Updating fission product chemistry database based on recent investigation in Fukushima-Daiichi Nuclear Power Station, 3; High-temperature thermochemistry of CaCO-CsOH

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

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

Gaseous and aerosol formations in the pseudo-binary CsI-MoO reaction system

Rizaal, M.; Nakajima, Kunihisa; Suzuki, Eriko; Miwa, Shuhei

Proceedings of 11th European Review Meeting on Severe Accident Research Conference (ERMSAR 2024) (Internet), 11 Pages, 2024/05

https://doi.org/10.5445/IR/1000174165

Revaporization behavior of cesium and iodine compounds from their deposits in the steam-boron atmosphere

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

ACS Omega (Internet), 6(48), p.32695 - 32708, 2021/12

https://doi.org/10.1021/acsomega.1c04441

Investigation of high-temperature chemical interaction of calcium silicate insulation and cesium hydroxide

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

Journal of Nuclear Science and Technology, 57(9), p.1062 - 1073, 2020/09

https://doi.org/10.1080/00223131.2020.1755733

The interaction of cesium hydroxide and a calcium silicate insulation material was experimentally investigated at high temperature conditions. A thermogravimetry equipped with differential thermal analysis was used to analyze thermal events in the samples of mixed calcium silicate and cesium hydroxide under Ar-5%H and Ar-4%H-20%H0 with maximum temperature of 1100C. Prior being mixed with cesium hydroxide, a part of calcium silicate was pretreated at high temperature to evaluate the effect of possible structural changes of this material due to a preceding thermal history and also the sake of thermodynamic evaluation to those available ones. Based upon the initial condition (preliminary heat treatment) of calcium silicate, it was found that if the original material consisted of xonotlite (CaSi0(0H)), the endothermic reaction with cesium hydroxide occurred over the temperature range 575-730C meanwhile if the crystal phase of original material was changed to wollastonite (CaSi0), the interaction occurred over temperature range 700-1100C. Furthermore, the X-ray diffraction analyses have indicated on both type of pretreated calsils that regardless of Ar-5%H and Ar-4%H-20%H0 atmosphere, cesium aluminum silicate, CsAlSi0 was formed with aluminum in the samples as an impurity or adduct.

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.

Evaluation of FP behavior models in SAs, 5; Evaluation of a chemical reaction model for Cs-I-B-H-O system in SA codes

Karasawa, Hidetoshi; Rizaal, M.; Miwa, Shuhei; Kino, Chiaki*

no journal, , 

In SA analysis, the importance of chemical reactions related to FP behavior has been pointed out. For this reason, the amount of gaseous iodine produced was evaluated by a gaseous chemical reaction model using the ECUME database in the previous CsI-TeRRa experiment. In this study, we investigated the gas phase chemical reaction model for the CsI-BO-TeRRa experiment, which evaluated the influence of B on CsI behavior. In the experiment, the addition of BO increased the production of gaseous iodine by about 10 times. To explain this behavior, we set up a Cs-I-B-H-O reaction mechanism in which HBO generated from BO is reacted with CsI and CsOH to produce gaseous iodine. Calculations of the chemical reaction model using chemical reaction rates in the ECUME database confirmed an increase in gaseous iodine (about 26 times at 1,273 K) due to the addition of BO. The results showed that gaseous iodine was sufficiently produced at high temperatures, indicating the possibility of reproducing the TeRRa experiment by calculating chemical reactions during the transition of decreasing temperature.

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, , 

Status of development and overview of R&D in Japan

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

no journal, , 

Study on revaporization of deposited CsI from stainless steel 304 surface in high-temperature steam atmosphere

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

no journal, ,