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Abstract  

The effect of different relative humidity (RH) on the response of a six-polymer coated Quartz Crystal Microbalance (QCM) sensor based electronic nose (EN) was investigated, RH 30 and 50% respectively. Increases in the sensor responses were observed for an increase in RH. A stainless steel pre-concentration tube (PCT) containing Porapak-S and a nichrome heating element was developed to minimise the effect and allow for chromatographic pre-separation. Breakthrough times of chemical compounds through the PCT were experimentally determined and used to select a mixture of water and toluene as a suitable sample for pre-separation. The PCT was capable of separating the water from the toluene and the EN was competent at evaluating the concentration of toluene in the solution.

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Abstract  

Nickel sulfide (NiS) fire assay was used for the pre-concentration of Ir and Au in rock samples. The beads obtained after fire assay were irradiated directly with neutrons to determine Ir and Au. To suppress the reaction of 58Ni(n,p)58Co, the fire assay was carried out by using a small amount of Ni (0.0625 g) and the NiS bead samples were irradiated by neutrons with high Cd ratios. Analytical results of Ir and Au for rock samples were close to literature values, confirming that our procedure of INAA with pre-concentration can be applied to rock samples for the determination of ppb to sub-ppb level of Ir and Au.

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Artificial 32P (T 1/2 = 14.28 days) can be used to tracethe behavior of a major nutrient, phosphate, in aquatic systems. Althoughliquid scintillation or Cerenkov counting of high energy betas of 32P is very sensitive, its usefulness for low level activities is limitedby inefficient pre-concentration techniques. We found that precipitation ofZrPO4 is an excellent method for pre-concentration of 32Pfrom natural waters. After acidification (pH ~2) of a 1-liter sample, about1 ml 20 mM phosphate carrier is added and equilibrated with natural phosphates.Excess Zr carrier (about 40 mg) is then added to fully precipitate both thenatural and added phosphates in the sample. The ZrPO4 precipitatesare collected onto a Whatman GF/B type filter which becomes translucent inUltima Gold A/B cocktail. We obtained constantly high 32P recoveries(about 97%) through the entire procedure for hundreds of samples during ahydrologic tracer test. Furthermore, we could process about one dozen samplesper hour, and when counting with a portable liquid scintillation counter theresults are about 500-fold more sensitive than direct Cerenkov counting.

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The determination of isotopic thorium by alpha spectrometric methods is a routine practice for bioassay and environmental measurement programs. Alpha-spectrometry has excellent detection limits (by mass) for all isotopes of thorium except 232Th due to its extremely long half-life. This paper discusses improvements in the detection limit and sensitivity over previously reported methods of pre-concentration neutron activation analysis (PCNAA) for the recovery corrected, isotopic determination of thorium in various matrices. Following irradiation, the samples weredissolved, 231Pa added as a tracer, and Pa isolated by two different methods and compared (extraction chromatography and anion exchange chromatography) followed by alpha spectrometry for recovery correction. Ion exchange chromatography was found to be superior for this application at this time, principally for reliability. The detection limit for 232Th of 3.5 · 10-7 Bq is almost three orders of magnitude lower than foralpha spectrometry using the PCRNAA method and one order of magnitude below previously reported PCNAA methods.

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Abstract  

An extraction chromatographic method is described for the pre-concentration and separation of thorium, uranium, plutonium and americium in human soft tissues. Tissues such as lung and liver are oven dried at 120°C, ashed at 450°C and the ashed sample is alternately wet (HNO3/H2O2) and dry ashed, and then dissolved in 8M HCl. Because of the complex matrix and large sample samples (up to 1500 g), the actinides were preconcentrated from the tissue solution using the TRUTM resin (EIChroM) prior to elemental separation by extraction chromatography and determination of americium, plutonium, uranium and thorium by alpha spectrometry. The actinides were eluted from the preconcentration column and each actinide was individually eluted on TEVATM and TRUTM resin columns in a tandem configuration. Actinide activities were then determined by alpha spectrometry after electrodeposition from a sulfate medium. The method was validated by analyzing human tissue samples previously analyzed for americium, plutonium, uranium and thorium in the United States Transuranium and Uranium Registries (USTUR). Two National Institute of Standards and Technology (NIST) Standard Reference Materials, SRM 4351-Human Lung and SRM 4352-Human Liver were also analyzed.

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Abstract  

The accurate and precise determination of232Th in biological samples is very important for the development of biokinetic models for thorium and for improving our knowledge on its distribution in human tissues. Radiochemical neutron activation analysis has long been one of the most sensitive methods for the determination of232Th. However, these determinations suffer in reliability because recovery information following the separation is not typically available. This information is particularly important for difficult matrices such as human bone where recoveries may be significantly less than unity. Also, the separation of difficult matrices following neutron activation may involve relatively high personal dose from the co-activated matrix. A novel approach for the determination of radiochemical yield has been developed which employs the use of a readily available, gamma-emitting isotope of thorium,227Th.227Th, obtained by radiochemical separation from227Ac, is added to each, dissolved sample prior to separation and the chemical yield determined by gamma-ray spectrometry following the separation. This pre-concentration step is then followed by neutron activation and the232Th determined via233Pa using gamma-ray spectrometry. Detection limits were approximately an order of magnitude lower than obtained by alpha-spectrometry.

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Abstract  

A revized method for determining 232Th using a pre-concentration neutron activation analysis (PCNAA) procedure was developed to accommodate irradiation in a dry irradiation tube environment. 232Th extracted by ion-exchange from a sample was electrodeposited onto 5/8″ diameter vanadium planchets, which are arranged in a stack and irradiated in the dry tube central irradiation facility (CIF) of the reactor. The higher neutron fluence of this facility improved sensitivity by approximately 37%, however, the higher temperatures required modifications to the irradiation procedure. Because the heat in the CIF would melt the plastic spacers used in the original method, a tube of high-purity quartz was used to contain samples, and high purity quartz spacers were used to separate the vanadium planchets during the irradiation. Test irradiations have determined that no significant transfer occurred from the disks to the silica disks and no significant variation in the neutron flux was observed. Finally, a thin film barrier was tested for its ability to reduce recoil contamination from 229Th onto the detector during alpha spectroscopy. The film was shown to reduce contamination to levels indistinguishable from normal background.

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Abstract  

A reactor fast neutron activation analysis was used in combinationwith a simple pre-concentration procedure for determining silicon in someiron reference standard materials of Japan Iron and Steel Federation. Thesamples were dissolved with aqua regia and digested with perchloric or sulfuricacid. The precipitated silica was collected on a filter paper and irradiatedin a cadmium case with reactor fast neutrons. Silicon can be determined intool steel SKD6, low-alloy steel Nos 2 and 4 and silico-manganese samplesby a present method measuring 1,273.4 keV rays from 6.63-minute 29Alproduced by 29Si(n,p)29 Al reaction.

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Abstract  

Rapid determination of 222Rn and 220Rn progeny (214Pb, 212Pb, 214Bi, 212Bi) is achievable using manganese dioxide (MnO2) precipitation with analysis by γ-spectrometry. This is of interest to environmental monitoring programmes that utilise gross activity methods to screen for anthropogenic radionuclides. The contribution from these naturally occurring radionuclides (NOR) varies, and is difficult to experimentally measure due to short half-lives (t ½ = 19.9 m–10.64 h) and low environmental activity (<0.1 Bq L−1). The extraction efficiency of the technique is above 90%, and above 80% for other nuclides (232Th, 238U, 235U, 228Ac, 226Ra, 224Ra, 210Pb, 54Mn). Short-lived NOR have been measured at two surface water locations, and indicates elevated 214Bi activity of 4.0 ± 1.1 Bq L−1.

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Abstract  

This paper describes the use of IBC′s AnaLig®Sr-01 molecular recognition technology product to effectively and selectively pre-concentrate, separate and recover strontium from radioactive waste samples. The use and effectiveness of AnaLig®Sr-01 gel was successfully validated by analysis of International Atomic Energy Agency (IAEA 375) reference soil and National Physical Laboratory (NPL)–High Alpha–Beta (2003) liquid sample. The second part of this paper focuses on analysis of radioactive waste samples from nuclear power plant A1 Jaslovske Bohunice in Slovak Republic (NPP A1).

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