Self-Sustaining Plutonium Recycle in Sodium Graphite Reactors

Technical Report · Tue Sep 01 04:00:00 EDT 1959

DOI:https://doi.org/10.2172/4213644· OSTI ID:4213644

Connolly, T. J. ^[1]

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1. North American Aviation, Inc., Canoga Park, CA (United States). Atomics International Div.

Plutonium is formed in any reactor fueled with uranium by the capture of neutrons in uranium-238. If the fuel is predominantly uranium-238, as in natural or slightly enriched uranium, the quantity of plutonium formed plays a significant role in the fuel cycle of the reactor. Although some of this plutonium is fissioned in situ, much of it will be in the fuel at the time of discharge from the core. The recovery of this plutonium and its reuse as fuel in the same reactor is referred to as plutonium recycle. The incentives for recycling plutonium vary somewhat with the reactor in question. In the case of natural uranium reactors the plutonium can extend the reactivity lifetime of the fuel. A study of this subject was made recently for the case of a gas-cooled graphite reactor. In reactors requiring slightly enriched uranium, the recycled plutonium lowers the consumption and inventory of uranium-235. Pigford and others recently made an investigation of this subject for the case of a light-water-moderated reactor. A special case of plutonium recycle may arise with slightly enriched uranium reactors in which the reactivity effect of the recycled plutonium is sufficient to reduce the required uranium-235 concentration in the feed material to that of natural uranium. This case may be referred to as self-sustaining plutonium recycle; a reactor which initially requires a source of reactivity above that supplied by natural uranium can, once steady-state plutonium recycle is established, operate with natural uranium as its only raw fuel material. In situations where a dependence on uranium enrichment may be undesirable, plutonium recycle offers the possibility of extending the range of acceptable reactor designs. The present study was undertaken to determine whether a sodium graphite reactor (SGR) could be designed to achieve self-sustaining plutonium recycle. Studies of this subject have been presented by Roderick for the case of an SGR of the Sodium Reactor Experiment (SRE) design, and by Benedict and Pigford. The current design of the SGR under development by Atomics International, a Division of North American Aviation, Inc., makes use of stainless steel for fuel and moderator cladding. It requires a fuel enrichment of about 3% uranium-235. The reactivity requirements of such a reactor are too high for self-sustaining plutonium recycle to be achieved, because eta for the equilibrium plutonium is less than is required for the fuel. However, certain design modifications and the development of cladding materials of lower neutron absorption offer good promise of reducing SGR fuel reactivity requirements. The purpose of the present study was to determine whether, in the light of these probable advances, self-sustaining plutonium recycle could be achieved in a SGR. This effort was limited in scope to the technical feasibility, although certain economic factors such as fuel burnup are also considered.

• Research Organization: North American Aviation, Inc., Canoga Park, CA (United States). Atomics International Div.
• Sponsoring Organization: US Atomic Energy Commission (AEC)
• DOE Contract Number: AT(11-1)-GEN-8
• NSA Number: NSA-14-004951
• OSTI ID: 4213644
• Report Number(s): NAA-SR--3912
• Country of Publication: United States
• Language: English

Related Subjects

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
22 GENERAL STUDIES OF NUCLEAR REACTORS
ABSORPTION
BURNUP
ECONOMICS
ENRICHMENT
FABRICATION
FUEL CANS
FUEL CYCLE
FUELS
GRAPHITE MODERATOR
LIQUID METAL COOLANT
MODERATORS
NEUTRONS
PLUTONIUM
POWER PLANTS
REACTIVITY
REACTOR CORE
REPROCESSING
SODIUM
STAINLESS STEELS
URANIUM 235
ZIRCONIUM