報告書番号

H11007

タイトル（和文）

熱・放射線ストレスによるケーブル絶縁体の劣化特性の調査および新劣化モデルの考案

タイトル（英文）

Literature Review and Model Formulation of Degradation Characteristics in Cable Insulating Polymers under Thermal and Radiation Stresses

概要 （図表や脚注は「報告書全文」に掲載しております）

原子力発電所の安全系ケーブル絶縁体の状態監視法開発では，絶縁体の誘電特性に依存する監視信号と機械的劣化指標の相関解明が必要である。当所では，この監視法の妥当性検証や絶縁体健全性評価に資するため，絶縁体劣化モデルの構築を目指している。文献調査より，熱・放射線相乗効果と線量率効果までは現行モデルで説明できることが分かった。ただし，実環境劣化推定に重要な活性化エネルギーの低下や，その支配要因と考えられる酸化防止剤はモデル化されていない。そこで，酸化防止剤特性を含めた新モデルを考案し，このモデルが熱加速劣化試験で得た劣化分布を再現できることを確認した。また，この新モデルによれば，種々の熱・放射線強度条件下で劣化生成物と酸化防止剤が不均一分布になる。状態監視法開発で必要な微小領域の材料分析データの解析にこのモデルが応用できると考えられる。

概要 （英文）

A condition monitoring method for safety cables used in nuclear power plants is now being promoted. Complying with recent trend of the viewpoint of scientific rationality, a model which can be used to investigate the monitoring mechanism of degraded parts is required. The literature review carried out in this the present study shows that current models can explain both the synergetic effects of radiation-thermal combined environments and the dose-rate effects. However, they do not assume the non-Arrhenius characteristic, which is important in estimating the results of the low-temperature degradation behavior. This non-Arrhenius characteristic seems to be attributed to antioxidants, but neither its degradation control effects nor the critical concentration behaviors are included in those models. Such antioxidant effects are added to conventional models in the present study to improve its applicability. As a result, it is confirmed that this new model successfully fits an aging behavior of cross-linked polyethylene. Since the antioxidant behavior is also estimated in this fitting simultaneously, the model is expected to further extend its ability to simulate to the non-Arrhenius characteristic. The model can also be expected to support an investigation of the monitoring mechanism because it can estimate the two above-mentioned kinds of distribution profiles for several intensities of radiation.

報告者

キーワード