Stabilization of post-experiment nuclear materials in Plutonium Fuel Research Facility

Sato, Takumi; Otobe, Haruyoshi; Morishita, Kazuki; Marufuji, Takato; Ishikawa, Takashi; Fujishima, Tadatsune; Nakano, Tomoyuki

JAEA-Technology 2023-016, 41 Pages, 2023/09

JAEA-Technology-2023-016.pdf:2.74MB

This report summarizes the results of the stabilization treatments of post-experiment nuclear materials in Plutonium Fuel Research Facility (PFRF) from August 2018 to March 2021. Based on the management standards for nuclear materials enacted after the contamination accident that occurred at PFRF on June 6, 2017, the post-experiment nuclear materials containing plutonium (Pu): samples mixed with organic substances that cause an increase in internal pressure due to radiolysis (including X-ray diffraction samples mixed with epoxy resin and plutonium powder which caused contamination accidents), carbides and nitrides samples which is reactive in air, and chloride samples which may cause corrosion of storage containers, were selected as targets of the stabilization. The samples containing organic materials, carbides and nitrides were heated in an air flow at 650 C and 950 C for 2 hours respectively to remove organic materials and convert uranium (U) and Pu into oxides. U and Pu chlorides in LiCl-KCl eutectic melt were reduced and extracted into liquid Cd metal by a reaction with lithium (Li) -cadmium (Cd) alloy and converted to U-Pu-Cd alloy at 500 C or higher. All of the samples were stabilized and stored at PFRF. We hope that the contents of this report will be utilized to consider methods for stabilizing post experiment nuclear materials at other nuclear fuel material usage facilities.

Stabilization treatment of Pu-bearing organic materials

Morishita, Kazuki; Sato, Takumi; Onishi, Takashi; Seki, Takayuki*; Sekine, Shinichi*; Okitsu, Yuichi*

JAEA-Technology 2021-024, 27 Pages, 2021/10

JAEA-Technology-2021-024.pdf:2.41MB

In the case of Plutonium (Pu)-bearing organic materials, organic materials are decomposed by alpha rays emitted mainly from Pu to generate hydrogen gas and other substances. Therefore, to safely store Pu-bearing organic materials for an extended period of time, organic materials must be eliminated. In addition, carbide and nitride fuels must be converted into oxides for safe storage in order to prevent the exothermal reaction of these fuels with oxygen/moisture in air. A survey of the literature on the stabilization treatment of Pu-bearing organic materials confirmed that organic materials can be decomposed and removed by heating at 950 C (1223.15 K) or greater in air. Furthermore, based on the calculated thermodynamic parameters of oxidation reaction of carbide and nitride fuels in air, it was estimated that these fuels would be oxidized in air at 950 C because the equilibrium oxygen partial pressure in the oxidation reaction at 950 C was lower than 2.110 Pa (oxygen partial pressure in air). Therefore, it was decided to stabilize Pu-bearing organic materials by heating at 950 C in air to remove the organic materials and oxidize the carbide and nitride fuels. As a mock-up test to remove the organic materials, thin sheets of epoxy resin were heated in air. The changes in appearance and weight before and after heating in air showed that organic materials can be removed. After the mock-up test, Pu-bearing organic materials were also stabilized by heating in the similar condition.

Ion radiation effect of chemical bonding on CuInS crystals

Murakami, Go*; Abe, Kenichiro*; Ashida, Atsushi*; Wakita, Kazuki*; Watase, Seiji*; Izaki, Masanobu*; Oshima, Takeshi; Morishita, Norio; Ito, Hisayoshi

no journal, , 

no abstracts in English

Analysis of nuclides in deposition collected from primary containment vessel of Fukushima Daiichi unit 1

Morishita, Kazuki; Onishi, Takashi; Maeda, Koji; Mizokami, Masato*; Ito, Kenichi*; Mizokami, Shinya*

no journal, , 

no abstracts in English

Investigation of in-reactor cesium chemical behavior in TEPCO's Fukushima Daiichi Nuclear Power Station accident, 13; Chemical analysis of samples collected from the operating floor of the reactor building of Unit 2

Morishita, Kazuki; Onishi, Takashi; Maeda, Koji; Mizokami, Masato*; Ito, Kenichi*; Mizokami, Shinya*

no journal, , 

Samples, collected from the operating floor of the reactor building of Fukushima Daiichi Unit 2, were immersed in deionized water and nitric acid. Immersed solutions were analyzed by gamma-ray spectrometry and ICP-MS. Analyses suggest small amount of Fe, Mn and Cu derived from structural materials of nuclear reactor, and Te, Cs and U derived from spent fuels.

Demonstration research on fast reactor recycling using low decontaminated MA-bearing MOX fuels, 11; Evaluation of phase states and thermal properties of MA-bearing MOX fuels

Yokoyama, Keisuke; Watanabe, Masashi; Onishi, Takashi; Morishita, Kazuki; Kato, Masato

no journal, , 

no abstracts in English