Accomplishment of OECD/NEA, PreADES (Preparatory Study on Analysis of Fuel debris) project

Nakayoshi, Akira; Koyama, Shinichi; Washiya, Tadahiro

Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR2022) (Internet), 4 Pages, 2022/10

The activity of the PreADES project was carried out under the collaboration with many international organizations, and accumulated useful expertise. Following project tasks were discussed: (1) the Characteristic table that clarified characteristics of fuel debris for 1F, TMI2, and Chernobyl from various analyses and experiments, (2) Compiling informative tables for fuel debris analysis (the Analytical table, the Major issue and methodology table; the Hot testing analysis capabilities table). The first one identified analysis data to be obtained, and the last one indicated practical appropriate and optimal methodologies for fuel debris handling, (3) future international R&D framework. Through these activities with many discussions, project partners re-realized that important aspects for the success of future collaborative initiative was to implement conditions for fluid dialogue and information exchange between involved organizations. Currently, post-PreADES project, "Fukushima Daiichi Nuclear Power Station Accident Information Collection and Evaluation (FACE)" project has been launched and discussion is ongoing enthusiastically.

Preliminary measurement of prompt gamma-ray from nuclear material for the classification of fuel debris and waste

Shiba, Tomooki; Kaburagi, Masaaki; Nomi, Takayoshi; Suzuki, Risa; Kosuge, Yoshihiro*; Nauchi, Yasushi*; Takada, Akira*; Nagatani, Taketeru; Okumura, Keisuke

Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR2022) (Internet), 3 Pages, 2022/10

An Investigation of the microstructure and phase composition of the Zr bearing metallic debris in a bypass channel of a BWR fuel after the exothermic reaction in the CLADS-MADE-04 test

Pshenichnikov, A.; Kurata, Masaki; Nagae, Yuji

Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR2022) (Internet), 4 Pages, 2022/10

The CLADS-MADE-04 is the next test in the series aiming at understanding of the melt propagation behaviour in the lower core region. In this contribution, recent results of the post-test analysis including microstructure of metallic debris investigated by Electron Probe Micro Analyzer (EPMA) are discussed. During the test, melting of the control blade happened with sudden wave of strong heat release relatively slowly (several cm/min) spread from the hottest area downwards along the degrading control blade and channel box consuming the walls made of Zircaloy-4. A significant damage happened with the sample supporting plate as well. The investigation of microstructure of such metallic debris would allow understanding of a mechanism of enhanced local core degradation. The nature of strong heat release and possibility of spreading to the surrounding materials is to be confirmed after thorough phase identification by EPMA. The difference between Fe-B eutectic debris and Zr-Fe eutectic debris will be outlined. It is especially important for understanding of the lower core plate melt-through and a possibility of a Zr-Fe molten material progression into the lower plenum.

Aerosol characterization during heating and mechanical cutting of simulated uranium containing debris; The URASOL project in the framework of Fukushima Daiichi fuel debris removal

Porcheron, E.*; Leblois, Y.*; Journeau, C.*; Delacroix, J.*; Molina, D.*; Suteau, C.*; Berlemont, R.*; Bouland, A.*; Lallot, Y.*; Roulet, D.*; et al.

Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR2022) (Internet), 5 Pages, 2022/10

One of the important challenges for the decommissioning of the damaged reactors of the Fukushima Daiichi Nuclear Power Station (1F) is the fuel debris retrieval. The URASOL project, which is undertaken by a French consortium consisting of ONET Technologies, CEA, and IRSN for JAEA/CLADS, is dedicated to acquiring basic scientific data on the generation and characteristics of radioactive aerosols from the thermal or mechanical processing of fuel debris simulant. Heating process undertaken in the VITAE facility simulates some representative conditions of thermal cutting by LASER. For mechanical cutting, the core boring technique is implemented in the FUJISAN facility. Fuel debris simulants have been developed for inactive and active trials. The aerosols are characterized in terms of mass concentration, real time number concentration, mass size distribution, morphology, and chemical properties. The chemical characterization aims at identifying potential radioactive particles released and the associated size distribution, both of which are important information for assessing possible safety and radioprotection measures during the fuel debris retrieval operations at 1F.

Investigation of the interface between cement and geopolymer

Cantarel, V.; Yamagishi, Isao

no journal, , 

Development of testing method for arm mounted robot based on Fukushima Daiichi Nuclear Power Station cases

Yamada, Taichi; Abe, Hiroyuki*; Kawabata, Kuniaki

no journal, , 

Quantitative imaging of radioactive Sr-90 using laser ablation-inductively coupled plasma-mass spectrometry

Yanagisawa, Kayo; Matsueda, Makoto; Furukawa, Makoto*; Hirata, Takafumi*; Takagai, Yoshitaka*

no journal, , 

LA-ICP-MS technique, both the elemental and isotopic mapping analyses can be made with high sensitivity over the traditional techniques such as XRF, EPMA, and SIMS. However, detection of Sr-90 is still challenging because of contributions of spectral interferences and tailing from neighboring abundant isotopes. To reduce the contribution of various interferences, ICP-MS/MS and reaction cell technique was adopted in this study. With the present analytical technique, the detection limit obtained from analysis area (100100 m square) was 0.64 mBq. The measured background intensity at m/z 90 u (1.62.2 cps) did not change significantly even under the presence of various interfering elements (Ni: 2,084 mg/kg, Ge: 21 mg/kg, Y: 23,004 mg/kg, Zr: 175 mg/kg). The measured abundance sensitivity on Sr-90 from Sr-88 was 2.6e-9. The data indicates sensitive and rapid analytical technique for the mapping analysis of both Sr-90 and other trace-elements.

Analysis of ex-vessel debris-pedestal structure interactions and debris cooling in Fukushima Daiichi Nuclear Power Station Unit-3

Li, X.; Yamaji, Akifumi*; Sato, Ikken; Furuya, Masahiro*; Oishi, Yuji*; Nagae, Yuji

no journal, , 

To facilitate the fuel debris retrieval as part of the decommissioning of Fukushima Daiichi Nuclear Power Station (1F), it is necessary to grasp the in-depth debris distribution and status in the pedestal regions of the damaged units. For 1F Unit-3, it has been confirmed that the deposits in the pedestal region can be up to 2-3 meters high from the PCV internal investigations performed with remotely operated vehicles by TEPCO HD. This study will focus on the detailed evaluation of radiative heat transfer and convective vapor cooling boundaries applied on the free surfaces of debris and structures in the pedestal. Sensitivity analysis with different debris distributions, environment temperature, and emissivities was performed. The results show that remelting of debris and melting of pedestal structures are not expected during the re-heating phase if the pedestal background temperature is less than 1300 K.

A Method of evaluating PuO particle diameters by an alpha particle imaging detector

Morishita, Yuki; Sagawa, Naoki; Takada, Chie; Momose, Takumaro; Takasaki, Koji

no journal, ,