A Radiochemical Investigation of Short-lived Selenium and Bromine Fission Products

From a sample of uranium bombarded with neutrons, Hahn and Strassmann, in 1939, separated four radioactive products which followed alkaline earth chemistry and were therefore tentatively attributed to isotope of radium. Each of these products decayed to a daughter activity which could be precipitated along with lanthanum; the daughter activities were then assumed to be isotopes of actinium. Subsequently, by accepted methods of fractional crystallization and precipitation, the radium and actinium isotopes were identified unequivocally as isotopes of barium and lanthanum, respectively. Within a relatively short time there were found more such radioactive products, which were identified as isotopes of elements between bromine and lanthanum. This startling result could be explained only by the assumption that the uranium nucleus, after capture of a neutron, split into two fragments of similar mass. Thus, by radiochemical methods, the phenomenon of nuclear fission was discovered. Within a year of the original discovery of Hahn and Strassmann, about fifty more radioactive fission-product nuclides had been isolated. By 1941, extensive physical and chemical studies had revealed the nature and implications of the fission phenomenon; during the period 1941-1945 fission radiochemistry was pursued intensively under wartime secrecy, and when in 1946 the results of this work were finally released and published, the number of known fission products had been extended to over 160

Does it Hold Water? Repudiating the "Singular Entity" or "Unitary Waters" Approach to the Clean Water Act

[no abstract

Does it Hold Water? Repudiating the "Singular Entity" or "Unitary Waters" Approach to the Clean Water Act

[no abstract

RATES AND MECHANISMS OF THE LOSS OF FISSION PRODUCTS FROM URANIUM-GRAPHITE FUEL MATERIALS

Evidence concerning high-temperature loss of fissionproduct atoms from U- graphite fuel material is presented. Results indicate that no single model can adequately describe the behavior of all fission-product elements. Variables which affect loss rates are temperature, chemical species or element, sample dimensions, U concentration, fabrication, and graphite porosity. Loss-rate processes are discussed. (J.R.D.

Decay characteristics of 84Se

The nuclide 84Se has been identified among the fission products of 235U. The selenium fraction was obtained by solvent extraction from HBr into 2,6-dimethyl-4-heptanone. The radiations were studied by [beta]- and [gamma]-ray scintillation spectroscopy, by [gamma]-ray spectroscopy with a Ge(Li) detector, and by coincidence measurements. The decay of 84Se shows a half life of 3[middle dot]1+/-0[middle dot]2 min and involves a single [beta] transition of 1[middle dot]4+/-0[middle dot]05 MeV and a coincident [gamma] ray of 407[middle dot]7+/-0[middle dot]5 keV.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/33090/1/0000476.pd