Preliminary integrated design of a RFP fusion core and a hybrid reactor blanket

The Reversed Field Pinch (RFP) is recognized as an attractive fast neutron source from D-T fusion in hybrid reactors due to the possibility to reach fusion condition with ohmic heating only and to the intrinsic simplicity of the machine (no large toroidal field coils, no additional heating systems, no divertor). In previous studies, a continuous pulsed operation, able to guarantee a quasicontinuous 14.1 MeV neutron production, has been identified, utilizing a purely inductive plasma rise and sustainment. Scaling laws, derived from the experimental results obtained in RFX-mod, allow predicting the plasma temperature and the loop voltage vs. the machine sizes and plasma current level. Considering these laws and on the basis of a preliminary poloidal coil design, it was investigated the relationship between the machine size and the attainable stored volt-second. The obtainable plasma parameters (current, loop voltage, pulse duration and temperature) with reasonable machine sizes, R=6 and a=1 for examples, match very well the performances required for an hybrid reactor in terms of neutron flux and machine stresses. Based on this configuration a blanket, surrounding the torus, composed by a lithium-lead eutectic mixture for tritium production and a three fission sectors fuelled by steel rods containing Pu+MA (60%)-Zr (40%) embedded in liquid lead was studied and designed. The nuclear analysis of this simple configuration shows the possibility to operate at keff ~ 0.97 corresponding to a total fission power of about 1.2 GW. Improvements of the RFX-mod machine are underway, introducing a new load assembly with reduced distance between plasma and conducting shell which will provide a smoother magnetic boundary. On the basis of present experimental data and model simulations, this is expected to produce an enhancement of the plasma confinement properties, confirming or even improving the present scaling laws towards higher currents and increasing the attractiveness of this fusion-fission reactor solution. This contribution, which will present in detail the above summarized aspects, is aimed at proposing on this basis a robust, innovative, highly reliable FFHR.