Study of an Accelerator Driven System Operating in an Epithermal Spectrum with a Constant KEFF

In any Pu burner operating with a thermal spectrum the fission/capture ratio is biased towards capture; therefore, instead of burning 239Pu and 241Pu through fission, their conversion into 240Pu and 242Pu prevails.One way to operate a system of this sort is to use very great proton currents; another is to add a neutron poison that is removed or burned as the concentration of the even Pu isotopes grows. An example of the removal of the neutron poison is the addition of 99Tc, while Er may be considered an example of burnable poison. Anyhow the ideal solution in this case is provided by Th which initially works as a poison absorbing the Pu's excess of reactivity and subsequently due to the production of 233U compensates for the poisoning caused by the Pu's even isotopes.There arises the problem of utilizing the 233U that is obtained.A possible solution of the problem is to consider an Accelerator Driven System (ADS) that operates at constant Keff, adding continuously growing quantities of Pu from LWRs to compensate for the gradual poisoning due to the build up of 240Pu and 242Pu.