RADIOCHEMICAL STUDIES ON THE MULTIPLE FISSION OF URANIUM. II. DETERMINATION OF THE FISSION YIELD OF THE Ni$sup 66$-Cu$sup 66$ CHAIN IN THE THERMAL FISSION OF U$sup 23$$sup 5$

The Ni activity found by Roy in the products of U fission could be confirmed. The fission yield was determined to be 2 x 10/sup -8%/. (tr-auth) In a previous publication on the quantitative evaluation of the Fe/sup 54/ alpha ,n)Ni/sup 57/ reaction initiated by fission alpha particles, a value of 1/625 was used for the frequency of fission with alpha emission. More accurate measurements on individual alpha reactions with Fe/sup 56/ have become available since that time. By multiplication of the individual pair of values and graphic integration, the function of the most frequent alpha energy in the single layers was determined. The relationship for the mean effective cross section leads to an effective layer density of 21 cm air equivalent and to an integral cross section of 60 mb. Therefore for the irradiation sample, a formation rate of 4.05 x 10/sup 9/ alpha particles/ sec was obtained. This value together with the number of normal binary fissions (1.23 x 10/sup 12/ sec) yields a frequency of 330 plus or minus 66 binary fissions/fission with alpha emission. (J.S.R.)