The Reversed Field Pinch as neutron source for Fusion-Fission Hybrid systems: strengths and issues

The fusion reactor remains one of the long term, final solution of energy production. This requires to control fusion reaction with an energy gain Q > 30 - 40. The tokamak configuration is nowadays the most investigated path to this goal. Meanwhile a proposed interim carbon-free solution, with the merit of nuclear waste transmutation, is the hybrid fusion-fission reactor, in which sub-critical fission is activated by fast neutron generated in a fusion reactor. In this case fusion could be produced in a device with lower Q, roughly in the order of 1. The Reversed Field Pinch (RFP) is an alternative configuration to tokamak and stellarator for the future fusion reactor. Its disruption-free configuration, the need of much weaker toroidal magnetic field and the capability of reaching thermonuclear temperatures without additional heating, are relevant advantages in a commercial reactor. While RFP plasmas have yet an energy confinement too low for a high Q reactor, reaching Q near 1 might be reasonable for a RFP machine with an appropriate R&D activity. Starting from the present knowledge in RFP configuration, the experimental results from the different machines and the theoretical advancement obtained in the last years, an analysis is presented on the possibility to use the RFP configuration as a fast neutron generator. It will be highlighted the advantages of this solution with respect to the tokamak - no disruption, toroidal field coils at room temperature and reduced size with more space for breeding blanket, superconductors limited to the magnetizing coil and no divertor - and the possible issues, as steady state operation.