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報告書

ナトリウム冷却金属燃料高速炉用炉心過渡挙動解析コード; EXCURSの改造と解析例

岡嶋 成晃; 軍司 康義*; 向山 武彦

JAERI-M 92-031, 81 Pages, 1992/03

JAERI-M-92-031.pdf:2.29MB

アクチノイド消滅処理専焼炉(ABR)の設計研究において、炉心過渡特性解析は安全性の観点から、重要である。そこで、Na冷却酸化物燃料高速炉用炉心過渡挙動解析コード「EXCURS」を、Na冷却金属燃料高速炉に適用できるように改造を行った。改造の妥当性を確認するために、ANLで行ったEBR-IIでの過渡試験解析結果や電中研で行った1000MWe級金属燃料高速炉の過渡特性解析結果と改造「EXCURS」の解析結果とを比較した。その結果、全般的に改造「EXCURS」の解析結果と他の解析結果は良い一致を示し、改造「EXCURS」がLMRやABRの炉心過渡現象を予測するのに使用できることが確認できた。改造「EXCURS」を用いて、Na冷却金属燃料専焼炉(M-ABR)のULOFおよびUTOP解析を実施した。さらに、安全性を検討するために、燃料の熱伝導率やフィードバック反応度係数のATWS解析結果に与える影響について、パラメータサーベイを行った。その結果、フラワリング係数、遅発中性子割合、燃料熱伝導率が燃料最高温度に強く影響することが分かった。

口頭

Autophagy activated by Auger effect induced by soft X-ray microbeam

野口 実穂; 横谷 明徳; 神長 輝一; 藤井 健太郎; 鈴木 啓司*; 宇佐美 徳子*

no journal, , 

In this study, to clarify activation of autophagy on energy deposition in the cell nucleus or cytoplasm by the photoelectric effect, we investigated change of autophagic activity in human fibroblast cells irradiated with soft X-ray microbeam (5.35keV).Using a synchrotron X-ray microbeam, we irradiated 25 to 61 cells by targeting nuclei with square X-ray microbeam (10 $$mu$$m $$times$$ 10 $$mu$$m). For irradiating cytoplasm, 60 $$mu$$m $$times$$ 60 $$mu$$m square X-ray microbeam was used with a metal mask of 10$$mu$$m $$times$$ 10 $$mu$$m central area not to irradiate the cell nucleus. Induction of autophagy was measured using the fluorescent probe, Cyto-ID Green, which stains specifically autophagic vacuoles. Irradiated cells were treated with the dye 15 min before observation. The cells observed by a fluorescent microscope were quantified as mean values of the fluorescent intensity per cell. We observed autophagic fluorescence in nucleus- or cytoplasm-irradiated cells at 1 day to 4 days after irradiation. Some of these cells showed highly localized strong fluorescence. Such localized fluorescence was rarely observed when irradiated with a wide beam from a conventional higher energy X-ray machine (150 kVp). A lot of nucleic irradiated cells, rather than cytoplasm-irradiated cell, showed cell death especially at 4 days after irradiation. When irradiated with the wide beam X-rays, on the other hand, the cells sustained irreversible growth arrest, and maintained their viability. These results indicate that the soft X-ray microbeam exposure is a powerful probe to provide us an aspect of autophagic activation by photoelectric (Auger) effect in a particular part of cells.

口頭

Exposure to X-rays enhances autophagy in human fibroblast cells

野口 実穂; 横谷 明徳; 鈴木 啓司*; 藤井 健太郎

no journal, , 

The exposure to ionizing radiation causes damage to not only DNA but also proteins or organelles in cytoplasm of cells. Recent studies report that, for most of normal human fibroblasts and some of solid carcinoma cells, cells exposed to ionizing radiation sustain irreversible growth arrest, but still maintain their viability with showing senescence character even though they might have severe DNA damage. These suggests that, in irradiated fibroblasts, intracellular degradation system "autophagy" eliminates accumulated damaged proteins or dysfunctional organelles to avoid induction of apoptosis. In this study, to clarify the role of autophagy on cell survival, we investigated change of autophagic activity in irradiated fibroblast cells in terms of escape from apoptosis. Induction of autophagy in normal human fibroblast BJ1-hTERT cells irradiated with 20 Gy X-rays were measured using the fluorescent probe, Cyto-ID Green, which stains specifically autophagic vacuoles. Irradiated cells were treated with Cyto-ID Green 15 min before observation. The cells observed by a fluorescent microscope were quantified as mean values of the fluorescent intensity per cell. Irradiated cells showed about 3 times higher induction of autophagic activity than non-irradiated cells at 24 h after irradiation. The activation of autophagy persisted for at least 5 days (120 h) after irradiation. These results strongly suggest that highly induced autophagy is involved in the elimination of damaged proteins and organelles to keep their physiological functions, and avoid apoptosis. Frequency of apoptosis is expected to increase if the autophagic pathway is blocked. Results will also be presented for the treatments with pharmacological agent inhibiting the autophagic process.

口頭

第4世代SFRを対象としたSAS4AコードによるATWS事象の起因過程解析

久保田 龍三朗; 鈴木 徹; 川田 賢一; 久保 重信; 山野 秀将; 小山 和也*; 森脇 裕之*; 山田 由美*; 島川 佳郎*

no journal, , 

様々な炉心状態について、炉心設計と整合性の高い出力及び反応度データを作成する手法を新たに整備した。この新手法を用いて、実証施設規模の第4世代SFRを対象に、SAS4Aコードによる、定格出力及び部分出力からのULOF及びUTOPの起因過程解析を実施し、即発臨界が回避される見通しを得た。

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