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Novel concept for a filtered containment venting system with an ionic liquid to remove organic iodine (2) - decomposition mechanism of an ionic liquid by heat and gamma-ray irradiation

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JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY 2025年第6期62卷 582-591页

作者： Fukui, Sohei Wada, Yoichi Ishida, Kazushige Tominaga, Kazuo Hitachi GE Nucl Energy Ltd Nucl Plant Engn Dept 3-1-1 Saiwai Cho Hitachi Ibaraki 3170073 Japan

A filtered containment venting system (FCVS) is being developed using an ionic liquid (IL), trihexyltetradecylphosphonium chloride ([P66614][Cl]), as a measure to reduce the release of radioactive organic iodine during severe accidents at nuclear power plants. To investigate the decomposition mechanism of [P66614][Cl] in alkaline solution (AS) contained in the FCVS and its temperature dependence under gamma-ray irradiation, a qualitative evaluation was conducted by varying the temperature in both irradiation and non-irradiation tests. In a comparison for 0.1 MGy absorbed dose at 433 K with the non-irradiation test condition, the concentrations of irradiated and non-irradiated [P66614][Cl] were almost the same values. It was confirmed that irradiation had a minimal impact on [P66614][Cl] decomposition. Decomposition of [P66614][Cl] primarily occurred through hydrolysis via its reaction with OH- in the AS at 433 K. At higher NaOH concentrations, hydrolysis converted [P66614] into an intermediate, phosphonium acid in the first stage. It was then converted into phosphine oxide which led to an increased amount of these hydrolysates. The decontamination factor (DF) decreased due to the formation of phosphine oxide, but it is possible to achieve a high DF by controlling the amount of phosphine oxide formed by optimizing the NaOH concentration of AS.

关键词： Accident management filtered containment venting system ionic liquid

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Effects of the operating strategies of filtered containment venting system on Cesium-137 releases during severe accidents

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ANNALS OF NUCLEAR ENERGY 2019年 127卷 469-478页

作者： Lee, Eun-Hye Kim, Hoe-Yeol Bang, Jungjin Jerng, Dong-Wook Kim, Tae Woon Chung Ang Univ Sch Energy Syst Engn 84 Heukseok Ro Seoul South Korea Korea Atom Energy Res Inst 98-1-1 Daedeok Daero Daejeon South Korea

The concept of filtered containment venting system (FCVS) has been adopted in the Republic of Korea for Pressurized Heavy Water Reactors to prevent over-pressurization of containment and to reduce the amount of radionuclides released to the environment. This strategy is considered suitable for Pressurized Light Water Reactors as well. As the effects of the FCVS on depressurization and decontamination differ, depending not only on nuclear power plant type but also on accident scenarios and venting strategies, this study analyzes the effects of FCVS operating strategies and accident scenarios on Cesium (Cs) release during severe accidents. Conservatively, the most extreme accident scenarios are chosen, namely, Station Blackout and Loss of Coolant Accident, without any mitigating measures except for the safety injection tank. Continuous and cyclic operation of the FCVS are investigated as operating strategies. In conclusion, installation of the FCVS allows the plant to meet the regulatory requirements, limiting the release of Cs-137 to under 100 TBq for limiting cases such as those considered here. Operating the FCVS to open at higher pressure in cyclic mode is found to be more effective in reducing the amount of Cs-137 release to the environment. (C) 2018 Elsevier Ltd. All rights reserved.

关键词： filtered containment venting system Cesium-137 release MELCOR Severe accident

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Removal of iodine by dry adsorbents in filtered containment venting system after 10 years of Fukushima accident

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ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH 2023年第30期30卷 74628-74670页

作者： Ahad, Jawaria Ahmad, Masroor Farooq, Amjad Waheed, Khalid Irfan, Naseem Pakistan Inst Engn & Appl Sci Dept Nucl Engn Islamabad Pakistan

Radioactive iodine is a hazardous fission product and a major concern for public health. Special attention is paid to iodine out of 80 fission products because of its short half-life of 8.02 days, high activity, and potential health hazards like its irreversible accumulation in thyroid gland and ability to cause thyroid cancer locally. Radioactive iodine can get released in the form of aerosols (cesium iodide), elemental iodine, and organic iodide after a nuclear accident and can cause off-site and on-site contamination. filtered containment venting system (FCVS) is a safety system whose main objective is mitigation of severe accidents via controlled venting and removal of different forms of iodine to ensure safety of people and environment. After nuclear accidents like Fukushima, extensive research has been done on the removal of iodine by using dry scrubbers. This review paper presents research status of iodine removal by dry adsorbents especially after 10 years of Fukushima to assess the progress, research gap, and challenges that require more attention. A good adsorbent should be cost-effective;it should have high selective adsorption towards iodine, high thermal and chemical stability, and good loading capacity;and its adsorption should remain unaffected by aging and the presence of inhibitors like CO, NO2, CH3Cl, H2O, and Cl-2 and radiation. Research on different dry adsorbents was discussed, and their capability as a potential filter for FCVS was reviewed on the basis of all the above-mentioned features. Metal fiber filters have been widely used for removal of aerosols especially micro- and nanoscale aerosols. For designing a metal fiber filter, optimal size or combination of sizes of fibers, number of layers, and loading capacity of filter should be decided according to feasibility and requirement. Balance between flow resistance and removal efficiency is also very important. Sand bed filters were successful in retention of aerosols, but they showed low trap

关键词： Iodine removal Environmental safety Removal of hazardous gases Dry adsorbents Dry scrubbers filtered containment venting system Porous adsorbents Fukushima Accident

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A Scaling Analysis for a filtered containment venting system

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NUCLEAR TECHNOLOGY 2016年第1期195卷 29-43页

作者： Song, Jin Ho Jo, Hyun-Joung Ha, Kwang Soon Jung, Jaehoon An, Sang Mo Kim, Hwan Yeol Revankar, S. T. Korea Atom Energy Res Inst 989-111 Daedeok Daero Daejeon 34057 South Korea Chungnam Natl Univ 99 Daehak Ro Daejeon 34134 South Korea Purdue Univ Sch Nucl Engn W Lafayette IN 47907 USA

A scaling method is proposed for the design of a reduced-scale experimental facility for testing the performance of a newly proposed filtered containment venting system (FCVS). A full-height facility at prototypic pressure and temperature conditions is chosen to preserve the fundamental physics such as depressurization rate, two-phase mixture level, and scrubbing process. The geometrical similarities in terms of the ratio of the cross-sectional area and geometric and frictional loss coefficient are preserved for each component in the FCVS. Scaling of the number of components in the reduced-scale test facility is suggested using the prototypic components of the FCVS including a venturi scrubber, a cyclone, a metal fiber filter, and a molecular sieve. This approach minimizes scaling distortions. A properly scaled test facility allows testing in a wide range of initial and boundary conditions such that it can predict the full performance of the prototypic FCVS.

关键词： filtered containment venting system scaling analysis aerosols

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Novel concept for a filtered containment venting system with an ionic liquid to remove organic iodine (1)-proof of concept for organic iodine removal

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JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY 2023年第12期60卷 1563-1572页

作者： Fukui, Sohei Ishida, Kazushige Tanaka, Motoi Tominaga, Kazuo Hitachi GE Nucl Energy Ltd Hitachi Works 3-1-1 Saiwaicho Hitachi 3178511 Japan

Ionic liquid (IL) as a chemical adsorbent used in a filtered containment venting system (FCVS) in a nuclear power plant was considered as a new mitigation method for radioactive organic iodine release in the event of a severe accident. In order to demonstrate proof of concept (PoC) for organic iodine removal with the IL, we evaluated the decontamination factor (DF) of the IL for the organic iodine at various temperatures as an index of removal performance. As a removal mechanism for organic iodine with the IL, it was assumed that the anions function to decompose organic halides such as by a Williamson ether synthesis reaction. We evaluated DF for organic iodine using the IL containing thiosulfate ions and while controlling temperature and residence time as changeable parameters. We determined the DF of the IL for the organic iodine was more than 100 in the temperature range from 393 to 433 K and residence time of 0.1 s or longer. The allowable chemical adsorption weight of organic iodine was 5.9 g kg-IL-1. It was concluded that IL was a possible candidate as an organic iodine adsorbent for a next-generation FCVS.

关键词： Severe accident iodine accident management filtered vent filtered containment venting system ionic liquid decontamination factor

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The Hydrogen Issue in the Initial Operation of a filtered containment venting system

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NUCLEAR TECHNOLOGY 2016年第3期195卷 329-334页

作者： Na, Young Su Cho, Song-Won Ha, Kwang Soon Korea Atom Energy Res Inst 989-111 Daedeok Daero Daejeon 305353 South Korea

This study evaluated the hydrogen issue in the initial operation of a filtered containment venting system (FCVS). We calculated the volumetric concentration of hydrogen, steam, and air in the postulated FCVS connected with the OPR 1000, as a target nuclear power plant, under a station blackout using the MELCOR computer code (version 1.8.6). A large amount of steam and a flammable mixture generated during a severe accident are immediately released from the containment building to the FCVS when the pressure in the containment building approaches a set value. The constituent ratio of the flammable mixture of hydrogen, steam, and air can change due to the different thermal-hydraulic conditions between those due to a severe accident in the containment building and the initial condition in the FCVS. The volumetric concentration of hydrogen was 6% in the containment building just before the operation of the FCVS. It increased up to 9% in the FCVS vessel during the early operation, and steam condensation occurred simultaneously. The atmospheric condition including steam, hydrogen, and air in the FCVS can enter the combustion zone in the Shapiro diagram.

关键词： filtered containment venting system severe accident hydrogen

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Performance of bubble column for iodine removal in a lab scale setup of filtered containment venting system

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PROGRESS IN NUCLEAR ENERGY 2023年 159卷

作者： Ahad, Jawaria Farooq, Amjad Ahmad, Masroor Waheed, Khalid Qureshi, Kamran Rasheed Siddique, Waseem Irfan, Naseem Pakistan Inst Engn & Appl Sci Dept Nucl Engn Islamabad Pakistan Pakistan Inst Engn & Appl Sci Dept Mech Engn Islamabad Pakistan

Iodine is one of the most hazardous fission products that can get released into environment after a severe nuclear accident and can cause thyroid cancer. Removal of iodine is necessary to ensure safety of people and environ-ment. Different experiments were performed in a lab scale setup of FCVS containing a bubble column. Purpose of this research was to understand the mechanism involved in wet scrubbing in order to improve the removal ef-ficiency of iodine. Influence of many parameters such as gas flowrate, liquid level height, gas holdup, additives, bubble diameter etc. on retention of iodine was studied. Results showed major dependance of decontamination factor on gas flowrate and liquid level height. Bubble diameter was observed to be dependent on gas flowrate, viscosity of liquid and density of liquid and gas. Decrease in bubble diameter was observed with increase in superficial gas velocity which enhanced overall mass transfer and hence, removal efficiency was increased as well. Overall, greater than 99.9% removal efficiency was achieved.

关键词： Environmental safety Chemical scrubbing of iodine Iodine removal Wet scrubbers Nuclear powerplants Severe accident mitigation filtered containment venting system

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Methodology developed for the definition of the design parameters and associated safety criteria of the filtered containment venting systems for Belgian NPPs

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ANNALS OF NUCLEAR ENERGY 2016年 93卷 58-64页

作者： Dejardin, Ph. Helman, T. Bulle, J. Dienstbier, J. Oury, L. Sallus, L. Tractebel Engn SA ENGIE Brussels BE Belgium

Following the post-Fukushima stress tests performed in Belgium, filtered containment venting systems (FCVS) are foreseen to be installed on Belgian Nuclear Power Plants (NPPs) as ultimate means to cope with slow pressurizations of the containments that could occur during potential Severe Accidents (SA). The present paper discusses the methodology supporting the definition of the FCVS main design parameters and associated safety criteria. This methodology, developed by Tractebel Engineering and accepted by the Belgian nuclear Safety Authorities, followed a series of subsequent steps starting with the definition of the safety referential applicable to the FCVS and leading to the identification of a reference sequence, namely the Complete Station BlackOut (CSBO). Then, key parameters for the FCVS design were defined (e.g. pressure range, venting flow, stored decay heat, stored mass, Decontamination Factors (DF)) along with the associated safety criteria. Several of them were assessed through a well-defined set of supporting calculations. This set included both best estimate representative cases as well as conservative bounding cases performed with state-of-the-art SA codes. The SA codes used were first of all the MELCOR 1.8.6 code and, subsequently, the ASTEC V2.0 code (CPA/IODE modules), considering a chaining methodology. The aim of this approach was to take advantage of the iodine chemistry models features in the CPA/LODE modules of ASTEC to calculate the iodine speciation in the containment and in the FCVS, without having to run a full scope ASTEC calculation. In conclusion, appropriate values for the safety criteria of each design parameters were assessed. In particular, the ones related to the minimum DF relied on a marginal gain approach to cope with the large uncertainties existing when performing dedicated radiological evaluations. Finally, the next steps of this continuous safety assessment of the FCVS that are foreseen to be installed on Belgian NPPs are hig

关键词： Severe accident filtered containment venting system Design parameters

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Experimental research on aerosols collection performance of self-priming venturi scrubber in FCVS

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PROGRESS IN NUCLEAR ENERGY 2015年 85卷 771-777页

作者： Zhou, Yanmin Sun, Zhongning Gu, Haifeng Miao, Zhuang Harbin Engn Univ Fundamental Sci Nucl Safety & Simulat Technol Lab Harbin 150001 Peoples R China

The self-priming venturi scrubber is the key component of filtered containment venting system to removal radioactive products during severe accident in nuclear power plant. In this paper, the collection performance of aerosols in the venturi scrubber is researched with experiment. The results indicate that the retention performance is closely related to the operating conditions and structures, and this relation is more closely for the removal of particle size under 0.5 mu m. The retention efficiency in a venturi scrubber increase with improving of both gas velocity and injection flow rate, and the influence of gas velocity on efficiency is more effective at low injection flow rate. The venturi scrubber with a long throat length or small diffuser angle performs excellent retention performance for small size aerosols. In condition of gas velocity higher as U-avg = 200 m/s and the sufficient injection flow rate, the retention efficiency maintains upon 99% for the aerosol that size range from 0.1 mu m to 10 mu m. The pressure loss of the venturi scrubber increase slightly with extending the length of throat, and also with reducing diffuser angles. The removal efficiency is usually at the expense of the energy loss, while the higher aerosol retention efficiency corresponds to bigger pressure loss. (C) 2015 Elsevier Ltd. All rights reserved.

关键词： Self-priming venturi scrubber Aerosols Retention performance filtered containment venting system

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Experimental study on aerosol scrubbing efficiency of self-priming venturi scrubber submerged in water pool

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ANNALS OF NUCLEAR ENERGY 2018年 114卷 571-585页

作者： Lee, Jongchan Jung, Woo Young Lee, Hyun Chul Kim, Gyu Tae Lee, Doo Yong FNC Technol Co Ltd 32 FlHeungdeok 1Ro Yongin 16954 Gyeonggi Do South Korea

Scrubber nozzles are key pieces of equipment used to remove aerosols in a wet-type filtered containment venting system (FCVS). This study deals with the aerosol scrubbing efficiency of a scrubber nozzle operating in self-priming mode. The scrubber nozzle that has been developed in this work consists of a reducer, a throat, a diffuser, a liquid suction slit, and an end cap with a rectangular section area. The aim of this study was to characterize scrubbing efficiency under various thermal hydraulic and aerosol conditions including nozzle inlet pressure (250600 kPa(g)), nozzle inlet temperature (102-164 degrees C), nozzle inlet flow rate (air: 42-132 m(3)/h, steam: 112269 m(3)/h), submergence from the nozzle exit (0.72.7 m), aerosol size (0.5, 0.7, 3 mu m), nozzle inlet aerosol concentration (0.13 g/m(3)), and steam mass fraction in the main carrier gas (01). Aerosol scrubbing efficiency was measured based on the inlet and outlet aerosol concentrations of the scrubbing vessel with isokinetic sampling systems including a glass microfiber filter. Experimental results show that the scrubbing efficiency increased with increasing aerosol size, steam mass fraction, nozzle submergence, and inlet aerosol concentration. We also showed that the scrubbing efficiency increased with an increase in inlet pressure at low scrubber nozzle submergence. However, at higher scrubber nozzle submergence, the nozzle inlet pressure did not significantly influence the scrubbing efficiency. The aerosol scrubbing efficiency with the developed self-priming scrubber nozzle submerged in the pool was over 97% for various thermal-hydraulic conditions. Thus, the experimental results can be used to design a wet scrubber system considering upstream conditions such as operation of the FCVS. (C) 2017 Elsevier Ltd. All rights reserved.

关键词： Venturi scrubber filtered containment venting system FCVS Scrubbing efficiency Nuclear power plant Pool scrubbing Decontamination factor

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