High temperature gas-cooled reactors

Takeda, Tetsuaki*; Inagaki, Yoshiyuki; Aihara, Jun; Aoki, Takeshi; Fujiwara, Yusuke; Fukaya, Yuji; Goto, Minoru; Ho, H. Q.; Iigaki, Kazuhiko; Imai, Yoshiyuki; et al.

High Temperature Gas-Cooled Reactors; JSME Series in Thermal and Nuclear Power Generation, Vol.5, 464 Pages, 2021/02

https://doi.org/10.1016/C2018-0-05383-9

As a general overview of the research and development of a High Temperature Gas-cooled Reactor (HTGR) in JAEA, this book describes the achievements by the High Temperature Engineering Test Reactor (HTTR) on the designs, key component technologies such as fuel, reactor internals, high temperature components, etc., and operational experience such as rise-to-power tests, high temperature operation at 950C, safety demonstration tests, etc. In addition, based on the knowledge of the HTTR, the development of designs and component technologies such as high performance fuel, helium gas turbine and hydrogen production by IS process for commercial HTGRs are described. These results are very useful for the future development of HTGRs. This book is published as one of a series of technical books on fossil fuel and nuclear energy systems by the Power Energy Systems Division of the Japan Society of Mechanical Engineers.

Initial quantum levels of captured muons in CO, CO, and COS

Yoshida, Go*; Ninomiya, Kazuhiko*; Inagaki, Makoto*; Higemoto, Wataru; Strasser, P.*; Kawamura, Naritoshi*; Shimomura, Koichiro*; Miyake, Yasuhiro*; Miura, Taichi*; Kubo, Kenya*; et al.

Journal of Radioanalytical and Nuclear Chemistry, 320, p.283 - 289, 2019/05

https://doi.org/10.1007/s10967-019-06470-4

The role of valence electrons for the muon capture process by molecules is experimentally investigated with the aid of cascade calculations. Low-momentum muons are introduced to gas targets below atmospheric pressure. The initial states of captured muons are determined from the measured muonic X-ray structure of the Lyman and Balmer series. We propose that the lone pair electrons in the carbon atom of CO significantly contribute to the capture of a muon with large angular momenta.

Elemental analysis system with negative-muon beam

Osawa, Takahito; Ninomiya, Kazuhiko*; Yoshida, Go*; Inagaki, Makoto*; Kubo, Kenya*; Kawamura, Naritoshi*; Miyake, Yasuhiro*

JPS Conference Proceedings (Internet), 8, p.025003_1 - 025003_6, 2015/09

https://doi.org/10.7566/JPSCP.8.025003

We report a new elemental analysis system that uses an intense negative-muon beam at J-PARC Materials and Life Science Experimental Facility, Muon Science Establishment. This paper presents the preliminary results of measurements for meteorites and standard material. The main system components are a water-cooled electromagnet, an Al flight tube, an Al sample chamber, a lead shielding body, and a Ge detector. Optimum currents for the electromagnet were determined by recording beam profiles with a CCD camera; the muon beam was shaped by collimators. The background and signal-to-noise ratio was significantly better than that obtained in a previous study, and all significant elements in the meteorite and standard samples were detected. Thus, this system can be used for muonic X-ray analysis of extraterrestrial materials.

Enhancement of the methodology of repository design and post-closure performance assessment for preliminary investigation stage, 3; Progress report on NUMO-JAEA collaborative research in FY2013 (Joint research)

Shibata, Masahiro; Sawada, Atsushi; Tachi, Yukio; Makino, Hitoshi; Wakasugi, Keiichiro; Mitsui, Seiichiro; Kitamura, Akira; Yoshikawa, Hideki; Oda, Chie; Ishidera, Takamitsu; et al.

JAEA-Research 2014-030, 457 Pages, 2015/03

JAEA-Research-2014-030.pdf:199.23MB

JAEA and NUMO have conducted a collaborative research work which is designed to enhance the methodology of repository design and post-closure performance assessment in preliminary investigation stage. With regard to (1) study on rock suitability in terms of hydrology, based on some examples of developing method of hydro-geological structure model, acquired knowledge are arranged using the tree diagram, and model uncertainty and its influence on the evaluation items were discussed. With regard to (2) study on scenario development, the developed approach for "defining conditions" has been reevaluated and improved from practical viewpoints. In addition, the uncertainty evaluation for the effect of use of cementitious material, as well as glass dissolution model, was conducted with analytical evaluation. With regard to (3) study on setting radionuclide migration parameters, based on survey of precedent procedures, multiple-approach for distribution coefficient of rocks was established, and the adequacy of the approach was confirmed though its application to sedimentary rock and granitic rock. Besides, an approach for solubility setting was developed including the procedure of selection of solubility limiting solid phase. The adequacy of the approach was confirmed though its application to key radionuclides.

An International initiative on long-term behavior of high-level nuclear waste glass

Gin, S.*; Abdelouas, A.*; Criscenti, L.*; Ebert, W.*; Ferrand, K.*; Geisler, T.*; Harrison, M.*; Inagaki, Yaohiro*; Mitsui, Seiichiro; Mueller, K. T.*; et al.

Materials Today, 16(6), p.243 - 248, 2013/06

https://doi.org/10.1016/j.mattod.2013.06.008

The nations producing borosilicate glass as a confinement material for high-level waste resulting from spent fuel reprocessing have decided to reinforce scientific collaboration in order to obtain consensus on the mechanisms controlling the long-term dissolution rate of glass. This goal is the most important issue for developing reliable predictive models usable for performance assessment and safety demonstration of geological storage of such materials. This collaboration involves numerous laboratories working either in fundamental or applied research and using all the modern tools available in material science. We present first the situation of the six countries involved in the project regarding their history in nuclear waste vitrification, current policy, and geological disposal project development. This provides an understanding of the common and country specific needs regarding the issue of long-term behavior of glass. Then main proposals and first results are briefly presented.

Influence of rock spalling on concrete lining in shaft sinking at the Horonobe Underground Research Laboratory

Tsusaka, Kimikazu; Inagaki, Daisuke; Nago, Makito*; Koike, Masashi*; Matsubara, Makoto*; Sugawara, Kentaro*

Dai-13-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (CD-ROM), p.911 - 916, 2013/01

A repository for high-level radioactive waste in deep underground consists of several underground structures such as access and disposal drifts and shafts. In deep geological disposal project, a shaft is the first underground structure to be constructed and the last one to be backfilled. Therefore, the stability of shaft is one of key factors to steadily manage the project in the construction and operation phases. In this paper, the authors discuss influence of rock spalling on concrete lining in shaft sinking. Japan Atomic Energy Agency has been constructing three shafts (one is for ventilation and the others are for access use) up to a depth of 500 m in the Horonobe Underground Research Laboratory. During the construction of the Ventilation Shaft (4.5 m in diameter) below a depth of 250 m, rock spalling occurred at several depths and an open crack has developed in a concrete lining installed just above rock spalling. The authors have measured geometry of shaft wall by using three-dimensional laser scanner. They also conducted numerical analysis in order to calculate change in stress distribution and deformation induced by rock spalling in a concrete lining and the surrounding rock. As a result, it was clarified that rock spalling induced tensile stress in the vertical direction in a concrete lining. Especially, the tensile stress in a concrete lining was likely to exceed tensile strength of a concrete lining in the case that it developed more than 100 cm in depth.

An Observational construction management in the Horonobe Underground Research Laboratory Project

Tsusaka, Kimikazu; Inagaki, Daisuke; Tokiwa, Tetsuya; Yokota, Hideharu; Nago, Makito*; Matsubara, Makoto*; Shigehiro, Michiko*

Proceedings of ITA-AITES World Tunnel Congress 2012 (WTC 2012)/38th General Assembly (CD-ROM), 8 Pages, 2012/05

http://www.wtc2012.com/PDF_Files/Proceedings_web.pdf

In the Horonobe URL Project, three shafts are planned to be excavated up to the depth of 500 m in the Neogene sedimentary rocks. The host rock of the URL site is comprised of diatomaceous and siliceous mudstones, which are the Koetoi and Wakkanai Formations, respectively. Approximately 100 m thick fracture zone with high hydraulic conductivity develops above about 400 m in depth in the Wakkanai Formation. The shaft sinking through the fracture zone is the most challenging issue from the aspect of tunnel engineering in the project. In the fracture zone, there is high possibility of severe breakout and spalling in shaft wall because the shafts might be intersecting faults with the size greater than shaft diameter in addition to low intact rock strength at great depth. In practice, prior to the construction of the Ventilation Shaft through the fracture zone below a depth of 250 m, the three dimensional fault distribution were predicted by integrating borehole investigation results and geological response to pre-excavation grouting operation. The countermeasure was also designed against massive spalling. During the shaft sinking, fracture mapping of shaft wall was carried out in order to evaluate the prediction of fault distribution. Roughness of shaft wall was also measured by three dimensional laser scanner in order to investigate the shape and volume of spalling resulting from the excavation work. Consequently, the Ventilation Shaft has successfully been constructed through the fracture zone. This is because the prediction of fault distribution was accurate, and the countermeasure against concrete lining damage due to spalling was promptly applied.

Spalling in response to shaft sinking at great depth in soft sedimentary rock

Tsusaka, Kimikazu; Inagaki, Daisuke; Nago, Makito*; Matsubara, Makoto*

Chika Kukan Shimpojiumu, Rombunshu, 17, p.155 - 162, 2012/01

Japan Atomic Energy Agency has been constructing an underground research laboratory in order to enhance the reliability of relevant disposal technologies of high-level radioactive waste in Horonobe, Hokkaido. A ventilation shaft (4.5 m in diameter) and two access shafts (6.5 m in diameter) are being excavated through the Neogene sedimentary rocks until the depth of 500 m. Based on the results of borehole investigation and pre-grounting operation in bedrock with high permeability from 250 m to 375 m in depth, the three dimensional fracture distribution map were built and the locations with high possibility of spalling in shaft wall in response to excavation were predicted prior to the shaft sinking from a depth of 250 m. Some amounts of spalling has occurred in several depths during shaft sinking from 250 m to 280 m in depth. The shape of each spalling was measured by means of three dimensional laser scaning system. As a result, spalling in shaft wall occurred along the faults predicted based on the three dimensional fracture distribution. In addition, spalling by brittle failure in shaft wall was also observed with a few extensile fractures which were expected to be induced by excavation. Based on the shape of spalling, it was confirmed that the applied shaft sinking procedure properly prevented a massive spalling.

Negative and positive ion trapping by isotopic molecules in cryocrystals in case of solid parahydrogen containing electrons and H radical cations

Shimizu, Yuta*; Inagaki, Makoto*; Kumada, Takayuki; Kumagai, Jun*

Journal of Chemical Physics, 132(24), p.244503_1 - 244503_8, 2010/06

https://doi.org/10.1063/1.3432780

We performed electron spin resonance studies of trapped electrons and H radical cations produced by radiolysis of solid para-H, para-H-ortho-D, and para-H-HD mixtures. Yields of both trapped electrons, and H radical cations, and its isotopic analogues increased with increasing the concentration of ortho-D and HD concentrations in solid para-H. We have concluded that electrons were found trapped nearby an ortho-D or an HD in solid para-H due to a the long-range charge-induced dipole and charge-induced quadrupole interactions between an electrons and an isotopic hydrogen molecules.

Measurement of HLW glass dissolution/alteration kinetics by using micro-reactor flow-through test method

Inagaki, Yaohiro*; Mitsui, Seiichiro; Makigaki, Hikaru*; Idemitsu, Kazuya*; Arima, Tatsumi*; Bamba, Tsunetaka; Noshita, Kenji*

Materials Research Society Symposium Proceedings, Vol.1193, p.219 - 228, 2009/05

https://doi.org/10.1557/PROC-1193-219

We developed a new flow-through test method using micro-reactor, and applied it to measurement of the dissolution/alteration kinetics for a simulated HLW glass (P0798). In this method, a glass coupon is placed just on a Teflon plate having a micro-channel, and a solution is injected into the inlet of micro-channel by micro-syringe pump at a constant flow rate. The injected solution flows through the micro-channel reacting with the glass to the outlet, and the outlet solution is retrieved at certain intervals to be analyzed for determination of the dissolution/alteration rate. This method has some major features, i.e., simple test apparatus with compact size, high S/V ratio, sensitive/precise measurement of the glass dissolution/alteration rate, adequate glass shape for analysis of reacted glass surface, and so on. By use of this method the dissolution/alteration rate for P0798 was measured as a function of pH, temperature, flow rate, and time, and some available results were obtained to evaluate the dissolution/alteration kinetics.