Method detection limits have often been misunderstood and misused. The basic definitions developed by Lloyd Currie and others have been combined with assumptions that are inappropriate for many types of radiochemical analyses. A practical way for determining detection limits based on Currie's basic definition is presented that removes the reliance on assumptions and that accounts for the total measurement uncertainty. Examples of proper and improper use of detection limits are also presented, including detection limits reported by commercial software for gamma spectroscopy and neutron activation analyses.
The independent isomeric yield ratio of146La and84Br in the thermal neutron fission of235U is reported for the first time with the values of 0.058±0.017 and 0.62±0.20, respectively. the yields have been determined using a fast radiochemical separation technique followed by -spectroscopy. The deduced rms angular momentum of84Br is 5.9 from the statistical model analysis and the rms angular momentum of146La is found too low to be determined.
Long-lived fission radionuclides spread out after the Chernobyl accident have been measured in samples collected from the Black Sea and at the Aegean coasts of Turkey between June 15 and September 15, 1987. Nondestructive analysis was performed using high resolution -spectroscopy. The activity remaining 16 months after the event was found to be enhanced in coniferous needles as well as in lichens, while foodstuff did not show any appreciable contamination. The relatively high106Ru/134Cs and144Ce/134Cs ratios compared to those found in analogous samples from Southern Europe, might result from a fractionation between refractory and volatile elements.
Authors:I. Yamaguchi, H. Terada, M. Takahashi, and H. Sugiyama
Radioactive nuclides with relatively long half-lives in the target assemblies of medical accelerators were investigated. The
samples were the target assembly of a 10 MV linear accelerator, a 20 MV microtron and screws of a cyclotron. Gamma-spectroscopy
was performed with a high-purity germanium (HPGe) detector. Detected nuclides were 51Cr, 54Mn, 59Fe, 57Co, 58Co, 60Co, 65Zn, 108mAg, and 110mAg. As the half-lives of some generated nuclides are relatively long, it is difficult to adapt to decay-in-storage.
Various mushrooms from Austria were analyzed for103Ru,137Cs and134Cs after the reactor accident at Chernobyl /19.6.–26.10. 1986/ by -spectroscopy. The following concentration (nCi/kg wet weight) values were found:103Ru 0.1–4 nCi/kg,137Cs 0.5–104 nCi/kg,134Cs 0.3–42 nCi/kg. The concentration of cesium isotopes in Cantharellus cibarius /lower Austria/, Leccinum scabrum /lower Austria/ and Xevocomus badius /lower Austria/ was considerably higher than in other mushroom samples.
Many mushrooms from Austria collected between May 25 and September 21, 1987 were analyzed for137Cs and134Cs by -spectroscopy one year after the reactor accident at Chernobyl. The following concentrations /nCi kg–1 wet weight/ were found:137Cs 0.4–43.2 nCi kg–1,134Cs 0.1–16.4 nCi kg–1. The concentration of cesium isotopes in Cantharellus cibarius /Klagenfurt/ and Xerocomus badius /Upper-Austria, Mühlviertel/ were considerably higher than the tolerance level /5 nCi kg–1/.
Authors:W. Andrews, M. Ham, L. Bennett, and E. Grandmaison
A radioactive aerosol and vapor dispersion model, RADiM, has been developed to predict the distribution of acquired doses from radionuclides escaping into the atmosphere following a marine reactor accident. Designed as a decision aid for emergency response teams, RADiM is based on a Gaussian plume model, which considers decay and transmutation, as well as meteorological and terrain effects. An initially estimated source term can be adjusted for strength and composition, based on subsequent field survey measurements and gamma-spectroscopy. RADiM was validated using field release data and was compared to predictions from established codes. Possible accident scenarios were also examined.
Authors:J. Laul, D. Case, M. Wechter, F. Schmidt-Bleek, and M. Lipschutz
A thermal neutron activation analysis technique has been developed for the analysis of terrestrial rocks and stony meteorites
for trace elements. The main emphasis of the method is directed toward minimizing chemical procedures and maximizing the use
of Ge(Li) gamma spectroscopy and computer data reduction. The validity of the technique is demonstrated by presenting data
obtained for synthetic samples, U.S G.S. Standard Rocks and three ordinary chondrite meteorites for the following elements:
As, Au, Co, Cs, Ga, Ge, Hg, Mo, Os, Re, Sb, Sc, Se, Te and Zn.
A method of comparing glass fragments of potential application to forensic sicence has been developed and evaluated. A representative
sample of window glass from England and Wales has been collected and analysed for about 25 elements. An automated radiochemical
separation followed by gamma-spectroscopy was used in order to determine the concentration of the maximum number of elements.
Frequency distributions of the elemental concentration are shown and used to assess the discrimination of the technique and
compare it with the measurement of refractive index. A few simulated cases have been included to demonstrate the possible
application to forensic science problems.
Authors:M. Vutchkov, C. Grant, C. Lalor, and J. Preston
The International Centre for Environmental and Nuclear Sciences (ICENS) has been involved in conducting multipurpose geochemical surveys, the results of which were published in "A Geochemical Atlas of Jamaican Soils". The primary analytical tool for these studies was neutron activation analysis (NAA) using the SLOWPOKE-2 reactor at the Centre. The neutron flux of the SLOWPOKE-2 reactor is extremely stable, thus allowing a semi-absolute method for quantitative NAA. This has several advantages, but requires preparation and measurement of the single- or multi-element standards for each gamma-spectroscopy system (GSS). The NAA laboratory at ICENS operates three GSSs. The primary ("master") GSS was standardized using single element standards for over 50 elements, naturally occurring in most geological and biological materials. The standardization of the secondary GSS's was achieved by transferring of the elemental sensitivities of the master GSS using an instrumentation-free standardization approach. The paper describes the implementation of this methodology and its utilization in the routine analytical work.