the safety of nuclear power plant designs. The traditional approach to deterministic safety analysis models is to model the nuclear core using point kinetics. However, this simplified approach does not fully reflect the real core behavior with proper moderator and fuel reactivity feedbacks during the transient. The use of Multi-Physics approach allows more precise simulation reflecting the inherent three-dimensionality (3D) of the problem by representing the detailed 3D core, with instantaneous updates of feedback mechanisms due to changes of important reactivity parameters like fuel temperature coefficient (FTC) and moderator temperature coefficient (MTC). This paper addresses a CEA ejection accident at hot full power (HFP), in which the underlying strong and un-symmetric feedback between thermal-hydraulics and reactor kinetics exist. For this purpose, a multi-physics analysis tool has been selected with the nodal kinetics code, 3DKIN, implicitly coupled to the thermal-hydraulic code, RELAP5, for real-time communication and data exchange. This coupled approach enables high fidelity three-dimensional simulation and is therefore especially relevant to reactivity initiated accident (RIA) scenarios and power distribution anomalies with strong feedback mechanisms and/or un-symmetrical characteristics as in the CEA ejection accident. The Systems Engineering approach is employed to provide guidance in developing the work in a systematic and efficient fashion.

• Nuclear Engineering and Technology
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• 제56권3호
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• pp.1022-1028
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• 2024

A neutronics study of a supercritical CO₂-cooled fast reactor core for nuclear propulsion has been performed in this work. The thermal power of the reactor core is 30 MWth and a ceramic UO₂ fuel can be used to achieve a 20-year lifetime without refueling. In order to make a compact core with inherent safety features, the drum-type reactivity control system and folding-type shutdown system are adopted. In addition, we suggest a cold shutdown system using gadolinium as a spectral shift absorber (SSA) against flooding. Although there is a penalty of U-235 enrichment for the core embedded with the cold shutdown system, it effectively mitigates the increment of reactivity at the flooding of seawater. In this study, the neutronics analyses have been performed by using the continuous energy Monte Carlo Serpent 2 code with the evaluated nuclear data file ENDF/B-VII.1 Library. The supercritical CO₂-cooled fast reactor core is characterized in view of important safety parameters such as the reactivity worth of reactivity control systems, fuel temperature coefficient (FTC), coolant temperature coefficient (CTC), and coolant temperature-density coefficient (CTDC). We can say that the suggested core has inherent safety features and enough flexibility for load-following operation.

• Nuclear Engineering and Technology
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• 제56권3호
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• pp.900-906
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• 2024

The Passively-Cooled Molten Salt Fast Reactor (PMFR) is one of the advanced design concepts of the Molten Salt Fast Reactor (MSFR) which utilizes a natural circulation for the primary loop and aims to attain a long-life operation without any means of fuel reprocessing. For an extended operation period, it is necessary to have enough fissile material, i.e., high excess reactivity, at the onset of operation. Since the PMFR is based on a fast neutron spectrum, direct implementation of a burnable absorber concept for the control of excess reactivity would be ineffective. Therefore, a localized moderator concept that encircles the active core has been envisioned for the PMFR which enables the effective utilization of a burnable absorber to achieve low reactivity swing and long-life operation. The modified PMFR design that incorporates a moderator and burnable absorber is presented, where depletion calculation is performed to estimate the reactor lifetime and reactivity swing to assess the feasibility of the proposed design. All the presented neutronic analysis has been conducted based on the Monte Carlo Serpent2 code with ENDF/B-VII.1 library.

• 대한본초학회지
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• 제20권4호
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• pp.69-76
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• 2005

Objectives : HERBA EPHEDRAE (HE) has been used cough and asthma for long time in korea. In the present study, we examined the effect HE on the ovalbumin (OVA)-induced airway hyper-reactivity (AHR). Methods : To examine the effect of HE on AHR, mice were sensitized with 100 mg of OVA and 1mg of alum intraperitoneally on day 0 and 14. On day 28, mice were challenged on 3 consecutive days with 3% OVA and AHR was assessed 24 h after the last challenge. To examine severity of airway hyper-reactivity, we examined eosinophil population and cytokine production in bronchoaveloar lavage fluid(BALF) and stained with hematoxylin and eosin in lung. Results : HE potently inhibited the development of airway hyper-reactivity and also reduced the number of eosinophil during OVA-induced airway hyper-reactivity. HE also inhibited cytokines production such as IL-4, IL-5, IL-13 in BALF. Furthermore, HE inhibited proliferation of eosinophil in a dose dependent manner. Conclusions : These results suggest that HE may be beneficial oriental medicine for AHR.

• 폴리머
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• 제24권2호
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• pp.168-173
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• 2000

자유 라디칼 개시제인 2,2'-azobisisobutyronitrile (AIBN)을 사용하여 1,4-dioxane 용매하에서 N-isopropylacrylamide (NIPAAM)와 methyl methacrylate (MMA)를 공중합하였다. 온도에 따른 NIPAAM과 MMA의 반응성비를 알아보기 위해 각각 50, 60, 7$0^{\circ}C$에서 중합하여 전환율이 10 wt%이하가 되도록 반응을 정지시켰다. 단량체 반응성비는 Finemann-Ross법으로 구하였으며, 그 값은 5$0^{\circ}C$에서는 ${\gamma}$$_2$=0.259, ${\gamma}$$_2$=2.782, 6$0^{\circ}C$에서는 ${\gamma}$$_1$=0.271, ${\gamma}$$^2$=0.819, 그리고 7$0^{\circ}C$에서는 ${\gamma}$$_1$=0.286, ${\gamma}$$_2$=2.915로 나타나, 반응온도가 높아질수록 ${\gamma}$$_1$, ${\gamma}$$_2$ 값이 증가함을 알 수 있었다. 또한 반응온도와 반응성비와의 관계로부터 활성화에너지의 차를 구할 수 있었으며, 그 결과 반응성비는 온도 의존성이 있는 것으로 나타났다.