PHYSICS · Multi-part · Fermi University Physics · Nuclear Physics · The nuclear force and nuclear models · Fission, fusion and nuclear energy
The Nucleus Resolved, Ch Fission: the double-humped barrier and the shells the drop cannot see
Problem
Thermal-neutron fission of 233U (compound nucleus 234U, mean neutron multiplicity νˉ=2.50) gives the measured post-neutron fragment yield Y(A) (percentage per fission) at selected mass numbers: A: 90, 96, 108, 118, 128, 139, 144 Y (%): 1.2, 6.8, 0.9, 0.014, 1.8, 6.5, 3.0
((a)) From this table, identify the light-fragment peak, the heavy-fragment peak and the valley, and give the peak-to-valley ratio using the larger of the two peak yields.
((b)) The heavy fragment's mass is set mainly by the shell correction of the forming fragment and stays close to AH=139 across the actinides. Using mass conservation, AL=ACN−AH−νˉ, with AH fixed at 139, predict the light peak's mass number and compare with the table.