238PuO2, the fuel used in Radioisotope Power Systems, undergoes a secondary (a,n) reaction with the naturally occurring 17O and 18O isotopes. Neutron radiation is a significant concern for worker dose rates and spacecraft components. Isotopic exchange with 16O is currently used to minimize the (a,n) reaction, but the mechanism and thermodynamics of this process are not well understood. Using a homebuilt vacuum chamber and atmospherically controlled reaction vessel, we have evaluated the oxygen exchange mechanism on CeO2, a cold surrogate, and found that the rate of the reaction has a first order dependence on the specific surface area of the particles and on the fraction of the reaction remaining. Rate constants, activation energy, and mechanistic data will be discussed. A comparison of the exchange data and time to equilibrium with previous PuO2 reports suggests that the mechanistic and thermodynamic data obtained here is a good approximation of PuO2 behavior.

Evaluation of the PuO<sub>2</sub> oxygen isotopic exchange mechanism using CeO<sub>2</sub> as a surrogate

245th National Meeting (2013)

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Evaluation of the PuO2 oxygen isotopic exchange mechanism using CeO2 as a surrogate

Evaluation of the PuO₂ oxygen isotopic exchange mechanism using CeO₂ as a surrogate