Experimental study on transport behavior of cesium iodide in the reactor coolant system under LWR severe accident conditions

Miyahara, Naoya; Miwa, Shuhei; Goullo, M.*; Imoto, Jumpei; Horiguchi, Naoki; Sato, Isamu*; Osaka, Masahiko

Journal of Nuclear Science and Technology, 57(12), p.1287 - 1296, 2020/12

https://doi.org/10.1080/00223131.2020.1782281

In order to clarify the cesium iodide (CsI) transport behavior with a focus on the mechanisms of gaseous iodine formation in the reactor coolant system of LWR under a severe accident condition, a reproductive experiment of CsI transport behavior was conducted using a facility equipped with a thermal gradient tube. Various analyses on deposits and airborne materials during transportation could elucidate two mechanisms for the gaseous iodine formation. One was the gaseous phase chemical reaction in Cs-I-O-H system at relatively high-temperature region, which led to gaseous iodine transport to the lower temperature region without any further changes in gas species due to the kinetics limitation effects. The other one was the chemical reactions related to condensed phase of CsI, namely those of CsI deposits on walls with surface of stainless steel to form CsCrO compound and CsI aerosol particles with steam, which were newly found in this study.

STRAD project for systematic treatments of radioactive liquid wastes generated in nuclear facilities

Watanabe, So; Ogi, Hiromichi*; Arai, Yoichi; Aihara, Haruka; Takahatake, Yoko; Shibata, Atsuhiro; Nomura, Kazunori; Kamiya, Yuichi*; Asanuma, Noriko*; Matsuura, Haruaki*; et al.

Progress in Nuclear Energy, 117, p.103090_1 - 103090_8, 2019/11

https://doi.org/10.1016/j.pnucene.2019.103090

Microanalysis of silica-based adsorbent for effective recovery of radioactive elements

Sano, Yuichi; Watanabe, So; Matsuura, Haruaki*; Nagoshi, Kohei*; Arai, Tsuyoshi*

Journal of Nuclear Science and Technology, 54(10), p.1058 - 1064, 2017/10

https://doi.org/10.1080/00223131.2017.1344574

For effective recovery of radioactive elements by adsorbents using polymer-immobilized silica (SiO-P) supports, the microstructure of SiO-P particles impregnated with CMPO as extractants and their change with the crosslinking degree of polymer (CDP) were investigated using STXM and EXAFS analyses; further, their relation with adsorption/elution behavior was discussed. The adsorption/elution tests using adsorbents with a different CDP demonstrated that a higher CDP inhibited the elution of adsorbed metal ions from the adsorbent. The results of STXM and EXAFS analyses suggested that adsorption by CMPO proceeds through the entire area in the adsorbent and the local structure around adsorbed metal ions is similar irrespective of the CDP. Conversely, STXM analyses implied the capture of eluents such as HO by polymers with high CDP, which suppresses the prompt elution of adsorbed metal ions from the adsorbent.

Microscopic analyses of complexes formed in adsorbent for Mo and Zr separation chromatography

Abe, Ryoji*; Nagoshi, Kohei*; Arai, Tsuyoshi*; Watanabe, So; Sano, Yuichi; Matsuura, Haruaki*; Takagi, Hideaki*; Shimizu, Nobutaka*; Koka, Masashi*; Sato, Takahiro*

Nuclear Instruments and Methods in Physics Research B, 404, p.173 - 178, 2017/08

https://doi.org/10.1016/j.nimb.2017.02.082

XAFS measurement of simulated waste glass samples (Borosilicate glass including vanadium)

Nagai, Takayuki; Kobayashi, Hidekazu; Sasage, Kenichi; Ayame, Yasuo; Okamoto, Yoshihiro; Shiwaku, Hideaki; Matsuura, Haruaki*; Uchiyama, Takafumi*; Okada, Yukiko*; Nezu, Atsushi*; et al.

JAEA-Research 2016-015, 52 Pages, 2016/11

JAEA-Research-2016-015.pdf:37.48MB

The local structure of waste elements in simulated waste glasses including V was estimated by using synchrotron XAFS measurement in this study. The results are as follows. (1) V has a high possibility which exists in the glass phase in the case of frit, and V can regard both samples as stable 4 coordination structure. (2) Zn, Ce, Nd, Zr, and Mo exist in the glass phase, and the difference is admitted by the percentage of Ce(III) and Ce(IV) by the composition. (3) Ru is separated from the glass phase as RuO crystalline, both of metal and oxide exist in Rh, and Pd is separated out as metal. (4) It was confirmed that the regularity of the local structure of Zr and Mo in the molten glasses retreats as a result of the XAFS measurement at high temperature. (5) The XAFS measurement of molten glasses were performed at 1200C, so it would be possible to acquire excellent data by improving the shapes of the sample cell.

Reliability enhancement of seismic risk assessment of NPP as risk management fundamentals, 3; Sensitivity analysis for the quantification of epistemic uncertainty on fragility assessment

Nishida, Akemi; Choi, B.; Itoi, Tatsuya*; Takada, Tsuyoshi*; Furuya, Osamu*; Muramatsu, Ken*

Transactions of 23rd International Conference on Structural Mechanics in Reactor Technology (SMiRT-23) (USB Flash Drive), 10 Pages, 2015/08

This study focused on uncertainty-assessment frameworks and the development of relevant software to improve the reliability of seismic probabilistic risk assessment (SPRA) for NPP and promote its further use. This research aimed at contributing to development of implementation guidelines on epistemic uncertainty. Some sensitivity analyses were performed using a three dimensional reactor-building model and a conventional evaluation model by using 3D vibration simulator for NPP of JAEA, and the results were provided to the experts for expert-opinion elicitation. The results of the sensitivity analyses were related to the uncertainty evaluation of the buildings and soil to evaluate the fragility of the equipment. In this paper, those results will be shown in comparison with a conventional evaluation model.

Reliability enhancement of seismic risk assessment of NPP as risk management fundamentals, 1; Uncertainty analysis with the SECOM2 code

Muta, Hitoshi*; Muramatsu, Ken*; Furuya, Osamu*; Uchiyama, Tomoaki*; Nishida, Akemi; Takada, Tsuyoshi*

Transactions of 23rd International Conference on Structural Mechanics in Reactor Technology (SMiRT-23) (USB Flash Drive), 10 Pages, 2015/08

Seismic PRA is an effective measure to consider the countermeasures and improvement plans to secure the further safety of nuclear power plants regarding to seismic risk for the earthquake exceeding the reference ground motion. However, the application of the seismic PRA has not been utilized sufficiently so far. One of the reasons is that there is not enough consensus among stakeholders regarding to the evaluation methods and consideration of uncertainty for decision-making. This study proposes the mathematic framework to treat the uncertainty properly related to the evaluation of Core Damage Frequency induced by earthquake, the method to evaluate the fragility utilizing expert knowledge, the probabilistic model to cope with the aleatory uncertainty as well as the development of analyzing code including these considerations for the improvement of the reliability of the method and enhancement of utilization of the products of Seismic PRA.

Structural response by ground motions from sources with stochastic characteristics

Igarashi, Sayaka*; Sakamoto, Shigehiro*; Nishida, Akemi; Muramatsu, Ken; Takada, Tsuyoshi*

Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 10 Pages, 2015/05

In the preceding study, the ground-motion time histories consistent with seismic hazard were generated by Nishida et al.. In this study, structural response analyses of general RC structure are conducted with the 2,736 waves of ground motions which were generated from one seismic source, minami-kanto earthquakes. These ground motions incorporate the differences of their seismic-source characteristics. The multi-regression analyses are also conducted with the results of response analysis. As a result, the seismic moment, stress drop and Q-value coefficient showed clear positive correlation with seismic intensities and maximum structural responses. This can be expressed by the relationship between the Fourier spectra of seismic source and seismic-source characteristics. On the other hand, asperity location showed negative correlation with seismic intensities and maximum structural responses. The trend can be expressed by the relationship of location between reference site and faults.

Development of a dynamic CT system for neutron radiography and consecutive visualization of three-dimensional water behavior in a PEFC stack

Murakawa, Hideki*; Hashimoto, Michinori*; Sugimoto, Katsumi*; Asano, Hitoshi*; Takenaka, Nobuyuki*; Mochiki, Koichi*; Yasuda, Ryo

Nippon Kikai Gakkai Rombunshu, B, 77(784), p.2255 - 2262, 2011/12

https://doi.org/10.1299/kikaib.77.2255

Natural analogue study on trace element migration in geological formation at Horonobe area, Japan

Iwatsuki, Teruki; Ishii, Eiichi; Mizuno, Takashi; Honda, Teruyuki*

Tokyo Toshi Daigaku Genshiryoku Kenkyusho Kenkyushoho, (36), p.1 - 13, 2010/07

http://ci.nii.ac.jp/naid/40017342457

Trace element analysis in deep rock formation of Horonobe area, Hokkaido was conducted to construct the estimation technique on trace element migration. The distribution of trace element in rock formations suggests that those has not migrate in wide area. However those concentration in and around several fault are inhomogenious indicating the faults has a role of migration path. The analysis of trace element concentration is available to estimate the migration path.