The insulation around the electrical cabling in nuclear power plants is frequently made of ethylene-propylene rubber and crosslinked polyethylene that is subjected to low levels of environmental stressors and radiation over the duration of their decades long service life. For the purpose of maintenance and reactor recertification, it is necessary to develop a non-destructive approach to determine the degree of damage the insulation has sustained. Accelerated aging experiments are used to develop these methods, although it is unclear how to relate these specimens to in situ aged ones. Here a kinetic rate model is used to investigate the impact of radiation dose rate and total dose on the crosslinking and chain scission of polyethylene. Analytical expressions for the concentration of crosslinking and scission sites as a function of time and dose rate, both during and post irradiation, are presented. During irradiation the concentration of crosslinking sites increases linearly with time, and when the dosing ends the crosslinking reaction terminates. The scission reaction begins slower, due to the necessity of forming intermediate species, but increases in rate, and eventually the concentration of scission sites overtakes crosslinking. However, at low dose rates, less than 10 Gy/hr, scission damage is always the primary form of damage. Unlike the crosslinking reaction, scission continues for months and years due to the slow decomposition of the intermediate species.

中文翻译：

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模拟剂量率和时间对辐照聚乙烯交联和断裂的影响

核电站中电缆周围的绝缘材料通常由乙丙橡胶和交联聚乙烯制成，它们在数十年的长使用寿命期间承受低水平的环境压力和辐射。为了维护和反应堆重新认证的目的，有必要开发一种非破坏性方法来确定绝缘材料的损坏程度。加速老化实验用于开发这些方法，尽管尚不清楚如何将这些样本与原位老化的样本联系起来。这里使用动力学速率模型来研究辐射剂量率和总剂量对聚乙烯交联和断链的影响。交联和断裂位点的浓度作为时间和剂量率的函数，在辐照期间和辐照后的分析表达式。在辐照期间，交联位点的浓度随时间线性增加，当加料结束时，交联反应终止。由于形成中间体的必要性，断裂反应开始较慢，但速率增加，最终断裂位点的浓度超过交联。然而，在低于 10 Gy/hr 的低剂量率下，断裂损伤始终是主要的损伤形式。与交联反应不同，由于中间体的缓慢分解，断裂会持续数月甚至数年。在辐照期间，交联位点的浓度随时间线性增加，当加料结束时，交联反应终止。由于形成中间体的必要性，断裂反应开始较慢，但速率增加，最终断裂位点的浓度超过交联。然而，在低于 10 Gy/hr 的低剂量率下，断裂损伤始终是主要的损伤形式。与交联反应不同，由于中间体的缓慢分解，断裂会持续数月甚至数年。在辐照期间，交联位点的浓度随时间线性增加，当加料结束时，交联反应终止。由于形成中间体的必要性，断裂反应开始较慢，但速率增加，最终断裂位点的浓度超过交联。然而，在低于 10 Gy/hr 的低剂量率下，断裂损伤始终是主要的损伤形式。与交联反应不同，由于中间体的缓慢分解，断裂会持续数月甚至数年。在低于 10 Gy/hr 的低剂量率下，断裂损伤始终是主要的损伤形式。与交联反应不同，由于中间体的缓慢分解，断裂会持续数月甚至数年。在低于 10 Gy/hr 的低剂量率下，断裂损伤始终是主要的损伤形式。与交联反应不同，由于中间体的缓慢分解，断裂会持续数月甚至数年。