Proposal of a Deuterium-Tritium Fusion/PWR Fission Hybrid Reactor

Abstract

This article proposes to associate a Deuterium-Tritium (D-T) fusion reactor with a PWR (fission Pressurized Water Reactor) in a hybrid reactor used as a power plant. A previous proposal of a D-D fusion associated with a PWR has been proposed by the author. The drawback of such D-D hybrid reactor is its enormous size (200 m). A D-T hybrid reactor is much smaller for the same power, but it is more complex due to the necessity to supply the necessary Tritium. In this proposal, the Tritium is produced thanks to leaky thermal fission neutrons rather than fusion neutrons. In this way, the production of Tritium is larger than the consumption of Tritium. Even if the mechanical gain (Q factor) of the D-T fusion reactor is below unity and consequently consumes more energy than it supplies, due to the high energy amplification factor of the PWR fission reactor, the global gain is widely superior to 1. As the energy supplied by the fusion reactor is relatively low, the problems of heat flux and neutron damage connected with materials are reduced. This type of reactor is able to incinerate natural Uranium and depleted Uranium (waste issued from enrichment plants). For natural thorium, which has no initial reactivity, a “primer” is necessary to start the reactor. A good “primer” is 1.8% of military Uranium (at 90% U235) mixed into 98.2% of natural Thorium. Once started, the natural Thorium is the best tested fuel. The high-level radioactive waste (stored spent fuel), cleansed of its minor actinides and of its fission products, taking advantage of the fissile materials in it, is the most reactive fuel tested in this paper. This type of reactor could constitute a source of energy for several thousand years, because it is about 90 times more efficient than a standard fission reactor, such as a PWR or a CANDU one, by extracting almost completely the energy from the fertile materials U238 and Th232. In this paper, it is targeted a reactor able to provide a net electric power of about 1000 MWe, as a standard fission power plant. For the fission part, the PWR technology is mature, even if the fuel assemblies will be more complex than the ones used in PWR. For the fusion part, it is based on a reasonable mechanical gain Q around 0.7 already reached by certain tokamaks and, certainly in the near future, by Stellarators. The reference fusion model is supposed to be the Stellarator Wendelstein 7-X, but with an interior radius enlarged to increase the provided power. The working of this reactor is continuous, 24 hours a day.