[en] A kinetic study of the dehydration decomposition of gamma irradiated and unirradiated Na/sub 2[Co(C/sub 4/H/sub 4/O/sub 4/sub 2/].7H/sub 2/O has been made using isothermal and dynamic thermogravimetric methods. The thermal dehydration occurs in one step, regulated by a random nucleation model (A3), while the decomposition of anhydrous salt is controlled by a phase boundary controlled model (R3). The kinetic parameters estimated isothermally are slightly different from those estimated dynamically. Irradiation activation energy decreases as radiation dose increases. (author)