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1.
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   

2.
The reaction U(3He, xn)Pu was studied by irradiating enriched235U (50.3%) and enriched238U (99.7%) targets with3He ions at the Åbo Akademi cyclotron (Turku, Finland). The incident3He ion energy in the irradiations was 27.0, 24.5 and 21.9 MeV. Plutonium was separated from the thin uranium targets by ion exchange. From the ion exchange fractions obtained, plutonium was electrodeposited on steel plates for alpha and X-ray counting. The activity of237Pu in the steel plates was determined with a Ge(Li) detector and the activity of236Pu and238Pu with a Si surface barrier detector. The cross sections of the reactions and the yields of plutonium isotopes are given.  相似文献   

3.
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   

4.
In order to investigate the sedimentary behaviour of neptunium,237Np together with Pu isotopes and241Am have been measured for the sediment cores collected from Lake Mikata (freshwater) and from Lake Kugushi (brakish water) both belonging to the Mikata Five Lakes, and from Nyu Bay (sea water). In all sediment core samples237Np was detected, and its concentrations were far below those of239,240Pu and241Am measured for the same samples. Inventories of237Np in Lake Mikata, Lake Kugushi and Nyu Bay were estimated to be 0.53, 0.29 and 0.34 MBq/km2, respectively. The activity ratio of237Np/239,240Pu calculted from the inventories in each sediment core was 0.29% for Lake Mikata, 0.15% for Lake Kugushi and 0.10% for Nyu Bay. These values except for the value for Lake Mikata are two or three times lower than the value of 0.3–0.4% observed for surface soils of 0–20 cm depth, suggesting that Np is more soluble compared with Pu.  相似文献   

5.
The237Np content of238Pu or239Pu samples were determined by the gammaspectrometry of238Np formed by thermal neutron activation. The measurements were carried out on irradiated238Pu samples directly, and after the chemical separation of239Pu samples. The237Np content of natural uranium was determined from the ratio of the alpha-activities of238Pu and239Pu isotopes formed from the decay of neptunium isotopes produced by the activation of237Np and238U isotopes, respectively.   相似文献   

6.
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   

7.
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   

8.
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   

9.
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   

10.
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   

11.
Diffusion coefficients of radionuclides237Np,239Pu and241Am in simulated alumina phosphate and alumina borosilicate glasses at temperatures lower than their transformation temperature were determined. Actinides are known to be the least mobile elements. In particular, the diffusion coefficients of actinides in alumina phosphate glasses at 673 K are about 10–18 m2·s–1, and in alumina borosilicate at 773 K about 10–19 m2·s–1. It is shown that crystallization of glasses leads to increasing237Np diffusion mobility. It is also shown that a rather small quantity of water absorbed by a crystallized alumina phosphate glass in tensifies low-temperature migration of237Np.  相似文献   

12.
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   

13.
Several samples of 237Np and 242Pu were irradiated in the guided cold neutron beam of the prompt gamma activation analysis facility at the Budapest Research Reactor. The thermal neutron capture cross sections of 237 Np and 242Pu were evaluated from the obtained prompt and delayed gamma ray data. The thermal neutron capture cross sections for 237Np(n,γ)238Np was found to be $ \sigma_{0} ({}^{237}{\text{Np}}) = 170.4 \pm 7.4\,{\text{b}} $ and for 242Pu(n,γ)243Pu to be $ \sigma_{0} ({}^{242}{\text{Pu}}) = 19.6 \pm 3.9\,{\text{b}} $ .  相似文献   

14.
Plutonium (Pu) metal samples from an interlaboratory exchange exercise and simulated swipe samples were dated using plutonium–uranium (Pu–U) and plutonium–americium (Pu–Am). Metal data were evaluated for consistency and the swipe data against its source material. Metal ages based on 239Pu versus 235U and 240Pu versus 236U agreed to within a few percent, while the 238Pu–234U and 241Pu–241Am measurements had larger uncertainties. Swipe ages compared favorably with the material’s known history. Neptunium (237Np) analyses were examined in the context of the 241Pu–241Am–237Np system to estimate whether Np can provide insights on material from which Am, Np, and U were removed.  相似文献   

15.
Simultaneous electrodeposition of actinides   总被引:1,自引:0,他引:1  
A new system for simultaneous electrodeposition of U, Np, Pu, Am and Cm has been developed. The system consists of (NH4)2C2O4–H2SO4–HCl. The effects on recovery of pH, current density, interfering ions and the amount of added HCl have been studied. The optimum condition for simultaneous electrodeposition of actinides has been recommended. Under the recommended condition recoveries of U, Np, Pu, Am and Cm have been obtained by using232U,237Np,241Am,242Pu and244Cm. The counting sources prepared are uniform, adherent and suitable for -spectrometry.  相似文献   

16.
A new method that allows rapid preconcentration and separation of plutonium and neptunium in water samples was developed for the measurement of 237Np and Pu isotopes by inductively-coupled plasma mass spectrometry (ICP-MS) and alpha spectrometry. 238U can interfere with 239Pu measurement by ICP-MS as 238UH+ mass overlap and 237Np via peak tailing. The method provide enhanced removal of uranium by separating Pu and Np initially on TEVA Resin, then moving Pu to DGA resin for additional removal of uranium. The decontamination factor for uranium from Pu is almost 100,000 and the decontamination factor for U from Np is greater than 10,000. This method uses stacked extraction chromatography cartridges and vacuum box technology to facilitate rapid separations. Preconcentration is performed using a streamlined calcium phosphate precipitation method. Purified solutions are split between ICP-MS and alpha spectrometry so that long and short-lived Pu isotopes can be measured successfully. The method allows for simultaneous extraction of 20 samples (including QC samples) in 4?C6 h, and can also be used for emergency response. 239Pu, 242Pu and 237Np were measured by ICP-MS, while 236Pu, 238Pu, and 239Pu were measured by alpha spectrometry.  相似文献   

17.
A radiochemical method is described for the determination of238Pu,239(240)Pu and241Am in a single soil sample. Plutonium is separated from a HNO3 leaching solution by a Microthene-TNOA column; amcricium is coprecipitated by oxalic acid, decontaminated from polonium by a TNOA-column in HCl medium, separated from the rare earth elements by a Microthene-HDEHP column, eluted with a 0.07M DTPA+1M lactic acid solution and finally purified by a PMBP-TOPO extraction. The method supplies a good decontamination of Am and Pu from natural alpha emitters; starting from 50 g soil, the average yields were 75.1±13.4% for plutonium and 57.7±10.8% for Am.239(240)Pu,238Pu and241Am concentrations (mBq/kg) in three different kinds of soil were the following: 255, 10.4, 81.3 (uncultivated soils); 236, 11.6, 76.7 (cultivated soils); 46, 1.9, 19.8 (river sediment). The average ratios238Pu to239(240)Pu and241Am to239(240)Pu were 0.044 and 0.350, respectively.  相似文献   

18.
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   

19.
The concentration of239,240Pu and238Pu in airborne effluents in the years 1985–1987 from two reactors VVER 440/total power of 880 MW/ of a nuclear power plant V-1 in Jaslovské Bohunice in Czechoslovakia, was determined. The concentration of239,240Pu in effluents ranged from 1.0 to 30.8 Bq.m–3 and of238Pu from 1.6 to 41.1 Bq.m–3. The activity ratio238Pu/239,240Pu in airborne effluents kept within the range of 1.0–2.4. Total annual discharged activities of239,240Pu in 1985, 1986 and 1987 were 28.5, 12.7 and 12.2 kBq, respectively. Total annual discharged activities of238Pu in 1986 and 1987 were 16.6 and 15.1 kBq, respectively.  相似文献   

20.
A gamma-spectrometric method using an intrinsic high resolution germanium detector has been developed for the determination of isotope ratios of plutonium from samples in solution form. The method is based on the assay of low energy gamma-rays of238Pu,239Pu,240Pu and241Pu and does not require the use of branching intensities or the knowledge of detection efficiencies for different gamma rays. Since low energy gamma-rays are used, the effect of241Am has also been studied. It is found that results are not affected up to 0.5 wt% of241Am in plutonium samples. An accuracy of 3% is achievable in the determination of240Pu/239Pu and241Pu/239Pu atom ratios as demonstrated by carrying out measurements on isotopic standards of plutonium.  相似文献   

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