Temperature-Accelerated Life Test stress level design methodology for HLW repository monitoring sensor

Abstract

The high-level nuclear waste (HLW) repository is subject to various stresses, including high temperatures, high humidity, and radiation. Over time, these stresses cause the structure to deteriorate and induce cracks. Hence, structural health monitoring with monitoring sensors is necessary for safety. Unfortunately, there are some problems with the installation of sensors. Not only can high temperature, high humidity, and radiation contribute to the deterioration of the repository, but they also shorten the life of the sensors. Additionally, since the sensors are installed within the bentonite buffer and backfill tunnel, they cannot be replaced even if they fail. That's why it is necessary to assess the sensors' life in the repository's environmental conditions before installing them. Accelerated Life Test can be used to assess the life of sensors under specific environmental conditions by creating a life model based on failure data obtained under conditions harsher than the environmental conditions in a short time. In order to conduct a reliability test, such as an accelerated life test, it is essential to get the same failure mode and to design appropriate stress levels. Therefore, this paper presents a literature review of failure modes of sensors for temperature conditions among repository environmental conditions and a methodology for designing stress levels for conducting accelerated life tests.