fission chambers of parallel-plate type are provided to measure the central fission rates of exp 237 np, exp 238 pu, exp 239 pu, exp 242 pu, exp 241 am, exp 243 am, exp 244 cm and exp 235 u in a series of the cores in fast critical assemblies fca. the chamber consists of the body made of a thin stainless steel wall, the collector of a circular disk and the electrodeposited source with a platinum disk of 0.2 mm thick. the gas filled in the chamber is a mixture of 97 ar and 3 n sub 2 at 1 atmosphere pressure. the weights of deposit are adjusted from strength of alpha -specific activity for each nuclide in the test using fca, characteristics of low alpha pile-up are obtained for all chambers prepared. the determination of masses by alpha -assay, correction for fissile impurities and the sensitivity of chambers are examined for the individual chamber. it is shown from the experiment that the actinide fission rates can be measured within errors of +-2 -- +-5. from this result, it concludes that the present chambers are effectively used for the experimental evaluation of nuclear cross sections for the actinide nuclides. (atomindex citation 13:696779)