NUCLEAR DECAY SCHEME STUDIES ON SHORT-LIVED NUCLIDES FROM THE (n,$gamma$) AND (n, FISSION) REACTIONS
A study was made of nuclear decay schemes, primarily of short-lived nuclides, utilizing the irradiation facilities of the Ford Nuclear Reactor at the University of Michigan. Multichannel pulse-height analysis was applied to the study of short-lived fission products and to a search for unreported isomeric transitions among the (n, gamma ) reaction products. Irradiation and handling techniques were developed and instrumental modifications made to facilitate the study of short-lived nuclides. The neutron flux and flux distribution at the irradiation position were measured. A simple and rapid separation of gaseous fission products into krypton and xenon fractions was developed. The primary gamma energies of 3.2-min Kr/sup 89/, 33 sec Kr/sup 90/, 1.2min Rb/sup 91m/, 41- sec Xe/sup 139/, and 66-sec Cs/sup 140/ we re determined and relative gamma intensities measured. Maximum beta energy end-points were measured for Kr/sup 89/ , Kr/sup 90/, Xe/sup 139/ s, Cs/sup 140/, and 9.5 min Cs/sup 139/, and lower limits established f or the decay energies of these nuclides. The gamma rays of the daughter activities, 14.9-min Rb/sup 89/, 2.7-min Rb/sup 90/, and Cs/sup 139/ , previously reported in the literature were verified. An upper limit of 2 minutes was established for the halflife of the fission product, Rh/sup 109/, by devising a chemical separation, requiring 6 min, giving decontamination factors of > 10/sup 5/ from other elements. An isomeric level of Pt/sup 199/ was detected and characterized by the (n, gamma ) reaction on normal and enriched platinum samples. The isomer decayed with a half-life of 14.1 plus or minus 0.3 sec by emission of gamma rays of 32 plus or minus 2 kev and 393 plus or minus 2 kev energy. The thermal neutron cross-section for the formation of the isomer was 28 plus or minus 3 mb. A long-lived isomer of Ag/sup 108/ was detected in Ag/sup 110//sup m/ tracer sources sufficiently old that the masking 270 day Ag/sup 110//sup m/ had decayed out. The half-life of the isomer was found to be > 5 years. 90% of the disintegrations proceeded by electron capture followed by a cascade of three gamma rays of 434-, 616-, and 722-kev energy, and 10% went by isomeric transition to 2.4-min Ag/sup 108/. New values were determined for the branching ratios in 2.4-min Ag/sup 108/. No unreported isomeric transitions, with half-lives in the range of 1 sec to 10 min, were detected in the (n, gamma ) reaction on ruthenium, palladium, mercury, rhenium, barium, lanthanum, cerium, praseodymium, samarium, europium, gadohinium, terbium, holmium, erbiu, thulium, ytterbium, or lutetium. (auth)
- Research Organization:
- Michigan. Univ., Ann Arbor
- DOE Contract Number:
- AT(11-1)-70
- NSA Number:
- NSA-15-025459
- OSTI ID:
- 4016698
- Report Number(s):
- TID-11807
- Resource Relation:
- Other Information: Orig. Receipt Date: 31-DEC-61
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
BETA DECAY
BETA SPECTROMETERS
CESIUM 139
CESIUM 140
CONFIGURATION
DECAY
ENERGY
FISSION
FISSION PRODUCTS
FORD NUCLEAR REACTOR
GAMMA RADIATION
GASES
HALF-LIFE
INSTRUMENTS
ISOMERS
KRYPTON
KRYPTON 89
KRYPTON 90
MEASURED VALUES
NEUTRON BEAMS
NEUTRON FLUX
NUCLEAR MODELS
NUCLEAR REACTIONS
NUCLEI
PULSE ANALYZERS
REACTORS
RUBIDIUM 89
RUBIDIUM 90
RUBIDIUM 91
SEPARATION PROCESSES
TRANSIENTS
XENON
XENON 139