Additions and corrections to the communications presented by France at the Geneva Conference in august 1955

A graphic correction is given for the communication number 442 of the C.E.A. at the Geneva conference about the measurement of atmosphere radioactivity and pollution near an atomic centre. An addition to the communication number 446 of the C.E.A. at the Geneva conference about the measurement of the cross section of fissile nucleus for slow neutrons is presented. It discussed the measurement of the cross section of 235U nucleus fission for neutrons of 25 keV by comparing the fission cross section of 235U and the activation cross section of 197Au with two different neutrons sources. The principle and experimental procedures are explained and the experimental data and results are given. A note about the cross section of 239Pu fission for slow neutrons is added. A modification of the appendix in the communication number 405 of the C.E.A. at the Geneva conference about the study of the energy dependent variation of the cross sections of 233U, 235U and 239Pu fission for fast neutrons is given. The variation of the fission cross sections of 233U, 235U and 239Pu with the neutrons energy is given as well as the variation of the counting ratio of fission between 239Pu and 235U with the neutrons sources distance. The efficiency of the 'long' counter is discussed. (M.P.)