Patent Number: 059600500
Section: claims

1. A method for determining the absolute value of fission flux of a prime fuel-bearing specimen containing Uranium 235 inserted into a test holder of a nuclear reactor, said method comprising: inserting into said test holder of said nuclear reactor at least one prime specimen, a plurality of bulk water channels and at least two thermocouple test specimens, said thermocouple test specimens being positioned at the same level in said test holder and comprising first and second outer clads, a central backclad and first and second fuel fillers disposed between respective outer clads and said backclad;  determining the temperature of said thermocouple test specimens and said bulk water channels, the gamma scan count ratios for said thermocouple test specimens and said at least one prime specimen, the thicknesses of said outer clads, said fuel fillers and said backclad of said thermocouple test specimens, and the water channel heat transfer coefficient of the thermocouple test specimens;  calculating, using the temperatures of said thermocouple test specimens, the ratio of the gamma scan counts of said thermocouple test specimens, the temperature of the bulk water channels, the thicknesses of said outer clads, said fuel fillers and said backclad of said thermocouple test specimens, and said surface water channel heat transfer coefficient, the absolute value of the fission heat fluxes for the thermocouple test specimens; and  calculating, using the absolute value of the fission heat fluxes for the thermocouple test specimens and the gamma scan ratio for said at least one prime specimen, the absolute value of the fission heat flux for the prime specimen.  inserting into said test holder a specimen assembly comprising a plurality of bulk water channels, at least one prime specimen comprising a prime fuel filler disposed between first and second prime clads, and at least two thermocouple specimens positioned at the same level as each other in said test holder, said thermocouple specimens comprising first and second outer clads, a central backclad and first and second fuel fillers disposed between respective outer clads and said backclad;  determining the temperature of said thermocouple test specimens and said bulk water channels, the gamma scan count ratios for said thermocouple test specimens and said at least one prime specimen, the thicknesses of said outer clads, said fuel fillers and said backclad of said thermocouple test specimens, the surface water channel heat transfer coefficient of the thermocouple test specimens, the reactor lobe power, and axial factor for gamma heat;  using the temperatures of said thermocouple test specimens, the ratio of the gamma scan counts of said thermocouple test specimens, the temperature of the bulk water channels, the thicknesses of said outer clads, said fuel fillers and said backclad of said thermocouple test specimens, said surface water channel heat transfer coefficient, the reactor lobe power, and axial factor for gamma heat, to calculate the absolute value of the fission heat fluxes for the thermocouple test specimens; and  using the absolute value of the fission heat fluxes for the thermocouple test specimens and the gamma scan ratio for said at least one prime specimen, to calculate the absolute value of the fission heat flux for the prime specimen. 2. A method of claim 1 further comprising determining the reactor lobe power and axial factor for gamma heat and using the lobe power and axial factor so determined to separate fission heat from total heat in determining the absolute value of the fission heat flux for said thermocouple test specimens. 3. A method according to claim 1 wherein determining said water channel heat transfer coefficient comprises determining a measured flow heat rate and deriving said water channel heat transfer coefficient. 4. A method for determining the absolute value of fission flux of a prime fuel-bearing specimen containing Uranium 235 inserted into a test holder of a nuclear reactor, said method comprising: 5. A method according to claim 4 wherein said prime specimen is disposed between a pair of said plurality of water channels, and each of said thermocouple test specimens is separately disposed between a pair of said plurality of water channels.