Although many have questioned its overall safety and cost benefits, nuclear power remains a major workhorse in low-carbon power generation today. The International Atomic Energy Agency (IAEA) has identified three technologies as the keys to the future success of nuclear energy: fast reactors, small modular reactors, and fusion reactors.
Fast reactors, also known as fast-neutron reactors, have been extensively investigated and widely deployed across the globe. Reactors that use this technology require no neutron moderating medium such as light and heavy water, and graphite, which are essential for transforming fast neutrons (high in kinetic energy) into thermal neutrons (key to sustain fission) in conventional reactors. Although fast reactors consume fuels that are more enriched, they generate less toxic nuclear waste, dramatically reduce the decay time of the waste, and exhaust almost all its fuel material (high burnup rate).
Small modular reactors are smaller in size, manufactured at a central location, and ready for shipment by trucks and planes to application site. This technology requires less on-site construction and a smaller budget, satisfies the electricity needs of remote communities, and come with built-in passive safety measure to ensure a meltdown-free operation.
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Unlike the two more tangible options mentioned above, fusion-based power generation is far from maturity. Despite having many advantages over fission-based reactors like reduced radiation and waste, almost endless fuel, and increased safety, fusion reactions in controlled environment are still facing technical challenges such as plasma heating and stability, confinement and exhaust of energy and particles, reactor safety and environmental compatibility, not to mention the overblown budgets for construction and testing. Large scale fusion projects include International Thermonuclear Experimental Reactor (ITER) in France and National Ignition Facility (NIF) in US. Considerable amount of progress has been made since mid last century, but so far none of experimented design has managed to produce positive net energy in a meaningful time window to allow power generation.
Source: IAEA