THE FUSION ERA – Understanding the Fusion Fuel Cycle

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Welcome to another blog post of THE FUSION ERA Today, we are diving into the fusion fuel cycle—an essential system for generating clean energy with fusion power. Understanding this cycle is crucial for addressing challenges in fuel availability and sustainability. Join us as we explore the importance of the fusion fuel cycle and Kyoto Fusioneering’s contributions to this fusion technology. 

In any power generation process, the “fuel cycle” refers to the entire journey the fuel takes, from its acquisition and preparation to its use in the power plant and the management of any byproducts. Fusion power utilises the fuel cycle system within the fusion plant itself. While other potential fusion fuels exist, we will focus on a well-known reaction, deuterium-tritium fusion. Deuterium can be readily extracted from seawater, while tritium, a rarer isotope of hydrogen, is “bred” within the reactor itself using lithium.  

The fusion fuel cycle is a system that ensures a steady supply of fuel for the fusion reaction and recycles unused tritium for future use. It begins with the extraction of deuterium from seawater and the breeding of tritium within the fusion reactor using lithium. Both isotopes undergo purification to separate them from other hydrogen isotopes and the purified streams of deuterium and tritium are injected into the reactor chamber. 

Within the plasma vessel, powerful magnetic fields confine and superheat the isotopes, turning them into plasma. Within this plasma, deuterium and tritium nuclei fuse together, releasing tremendous amount of energy in the form of neutrons and helium gas. The exhaust gases from the plasma vessel primarily consist of unreacted deuterium and tritium fuel, along with helium and impurity gases. Specialised techniques like cryogenic distillation or membrane separation are used to separate and recover the valuable fuel from the helium and impurities. The recovered and purified deuterium and tritium are then combined and reintroduced back into the plasma vessel when required, completing the cycle. This process ensures efficient fuel utilisation and minimises waste, making fusion a highly sustainable energy source. 

Fuel Cycle Research at the Kyoto Research Center in Kumiyama, Kyoto  

Kyoto Fusioneering established the Kyoto Research Centre (KRC) in Kumiyama, Kyoto, where vital components for the fuel cycle are under development. KRC houses exhaust pumping systems essential for pumping tritium around the fuel cycle including Kyoto Fusioneering’s reciprocating pump as well as high vacuum pumping technologies. Tritium separation systems are also under development including the palladium diffuser which selectively separates hydrogen isotopes from the exhaust gas stream via diffusion across a palladium membrane. Analytical techniques, sensors, hydrogen isotope pumping, and storage systems are all under development. These components will be demonstrated in Kyoto Fusineering’s fully integrated tritium fuel cycle being developed in collaboration with Canadian Nuclear Laboratories (CNL) called UNITY-2 (Unique Integrated Testing FacilitY). 

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