In such a subcritical nuclear reactor the neutrons produced by spallation would be used to cause fission in the fuel, assisted by further neutrons arising from that fission. One then has a nuclear reactor which could be turned off simply by stopping the proton beam, rather than needing to insert control rods to absorb neutrons and make the fuel assembly subcritical. The fuel may be mixed with long-lived wastes from conventional reactors (see below). India is actively researching ADS as an alternative to its main fission program focused on thorium.
Commercial application of partitioning and transmutation (P&T), which is attractive particularly for actinides, is still a long way off, since reliable separation is needed to ensure that stable isotopes are not transmuted into radioactive ones. New reprocessing methods would be required, including pyroprocessing. The cost and technology of the partitioning together with the need to develop the necessary high-intensity accelerators seems to rule out early use.
Т.о. всё упирается в практичность ускорителя и прочие инженерные проблемы. По-моему, предыдущая запись по теме, называвшая всё бредом, была несправедлива.