  We analyse fast reaction limit in the reaction-diffusion system with
nonmonotone reaction function and one non-diffusing component. As speed of
reaction tends to infinity, the concentration of non-diffusing component
exhibits fast oscillations. We identify precisely its Young measure which, as a
by-product, proves strong convergence of the diffusing component, a result that
is not obvious from a priori estimates. Our work is based on analysis of
regularization for forward-backward parabolic equations by Plotnikov. We
rewrite his ideas in terms of kinetic functions which clarifies the method,
brings new insights, relaxes assumptions on model functions and provides a weak
formulation for the evolution of the Young measure.
