J. N. Beck

Atmospheric residence times of strontium-90 and lead-210

The concentrations of89Sr,90Sr,210Pb and210Po were measured in a series of rain samples collected at Fayetteville (36°N, 94°W), Arkansas, after the 14th Chinese test of March 18, 1972, which occurred at Lop Nor (40°N, 90°E), China. Approximately concordant tropospheric residence times were obtained from the89Sr/90Sr and210Po/210Pb ratios in rain. The89Sr/90Sr ratios were also measured for the rain samples collected at Tokyo (36°N, 140°E), Japan, and at Ankara (40°N, 33°E), Turkey.

Distribution of fission yields in the 14·8 MeV neutron-induced fission of 238U

Abstract The mass yield distribution for the 14·8 MeV neutron-induced fission of 238 U has been measured radiochemically for 46 mass chains in the region A = 83–157. The absolute activities of each nuclide measured in this mass region were determined by gross beta counting and the cumulative fission yields were measured relative to 99 Mo. The yields determined in this work are compared to all known literature values. Eleven fission yields are presented that have been experimentally measured for the first time for the 14·8 MeV neutron-induced fission of 238 U. The yields measured make up about 115% of the total of 200% expected from fission. As reported previously in the literature, fine structure was observed to exist at mass number 134 and no clear evidence could be found for fine structure at other mass numbers.

Mass distribution of 3MeV neutron induced fission of 232Th

Abstract The 3 MeV neutron induced fission yields of 232Th in the mass regions of A = 77–93 and A = 141–156 were radiochemically determined by isolating fission products belonging to 15 mass chains. The absolute activities for the nuclides were determined by β- and γ-counting and the cumulative fission yields were calculated relative to 99Mo. These data were used to define the extreme wings of the mass yield curve for 232Th. By comparison of complementary fission fragments it was determined that 2·4 secondary neutrons are emitted per fission of 232Th at 3 MeV. A qualitative comparison is made concerning the general features of the 232Th mass yield curves from 14·8 MeV and 3 MeV neutron induced fission.

Nine MeV bremsstrahlung fission of 238U

Abstract The mass yield distribution of fission products produced in the photofission of 238 U using 9 MeV bremsstrahlung have been radiochemically measured for 21 mass chains. The absolute activities of the nuclides measured were determined from gross β counting and total chain yields were measured relative to 99 Mo. The peak to valley ratio was found to be about 310, which is comparable with previous results measured at 10 MeV. Fine structure was found to be a prominent feature and occurred around mass number 133, although mass number 134 could not be measured in the present investigation. The fission yields measured in this work have been compared to all known existing values for work in photon energy range of 9 ± 1 MeV.

Investigation of the reported mass distribution curves in the fission of 233U with 14·8 MeV neutrons

Abstract The mass yield distribution of fission products produced in the fission of 233U with 14·8 MeV neutrons has been measured for eight mass chains in the symmetric region. This investigation was initiated to resolve existing discrepancies in published data with respect to the fission yields in the valley region and the peak-to-valley ratio. The absolute activities of the nuclides measured were determined from gross beta counting and total yields were measured relative to 132Te or 99Mo. The standard yields were chosen due to the close agreement of previous data for those mass chains. The peak-to-valley ratio calculated was about 3·5. The fission yields measured in this work have been compared to known existing values for 14·8 MeV neutron-induced fission of 233U.