Patent Number: 
Section: claims

1. A method of transmuting at least one long-lived isotope of fission fragment radioactive waste, the method comprising the steps of:providing an inner buffer region around a neutron source for providing a first reduction in neutron energy by inelastic scattering;providing an activation region around said inner buffer region, the activation region being made of heavy elements of at least one of lead and/or bismuth;distributing a material containing said long-lived isotope of fission fragment radioactive waste throughout the whole volume of the activation region the inner buffer region and the neutron source being devoid of radioactive waste; andactivating the neutron source to emit a neutron flux, wherein multiple elastic collisions between the neutrons in the neutron flux and the heavy elements in the activation region result in an enhanced neutron flux in the activation region, and rate of progressive decrease in neutron energy such that increased neutron capture in the resonance spectrum of said material is exploited to enhance neutron capture in said material. 2. A method according to claim 1, wherein said transmuted isotope comprises 99Tc. 3. A method according to claim 1, wherein said transmuted isotope comprises 129I. 4. A method according to claim 1, wherein said transmuted isotope comprises 79Se. 5. A method according to claim 1, wherein the neutron source is a critical fast breeder reactor core, out of which fast neutrons leak. 6. A method according to claim 1, wherein the neutron source is an energy amplifier core comprising a spallation target and a nuclear fuel material, wherein the spallation target is bombarded by a high-energy charged particle beam to produce high-energy neutrons which initiate a sub-critical process of breeding a fissile element from a fertile element of the fuel material and fission of the fissile element, whereby fast neutrons leak out of the energy amplifier core toward the activation region. 7. A method according to claim 6, wherein lead and/or bismuth form both said spallation target and said inner buffer region, at least some of said lead and/or bismuth being in liquid phase and circulated along a cooling circuit to extract heat from the energy amplifier core. 8. A method according to claim 6, wherein the nuclear fuel material comprises further fissile elements consisting of actinides to be disposed of.