Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Kumagai, Yuta; Takano, Masahide; Watanabe, Masayuki
Proceedings of 20th Nuclear Plant Chemistry International Conference (NPC 2016) (USB Flash Drive), 6 Pages, 2016/10
In the severe accident at Fukushima, the reactor cores of Unit 1, 2 and 3 largely melted. Intense ionizing radiations in the reactors may induce leaching of the molten fuel debris. Water radiolysis generates hydrogen peroxide (H
O), which would oxidize uranium (U) to more soluble hexavalent on the debris surface. To understand the effect of HO, reaction of HO with simulated fuel debris was studied. The simulated debris used in this study was solid solution of U and zirconium oxides ((U,Zr)O). The dissolution rate of U from (U,Zr)O was remarkably lower than that from U(IV) oxide (UO). Meanwhile, production of oxygen (O) was observed as the product of the reaction with (U,Zr)O and was approximately half the consumption of HO, indicating the catalytic decomposition of HO. This suggests that the leaching of U from (U,Zr)O was inhibited due to the catalytic decomposition of HO. The fuel debris is expected to be more resistant to HO than UO.
Hanawa, Satoshi; Uchida, Shunsuke; Hata, Kuniki; Chimi, Yasuhiro; Kasahara, Shigeki*; Nishiyama, Yutaka
Proceedings of 20th Nuclear Plant Chemistry International Conference (NPC 2016) (USB Flash Drive), 11 Pages, 2016/10
ECP is the exclusive index to evaluate corrosion condition directly at the points of interest in the mixing of neutron and 
-ray environment. ECP can be calculated through the combination of water radiolysis and ECP model. A water radiolysis model have been applied to experiments performed in in-pile loops in the experimental reactors and applicability was confirmed. An ECP model based on the Butler-Volmer equation was also prepared. ECP of stainless steel was measured under well controlled water chemistry condition in in-pile loop in the Halden reactor, and the model was applied to evaluate ECP measured in the Halden reactor. The measured data were well explained by the water radiolysis calculation and ECP model. Accumulation of in-pile ECP data are expected for further validation of the models.
Hanawa, Satoshi; Uchida, Shunsuke; Hata, Kuniki; Chimi, Yasuhiro; Kasahara, Shigeki*; Nishiyama, Yutaka
Proceedings of 20th Nuclear Plant Chemistry International Conference (NPC 2016) (USB Flash Drive), 10 Pages, 2016/10
The authors proposed and ECP evaluation model introducing irradiation-induced diffusion in the oxide layer to simulate neutron irradiation effect, and predicted with this model that ECP is started to depress from the neutron flux of about ten to the fourteenth per square meter. As the JMTR has in-pile loops applicable to water chemistry experiments, degree of irradiation effect on ECP appears in the in-pile loop was estimated by the model. Under oxygen injected condition, ECP in a capsule becomes constant along the vertical direction due to the presence of high amount of oxygen and hydrogen peroxide in a capsule. However, if neutron irradiation depress ECP, ECP in a capsule along vertical direction wouldn't become constant, and the degree to the decrement is detectable by experiments.