As for polymeric cable insulations used in nuclear power plants, acceleration aging is used both for type tests and for aging estimation. In order to explain both degradation phenomena, which occur under the test conditions and under actual operation environments, numerical calculation programs are needed. The present paper refines such program to fit to so-called reversed sequential acceleration that applies radiation followed by thermal aging. The advantage of the calculation is to provide correlation map of several parameters such as the dose rate, radiation exposure time, heating temperature, and heating time. The program also judges the feasibility for acceleration aging by estimating the homogeneity of degradation inside the bulk. The correlation between radiation and heating is numerically investigated by changing dose rate and heating time, and the result shows complex three-dimensional surface. Two kinds of featured dose-rate dependencies are obtained for the cases that the target degradation is achieved only by the radiation or heating. These characteristics show an intersection on the dose rate dependency, which results in providing a key factor to divide the role and contribution against the target degradation. The paper also discusses the effect of heating temperature on such a time-based relation between radiation and heating time.