Long-term control of excess reactivity by burnable particles

An analysis IS presented of the feasibility of the use of burnable particles with spherical m cylindrical geometry in graphite moderated reatms. This is in fact an application of the phenomenon of so-called burn up waves in strongly absorbing media. A simple ʹpeeling modelʹ is used to treat the wave progression in neutronically ʹblackʹ particles. It is shown that this special case of heterogeneous poisoning offers some degrees of freedom in design that can be used to ʹtailorʹ the excess reactivity as a function of core burn up