Patent Number: 
Section: claims

1. A method for the quantitative determination of fissile material content in small size particles present in samples wherein: the samples are sandwiched in organic sheets and then submitted to a defined thermal neutrons fluence whereupon fission products of the fissile material in the sample create fission tracks in the sheets,  the tracks are enhanced by a chemical etching process,  the size of selected particles having created such tracks is determined by means of a microscope,  and thereafter these visible tracks of said selected particles are compared to pre-established standard tracks obtained by the same process from particles of different stepped down size and enrichment ratio. 2. A method according to  claim 1 , wherein many distinct samples are collected on a common carrier tape and are submitted simultaneously to the neutron flux. claim 1 3. A method according to  claim 1  or  2 , wherein the fission tracks are interpreted by an automated image processing treatment using reference data derived from said pre-established standard tracks. claim 1 2 4. A method according to  claim 1  or  2 , wherein samples are sandwiched between a first organic sheet which is covered on the side of the ,sample with a metal foil, and a second organic sheet without such foil, in order to permit both the analysis of alpha tracks and that of fission products. claim 1 2