PREDICTIVE AGING RESULTS IN RADIATION ENVIRONMENTS

We have previously derived a time-temperature-dose rate superposition methodology, which, when applicable, can be used to predict polymer de gradation versus dose rate, temperature and exposure time. This method ology results in predictive capabilities at the low dose rates and lon g time periods appropriate, for instance, to ambient nuclear power pla nt environments. The methodology was successfully applied to several p olymeric cable materials and then verified for two of the materials by comparisons of the model predictions with 12 year, low-dose-rate agin g data on these materials from a nuclear environment. In this paper, w e provide a more detailed discussion of the methodology and apply it t o data obtained on a number of additional nuclear power plant cable in sulation (a hypalon, a silicone rubber and two ethylene-tetrafluoroeth ylenes) and jacket (a hypalon) materials. We then show that the predic ted, low-dose-rate results for our materials are in excellent agreemen t with long-term (7-9 year) low-dose-rate results recently obtained fo r the same material types actually aged under nuclear power plant cond itions. Based on a combination of the modelling and long-term results, we find indications of reasonably similar degradation responses among several different commercial formulations for each of the following ' 'generic'' materials: hypalon, ethylene-tetrafluoroethylene, silicone rubber and PVC. If such ''generic'' behavior can be further substantia ted through modelling and long-term results on additional formulations , predictions of cable life for other commercial materials of the same generic types would be greatly facilitated.