Estimation method for residual sodium amount on unloaded dummy fuel assembly

Kawaguchi, Munemichi; Hirakawa, Yasushi; Sugita, Yusuke; Yamaguchi, Yutaka

Nuclear Technology, 210(1), p.55 - 71, 2024/01

https://doi.org/10.1080/00295450.2023.2214261

This study has developed an estimation method for residual sodium film and sodium lumps on dummy fuel pins in Monju and demonstrated sodium draining behavior through gaps among the pins, experimentally. The amounts of the residual sodium on the surface of the pins were measured using the three-type test specimens: (a) single pin, (b) 7-pin assembly, and (c) 169-pin assembly. The experiments revealed that the withdrawal speed of the pins and improvement of the sodium wetting increased drastically the amounts of the residual sodium. Furthermore, the experiments using the 169-pin assembly measured the practical amounts of the residual sodium in the dummy fuel assembly of short length and demonstrated sodium draining behavior through the dummy fuel assembly. The estimation method includes four models: a viscosity flow model, Landau-Levich-Derjaguin (LLD) model, an empirical equation related to the Bretherton model, and a capillary force model in a tube. The calculation predicted comparable amounts of the residual sodium with the experiments. An uncertain of the sodium wetting effects were close to 1.8 times the estimation values of the LLD model. With this estimation method, the amounts of the residual sodium on the unloaded Monju dummy fuel assembly can be evaluated.

Reports of electropolishing implementation for quarter-wave resonators

Nii, Keisuke*; Ida, Yoshiaki*; Ueda, Hideki*; Yamaguchi, Takanori*; Kabumoto, Hiroshi; Kamiya, Junichiro; Kondo, Yasuhiro; Tamura, Jun; Harada, Hiroyuki; Matsui, Yutaka; et al.

Proceedings of 18th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.334 - 337, 2021/10

no abstracts in English

Metabolic alterations in leaves of oxalate-rich plant L. irradiated by rays

Kitano, Sayaka*; Miyagi, Atsuko*; Ono, Yutaka; Hase, Yoshihiro; Narumi, Issey*; Yamaguchi, Masatoshi*; Uchimiya, Hirofumi*; Kawai, Maki*

Metabolomics, 11(1), p.134 - 142, 2015/02

https://doi.org/10.1007/s11306-014-0684-4

Effects of thermal aging on microstructure and hardness of stainless steel weld-overlay claddings of nuclear reactor pressure vessels

Takeuchi, Tomoaki; Kakubo, Yuta*; Matsukawa, Yoshitaka*; Nozawa, Yasuko*; Toyama, Takeshi*; Nagai, Yasuyoshi*; Nishiyama, Yutaka; Katsuyama, Jinya; Yamaguchi, Yoshihito; Onizawa, Kunio; et al.

Journal of Nuclear Materials, 452(1-3), p.235 - 240, 2014/09

https://doi.org/10.1016/j.jnucmat.2014.04.003

Microstructures and hardness of stainless steel weld overlay cladding of reactor pressure vessels subjected to the thermal aging at 400 C for 100-10,000 h were investigated using atom probe tomography and nanoindentation technique. The Cr concentration fluctuation in the -ferrite phase caused by spinodal decomposition rapidly progressed by the 100 h aging while NiSiMn clusters increased in number density at 2,000 h and coarsened at 10,000 h. The hardness of the -ferrite phase also rapidly increased at the short aging time. The Cr concentration fluctuation and the hardness were in good correlation with the degree of the Cr concentration fluctuation rather than the formation of the NiSiMn clusters. These results strongly suggested that the dominant factor of the hardening of the -ferrite phase by the thermal aging was Cr spinodal decomposition.

Effects of neutron irradiation on microstructures and hardness of stainless steel weld-overlay cladding of nuclear reactor pressure vessels

Takeuchi, Tomoaki; Kakubo, Yuta*; Matsukawa, Yoshitaka*; Nozawa, Yasuko*; Toyama, Takeshi*; Nagai, Yasuyoshi*; Nishiyama, Yutaka; Katsuyama, Jinya; Yamaguchi, Yoshihito; Onizawa, Kunio

Journal of Nuclear Materials, 449(1-3), p.273 - 276, 2014/06

https://doi.org/10.1016/j.jnucmat.2014.01.004

Microstructural changes and hardness of stainless steel weld overlay cladding of reactor pressure vessels subjected to the neutron irradiation with a dose of 7.2 10n cm (E 1 MeV) and a flux of 1.1 10n cm s at 290C were investigated by atom probe tomography and with nanoindentation technique. In order to isolate the effect of the irradiation, we compared the results of the measurements of the irradiated sample with that of the aged one at 300C for the time equivalent to the irradiation. The Cr concentration fluctuation was enhanced in the -ferrite phase of the irradiated sample. In addition, the enhancement of the concentration fluctuation of Si, which was not observed in the aged sample, was observed. The hardening at the -ferrite phase was occurred by both the irradiation and the aging. However, the former was more than that expected from the Cr concentration fluctuation, which suggested that the Si concentration fluctuation and irradiation-induced defects were possible origins of the additional hardening.

Introduction of vacancy drag effect to first-principles-based rate theory model for irradiation-induced grain-boundary phosphorus segregation

Ebihara, Kenichi; Suzudo, Tomoaki; Yamaguchi, Masatake; Nishiyama, Yutaka

Journal of Nuclear Materials, 440(1-3), p.627 - 632, 2013/09

https://doi.org/10.1016/j.jnucmat.2013.05.066

In order to examine the vacancy drag effect on phosphorus segregation at grain-boundaries, we estimated partial diffusion coefficients by kinetic Monte Carlo simulations considering atomic transitions for all the binding states of a phosphorus atom and a vacancy, and incorporated them into a rate theory model to simulate grain-boundary phosphorus coverage in neutron-irradiated reactor pressure vessel steels. As a result, it was confirmed that phosphorus atoms are transported to grain-boundaries by the vacancy drag effect. We found that the vacancy drag effect occurs even when only the first-nearest-neighbor binding states are considered, though it does not occur if the partial diffusion coefficients are obtained through the expression derived by theoretical analysis. In addition, we found that grain-boundary phosphorus segregation is suppressed by the vacancy mechanism of phosphorus transport regardless of the vacancy drag effect.

GEM-MSTPC; An Active-target type detector in low-pressure He/CO mixed gas

Ishiyama, Hironobu*; Yamaguchi, Kanako*; Mizoi, Yutaka*; Watanabe, Yutaka*; Das, S. K.*; Hashimoto, Takashi*; Miyatake, Hiroari*; Hirayama, Yoshikazu*; Imai, Nobuaki*; Oyaizu, Mitsuhiro*; et al.

Journal of Instrumentation (Internet), 7(3), p.C03036_1 - C03036_14, 2012/03

https://doi.org/10.1088/1748-0221/7/03/C03036

We developed an active-target type gas counter operating with low He/CO (10%) detector gas for application in studying low-energy nuclear reactions using radioactive beams. A 400-m-thick gas electron multiplier (THGEM) was used as the proportional counter for high injection rate capability. We examined the gas gain stability and the influence of ion feedback on particle tracks at high beam injection rates of up to 10 particles per second (pps) using a low-energy C beam. From the result of this examination, we found that the THGEM was found to be applicable for our active target at high injection rates of up to 10 pps.

Effect of Sn and Nb on generalized stacking fault energy surfaces in zirconium and hydride habit planes

Udagawa, Yutaka; Yamaguchi, Masatake; Tsuru, Tomohito; Abe, Hiroaki*; Sekimura, Naoto*

Philosophical Magazine, 91(12), p.1665 - 1678, 2011/04

https://doi.org/10.1080/14786435.2010.543651

We have investigated the effects of Sn and Nb on dislocation properties in a Zr lattice in order to elucidate the role of these alloying elements in hydride nucleation processes. According to experimental observations, -hydride habit planes are close to the prismatic plane in pure Zr and close to the basal plane in zircaloy. Dislocation loops are observed around hydride precipitates, implying they play a part in hydride formation. Our ab initio generalized-stacking-fault energy calculations showed remarkable effects of Sn on unstable-stacking energy and stacking-fault energy: these parameters for basal slip were considerably reduced while those for prismatic slip were increased in the presence of Sn. These results suggest selective stabilization and enhancement of dislocation spreading in the basal plane, promoting possible elementary processes of hydride precipitation with basal habit plane, i.e. screw-dislocation spreading and edge-dislocation emission in the basal plane.

Proton resonance elastic scattering in inverse kinematics on the medium heavy nucleus Zn

Imai, Nobuaki*; Hirayama, Yoshikazu*; Ishiyama, Hironobu*; Jeong, S.-C.*; Miyatake, Hiroari*; Watanabe, Yutaka*; Makii, Hiroyuki; Mitsuoka, Shinichi; Nagae, Daisuke*; Nishinaka, Ichiro; et al.

European Physical Journal A, 46(2), p.157 - 160, 2010/11

https://doi.org/10.1140/epja/i2010-11054-5

Assessment on long-term safety for geological disposal of high level radioactive waste; Application of probabilistic safety assessment methodology to uncertainties in hypothetical geological disposal system (Contract research)

Takeda, Seiji; Yamaguchi, Tetsuji; Nagasawa, Hirokazu; Watanabe, Masatoshi; Sekioka, Yasushi; Kanzaki, Yutaka; Sasaki, Toshihisa; Ochiai, Toru; Munakata, Masahiro; Tanaka, Tadao; et al.

JAEA-Research 2009-034, 239 Pages, 2009/11

JAEA-Research-2009-034.pdf:33.52MB

In safety assessment for geological disposal of high level radioactive waste, it is of consequence to estimate the uncertainties due to the long-term frame associated with long-lived radionuclides and the expanded geological environment. The uncertainties result from heterogeneity intrinsic to engineered and natural barrier materials, insufficient understanding of phenomena occurring in the disposal system, erroneous method of measurement, and incomplete construction. It is possible to quantify or to reduce the uncertainties according to scientific and technological progress. We applied a deterministic and a Monte Carlo-based probabilistic method simulation techniques to the uncertainty analysis for performance of hypothetical geological disposal system for high level radioactive waste. This study provides the method to evaluate the effects of the uncertainties with respect to scenarios, models and parameters in engineering barrier system on radiological consequence. The results also help us to specify prioritized models and parameters to be further studied for long-term safety assessment.