Reliable prediction of material service lifetime is important for ensuring safe operation in safety-critical systems such as nuclear facilities. Materials in these environments degrade due to several simultaneous effects, most important stressors are heat and radiation. In this work, samples of medium density polyethylene cable insulation were subjected to thermal (110 °C) and γ-radiation stress (500 Gy h⁻¹); a combined thermal and radiation test (85 °C and 4.5 Gy h⁻¹) was also performed. Stability of cable insulation was studied by differential scanning calorimetry and isoconversional kinetic analysis employing a non-Arrhenian temperature function was carried out. From the dependence of residual stability on the degradation dose a predictive model for the cable service life was developed based on the thermal and radiation stress tests; the model validity was verified using the combined stress test results. The model assumes a first-order exponential decay of the residual stability with degradation dose. It allows to predict the degree of insulation damage in wide range of environmental conditions as both temperature and radiation dose effects are considered and radiation dose rate effect is also taken into account.

对材料使用寿命的可靠预测对于确保在关键安全系统（例如核设施）中的安全运行非常重要。这些环境中的材料会由于多种同时作用而降解，最重要的压力因素是热量和辐射。在这项工作中，对中密度聚乙烯电缆绝缘层的样品进行热（110°C）和γ辐射应力（500 Gy h ^-1）。热辐射试验（85°C和4.5 Gy h ^-1）也已执行。通过差示扫描量热法研究了电缆绝缘的稳定性，并利用非阿里尼亚温度函数进行了等转换动力学分析。根据残余稳定性对降解剂量的依赖性，在热应力和辐射应力测试的基础上，建立了电缆使用寿命的预测模型。使用组合压力测试结果验证了模型的有效性。该模型假设残留稳定性随降解剂量的一阶指数衰减。由于考虑了温度和辐射剂量的影响，并且还考虑了辐射剂量率的影响，因此可以预测各种环境条件下的绝缘破坏程度。