DEVELOPMENTS FOR STELLARATOR-MIRROR FUSION-FISSION HYBRID CONCEPT
Conceptual development activities on a stellarator-mirror-based fission-fusion hybrid system (SM hybrid) are reviewed. Intended for transmutation of spent nuclear fuel and safe fission energy production, SM hybrid consists of a fusion neutron source and a powerful sub-critical fast fission reactor core. Its fusion component is a stellarator with an embedded magnetic mirror. The stellarator allows for the confinement of a moderately hot (1-2 keV) deuterium plasma. In the magnetic mirror, the hot sloshing tritium ions are trapped and fusion neutrons are generated. The magnetic mirror is surrounded by a fission mantle, where transmutation of minor actinides and energy generation take place. One candidate magnetic confinement device for the SM hybrid is the advanced DRACON magnetic trap system, which, unlike the «classical» DRACON version, has one short, rather than two longer mirrors with a relatively short size of 3-6 m. A comparative numerical analysis of collisionless losses occurring in the magnetic trap part of the single-mirror DRACON leads to a conclusion about the possibility for high-energy tritium ions to be fairly well confined in the magnetic trap area. The Uragan-2M (U-2M) stellarator is used to test the SM hybrid concept with experiment. To fit a magnetic trap into U-2M system, one of the toroidal coils had to be switched off. A radial escape of charged particles may spontaneously give rise to a weak radial electric field, which may result in closing the particles’ drift trajectories and thereby substantially improve their confinement. Background plasma confinement without destructive instabilities is demonstrated in the stellarator-mirror regime of U-2M) operation. The sloshing ions driven by radio-frequency heating are detected in the mirror part of the device with NPA diagnostics. A novel fission mantle design for the SM hybrid is proposed.