Canadian laboratory validates molten salt separation process with real spent fuel, extracting nearly 90% of plutonium in 24 hours

A chemical experiment in Canada involving real commercial reactor spent fuel has achieved noteworthy progress. Canadian Nuclear Laboratories, in shielded hot cells at Chalk River, used irradiated spent fuel from CANDU reactors to validate the first phase of Moltex Energy's “waste-to-stable-salt” process. The experiment showed that within 24 hours, 89.4% of the plutonium was transferred into the molten salt; by 60 hours, this proportion rose to 94.3%. Meanwhile, the vast majority of uranium remained outside the salt phase, indicating that the process exhibits strong selectivity in separating target elements.

This process, named WATSS, is not a plutonium purification route but rather a group separation technology. In addition to large quantities of uranium, spent fuel contains fission products as well as transuranic elements such as plutonium and americium, the latter being a significant source of long-term radiological risk. WATSS uses high-temperature chloride molten salt and specific reducing metals to convert transuranic oxides into salt-soluble forms, while most uranium oxides remain solid. In this experiment, researchers used niobium as the reducing metal; after 24 hours, only 0.05% of uranium entered the salt, dropping to 0.02% after 60 hours, demonstrating that it does not carry large amounts of uranium into the molten salt system.

The significance of this result lies in the fact that it was not based on computer simulations or surrogate material experiments, but was completed under real spent fuel conditions. Nuclear waste treatment technologies often face a gap between laboratory models and actual irradiated materials, because real spent fuel has complex composition and high radioactivity, imposing greater demands on chemical reaction control and engineering operations. The fact that this test was completed in a hot cell means that WATSS has crossed a threshold closer to practical application, at least in the early critical chemical stages.

However, this progress does not mean that the nuclear waste problem has been solved, nor does it imply that the relevant nuclear power facility has entered operation. Moltex's planned 300 MW electric reactor remains in the development stage and still requires more in-depth regulatory review, engineering validation, and safety assessment. This experiment validated the chemical step of separating some long-lived transuranic elements from spent fuel, rather than proving that the recovered material can already generate electricity, nor demonstrating that the complete fuel cycle has been commercialized.

If the subsequent technology chain can be completed, separating and fissioning a substantial portion of transuranic elements could, in theory, help reduce the longest-term radiological burden in nuclear waste and diminish the risk sources that require geological timescale isolation. However, this process will still generate other waste streams and cannot make nuclear waste completely disappear. Its more realistic value lies in providing a potential pathway for spent fuel reuse and reducing the burden of long-term disposal, while its true impact depends on whether subsequent reactor development, fuel fabrication, regulatory licensing, and economic viability can keep pace.