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1.
Host phases of fallout 239,240Pu and 241Am were studied in the surface sediments obtained in 1994 from abyssal basins of relatively small area of the western North
Pacific. An analytical procedure involving sequential chemical extraction was employed for partitioning the host phases of
the nuclides in sediment into five fractions: (1) exchangeable (2) bound to carbonate, (3) bound to hydrous Fe-Mn oxides,
(4) bound to organic matter and (5) residual. Decrease of total 239,240Pu concentration with decreasing association of 239,240Pu with organic matter, high 241Am/ 239,240Pu activity ratio in carbonate phase and somewhat high proportion of oxidized 239,240Pu in leachable phases suggest a possibility of post-depositional diagenetic remobilization of Pu from sediment to water column. 相似文献
2.
More than 200 samples of marine products have been collected and analyzed for plutonium and almost 100 samples for americium around Hitachi, Tokai and Oarai in the pacific coast of Ibaraki prefecture. The data have shown that the concentration factor (CF) values for plutonium were 330 for bivalve, 770 for abalone (muscle) and 610 for brown algae. For americium, the CF was calculated as 2400 for bivalve, 1000 for abalone (muscle) and 420 for brown algae. 相似文献
3.
This paper gives the first data on 239,240Pu and 241Am in Chinese soils. Surface soil samples with a set of 0–5 cm and 5–20 cm depth were collected from Beijing, Taiyuan, Shijiazhuang and Jinang of China in 1990, and 239,240Pu, 241Am and 137Cs, including naturally occurring radionuclides, in these samples were measured to evaluate their present levels and distributions. From these results, the average accumulated depositions were estimated roughly to be 24±13 MBq/km 2 for 239,240Pu, 10±5 MBq/km 2 for 241Am and 1.2±0.7 GBq/km 2 for 137Cs. The activity ratios of 239,240Pu/ 137Cs and 241Am/ 239,240Pu ranged from 0.016 to 0.026 with a mean value of 0.020±0.004 and 0.35 to 0.49 with a mean value of 0.43±0.05, respectively. 相似文献
4.
The vertical distribution of 137Cs, 90Sr, 239,240Pu, 238Pu and 241Am was determined in soil samples collected from the Chernobyl exclusion zone in 1994. The results show very close distribution profiles for all radionuclides, with about 90% of the total activity of each nuclide lying between the surface and the fourth centimeter. Sequential extraction methods were used to determine the association of radionuclides in soil. The data on vertical distribution of radionuclide species were used to calculate their vertical migration parameters. 相似文献
5.
A procedure has been developed using 242Pu as tracer for simultaneous determination of 237Np and 239,240Pu in environmental samples. The validity of the method has been demonstrated by ICPMS and a-spectroscopy for up to 10 gram soil and sediment, seawater up to 200 litres. The paper describes a suitable chemical procedure for Np and Pu including a quantitative pre-concentration of neptunium and plutonium, preparation of Np 4+ and Pu 4+, Np(NO 3) 6
2- and Pu(NO 3) 6
2-. The ratio of 237Np/ 242Pu (or 237Np/ 239Pu) before and after the procedure has been determined using 10 g soil (free from Np and Pu) R
before/ R
after = 1.004±3.3% (S.D n = 20) and 1 litre seawater R
before/ R
after = 1.019±1.9% (S.D., n = 12). Results from the intercomparison samples IAEA-135, IAEA-381 and from environmental samples are presented. 相似文献
6.
This paper describes the analytical methods for the determination of 237Np, Pu isotopes, and 241Am, with particular emphasis on 237Np by alpha-ray spectrometry and 241Pu by liquid scintillation technique. Results are also presented for the sediment cores collected from Mikata Five Lakes in Fukui Prefecture, Japan. 相似文献
7.
The aim of this work is to present the method for sequential plutonium and americium activity determination in air filters using chromatographic radionuclide separation and alpha spectrometry measurement. The developed method may be employed for the purposes of workplace monitoring and as an indicator of the need of introducing the individual monitoring as well as a useful complementation of individual monitoring. Basic parameters describing the developed method such as values of chemical recoveries and minimum detectable activities for plutonium and americium isotopes have been determined. Applied counting efficiency was obtained using Monte Carlo calculation method. 相似文献
8.
Concentrations of 239,240Pu and 241Am in filtered seawater, particulate fraction and sediment were measured. Methods for determination of these nuclides were critically chequed and a new rapid method for 241Am in sediment was developed. Due to seasonal variation a significant decrease of plutonium and americium concentrations in surface water takes place in summer. Americium is more efficiently associated with particulate matter than plutonium. From May 1980 to September 1984 soluble plutonium in the water was reduced to about half. The residence half-time of 239,240Pu in the water of Baltic Sea is of the order of 5 years. About similar concentrations of 239,240Pu and 241Am were found in particulates in water as in the surface layer of the sediment. The average K d-values for plutonium and americium were 10 5 and 10 5–10 6 ml/g, respectively. 相似文献
9.
The simultaneous determination of multiple actinide isotopes in samples where total quantity is limited can sometimes present
a unique challenge for radioanalytical chemists. In this study, re-determination of 238Pu, 239+240Pu, and 241Am for soils collected and analyzed approximately three decades ago was the goal, along with direct determination of 241Pu. The soils had been collected in the early 1970’s from a shallow land burial site for radioactive wastes called the Subsurface
Disposal Area (SDA) at the Idaho National Lab (INL), analyzed for 238Pu, 239+240Pu, and 241Am, and any remaining soils after analysis had been archived and stored. We designed an approach to reanalyze the 238Pu, 239+240Pu, and 241Am and determine for the first time 241Pu using a combination of traditional and new radioanalytical methodologies. The methods used are described, along with estimates
of the limits of detection for gamma-and alpha-spectrometry, and liquid scintillation counting. Comparison of our results
to the earlier work documents the ingrowth of 241Am from 241Pu, and demonstrates that the total amount of 241Am activity in these soil samples is greater than would be expected due to ingrowth from 241Pu decay. 相似文献
10.
Activity concentrations of Pu radioisotopes and 241Am were determined in the organic and mineral layers of four soil sections collected in 1996, providing for the first time information on the levels of these radionuclides in soil samples from Romania . The investigated site was an alpine pasture located in the Charpathian Mountains, in an area found as one of the most affected in Romania after the Chernobyl accident. In the examined soil sections radioactive inventories were estimated to be 500 Bq/m 2 for 241Pu, 115 Bq/m 2 for 239+240Pu, 8 Bq/m 2 for 238Pu and 50 Bq/m 2 for 241Am. On the basis of activity ratios in the soil profile, the source of the radioactive release is discussed. 相似文献
11.
This paper presents an improved radiochemical procedure for the determination of alpha-emitting Pu isotopes in environmental samples (soils, sediments, vegetation) by alpha-particle spectrometry. Quantitative Pu recovery yields were obtained (average 60%), 0.1 mBq being the average minimum detectable activity by the complete technique. Special efforts were made to ensure the removal of traces of different natural alpha-emitting radionuclides, which can interfere with the correct determination of 239+240Pu and 238Pu concentrations. The radiochemical procedure was validated by application to reference material and by participation in intercomparison exercises. This radiochemical procedure was applied to the different layers of a high-resolution sediment core taken from a lake in Sweden. The 239+240Pu and 238Pu/239+240Pu profiles obtained in the high-resolution sediment core correctly reproduced the expected evolution of these quantities as observed historically in the atmosphere, validating the procedure for this purpose and showing the power of these radionuclides for dating purposes. 相似文献
12.
Strontium-90, plutonium and americium activity concentrations in a few samples of forest soils, some species of mushrooms and fern leaves have been determined. These results are compared with cesium activity concentrations in the same materials obtained in a previous work. Radiochemical procedures are described. The origin of the contamination (Chernobyl accident or nuclear test explosion release) is discussed. The 90Sr activity concentration ranges from 0.6 Bq/kg (mushroom samples) to 48.4 Bq/kg (fern leaves). For 239+240Pu, it ranges from not detected above background (mushrooms, fern) to 10.8 Bq/kg (humus layer of forest soil). The maximum concentration of 241Am is found to be 2.4 Bq/kg (humus sample) and for 238Pu it is 0.85 Bq/kg (also in the humus sample). 相似文献
13.
A combined procedure for sequential determination of low level activity concentrations of 90Sr, 241Am and Pu radionuclides is described. The analysis of -emitters is performed by isotope dilution -spectrometry using 242Pu or 236Pu and 243Am tracers. Strontium-90 is analyzed by liquid scintillation counting using the double energetic windows method. The method combines the well established, procedure for Pu analysis based on anion exchange, the powerful and selective method for Sr isolation based on extraction chromatography using Sr-Spec resin and finally it includes the application of the TRU-Spec column for separation and purification of the Am fraction. The radiochemical procedure was tested using IAEA reference and intercomparison materials. Major parameters of the procedure as well as advantages and drawbacks are discussed in detail. 相似文献
14.
Intertidal coastal and estuarine sediments from 24 sites in the Irish Sea have been analyzed for 99Tc, 237Np, 238Pu, 239,240Pu and 241Am. The 237Np activity and 239Pu/ 240Pu ratio were measured simultaneously by ICP-MS, and 99Tc was determined by HR-ICP-MS which is ten times more sensitive than Q-ICP-MS.The activities of 99Tc, 237Np, 239,240Pu and 241Am were distributed over a wide range of 1.5–70.5, 0.01–13.3, 2.3–1589, 2.6–1894 Bq/kg, respectively. Activities of these radionuclides decreased exponentially with distance from the Sellafield source. The 241Am/ 239,240Pu and 237Np/ 239,240Pu ratios were almost constant with distance from the Sellafield. This result suggests that the distribution and behavior of Np and Pu are controlled by complicated factors such as the influence of transport, the variation with time of Np/Pu ratio in the Sellafield discharges and sedimentary mixing processes in the Irish Sea. 相似文献
15.
A liquid scintillation counting method for the simultaneous determination of Pu and Am, with a two-phase cocktail, has been applied to the analysis of a tissue sample from an accidental exposure incident. The sample contained 239Pu, 241Pu, and 241Am. In addition to analysis by two liquid scintillation counting techniques, analysis of the sample was performed by -spectroscopy and ZnS scintillation techniques, and the results were compared. The presence of 241Pu interfered with the liquid scintillation determination of 241Am when the two-phase cocktail was used, but the results were in agreement sufficient to be useful in determining what course of treatment, if any, might be necessary for the patient. 相似文献
16.
Irradiation and post-irradiation losses in 7 crude oils encapsulated in polyethylene and irradiated in a flux of 10 12n·cm −2 sec −1 have been thoroughly studied. The fraction of mercury released during irradiations ranging from 10 minutes to 2 hours is
proportional to the integrated flux received by the samples and does not differ substantially from one oil to another. Post-irradiation
loss rates at 20°C range between 0.017 and 0.027%·hr −1. Storage at−20°C reduces them by at least a factor of 2. The influence on the activity of 197Hg due to losses in sample weight occuring during the post-irradiation period has been examined. The fraction of radiomercury
retained inside the walls of the irradiation vials versus the irradiation time has been assessed. Contamination of an inner
irradiation site following prolonged irradiations of oils containing 150 μg/g of this element has been evaluated and found
to have a negligible impact for trace measurements above the ng/g level. 相似文献
17.
In order to deliver reliable results for a multitude of different scenarios, e.g. emergency preparedness, environmental monitoring, nuclear decommissioning and waste management, there is a constant process of method development in the field of radioanalytical chemistry. This work presents the results of a method comparison exercise aimed at quantifying 90Sr and 239,240Pu in environmental soil samples, with the intention of evaluating the performance and applicability of different methods. From the methods examined in this work, recommendations are given in order to find a radioanalytical measurement procedure, for 90Sr and 239,240Pu analysis, which is fit-for-purpose for a particular scenario. 相似文献
18.
Adsorption experiments were performed to measure distribution coefficients of 237Np(V), 238Pu(IV) and 241Am(III) for sedimentary sequential chemical extraction of the adsorbed radionuclides was carried out with water, CaCl 2, KCl, NH 2OH−HCl, K-oxalate and H 2O 2 solutions, to elucidate their dominant sorption mechanisms. The distribution coefficient of 237Np was two orders of magnitude smaller than that of 238Pu and 241Am. Most of 237Np adsorbed was extracted with CaCl 2 solution and its sorption was controlled by a reversible ion exchange reaction. The adsorbed 238Pu was mainly extracted with NH 2OH−HCl+K-oxalate solution and its sorption was possibly controlled by irreversible reactions. 相似文献
19.
241Pu was measured in reference materials and marine samples using a novel method based on rare earth fluoride co-precipitation followed by liquid scintillation spectrometry (LSS). Disc sources used for -spectrometry of 238Pu and 239+240Pu were leached with concentrated nitric acid before neodymium fluoride co-precipitation to scavenge plutonium in the lower oxidation states was carried out. After the determination of the chemical recovery by -spectrometry, the precipitate was recovered in a H 3BO 3/HNO 3 based dissolver and mixed with Packard Insta-Gel Ò Plus cocktail before LSS. Reasonable agreement has been obtained between the results obtained using this methods and the data obtained by direct disc analysis by LSS and ICP-MS. The 241Pu/ 239+240Pu ratios were coherent with the expected origin of the Pu contaminant in the marine environment showing the validity of the method.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
20.
A radiochemical procedure is described for the simultaneous determination of 238Pu, 239+240Pu, 241Pu, 241Am, 242Cm, 244Cm, 89Sr, and 90Sr in vegetation samples. The method was applied for the determination of these, radionuclides in grass, collected near Munich after the fallout from the reactor accident at Chernobyl, USSR. The specific activities observed were (in Bq kg –1 dry weight): 238Pu, 0.077; 239+240Pu, 0.15; 241Pu, 3.9; 241Am, 0.031; 242Cm, 3.0; 244Cm, 0.008; 89Sr, 2000; 90Sr, 99. 相似文献
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