Cosmic-ray muons to help evaluate radioactive materials in nuclear fuel debris

In 2011, an earthquake and tsunami triggered a core meltdown at Japan’s Fukushima Daiichi Nuclear Power Plant. The metallic cladding on the fuel rods and the nuclear fuel within melted and subsequently resolidified as fuel debris. Work has been ongoing to analyze structural damages and fuel debris distributions, which contain mixtures of nuclear fuel and other materials, and it is imperative to manage them based on their radioactive content for safe handling and storage.

Miyadera et al. demonstrated that muon scattering tomography, which creates images by measuring how muons deflect as they penetrate materials, is a promising tool for the task. After developing a prototype muon scanner, they used muon scattering to evaluate nuclear materials in fuel debris.

“The most challenging part was developing a prototype muon scanner capable of operating in a radiation environment,” said Miyadera. “Our muon scanner is resistant to radiation and can identify muon events even in the presence of gamma rays.”

The researchers also introduced an analytical method that incorporates muon scattering angles, muon stopping rate, and debris weight to estimate uranium dioxide levels in the debris. While the use of artificial intelligence for analysis is possible, this approach provides for a simpler understanding of the estimations.

“The muon scattering method is highly sensitive to high-atomic-number materials like uranium,” said Miyadera.

The study revealed that muon scattering measurements lasting for just a few hours can predict nuclear material amounts in debris with reasonable accuracy. The team thinks the approach could significantly enhance the safety and efficiency of handling and storing fuel debris from nuclear accidents like Fukushima and, as necessary, elsewhere.

Source: “Cosmic-ray muon scattering method to evaluate nuclear materials in fuel debris,” by Haruo Miyadera, Naoto Kume, Takuro Fujimaki, Yuki Nakai, Kyohei Noguchi, Souichi Ueno, Tsukasa Sugita, Kenji Kurihara, Takahiro Tanaka, Ryunosuke Mizuguchi, and Masaki Yoda, Journal of Applied Physics (2025). The article can be accessed at https://doi.org/10.1063/5.0288371 .

This paper is part of the Muography: Discoveries, Innovations, and Applications Collection, learn more here .