Date of Award


Degree Type


Degree Name

Bachelor of Science (BS)



First Advisor

Donald R. Ferguson


The computer code FX2 is used to model liquid-metal fast-breeder reactors now being developed by the U. S. Atomic Energy Commission. These reactors differ from thermal reactors in that they have no moderator material in their cores and thus operate at mean neutron energies of 100 keV or more as opposed to neutron energies of less than 1 keV for thermal reactors. Also these reactors have the advantage that as a consequence of the high neutron energies, these reactors can be used to "breed" their own fuel: enriched 238U placed in the core is changed into plutonium which can then be used as fuel for the reactor.

The basic problem that FX2 solves is the time-dependent, multigroup diffusion equation. In this equation neutrons are divided into various energy groups. The rate of change of the neutron population for a particular group is found by adding the number of neutrons entering the system, the number of prompt neutrons which are produced directly by fission, and the number of delayed neutrons which are emitted by unstable isotopes which have been excited by neutron absorption, and then subtracting the number of neutrons escaping and the number of neutrons being absorbed.

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