Studies of fission induced by 14 MeV neutrons

Abstract

The fission yields of ten nuclides ((^84)3r, (^91)Sr, (^93)Y, (^99)Eo. (^105)Ru, (^112)Pd, (^113)Ag, (^129)Sb, (^132)Te and (^143)Ce) from the fission of (^231)Pa by 14 Mev neutrons have been determined relative to the fission yield of (^97)Zr. The protactinium (as oxide) in thin uniform adherent layers (about 1 mg. cm(^-2) lightly covered with gold (about 0.5 mg. cm(^-2) was supported an circular discs of platinum foil (2 cm. diameter). Recoiling fission products were collected in thin catcher foils of various substances (aluminium, polystyrene or copper) the choice depending on the elements to be recovered. Preliminary experiments using target discs prepared in a similar way from uranium-238 (oxide) showed that good agreement is obtained between relative yields measured by this method and by irradiation of bulk samples of uranium. The relative yields from (^231)Pa have been corrected to total chain yields by application of the equal charge displacement hypothesis and converted to absolute yields by imposing the condition that the sum of the yields of all the fission products must be 200%. The value of ū was, taken to be 4.25; this was found to give a good fit of reflected points on the mass yield curve. Mien chain yields are plotted against mass number a mass-yield curve is obtained showing three maxima at mass numbers 93, 114 and 135. The yields at the maxima are 6.80%, 2.48% and 6.80% and the peak widths at half height are 14, 17.5 and 14 mass units.