The following thermal-neutron fission cross sections have been measured in the thermal column of the Materials Testing Reactor at Idaho Falls, Idaho: ${\mathrm{Pu}}^{238}$, 18.4±0.9 barns; ${\mathrm{Am}}^{241}$, 3.13±0.15 barns; ${\mathrm{Am}}^{242}$, 6390±500 barns; ${\mathrm{Am}}^{243}$, <0.072 barn; ${\mathrm{Cm}}^{243}$, 690±50 barns; ${\mathrm{Cm}}^{245}$, 1880±150 barns. In addition, a pile neutron capture cross section of 520±40 barns has been measured for ${\mathrm{Pu}}^{238}$.

• Received 29 May 1957

DOI:https://doi.org/10.1103/PhysRev.107.1294