Muons for Non-Destructive Analysis of Deep Geological Repository Barriers

Abstract

The concept of deep geological repositories is adopted internationally for the long-term management of used nuclear fuel. The Nuclear Waste Management Organization of Canada uses an engineered barrier system composed of both natural and man-made barriers for the safe containment of spent fuel. This system and the repository design are designed for one million years of safe containment. Thus, the evaluation of the long-term performance of the system is crucial to its practical use. As such, many analytical methods have been used to monitor corrosion barrier performance and degradation. We will use a novel muon spectroscopy method to achieve this. The technique is similar to X-ray fluorescence, however, using negative muons. Proton accelerators are used to send protons to hit a target, producing pions, which then decay into muons, which generally come in both positive and negative forms. Negative muons are comparable to heavy electrons and are used here as an analytical tool. Using Monte Carlo simulations to estimate the Stopping and Range of Ions in Matter, we have established the precise momenta required for desired muon implantation depths. These values are used to implant muons at selected depths in the sample. As the muon decays, it emits X-rays indicative of the elemental composition of its surroundings. In this way, complete non-destructive analysis of species underneath the surface of used fuel containers can be achieved. Our focus is on elemental analysis of the copper and steel layers of these containers where the tuning of momenta allows us to position muons within the layers and at the copper-steel metal layer interface in the Canadian container design. This enables a unique analysis of the layer purities and diffusion behaviour of any species in deep geological repository barriers.