Operando Br K-edge dispersive X-ray absorption fine structure analysis for Br/Br redox mediator for Li-Air batteries

Ito, Kimihiko*; Matsumura, Daiju; Song, C.*; Kubo, Yoshimi*

ACS Energy Letters (Internet), 7(6), p.2024 - 2028, 2022/06

https://doi.org/10.1021/acsenergylett.2c00912

Proposal of evaluation method of graphite incombustibility

Hamamoto, Shimpei; Ohashi, Hirofumi; Iigaki, Kazuhiko; Shimazaki, Yosuke; Ono, Masato; Shimizu, Atsushi; Ishitsuka, Etsuo

Proceedings of 2021 International Congress on Advances in Nuclear Power Plants (ICAPP 2021) (USB Flash Drive), 6 Pages, 2021/10

Since the HTGR has a large amount of graphite material in the core, it is necessary to assume an accident in which the reactor pressure boundary is damaged and air flows into the core. It is important to state that at the time of this accident, graphite does not burn and the accident does not develop due to the heat of oxidation reaction. Therefore, in this study, in order to evaluate the combustibility of graphite materials, we propose a method to compare the calorific value and heat removal amount of the material. When calculating the calorific value, the structural material of HTTR, a high-temperature gas reactor in Japan, was used as a reference. The amount of air in contact with the structural material is a value determined from the chimney effect. The amount of heat release is the sum of convection and radiation. As a result of comparing the heat generation amount with the heat removal amount, it was shown that the heat release amount was always larger than the heat generation amount. This result shows that the graphite material does not depend on the state at the time of the air inflow accident, the temperature decreases and does not burn. It is important to clearly explain the non-flammability of graphite materials when deciding how to deal with severe accidents in HTGRs. This quantitative evaluation method based on a simple theory is considered useful.

Design approach for mitigation of air ingress in high temperature gas-cooled reactor

Sato, Hiroyuki; Ohashi, Hirofumi; Nakagawa, Shigeaki

Mechanical Engineering Journal (Internet), 4(3), p.16-00495_1 - 16-00495_11, 2017/06

http://doi.org/10.1299/mej.16-00495

This paper intends to propose a practical solution to protect the HTR from severe oxidation against air ingress accidents without reliance on subsystems. Firstly, a change is made to the center reflector structure to minimize temperature difference during the accident condition in order to reduce buoyancy-driven natural circulation in the reactor. Secondly, a modified structure of the upper reflector is suggested to prevent massive air ingress against a rupture in standpipes. As a preliminary study, a numerical analysis is performed for a typical prismatic-type HTGR. The results showed that amount of air ingress into the reactor can be significantly reduced with practical changes to local structure in the reactor.

Design approach for mitigation of air ingress in high temperature gas-cooled reactor

Sato, Hiroyuki; Ohashi, Hirofumi; Nakagawa, Shigeaki

Proceedings of 24th International Conference on Nuclear Engineering (ICONE-24) (DVD-ROM), 8 Pages, 2016/06

https://doi.org/10.1115/ICONE24-60232

This paper intends to propose a practical solution to protect HTGR from severe oxidation against air ingress accidents without reliance on subsystems. Firstly, a change is made to the center reflector structure to minimize temperature difference during the accident condition in order to reduce buoyancy-driven natural circulation in the reactor. Secondly, a modified structure of the upper reflector is suggested to prevent massive air ingress against a rupture in standpipes. As a preliminary study, a numerical analysis is performed for a typical prismatic-type HTGR to study the effectiveness of the proposed design concept using simplified lumped element models. The results showed that amount of air ingress into the reactor can be significantly reduced with practical changes to local structure in the reactor.

Evaluation of heat exchange performance for air-cooler in HTTR

Tochio, Daisuke; Nakagawa, Shigeaki

JAERI-Tech 2005-041, 109 Pages, 2005/08

JAERI-Tech-2005-041.pdf:4.48MB

In High Temperature Engineering Test Reactor (HTTR) of 30MW, the generated heat at reactor core is finally dissipated at the air-cooler by way of the heat exchangers of the primary pressurized water cooler and the intermediate heat exchanger. To remove generated heat at reactor core and to hold reactor inlet coolant temperature to specified temperature, heat exchangers in main cooling system of HTTR should have designed heat exchange performance. In this report, heat exchange performance for ACL in main cooling system is evaluated with previous operation data, and evaluated values are compared with designed value. Moreover, heat exchange performance at full power operation is estimated for the air temperature. As the result, ACL has heat exchange performance removing generated heat at reactor core under the designe ACL inlet air temperature of 33C.

Estimation of heat removal characteristics for air-cooler in HTTR

Tochio, Daisuke; Nakagawa, Shigeaki; Takada, Eiji*; Sakaba, Nariaki; Takamatsu, Kuniyoshi

JAERI-Tech 2003-097, 55 Pages, 2004/01

JAERI-Tech-2003-097.pdf:3.34MB

In high temperature engineering test reactor (HTTR) of 30 MW, the generated heat at reactor core is finally dissipated at the air-cooler (ACL) by way of the heat exchangers of the primary pressurized water cooler (PPWC) and the intermediate heat exchanger (IHX). Therefore, air temperature (secondary-side condition at ACL) is important factor for the heat removal capability of the reactor. Coping with the air temperature, stable reactor inlet temperature control is achieved by adjusting of ACL coolant temperature with coolant (pressurized water and air) flow rate. ACL heat removal characteristic was based on the previous operation data in rise-to-power test and in-service operation at HTTR. And evaluate heat removal capability at summertime air temperature as the most severe condition was estimated. As the result, it was confirmed that the rated power of 30 MW can be removed at the condition of summertime air-temperature.

Characteristics of a simultaneous sampling system for the speciation of atmospheric T and C, and its application to surface and soil air

Amano, Hikaru; Koma, T.*; Atarashi-Andoh, Mariko; Koarashi, Jun; Iida, Takao*

Journal of Radioanalytical and Nuclear Chemistry, 252(2), p.353 - 357, 2002/00

https://doi.org/10.1023/A:1015782726049

no abstracts in English

Radiation control on wastes recovery work in wastes storage pit

Ito, Yasuhisa; Noda, Kimio; ;

JNC TN8410 2001-018, 67 Pages, 2001/04

JNC-TN8410-2001-018.pdf:2.96MB

There are waste storage pits where non-radioactive wastes generated from plutonium fuel facilities were stored in JNC Tokai Works. But radioactive wastes were found in one of the pit during wastes arrangement works. Therefore we set the pit temporary controlled area and recovered wastes from it. This report describes the radiation control technique of recovery work in detail.

Improvement of the technique for stack monitoring based on behavior analysis of natural radio-nuclides; The technique for reducing the value of the exhaust monitor's background

Izaki, Kenji; Noda, Kimio; ; Kashimuta, Yoshio*

JNC TN8410 2001-005, 30 Pages, 2001/01

JNC-TN8410-2001-005.pdf:0.62MB

Stack monitoring is the most important work in radiation control works. Exhaust monitors used for stack monitoring have the background (which is the counts by natural radio-nuclides) on normal condition, and the values of the background vary with the facilities. Therefore, if the value of background is high, it is difficult to estimate rapidly the radioactive concentration in the exhaust. In order to estimate rapidly the radioactive concentration in exhaust, we analyzed the behavior of natural radioactivity in the facilities and examine the technique fo reducing the value of the background. As a result of the examination, we found that it is possible to estimate rapidly if we change over the monitoring point to immediately after the HEPA filters on the exhaust duct. In this reports, the analyzed results of behavior of natural radio-nuclides in the facilities and the technique for reducing the values of the background are described. To reduce the value of the background has a major effect on not only rapidly estimating the radioactive density in the exhaust but also finding the unusual things on stack monitoring.

Derived air concentrations of the radionuclides not listed in the present regulations and ICRP Publications 68 and 72; Supplement of JAERI-Data/Code 2000-001

Kawai, Katsuo; Endo, Akira

JAERI-Data/Code 2000-033, 59 Pages, 2000/10

JAERI-Data-Code-2000-033.pdf:3.35MB

no abstracts in English