The lattice expansion and thermal behavior of gamma-irradiated unstable clathrate hydrates are explored to understand the complex physicochemical properties of clathrate hydrates. A previous study revealed that enclathrated methyl vinyl ketone molecules show a peculiar conformational change via a ketyl radical anion after c-irradiation with an annealing process. We measured the lattice parameters of gamma-irradiated binary methyl vinyl ketone + CH4, O-2, and N-2 hydrates at various temperatures. We observed that induced radical affects the lattice expansion behavior, and the thermal expansion coefficients of gamma-irradiated hydrates highly depend on the types of secondary gaseous guest molecules. (C) 2018 Elsevier B.V. All rights reserved.