a Quantitative Method for Analyzing Radioactive Nuclides in Infinite Composite Materials Using High-Resolution Gamma-Ray Spectroscopy.
A theory is formulated in which the concentration of a radionuclide uniformly distributed throughout an infinite medium is related to the photopeak count rate of a signature gamma ray acquired by a detector within the medium. The mass fraction of the i('th) radionuclide in the medium is given by f(,i) = W(,i)(psi)(,i) (E)/(lamda)(,i)I(,I)(E)K(E); where (psi)(,i)(E) and I(,i)(E) are the observed photopeak count rate and absolute intensity for a gamma-ray emission of energy E. (lamda)(,i) and W(,i) are the decay constant and isotopic mass, respectively. It is shown that the function K(E) is a source volume integration over(' )(epsilon)(E,R)B(E,R)exp( -(SIGMA)(mu)(E)r(R))/(VBAR)R(VBAR)('2) which depends on gamma-ray energy only. Values of the narrow-beam attenuation coefficient (mu) are known for many materials. However, several laboratory experiments are performed in order to obtain data from which to empirically determine the detector response function (epsilon)(E,R)(' )and the gamma-ray build -up-factor(' )B(E,R). Special experimental instrumentation for analyzing radionuclides in infinite composite materials using high -resolution gamma-ray spectrometry is introduced. A probe is constructed which contains a coaxial high-purity germanium crystal to detect the gamma rays, a cryostat to cool the crystal and electronic circuitry to process the signal from the detector. Laboratory models of natural formations are prepared using high-grade radioactive samples diluted with silicon dioxide to obtain the desired concentrations. Each model is sampled to obtain X-ray fluorescence, delayed neutron and fluorimetric analysis from independent laboratories to compare with results using the method presented in this work.
- Pub Date:
- March 1982
- Physics: Radiation