Cumulative yields in the 14 MeV neutron fission of ²³²Th and ²³⁸U in the symmetric region

Abstract

The radiochemical yields of molybdenum-99, ruthenium-103 and -105, palladium-109 and -112, silver-11 1 and -113, cadmium-115, and tin-121 and -125 formed in the 14 MeV fission of thorium-232 and uranium-238 have been determined using a low background Geiger-Muller counter, NaI(T1) crystal, and Ge(Li) detector. The absolute mass yield for molybdenum-99 has been obtained using a copper monitor for neutron flux and for the other nuclides using molybdenum-99 as an internal standard. The mass distribution curves derivcd from the chain yields, in the symmetric region show the presence of a third peak in thorium-232, and only the familiar two peaks for uranium-238 in the asymmetric region. By comparison of normalized cumulative mass yields from this study with prompt fission yield data, the average number of prompt neutrons emitted from fission fragments has been obtained as a function of mass in Z 3 8 U + n fission. It appears that there are two regions of enhanced neutron emission in the mass range 103-128, and that the heavy fragments emit more neutrons than the light ones.

Mass distribution in the 50-, 60-, and 70-MeV bremsstrahlung-induced fission of232Th

“…We also observed higher yields of fission products around mass numbers 133-134, which corresponds to a most probable charge of 52 in the electromagnetic fission of lighter actinides [44][45][46]. Similarly, higher yields of fission products around mass numbers 133-134 in the 3-and 14.8-MeV monoenergetic neutron-induced [17][18][19][20][21][22] and in the 9-, 15-, and 31-MeV bremsstrahlung-induced [51] fissions of 232 Th have been observed earlier. On the other hand, in the 6.44-13.13- [52,53] and 25-40-MeV [50] bremsstrahlung-induced fission of 232 Th, the yields of fission products are more pronounced around mass numbers 143-144 compared to those with mass numbers 133-134, which is contradictory to the earlier observations [17][18][19][20][21][22]51].…”

“…However, most of the fissionyield data available in the literature are for the thermal neutron- [4][5][6][7] or the reactor neutron-induced [8][9][10][11][12][13][14][15][16] fission * gnkim@knu.ac.kr of actinides. For monoenergetic neutron-induced fission, most of the data available are for actinides induced by either 3-or 14-MeV neutrons [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32]. Some of the data on various monoenergetic neutron-induced fissions of actinides are available for specific nuclides, such as 232 Th [33][34][35], 233,235,238 U [36][37][38][39][40], 237 Np [41,42], and 239 Pu [28,43].…”

Mass distribution in the bremsstrahlung-induced fission of 232Th, 238U and 240Pu

“…Similarly, higher yields of fission products around mass numbers 133-135 in the 3 and 14 MeV mono-energetic neutron-induced [28][29][30][31][32][33][34] and in the 9, 15 and 31 MeV bremsstrahlunginduced [59] fission of 232 Th have also been observed earlier. However, in the 6.44-13.13 MeV bremsstrahlung-induced fission of 232 Th [60], yields of fission products are more pronounced around mass numbers 143-145 compared to mass numbers 133-135, which is contradictory to the earlier observations [23][24][25][26][27]59]. Besides this, it can be found in Ref.…”

“…However, most of the fission yield data available in the literature are for the thermal neutron- [10][11][12][13] or reactor neutron-induced [14][15][16][17][18][19][20][21][22] fission of actinides. For mono-energetic neutron-induced fission, most of the data available are for actinides induced by either 3 or 14 MeV neutrons [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37]. Some of the data on various mono-energetic neutron-induced fissions of actinides are available for specific nuclides such as 232 Th [38][39][40][41][42], 233,235,238 U [43][44][45][46][47][48], 237 Np [49,50] and 239 Pu [33,51].…”

Measurement of fission product yields in the quasi-mono-energetic neutron-induced fission of 238U

“…Most of the fission product yields in the 238 U(n, f ) based on off-line and γ -ray spectrometric technique are available within neutron energy of 1. 5-11.3 MeV [24][25][26] and around 14 MeV [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][27][28][29][30][31][32][33]. Some data in the reactor neutron [6,7] and 3.72-10.09 MeV quasi-mono-energetic neutron [35] induced fission of 238 U are also determined by using off-line gamma ray spectrometric technique, where the nuclear structure was clearly shown.…”