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論文

Material characterization of the VULCANO corium concrete interaction test with concrete representative of Fukushima Daiichi Nuclear Plants

Brissonneau, L.*; 池内 宏知; Piluso, P.*; Gousseau, J.*; David, C.*; Testud, V.*; Roger, J.*; Bouyer, V.*; 北垣 徹; 仲吉 彬; et al.

Journal of Nuclear Materials, 528, p.151860_1 - 151860_18, 2020/01

 被引用回数:5 パーセンタイル:89.87(Materials Science, Multidisciplinary)

In the framework of JAEA-CEA collaboration, experimental studies have been conducted for estimating the material characteristics of corium debris representative of the Fukushima Daiichi nuclear damaged plants. A test has been performed in the VULCANO facility in CEA Cadarache to simulate the concrete corium interaction (CCI) with prototypic corium (using depleted uranium) and concrete of Fukushima Daiichi 1F1 Nuclear Plant. This paper presents the Post Test Analyses on 9 samples representative of the CCI during this test: in the corium pool, in the crusts and at the vertical and horizontal interfaces with the concrete. Analyses have been performed by SEM/EDS, X-Ray Diffraction, complete dissolution and ICP, micro-hardness measurements of the main phases. The major phases encountered are uranium rich and zirconium rich oxides forming nodules from micrometers to millimeters size, chromium-iron rich precipitates of several micrometers, metallic Fe-Ni droplets and chromium-silicon rich filaments in a matrix, likely vitreous, rich in concrete elements: Si, Al, Ca, but containing up to 12 cations. The matrix is the softer oxide phase, when the Cr rich precipitates are the harder. The analyses are consistent with the estimated macroscopic ablation ratio, but do not still explain the important axial ablation observed for this specific basaltic concrete. The different phases formation, distribution and solidification path are discussed. First comparisons are proposed with the former CCI tests with European concretes. These results give helpful insights for the future dismantling of the plant and for a deeper understanding of the CCI process for basaltic concrete.

論文

Knowledge obtained from dismantling of large-scale MCCI experiment products for decommissioning of Fukushima Daiichi Nuclear Power Station

仲吉 彬; 池内 宏知; 北垣 徹; 鷲谷 忠博; Bouyer, V.*; Journeau, C.*; Piluso, P.*; Excoffier, E.*; David, C.*; Testud, V.*

Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR 2019) (Internet), 4 Pages, 2019/05

A large-scale Molten Core-Concrete Interaction (MCCI) test (VF-U1) under the Fukushima Daiichi Nuclear Power Station (1F) conditions (core material composition, concrete, and decay heat) was conducted at the large MCCI test facility (VULCANO) owned by French Alternative Energies and Atomic Energy Commission (CEA) in France. About 50 kg of simulated debris was melted and brought into contact with concrete to erode concrete under 1F conditions. After cooling, the concrete test section (concrete and MCCI product) was dismantled. Main observations of the structure of solidified pool (crust, porosity, oxide/metal layer, etc.) and of the ablation are given. The technical results obtained herein are summarized, and they provide interesting knowledge that will help with the decommissioning of 1F.

論文

Large scale VULCANO molten core concrete interaction test considering Fukushima Daiichi condition

Bouyer, V.*; Journeau, C.*; Haquet, J. F.*; Piluso, P.*; 仲吉 彬; 池内 宏知; 鷲谷 忠博; 北垣 徹

Proceedings of 9th Conference on Severe Accident Research (ERMSAR 2019) (Internet), 13 Pages, 2019/03

Fuel debris removal is one of the most important processes for decommissioning a severely damaged nuclear power plant (NPP) such as Fukushima Daiichi NPP (1F). In order to develop relevant removal tools, characteristics of fuel debris are required. In the frame of a JAEA-CEA cooperation, a large-scale MCCI test was performed at the CEA/VULCANO facility using a prototypic metal and oxide corium representative from Fukushima Daiichi unit 1 conditions. Conclusions arising from the material analysis of the selected samples will be relevant for future dismantling operations. This paper deals with the experimental device and process, objective and initial conditions of this MCCI test, and ablation of the concrete quantified in term of volume, depths and velocities. The test section concrete, made with Japanese components, is siliceous with basaltic origin. The main objective of the test was to get a significant ablation leading to an ablation volume ratio of 1.6 in order to produce fuel debris with a composition corresponding to expected conditions in the damaged plant. On a phenomenological point of view, it must be noted that the concrete ablation was clearly anisotropic with a predominantly downwards ablation contrary to previous experiments with silica and limestone concrete.

論文

Characterization of the VULCANO test products for fuel debris removal from the Fukushima Daiichi Nuclear Power Plant

北垣 徹; 池内 宏知; 矢野 公彦; 荻野 英樹; Haquet, J.-F.*; Brissonneau, L.*; Tormos, B.*; Piluso, P.*; 鷲谷 忠博

Progress in Nuclear Science and Technology (Internet), 5, p.217 - 220, 2018/11

Characterization of the fuel debris is required to develop fuel debris removal tools for the decommissioning of Fukushima Daiichi Nuclear Power Plant (1F). In this study, the VULCANO MCCI test, VBS-U4, was selected as 1F similar conditions and the characteristics of the samples were examined. In the molten pool sample, the round-edged corium-rich oxides region, with diameters of 1-10 mm, is surrounded by a concrete-rich oxide region. It shows convection of the molten pool. Other samples also show the features of the MCCI progression. The main chemical forms of the samples are SiO$$_{2}$$, (U,Zr)O$$_{2}$$, Fe and so on. The microstructure of the samples is heterogeneous structure composed of these phases. The difference in Vickers hardness between the metallic phases and the oxide phases is a distinctive characteristic. It can be noted that the heterogeneous distribution of metallic phases in 1F MCCI products interrupt with the removal operation such as by damaging the core-boring bit.

論文

Study on the distribution of boron in the in-vessel fuel debris in conditions close to Fukushima Daiichi Nuclear Power Station Unit 2

池内 宏知; Piluso, P.*; Fouquart, P.*; Excoffier, E.*; David, C.*; Brackx, E.*

Proceedings of 8th European Review Meeting on Severe Accident Research (ERMSAR 2017) (Internet), 12 Pages, 2017/05

福島第一原子力発電所(1F)からの燃料デブリ中のホウ素(B)の分布や含有量に係る情報は、取出し時の機械的特性や取出し後の未臨界を担保の検討を行う上で重要な情報と考えられる。本発表では、仏国CEAとの協力のもと、圧力容器内燃料デブリ中のBの挙動を、解析的および実験的に推定した結果について概要を報告する。2号機に対して想定される事故進展シナリオから、材料組成、温度、および酸化量の変遷を推定し、これらの情報を入力とする熱力学計算により、Bの化学形の推定を行った。計算に用いた熱力学データベース(NUCLEA)ではB-O系の実験データが不足しており、これにより酸素濃度が低い条件での制御棒(B-C-Fe-O系)の溶融・凝固過程の計算結果には大きな不確かさを含むと考えられる。不確かさを低減し計算結果の妥当性を検証するため、Fe, B$$_{4}$$C, B$$_{2}$$O$$_{3}$$, Fe$$_{2}$$O$$_{3}$$を高温で溶融・混合させる小規模試験を実施し、凝固後の試料の相状態を分析した。その結果、凝固後の相が金属相(Feリッチな相)と酸化物相(BとOがリッチな相)に分かれ、Fe, Bがそれぞれの相に一定の割合で分配されることが分かった。このような元素の分配挙動は、酸素ポテンシャルを適切に設定した条件で、NUCLEAデータベースによる熱力学計算結果により説明できることが分かった。

口頭

燃料デブリの性状把握(27'A),7; TOLBIAC-ICBによる福島第一原子力発電所1号機のMCCIシミュレーション

北垣 徹; 矢野 公彦; 鷲谷 忠博; Haquet, J.-F.*; Boulin, A.*; Piluso, P.*

no journal, , 

Simulation of the MCCI phenomenon in a sump pit at Fukushima Daiichi NPP unit 1 was performed using the TOLBIAC-ICB. As the results, the concrete ablation rate on the bottom wall after 36 hours into the MCCI was estimated to become stable. Main components of the molten pool could be low-density and Fe, and those of the crust be dense oxides.

口頭

Characterization of fuel debris (28'A), 5; Phase and microstructure of large scale MCCI test product

北垣 徹; 池内 宏知; 矢野 公彦; 荻野 英樹; Brissonneau, L.*; Tormos, B.*; Piluso, P.*

no journal, , 

Under a collaborative agreement with CEA, the phases and microstructures of large-scale MCCI test products from PLINIUS/VULCANO experiments have been analyzed. The phases and microstructures vary at different sampling locations, each of which is representative of a product to be generated under severe accident conditions and which is considered to be close to that of Fukushima Daiichi Nuclear Power Station Unit 1.

口頭

Solidification test of B-C-Fe-O melt in the PLINIUS/VITI facility

池内 宏知; Piluso, P.*; Fouquart, P.*; Bailly, J. S.*; Brackx, E.*; David, C.*; Domenger, R.*; Excoffier, E.*

no journal, , 

少量の酸素を含むB-C-Fe-O系の溶融物が凝固した後のBの化学形に関するデータを取得するため、JAEA-CEA間の国際協力のもと、CEAが有する試験施設(PLINIUS/VITI)において小規模溶融試験を2015年度に実施した。本報告は、欧州・SARNETの年会において、国際協力の現状に関するトピックスのひとつとして、当該実験の実施状況を紹介するものである。

口頭

Characterization of the large-scale MCCI test products for fuel debris removal from the Fukushima Daiichi Nuclear Power Plant

池内 宏知; 平野 弘康; 鷲谷 忠博; Piluso, P.*; Brissonneau, L.*

no journal, , 

大規模MCCI試験によりMCCI生成物の特性の不均一性を調べ、試験サンプルの分析により得られた相や硬さ等の情報から燃料デブリ取出し作業への提言を取りまとめた。

口頭

First analyses of concrete-corium solids surrogate for the Fukushima Daiichi severe accidents

Brissonneau, L.*; Gousseau, J.*; Piluso, P.*; Bouyer, V.*; 北垣 徹; 池内 宏知; 矢野 公彦; 鷲谷 忠博

no journal, , 

In case of severe accident in a nuclear reactor, the mixture obtained from fuel core and pins (mainly UO$$_{2}$$ and zirconium), called corium, can penetrate the steel vessel and interact with the concrete, as in the Fukushima Daiichi NPP (1F) severe accidents. A specific test has been realized with a concrete similar to the one of the Fukushima Daiichi NPP (1F) and an "oxide metal" corium. Ten samples were collected from representative places (corium core, crust, vertical and horizontal interfaces) and examined by SEM and XRD. The talk will present some of the main features of the solids formed after CCI.

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