Spectral antineutrino signatures and plutonium content of reactors

It is well known that nuclear reactors are intense sources of antineutrinos due to the ß-decay of ?ssion fragments. Since the ?ssion fragment yields are di?erent for ?ssion of the various ?ssile isotopes, in particular for 235U, 238U, 239 Pu and 241 Pu, the resultant antineutrino ?uxes show clear di?erences as well. These di?erences are most robustly detected in the energy distribution of antineutrinos, allowing for a simultaneous measurement of both the reactor power and the ?ssion rates for each of these isotopes. The ?ssion rates are directly related to the actual isotopic mass inventory and thus, the mass of plutonium in the core can be determined using antineutrinos. This measurement can be performed in situ at a stand-o? of several 10 m and thus has obvious applications for non-proliferation safeguards.