Chemistry and Chemical Biology ETDs

Publication Date

Spring 4-23-1973

Abstract

A new precision gamma scanning system is described. The system is designed for the thorough, detailed, nondestructive characterization of irradiated fast reactor fuel pins. Gamma scanning data are given for failed fuel pin , transfer mechanisms of fission products, quantitative isotopic scan­ning, and differential burnup profiles.

The system consists of a scanning mechanism for the precise positioning (±0.001 in.) of the irradiated fuel pin, high density tungsten alloy collimators for defining the volume segment from which the gamma-ray spectra are collected, a large high resolution an anticoincidence detector assembly for resolving complex gamma-ray spectra, and a computer con­trolled data acquisition unit with magnetic tape storage for processing an storing the gamma-ray spectra.

The complete calibration of the gamma scanning system is presented. This includes the calibration of the effective collimating slit aperture, and the determination of the sur­face response matrices for the Ge(Li) detector as a function of gamma photon energy.

The gamma scanning system is utilized for the character­ization of irradiated fuel pins to determine physical dimen­sions, specific fission product distributions, fuel cladding

failure of doubly encapsulated fuel pins, fast and thermal neutron flux profiles, and relative and absolute burnup profiles. The transfer mechanisms of 134Cs and 137Cs are investigated, showing the selective deposition of cesium on fuel pellets with high oxygen content. The determination of the differential burnup profiles of 235U and 239Pu mixed-­oxide fuel materials is presented. The nondestructive quan­titative determination of specific fission products by gamma scanning of irradiated materials is compared to destructive radiochemical assay. These gamma scanning results indicate that the method can be applied to the precise quantitative determination of specific fission products.

A computer code, COLLIM, is described for the determina­tion of the effective slit aperture of complex rectangular collimating slit assemblies. The quantitative determination of specific fission products is accomplished by applying a second computer code, QUADET, which allows the calculational simulation of the source response of cylindrical fuel pins.

The integration of the scanning mechanism, collimators, detector assembly, and data acquisition unit has resulted in a completely automated gamma scanning system. The new non-destructive techniques have been applied to the examination of over a hundred irradiated fast reactor fuel pins.

Document Type

Dissertation

Degree Name

Chemistry

Level of Degree

Doctoral

Department Name

Department of Chemistry and Chemical Biology

First Committee Member (Chair)

Nicholas Ernest Vanderborgh

Second Committee Member

Glenn R. Waterbury

Third Committee Member

Unknown

Fourth Committee Member

Bernard Thomas Kenna

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