Development of Cable Aging Acceptance Criteria for Nuclear Facilities

Project Description

Over time, exposure to harsh environmental conditions such as elevated temperatures, radiation, and humidity in nuclear installations can result in age-related degradation and failure of cables. In the current fleet of nuclear reactors, there are thousands of miles of cabling, many of which are exposed to harsh environmental conditions. For these cables, the jacket and insulation polymers harden and become brittle, making them more susceptible to crack formation and growth, moisture intrusion, and other mechanisms that can lead to cable failure. Moreover, the existing U.S. fleet of 99 nuclear reactors is aging with the average age of operation being 37 years. A majority of these nuclear power plants have applied for license renewals to operate beyond their original 40-year life for 60 years and almost all have been granted regulatory approval to extend their life. Further, a second license renewal referred to as subsequent license renewal or SLR is underway with a few nuclear sites already in the process of applying to operate up to 80 or more years. As these reactors pursue operating life extensions, the utilities must find a way to address issues associated with age-related degradation of cables. Designers of small modular reactors and advanced reactors are also in need of technologies that can be used to assess the performance of cables that will be installed in harsher environments (e.g. higher temperatures, radiation doses, humidity, etc.) than those in current generation of nuclear reactors.

The purpose of the proposed research collaboration between Analysis and Measurement Services Corporation (AMS) and researchers at Oak Ridge National Laboratory (ORNL) and Pacific Northwest National Laboratory (PNNL) is to develop acceptance criteria for mechanical, electrical, thermal, and chemical condition monitoring (CM) tests that trend with age-related degradation of electrical cables. The work to be performed under the project includes subjecting cables to thermal accelerated aging, radiation exposure, and periodic testing using CM techniques to trend their properties as they age. After the cable samples have been subjected to thermal and radiation aging, they will then be exposed to loss of coolant accident (LOCA) conditions to determine their point of failure. These LOCA test results will be used in conjunction with the CM data collected during the aging process to develop acceptance criteria that directly correlates with the end-of life-condition of a cable polymer.