The naturally-occurring abundant thorium isotope ²³²Th is a fertile fuel, meaning it cannot by itself sustain a nuclear chain reaction for power generation but can be transmuted into the fissile nuclide 233U during an active nuclear process. Therefore, DBI will deploy a two-stage implementation of its all-thorium fueled economy.

The DBI Thorium Reactor Program will consist of a series of modular reactor cores that could be started up with an initial fuel load of fertile thorium oxide, with some fissile material to initiate the reaction. As shown below, within about 10 years the fissile starter will become depleted of ²³⁵U while breeding ²³⁹Pu. The combination of this plutonium and the ²³³U accumulating in the reactor will be sufficient to maintain core reactivity in the presence of neutron absorbing fission products for this time period. Beginning around year 10, shuffling fuel bundles within the core to locations based upon reactivity levels will allow for most of the ²³⁹Pu to be selectively destroyed, with fresh ThO2 added periodically. DBI has developed a proprietary fuel encapsulation system to allow the fuel to remain in use for the entire life of the reactor, far beyond the conventional reactor fuel cladding life of 3-5 years.

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When the reactor vessel is decommissioned at the end of its operational life, there will be sufficient ²³³U in the active core to start up another, identical reactor core by transferring the fuel from the decommissioned core. Chemical reprocessing will not be necessary because the breeder fuel initially accumulates ²³³U much faster than it develops fission poisons.

In this way the thorium fuel cycle can be perpetuated without the need to enrich any more uranium, breed any more plutonium, or reprocess fuel for future reactors.

In addition to perpetuating itself by breeding ²³³U from ²³²Th, computer models indicate that the DBI Thorium Reactor core may be able to breed enough extra fuel to start additional reactors over a period of decades, keeping up with world economic growth.

For faster nuclear industry growth, additional enriched uranium fuel can be added to start up as many DBI reactors as needed on an annual basis. Starting up DBI reactors with an initial load of "proliferation-resistant" MOX (uranium/plutonium/thorium oxide) fuel rather than conventional UO₂ would make the fuel inventory more complex than that shown in this graph, but it would also make the fuel practically unusable for nuclear weapons at all stages of the fuel cycle.