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1.
This paper describes the analytical methods for the determination of237Np, Pu isotopes, and241Am, with particular emphasis on237Np by alpha-ray spectrometry and241Pu 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   

2.
Depth profiles and inventories of237Np in sediment cores from the Ribble Estuary in the Irish Sea have been studied along with those of Pu isotopes,241Am and137Cs, to allow a more detailed look of anomalously high237Np content observed in this estuary previously. The comprehensive data obtained showed that the depth profiles of both237Np contents and237Np/239,240Pu activity ratios were clearly different from those of239,240Pu,241Am, and137Cs and their activity ratios. As much as 80–90% of237Np inventories (0.32–1.06 kBq/m2), found in three cores, were estimated to be derived from a source other than Sellafield, on the basis of comparison of the237Np/239,240Pu inventory ratio (0.65–1.74%) found in the Ribble Estuary cores with those (0.10–0.16%) in the Ravenglass Estuary cores.  相似文献   

3.
Intertidal coastal and estuarine sediments from 24 sites in the Irish Sea have been analyzed for99Tc,237Np,238Pu,239,240Pu and241Am. The237Np activity and239Pu/240Pu ratio were measured simultaneously by ICP-MS, and99Tc was determined by HR-ICP-MS which is ten times more sensitive than Q-ICP-MS.The activities of99Tc,237Np,239,240Pu and241Am 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. The241Am/239,240Pu and237Np/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   

4.
Long-lived radionuclides,99Tc,137Cs,237Np, Pu isotopes and241Am were determined in the long sediment cores collected from nine intertidal sites around the west Cumbria of the Irish Sea, UK. The inventories of all nuclides measured varied considerably among the sampling sites, but generally their inventories decreased with increasing distance from Sellafield. Furthermore, the inventory ratios with respect to relationship with distance from Sellafield enabled comparison of transport behavior of99Tc,137Cs,237Np and241Am compared with239,240Pu. As a consequence, the apparent fractional rate of solution transport to the intertidal sediment was found to increase as follows:99Tc>137Cs>237Np>239,240Pu≥241Am.  相似文献   

5.
Chemical leaching experiments of237Np in the sediments from the Esk Estuary and the Ribble Estuary in the Irish Sea, U. K., have been carried out, in comparison with those of239, 240Pu and241Am, to understand the geochemical associations of these long-lived radionuclides with sediment. Experimental results show that partitioning behavior of237Np is obviously different from those of239, 240Pu and241Am.  相似文献   

6.
Concentrations of239,240Pu and241Am in filtered seawater, particulate fraction and sediment were measured. Methods for determination of these nuclides were critically chequed and a new rapid method for241Am 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 of239,240Pu in the water of Baltic Sea is of the order of 5 years. About similar concentrations of239,240Pu and241Am were found in particulates in water as in the surface layer of the sediment. The average Kd-values for plutonium and americium were 105 and 105–106 ml/g, respectively.  相似文献   

7.
Host phases of fallout239,240Pu and241Am 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 total239,240Pu concentration with decreasing association of239,240Pu with organic matter, high241Am/239,240Pu activity ratio in carbonate phase and somewhat high proportion of oxidized239,240Pu in leachable phases suggest a possibility of post-depositional diagenetic remobilization of Pu from sediment to water column.  相似文献   

8.
Adsorption experiments were performed to measure distribution coefficients of237Np(V),238Pu(IV) and241Am(III) for sedimentary sequential chemical extraction of the adsorbed radionuclides was carried out with water, CaCl2, KCl, NH2OH−HCl, K-oxalate and H2O2 solutions, to elucidate their dominant sorption mechanisms. The distribution coefficient of237Np was two orders of magnitude smaller than that of238Pu and241Am. Most of237Np adsorbed was extracted with CaCl2 solution and its sorption was controlled by a reversible ion exchange reaction. The adsorbed238Pu was mainly extracted with NH2OH−HCl+K-oxalate solution and its sorption was possibly controlled by irreversible reactions.  相似文献   

9.
This paper gives the first data on239,240Pu and241Am 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, and239,240Pu,241Am and137Cs, 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/km2 for239,240Pu, 10±5 MBq/km2 for241Am and 1.2±0.7 GBq/km2 for137Cs. The activity ratios of239,240Pu/137Cs and241Am/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   

10.
The plutonium and americium concentration and vertical distribution in some Italian mosses and lichens have been determined. The239,240Pu,238Pu and241Am concentration ranges in tree trunk lichens 0.83–1.87, 0.052–0.154 and 0.180–0.770 Bq/kg, respectively. The corresponding values in tree mosses are higher and more scattered ranging from 0.321 to 4.96, from 0.029 to 0.171 and from 0.200 to 1.93 Bq/kg. The mean238Pu/239,240Pu and241Am/239,240Pu ratios are 0.088±0.037 and 0.38±0.13 in lichens and 0.091±0.072 and 0.54±0.16 in tree mosses. The Pu and Am concentrations are relatively low in terrestrial mosses. The239,240Pu,238Pu and241Am vertical distributions in a terrestrial moss core (Neckera Crispa) collected near Urbino (central Italy) show an exponential decrease with the height. On the contrary the241Am vertical distribution in another terrestrial moss core (Sphagnum Compactum) collected in the Alps (northern Italy) shows an interesting peak at 16 cm which corresponds to the deposition of fallout from the nuclear weapon tests in 1960's. The241Am movement upward and downward in the moss core is also studied. The results show once again that both mosses and lichens are very effective accumulators of Pu and Am and that they can be used as good biological indicators of the radionuclide airbome pollution from nuclear facilities and nuclear weapon tests. They can play a very impotant role in cycling naturally or artificially enhanced radionuclides in the atmosphere over long time scales.  相似文献   

11.
Primary coolant samples from a research have been analyzed for239,240Pu,238Pu,238U,237Np and239Np. The determination of237Np and238U was carried out with the help of isotope dilution neutron activation analysis with239Np or238Np as tracer. For determination of239,240Pu and238Pu alpha spectroscopic isotope dilution analysis with238Pu as tracer was used.239Np was determined with the help of isotope dilution analysis using238Np as tracer. Nuclides were isolated by chemical separation on anionite resin. Before measurement, Pu isotopes were electrolytically deposited on stainless steel plates. Activity ratios referred to238U were reported. They are helpful for identification of the sources of actinide activity in reactor effluents.  相似文献   

12.
The concentration of239,240Pu and241Am in different samples collected from the coastal marine environment of Ibaraki Prefecture, Japan facing the Pacific Ocean have been studied. Seawater samples have been collected since 1975 and sea-biota since 1981. The mean concentration levels of239,240Pu and241Am were 0.51, 0.20 for anchovy, 0.22, 0.11 for flounder, 4.9, 0.77 for brown algae, 2.0, 2.4 for shellfish, and 0.022, 0.0028 for seawater (in mBq/kl), respectively. The chronological change of239,240Pu in seawater was influence by fallout amounts. The activity ratio between the nuclides showed steady levels after two years from the end of atmospheric nuclear explosion tests. Activity levels and the ratios for each type of sample are briefly discussed.  相似文献   

13.
The cross sections for the3He induced nuclear reactions on237Np leading to the formation of236sNp,238Np,236Pu,237Pu,238Pu,237Am and239Am were studied by the irradiation of thin and thick targets of237Np. The cross sections were determined in the energy range of 20–26 MeV using the stacked-foil technique with thin targets. The cross sections were used for the calculation of the thick-target yields for the production of236Pu,237Pu and238Pu from237Np irradiated with3He2+ ions in the energy range of 20–26 MeV.  相似文献   

14.
This paper describes the validation of a multi-technique analytical methodology that uses inductively coupled plasma-mass spectrometry, α-spectrometry, and γ-spectrometry for the routine analysis of samples containing transuranic radionuclides. This methodology is capable of the determination of concentrations of both238Pu and241Pu in the presence of238U and241Am without the need for chemical separations. The relative merits of these three techniques were evaluated as they are applied in a nuclear waste material and spent nuclear fuel testing program by analytical (1) standards and (2) solutions prepared from the dissolution of glasses doped with237Np,239Pu, and241Am. The uncertainty associated with technique was within ±4% for standards and ±10% for doped nuclear waste glasses. The methodology was then used to analyze three fully radioactive waste glasses.  相似文献   

15.
An accurate and reliable method has been developed and routinely carried out for the sequential determination of239,240Pu and241Am in environmental samples. After suitable pretreatment.239,240Pu and241Am are separated from other elements by means of the anion exchange resin method. Americium-241 is purified by coprecipitation with calcium oxalate and then ion exchanged in mixed media of the mineral acid-methanol. In the analysis,242Pu (or236Pu) and244Cm are used as chemical yield monitors. The recoveries of the yield monitors in the analyses of some kinds of environmental samples were 7080% for plutonium and 7686% for curium. The concentration of239,240Pu in the coastal sea water were 7.022 Bq/l and that of241Am was 1.26.3 Bq/l. The mean concentrations of239,240Pu in the edible parts of the marine products ranged from 0.22 to 7.4 mBq/kg · fresh and those of241Am ranged from 0.11 to 2.6 mBq/kg · fresh.  相似文献   

16.
Preparation of source and sample holder is described for the Mössbauer studies of237Np and238U. For the Mössbauer measurement of237Np, a source assembly with small sources of241Am metal was developed taking account of the transport regulations for radioactive substances. The source assembly of241Am showed a sufficient activity enough to measure the Mössbauer spectra of237Np. In order to handle237Np compounds safely, trebly sealed holders were designed which could encapsulate237Np samples without the seepage of liquid helium. A source for238U Mössbauer measurement was also developed from a highly pure242PuO2.  相似文献   

17.
A survey has been carried out of40K,60Co,99Tc,106Ru,125Sb,129I,134Cs,137Cs,154Eu,226Ra,228Ra,237Np,238Pu,239,240Pu,241Pu,241Am,242Cm, and243,244Cm activities in sediments from the Irish Sea. Several of these radionuclides were measured independently at two separate laboratories to enable the intercomparison of the results produced. The comprehensive data set generated allows the present spatial distributions of these radionuclides in coastal sediments to be examined in relation to sediment textural characteristics and by comparison with earlier survey, enables the temporal trends in their activities to be determined. In general all artificial radionuclides showed lower activities in sediments in response to falling discharges from Sellafield and relationships with either grain size, distance from Sellafield or both. Isotope ratios were similar to cumulative weighted activity ratios rather than present day values due to sediment mixing. Pu levels supplied evidence for the lag in response of sediment deposits with increasing distance from Sellafield due to sediment transport.  相似文献   

18.
Summary A procedure is described to extend the current radiochemical method of seawater analysis for Pu and Am including Np. Short-lived 239Np tracer was prepared by separation from its 243Am parent. Irish Sea Water reference material (IAEA-381) containing known concentrations of 237Np, Pu isotopes and 241Am was used to test the procedure for small water volumes. Inductively-coupled plasma mass spectrometry (ICP-MS) was used in addition to alpha spectrometry for measurement of 237Np in the purified final Np fractions.  相似文献   

19.
Summary A radioactively contaminated marine sediment core stemming from Irish Sea has been characterized by radiometric and mass spectrometric techniques as for 237Np, 241Am, 239Pu, 240Pu, 241Pu, 137Cs and 154Eu. The data obtained with independent methods in the framework of a QA/QC program as compared with the source term discharges, as well as with those reported in literature, are in good agreement.  相似文献   

20.
A procedure for the analysis of90Sr,154Eu,237Np,239Pu,241Am and242−244Cm was developed. Separation was done with the separating agent, di-2(ethyl hexyl)-phosphoric acid (HDEHP), and results in fractions containing the different elements to be analysed.90Sr analysis was done by analysing its daughter nuclide90Y, detected through the Cherenkov radiation emitted by this high energy β-emitter.154Eu was detected using γ-spectrometry with a lower Compton background as a result of the removal of other fission products.241Am could also be detected with γ-spectrometry or together with242−244Cm with α-spectrometry. The long-lived radionuclides237Np and239Pu were detected using inductively coupled plasma mass spectrometry (ICP-MS).  相似文献   

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