The problem with the early breeders is that they were were liquid-sodium cooled, fast neutron reactors. Not only was liquid sodium extremely dangerous circulating through heat exchangers just inches from superheated water at high pressure, they were also inherently unstable. Any bubble or eddy in the coolant created cavitation that allowed neutrons to be unmoderated by the sodium, causing more fission, more heat, which in turn made the void larger, and so on. A portion of the reactor could find itself without coolant and fail. In a thermal neutron LWR, any void or eddy SLOWED the reaction, causing the void to get smaller, an important negative feedback fail-safe feature.

If this design can act as breeder, fission the Plutonium it produces and do it with water coolant, it would definitely be an advance over existing LWR designs. If it can do this AND leave its wastes in a neat pile with no further chemical separation processing necessary, it may be the breakthrough we've been looking for.