On-going R&D program at JAEA on the Advanced Technology Fuels; An Update on the Cr-coated Zry cladding research

Mohamad, A. B.; Yamashita, Shinichiro; Nemoto, Yoshiyuki; Abe, Yosuke; Pham, V. H.; Ioka, Ikuo; Soma, Yasutaka; Ishijima, Yasuhiro; Sato, Tomonori; Rizaal, M.; et al.

Proceedings of TopFuel 2025; Nuclear Reactor Fuel Performance Conference (Internet), 8 Pages, 2025/10

https://www.ans.org/pubs/proceedings/issue-3431/

Updating fission product chemistry database based on recent investigation in Fukushima-Daiichi Nuclear Power Station, 2; Temperature effects on the deposition behavior of CsOH aerosols on concrete main phase-CaCO

Luu, V. N.; Nakajima, Kunihisa; Rizaal, M.; Miwa, Shuhei

Proceedings of International Topical Workshop on Fukushima Decommissioning Research 2024 (FDR2024) (Internet), 4 Pages, 2024/10

Advances in understanding cesium retention on calcium silicate material

Rizaal, M.; Nakajima, Kunihisa

Chemosphere, 363, p.142870_1 - 142870_9, 2024/09

https://doi.org/10.1016/j.chemosphere.2024.142870

High-temperature gaseous reaction of cesium with siliceous thermal insulation; The Potential implication to the provenance of enigmatic Fukushima cesium-bearing material

Rizaal, M.; Nakajima, Kunihisa; Saito, Takumi*; Osaka, Masahiko; Okamoto, Koji*

ACS Omega (Internet), 7(33), p.29326 - 29336, 2022/08

https://doi.org/10.1021/acsomega.2c03525

Computational approach to the evaluation of fission product behaviors

Miwa, Shuhei; Nakajima, Kunihisa; Suzuki, Chikashi; Rizaal, M.; Suzuki, Eriko; Horiguchi, Naoki; Osaka, Masahiko

Proceedings of Joint International Conference on Supercomputing in Nuclear Applications + Monte Carlo 2020 (SNA + MC 2020), p.253 - 260, 2020/12

We have proceeded the fundamental study for the improvement of the evaluation of fission product (FP) chemistry and the treatment of fine space resolution which are main issues for the evaluation of FP behaviors in a severe accident (SA). We have been developing FP chemistry database named ECUME for the improvement of SA analysis codes. We prepared thermodynamic data for Cs compounds which is no experimental data available by computational approach. Regarding the space resolution issue, we have been developing analysis tool named CHASER based on 3D-CFD code with the model for FP chemistry. More accurate evaluation of FP behavior can be achieved by incorporating ECUME to the CHASER.

Room-temperature adsorption behavior of cesium onto calcium silicate insulation

Rizaal, M.; Saito, Takumi*; Okamoto, Koji*; Erkan, N.*; Nakajima, Kunihisa; Osaka, Masahiko

Mechanical Engineering Journal (Internet), 7(3), p.19-00563_1 - 19-00563_10, 2020/06

https://doi.org/10.1299/mej.19-00563

The adsorption of cesium (Cs) on calcium silicate insulation of primary piping system is postulated to contribute in high dose rate of surrounding pedestal area in Fukushima Daiichi NPP unit 2. In this study, room-temperature experiment of Cs adsorption on calcium silicate has been studied as an initial approach of Cs adsorption behavior toward higher temperature condition. As the result of analyzing of Cs adsorption kinetics, it was expected that the underlying adsorption mechanism is chemisorption. Furthermore, analysis of adsorption isotherm suggested unrestricted monolayer formation followed by multilayer formation.

Fission products chemistry in achieving reliable LWR source term prediction; An Outlook to Cs-Cr vapor species interaction

Rizaal, M.; Nakajima, Kunihisa; Karasawa, Hidetoshi; Miwa, Shuhei

no journal, , 

Evaluation of Cs deposition mechanism between shield plugs, 1; Estimation of Cs deposition by FP behavior models using for severe accident analysis

Karasawa, Hidetoshi; Rizaal, M.; Luu, V. N.; Nakajima, Kunihisa; Miwa, Shuhei; Kino, Chiaki*

no journal, , 

We are investigating the Cs accumulation mechanism between shield plugs observed in the Fukushima Daiichi Nuclear Power Plant accident. Previously, it was thought that there was no gas flow path in the gap between the shield plugs, but it was found that a high concentration of Cs-137 was accumulated. Also, the Nuclear Regulatory Commission clarified that the deformation of the shield plug due to gravity causes the formation of a gas flow path. In this study, the chemical adsorption rate of CsOH aerosol on concrete was added to the FP transfer behavior analysis module of the severe accident analysis code SAMPSON, and a trial analysis was performed on the shield plug of Unit 2. Then, the effects of gap spacing between shield plugs, gas flow velocity, gas temperature, CsOH aerosol concentration, etc. on Cs accumulation are evaluated, and the main mechanisms of Cs accumulation are examined.

Thermochemical investigation of calcium silicate insulation with cesium hydroxide

Rizaal, M.; Nakajima, Kunihisa; Osaka, Masahiko; Saito, Takumi*; Erkan, N.*; Okamoto, Koji*

no journal, , 

Experimental study using thermogravimetry and X-ray diffractometry was conducted to investigate chemical interaction between calcium silicate insulation and cesium hydroxide under steam and hydrogen atmospheres. This interaction might be one of the causes for the high dose rate reading outside the pedestal in 1F, Unit2. Our results suggested that some chemical interaction occurred in temperature range of 575-730C regardless of atmospheres.

Investigation of effect by the late-phase release of boron containing atmosphere on CsI deposit formed on reactor structural material SUS304L

Rizaal, M.; Miwa, Shuhei; Suzuki, Eriko; Imoto, Jumpei; Osaka, Masahiko; Goullo, M.*

no journal, ,