Differential pressure rise event for filters of HTTR primary helium gas circulators, 1; Investigation of differential pressure rise event

Nemoto, Takahiro; Arakawa, Ryoki; Kawakami, Satoru; Nagasumi, Satoru; Yokoyama, Keisuke; Watanabe, Masashi; Onishi, Takashi; Kawamoto, Taiki; Furusawa, Takayuki; Inoi, Hiroyuki; et al.

JAEA-Technology 2023-005, 33 Pages, 2023/05

JAEA-Technology-2023-005.pdf:5.25MB

During shut down of the HTTR (High Temperature engineering Test Reactor) RS-14 cycle, an increasing trend of filter differential pressure for the helium gas circulator was observed. In order to investigate this phenomenon, the blower of the primary helium purification system was disassembled and inspected. As a result, it is clear that the silicon oil mist entered into the primary coolant due to the deterioration of the charcoal filter performance. The replacement and further investigation of the filter are planning to prevent the reoccurrence of the same phenomenon in the future.

Alteration of organic compounds of interstellar origin in the solar system; Simulation experiments on the ground and in space

Kobayashi, Kensei*; Kawamoto, Yukinori*; Sarker, P. K.*; Ono, Keisuke*; Kuwahara, Hideharu*; Obayashi, Yumiko*; Kaneko, Takeo*; Mita, Hajime*; Yabuta, Hikaru*; Yoshida, Satoshi*; et al.

no journal, , 

Remediation mechanisms of uranium mill-tailing site at Ningyo-toge, Japan, under the circumneutral condition

Kawamoto, Keisuke*; Ochiai, Asumi*; Takeda, Ayaka*; Nakano, Yuriko*; Yokoo, Hiroki*; Oki, Takumi*; Onuki, Toshihiko*; Ohara, Yoshiyuki; Fukuyama, Kenjin; Utsunomiya, Satoshi*

no journal, , 

In the Ningyo-toge uranium mine, Okayama, Japan, various toxic elements such as U, As, and Ra are present in the mine wastewaters, of which the concentration except for Ra in the wastewater decrease below the regulatory limit by transport to the slag dumping pond. The mechanisms of decreasing their concentrations in the wastewaters are not fully understood. In order to understand the fundamental processes of natural attenuation at this site, we have investigated the wastewaters and solids from upstream to the pond at the downstream. Wastewater was contacted with oxygenated water and the amount of dissolved oxygen increased. Simultaneously dissolved ferrous iron was oxidized to form ferrihydrite nanoparticles, which are associated with silica colloids, As and U. The ferrihydrite nanoparticles as suspended colloids were transported to the pond in downstream, where the waste stream is completely oxidized. In the slag dumping pond, Mn dioxide, birnessite, dominantly occurs forming a mixture with ferrihydrite + silica colloid, which has a potential to adsorb Ra. Consequently, Fe hydroxides nanoparticles and Mn dioxides in Ningyo-toge play a key role on removing U, As and Ra from the wastewater.