LONG IRRADIATION OF NATURAL URANIUM

Technical Report · Sat Oct 31 04:00:00 EST 1959

OSTI ID:4259604

Craig, D S; Hanna, G C

The principal factors controlling the change of reactivity with irradiation are the destruction of U/sup 235/, the production of Pu/sup 235/ and higher plutonium isotopes, and the accumulation of fission products. Cross sections appropriate to reactor neutron spectra were calculated from basic nuclear data. With increased irradiation, changes in the neutron spectrum in the fuel result from self-shielding in the resonance region and increased thermal neutron absorption cross section. The fissionproduct absorption cross section of irradiated fuel can be closely simulated by using three pseudo fission products with cross sections of 600, 300, and 25 barns. Measurements were made of the spatial distribution of U/sup 235/, plutonium isotopes, and Cs/sup 137/ in an NRX rod irradiated to 3000 Mwd/ton. Precise mass-spectrometer analyses of the uranium and plutonium isotopes combined with chemical analyses for plutonium gave accurate values of the conversion factor and the effective capture cross sections of the plutonium isotopes. These results have been satisfactorily reconciled with the basic nuclear data and the calculated effects of changing neutron spectra. (auth)

• Research Organization: Atomic Energy of Canada Ltd., Chalk River, Ont.
• NSA Number: NSA-13-006853
• OSTI ID: 4259604
• Report Number(s): A/CONF.15/P/205; AECL-615
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

ABSORPTION
CAPTURE
CESIUM 137
CONVERSION
CROSS SECTIONS
DISTRIBUTION
ENRICHMENT
FISSION PRODUCTS
FUEL ELEMENTS
FUELS
IRRADIATION
MASS SPECTROMETERS
MEASURED VALUES
NEUTRONS
NUMERICALS
PHYSICS AND MATHEMATICS
PLUTONIUM 239
PLUTONIUM ISOTOPES
PRODUCTION
QUALITATIVE ANALYSIS
RADIATION DOSES
REACTIVITY
REACTORS
RESONANCE ESCAPE PROBABILITY
SHIELDING
SPECTRA
THERMAL NEUTRONS
URANIUM
URANIUM 235
URANIUM ISOTOPES
VARIATIONS