Development of fission product chemistry database ECUME for the LWR severe accident

Miwa, Shuhei; Nakajima, Kunihisa; Miyahara, Naoya; Nishioka, Shunichiro; Suzuki, Eriko; Horiguchi, Naoki; Liu, J.; Miradji, F.; Imoto, Jumpei; Afiqa, B. M.; et al.

Mechanical Engineering Journal (Internet), 7(3), p.19-00537_1 - 19-00537_11, 2020/06

https://doi.org/10.1299/mej.19-00537

We constructed the fission product (FP) chemistry database named ECUME for LWR severe accident. This version of ECUME is equipped with dataset of the chemical reactions and their kinetics constants for the reactions of cesium(Cs)-iodine(I)-boron(B)-molybdenum(Mo)-oxygen(O)-hydrogen(H) system in gas phase, the elemental model for the high temperature chemical reaction of Cs with stainless steel applied as the structural material in a reactor, and thermodynamic data for CsBO vapor species and solids of CsSiO and CsFeSiO for these chemical reactions. The ECUME will provide estimation of Cs distribution due to the evaluation of effects of interaction with BWR control material B and stainless steel on Cs behavior in the Fukushima Daiichi Nuclear Power Station.

Boron chemistry during transportation in the high temperature region of a boiling water reactor under severe accident conditions

Miwa, Shuhei; Takase, Gaku; Imoto, Jumpei; Nishioka, Shunichiro; Miyahara, Naoya; Osaka, Masahiko

Journal of Nuclear Science and Technology, 57(3), p.291 - 300, 2020/03

https://doi.org/10.1080/00223131.2019.1671913

For the evaluation of transport behavior of control material boron in a severe accident of BWR from the viewpoint of chemical effects on cesium and iodine behavior, boron chemistry during transportation in the high temperature region above 400 K was experimentally investigated. The heating tests of boron oxide specimen were conducted using the dedicated experimental apparatus reproducing fission product release and transport in steam atmosphere. Released boron oxide vapor was deposited above 1,000 K by the condensation onto stainless steel. The boron deposits and/or vapors significantly reacted with stainless steel above 1,000 K and formed the stable iron-boron mixed oxide (FeO)BO. These results indicate that released boron from degraded BWR control blade in a severe accident could remain in the high temperature region such as a Reactor Pressure Vessel. Based on these results, it can be said that the existence of boron deposits in the high temperature region would decrease the amount of transported cesium vapors from a Reactor Pressure Vessel due to possible formation of low volatile cesium borate compounds by the reaction of boron deposits with cesium vapors.

Study on chemisorption model of cesium hydroxide onto stainless steel type 304

Nakajima, Kunihisa; Nishioka, Shunichiro; Suzuki, Eriko; Osaka, Masahiko

Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 8 Pages, 2019/05

Cesium chemisorption models were developed for estimation of amount of cesium chemisorbed onto stainless steel type 304 (SS304) during light water reactor severe accident. However, existing chemisorption models cannot accurately reproduce experimental results. In this study, a modified cesium chemisorption model was constructed based on a penetration theory for gas-liquid mass transfer with chemical reaction and was able to adequately describe effects on concentration of cesium hydroxide in gaseous phase and silicon content in SS304. It was found that the modified model can more accurately reproduce the experimental data than the existing model.

Experimental study on Cs chemisorption behaviour onto stainless steel at around 873 K

Suzuki, Eriko; Takase, Gaku; Nakajima, Kunihisa; Nishioka, Shunichiro; Hashimoto, Naoyuki*; Isobe, Shigehito*; Osaka, Masahiko

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

In order to acquire the knowledge of the Cs chemisorption behaviour in the lower temperature region, the Cs chemisorbed compounds and the surface reaction rates were investigated by conducting the Cs chemisorption tests onto stainless steel at 873 and 973 K. As a result, The cesium ferrate compounds were revealed to be formed at this temperatures. It was seen that the dependences of surface reaction rate constant on this temperature were different from that at the higher temperature region. This behaviour leads to the conclusion that the Cs chemisorption model in the low temperature region should be newly constructed.

Influence of electron doping on magnetic order in CeRuAl

Kobayashi, Riki*; Kaneko, Koji; Saito, Kotaro*; Mignot, J.-M.*; Andr, G.*; Robert, J.*; Wakimoto, Shuichi; Matsuda, Masaaki*; Chi, S.*; Haga, Yoshinori; et al.

Journal of the Physical Society of Japan, 83(10), p.104707_1 - 104707_5, 2014/10

https://doi.org/10.7566/JPSJ.83.104707

Fundamental research on FP chemistry; Boron effects on cesium and iodine chemistry

Miwa, Shuhei; Nakajima, Kunihisa; Miyahara, Naoya; Nishioka, Shunichiro; Suzuki, Chikashi; Suzuki, Eriko; Horiguchi, Naoki; Imoto, Jumpei; Liu, J.; Miradji, F.; et al.

no journal, , 

We have been conducting the fundamental study on fission product (FP) chemistry under severe accident (SA) conditions. The objective is to construct the FP chemistry database and to improve FP chemistry model for the improvement of source term evaluation technology. We have established the technical basis, such as experimental set-up and analysis tool, for the evaluation of FP chemistry in SA conditions. Fundamental knowledges on the effects of boron on the cesium and iodine chemistry were also obtained.

Cesium chemisorption behavior onto stainless steel at temperatures higher than 1073 K

Nakajima, Kunihisa; Nishioka, Shunichiro; Suzuki, Eriko; Miradji, F.; Osaka, Masahiko

no journal, , 

Radioactive cesium (Cs) localized in the upper region of reactor pressure vessel (RPV) is one of the major concerns, especially in the case of the fuel debris retrieval accessing from top of the RPV. For estimation of amount of Cs chemisorbed onto structure materials, Cs chemisorption model is developed and incorporated into present severe accident codes. However, this chemisorption model cannot accurately reproduce experimental results. Therefore, this study elucidates essential factors influencing the Cs chemisorption behavior and construct the Cs chemisorption model considering these factors. It was found that this model can more accurately reproduce not only our experimental results but also the results used to construct the existing chemisorption model.

Comparative study of Cs silicates properties between DFT calculation and experimental data

Miradji, F.; Suzuki, Eriko; Nishioka, Shunichiro; Suzuki, Chikashi; Nakajima, Kunihisa; Oishi, Yuji*; Muta, Hiroaki*; Kurosaki, Ken*; Do, Thi Mai Dung*; Osaka, Masahiko

no journal, , 

Present status and evaluation methods of contaminated water

Kino, Chiaki*; Karasawa, Hidetoshi*; Uchida, Shunsuke*; Nishioka, Shunichiro; Osaka, Masahiko

no journal, , 

To evaluate the remigration behavior of FP through the aqueous phase in FDNPS for a long term, an analysis methodology of contaminated water was developed based on SAMPSON code. The test analysis result for cesium concentration in the contaminated water in FDNPS unit 1 for 1 year, with the consideration of cesium release from the fuel debris to the aqueous phase had a good agreement with the actual measured cesium concentration.

Cs chemisorption behaviour onto stainless steel during LWR severe accident, 1; Experimental study on Cs chemisorption behaviour at temperature around 600C

Suzuki, Eriko; Takase, Gaku; Nakajima, Kunihisa; Nishioka, Shunichiro; Osaka, Masahiko

no journal, , 

In order to estimate the cesium (Cs) distribution in the reactor pressure vessel under severe accident (SA), Cs chemisorption behaviour onto stainless steel have been investigated. In our previous study on Cs chemisorption behaviour at above 800C, it was found that the Cs silicate compounds were formed as Cs chemisorbed compounds. In this study, Cs chemisorption tests at lower temperatures around 600C were carried out to investigate the Cs chemisorbed compounds at lower temperatures. As a result, cesium ferrate compounds were formed and it was suggested that the chemical reaction at lower temperatures would be different from that at above 800C.