  The Independent Reaction Time method is a computationally efficient
Monte-Carlo based approach to simulate the evolution of initially
heterogeneously distributed reaction-diffusion systems that has seen wide-scale
implementation in the field of radiation chemistry modeling. The method gains
its efficiency by preventing multiple calculations steps before a reaction can
take place. In this work we outline the development and implementation of this
method in the Geant4 toolkit to model ionizing radiation induced chemical
species in liquid water. The accuracy and validity of these developed chemical
models in Geant4 is verified against analytical solutions of well stirred
bimolecular systems confined in a fully reflective box.
