ABSTRACT
Our laboratory has purchased four LaCl (3)(Ce) scintillation crystals over the course of the last year for evaluation as part of an environmental management research and development project. In addition to the expected content of naturally radioactive (138)La, we have found that all four of these detectors are contaminated to various degrees with alpha particle emitting nuclides that we have determined to be (227)Ac and its daughters. The impact of these radionuclides on the background spectra and, thus, on the detection sensitivity of these detectors is presented and discussed.
Subject(s)
Artifacts , Background Radiation , Lanthanum/chemistry , Lanthanum/radiation effects , Scintillation Counting/instrumentation , Scintillation Counting/methods , Alpha Particles , Dose-Response Relationship, Radiation , Equipment Design , Equipment Failure Analysis , Radiation DosageABSTRACT
We propose practices to optimize the quality of acquired gamma-ray spectra at a radioanalytical laboratory and to assist in the identification of extraneous spectral peaks including those from limitations in the physical setup, electronics, and counting conditions. This paper offers visible comparisons of high-quality spectra with those of inferior quality. We demonstrate the impacts on gamma-ray spectra taken with germanium (HPGe) detectors due to detector size, shape and energy resolution, background radiation, high-energy beta- or beta+ decay in the sample, beta(-)-, beta(+)- and gamma-ray backscatter, pole-zero cancellation, pulse pileup, coincidence summing, and unwanted sources of radiation.
ABSTRACT
The decay of 182Hf, now extinct, into stable 182W has developed into an important chronometer for studying early solar system processes such as the accretion and differentiation of planetesimals and the formation of the Earth and the Moon. The only 182Hf half-life measurements available were performed 40 years ago and resulted in an imprecise half-life of (9+/-2)x10(6) yr. We redetermined the half-life by measuring the specific activity of 182Hf based on two independent methods, resulting in a value of t(1/2)(182Hf)=(8.90+/-0.09)x10(6) yr, in good agreement with the previous value, but with a 20 times smaller uncertainty. The greatly improved precision of this half-life now permits very precise intercalibration of the 182Hf-182W isotopic system with other chronometers.
ABSTRACT
A non-destructive technique to determine the time since last purification of weapons grade plutonium based on the 241Pu decay series has been developed and demonstrated to provide results that are consistent with our historical and process knowledge. This method is based on the use of the Bateman equations and the decay chain 241Pu-->237U & 241Am-->237Np-->233Pa. Secular equilibrium is assumed between the (2.1 x 10(6) year) 237Np and the (27 day) 233Pa. The proposed method is dependent upon the efficiency of the plutonium separation process but makes no assumption about the relative abundance of 241Pu in 239Pu. Even though the technique was developed for weapons grade plutonium, it is expected to apply to almost any material that contains plutonium.
Subject(s)
Algorithms , Models, Chemical , Plutonium/analysis , Plutonium/isolation & purification , Radioactive Waste/analysis , Radiometry/methods , Spectrometry, Gamma/methods , Half-Life , Plutonium/chemistry , Radiation Dosage , Reproducibility of Results , Sensitivity and SpecificityABSTRACT
Population of the 6+ 332 keV level in 232Th from the decay of 236U was observed for the first time. The 49, 112, and 171 keV gamma-ray energies and relative intensities from the decay of 236U were measured.
