共查询到20条相似文献,搜索用时 15 毫秒
1.
H. Kazemian H. Zakeri M. S. Rabbani 《Journal of Radioanalytical and Nuclear Chemistry》2006,268(2):231-236
Summary Potassium
nickel hexacyanoferrate, KNiFC, was incorporated in the porous matrix of
zeolites by successive impregnation with Ni(NO3)2 and</o:p></p>
K4Fe
(CN)6.1 CFC and PFC exchangers were first prepared by
impregnating the potassium nickel hexacyanoferrate into the clinoptilolite and
the synthetic P zeolite, respectively. Ion-exchange isotherms and breakthrough
curves were plotted. Results showed that the CFC sorbent is suitable for
removal of Cs+ where PFC is more suitable for Sr2+.
Negative effect of Na+ as a competing ion in these exchangers was
less than in the parent zeolites. Isotherm plots fitted the Langmuir equation.</p>
</p> 相似文献
2.
J. Solecki 《Journal of Radioanalytical and Nuclear Chemistry》2006,268(2):357-364
Summary Results
of studies of Na+, K+ and Cs+ influence on the
adsorption of 85Sr on soil samples of the different types of
successive horizons are presented. It was proved that the adsorption isotherms
in log-log coordinates are of straight-line type and may be described by the
Freundlich equation. Monovalent cations influence the coverage degree of the
soil surface by 85Sr (most often lowering it) in the following order
K+3Na+3Cs+.
The investigation of pH influence proved its essential meaning in the process.
The plateau of surface coverage degree versus pH lies above pH 5.5 or 6.5
depending on the soil type. Generally, in the studied system, the size of 85Sr
adsorption depends on the concentration of the isotope, pH of the solution,
type of monovalent cation, and on the soil properties.</p>
</p> 相似文献
3.
P. Mell J. Megyeri L. Riess Z. Máthé G. Hámos K. Lázár 《Journal of Radioanalytical and Nuclear Chemistry》2006,268(2):411-417
Summary Diffusions of85Sr,137Cs,60Co and125I radionuclides have been studied in
borecore samples from Boda siltstone/claystone formation (BCF) under ambient
and in situ conditions. In-diffusion (85Sr,137Cs,60Co and125I) and through-diffusion measurements (125I) were performed at ambient
conditions, and for iodine, in-diffusion measurements were also carried out at
in situ conditions (100 bar, 50 °C). In the case of cationic species
carrier-containing solutions were also applied.60Co was detected only in the first
slice of borecore at each sample, while137Cs was detected also in the first-, second- and
third slices according to the concentration-increase of inactive carrier. Among
the investigated cations,85Sr exhibited the fastest diffusion rate with
2.7-6.0 . 10-12m2/s
apparent diffusivity values. In the course of in-diffusion measurements 4.7
. 10-11
m 2 /s, during through-diffusion investigations 1.4-1.6 .
10-12m2/s and at in situ conditions 5.0-8.0
. 10-12
m2/s
apparent diffusivities were obtained for125I.Modest sorption of125I can also be deduced from the
results.</p>
</p> 相似文献
4.
P. Mell J. Megyeri L. Riess Z. Máthé J. Csicsák K. Lázár 《Journal of Radioanalytical and Nuclear Chemistry》2006,268(2):405-410
Summary Sorption of60Co,85Sr, 137Cs and125I have been studied on samples
originated from Boda (siltstone-) claystone formation (BCF) (Hungary). The
distribution of Kdvalues have been determined in static batch
experiments using natural groundwater. The order of sorption of isotopes was
Co>Cs>Sr>I, where iodine exhibits sorption properties in a modest
extent. The sorption isotherm was determined for Cs from measurements carried
out in 10-5-10-1M initial concentration range. The
isotherm can be described with non-linear Freundlich approximation in the range
of</o:p></p>
10-7-10-4M equilibrium concentration. At
concentrations >10-2M the isotherm achieves saturation. Hence, it is suggested that sorption
of Cs on BCF is dominated by cation-exchange reactions on the illite mineral
component. In the case of Co and Sr, precipitation reactions occurred during
the experiments performed with carrier-containing solutions. This can be
attributed to the low values of solubility product constants of SrCO3, SrSO4and Co(OH)2, formed from anions present in the
natural groundwater.</p>
</p> 相似文献
5.
The determination is based on the evaluation of experimentally obtained breakthrough curves using the erfc-function. The first
method is founded on the assumption of a reversible linear sorption/desorption isotherm of radionuclides on solid phase with
constant distribution and retardation coefficients, whereas the second one is based on the assumption of a reversible non-linear
sorption/desorption isotherm described with the Freundlich equation, i.e., with non-constant distribution and retardation coefficients. Undisturbed cores of 5 cm in diameter and 10 cm long were embedded
in the Eprosin-type cured epoxide resin column. In this study the so-called Cenomanian background groundwater was used as
transport medium. The groundwater containing radionuclides was introduced at the bottom of the columns at about 4 mL h−1 constant flow-rate. The results have shown that in the investigated fucoidic sands: (i) the sorption was in principle characterized
by linear isotherms and the corresponding retardation coefficients of 137Cs and 85Sr, depending on the type of sample, were approximately 13 or 44 and 5 or 15, respectively; (ii) the desorption was characterized
by non-linear isotherms, and the retardation coefficients of the same radionuclides ranged between 23–50 and 5–25, respectively.
The values of the hydrodynamic dispersion coefficients of these radionuclides varied between 0.43–1.2 cm2 h−1.
相似文献
6.
Strontium
isolation from natural samples with Sr resin and subsequent determination of 90Sr</p>
</p>
Ž. Grahek K. Košutić M. Rožmarić-Mačefat 《Journal of Radioanalytical and Nuclear Chemistry》2006,268(2):179-190
The
reliability of an 90Sr determination method was tested using an Sr
extraction chromatographic resin for strontium isolation. The 90Sr-content
in samples of vegetables, soil and water (obtained from Environmental
Measurement Laboratory, USA) were determined and the results were controlled by
classical methods and by using an anion-exchanger and an alcohol solution of
nitric acid for the strontium isolation. These methods were previously tested
by determining 90Sr in IAEA 326 and 327 samples of soil. It is shown
that the isolation process with Sr resin is simpler and faster than the
classical and mixed solvent anion-exchange methods. The efficiency of isolation
on a Sr column depends on the resin quantity and separation conditions; and is
the highest with a Sr column, compared to the classical and anion-exchange
methods. Experimental data and theoretical models were used to calculate the
parameters that enable the estimation of optimum dimensions of the column for
isolation. A simple relation is proposed for the calculation of breakthrough
volume, which defines the sample and eluent volumes for an optimal strontium
isolation.</p>
</p> 相似文献
7.
Y. Spasova U. Wätjen T. Altzitzoglou 《Journal of Radioanalytical and Nuclear Chemistry》2008,277(1):211-215
Recently, the Institute for Reference Materials and Measurements (IRMM) has assumed responsibility for organizing regular
measurement comparisons among those laboratories which provide radioactivity monitoring data from their country to authorities
of the European Commission (EC) under various EC legislation articles. The most recent exercise under this International Comparison
Scheme for Radioactivity Environmental Monitoring (ICS-REM) in measuring the 137Cs, 40K and the 90Sr activity concentration in milk powder is presented here. The complete cycle of the comparison is described, including the
establishment of reference values traceable to SI units, the demonstration of the homogeneity of the distributed samples,
the treatment and measurement of samples in the participating laboratories, and the evaluation of the results. 相似文献
8.
A. B. Mackenzie M. S. Baxter I. G. Mckinley D. S. Swan W. Jack 《Journal of Radioanalytical and Nuclear Chemistry》1979,48(1-2):29-47
Multi-radionuclide analyses of coastal marine sediments and seawater can be of considerable value in defining rates and mechanisms
of nearshore processes. A preliminary study of134Cs,137Cs,210Pb,226Ra and228Ra in the Clyde Sea Area has been performed. A summary of the marine geochemistries of these species and a detailed account
of methods involved in their routine analysis are described. 相似文献
9.
L. I. Tsikritzis 《Journal of Radioanalytical and Nuclear Chemistry》2005,264(3):651-656
Summary The distribution and origin of 40K, 226Ra, 228Ra and 137Cs has been investigated in trees, mosses and lichens in the basin of the West Macedonia Lignite Centre. In tree leaves 137Cs is negligible, while the 226Ra and 228Ra concentrations are affected by the fly ash particles. Concerning 226Ra and 228Ra values of mosses and lichens, which are systematically larger than those of unpolluted areas, the application of chemometrics proved that they originate mainly from the lignite fly ash. 相似文献
10.
N. Kamei-Ishikawa S. Uchida K. Tagami 《Journal of Radioanalytical and Nuclear Chemistry》2008,277(2):433-439
The performance of several commercially available portable radiation spectrometers containing small NaI(Tl) scintillation
detectors has been studied. These devices are used by field inspection personnel to detect and identify illicit radioactive
materials. The detection and identification of enriched uranium is an important deterrent to undeclared nuclear proliferation
and nuclear terrorism. This study was conducted using a variety of shielded and unshielded uranium sources in a simulated
maritime environment. The results indicate adequate identification capability for various uranium enrichments using the manufacturer’s
spectral analysis firmware. More sophisticated methods for analyzing the spectra can be applied to these short field measurements
to determine the isotopic enrichment. 相似文献
11.
Simultaneous
measurement of gamma-rays and neutron fluences</p>
using
a HPGE detector</o:p></p>
</p>
Z. B. Alfassi T. Zlatin U. German 《Journal of Radioanalytical and Nuclear Chemistry》2006,268(2):237-241
Summary A
simultaneous determination of gamma and neutron fluences in a mixed neutron +
gamma field can be achieved by gamma-ray spectrometry, optimizing the
moderator-converter-detector assembly and measuring both the direct gamma-lines
and the neutron induced prompt gammas. For the prompt gamma-lines a combination
of high efficiency and low background is the goal, and it can be best achieved
if the gamma-energy is in the range above about 1 MeV up to 2.5 MeV. The
optimal moderator-converter thickness can be determined experimentally. Most
converter elements produce gamma-rays in the low energy range. If chlorine is
used as a converter, the 1164.7 keV peak and the 1950-1960 keV peaks seems to
be a good choice. A very practical material containing chlorine is PVC. It is
an efficient moderator, it is solid, common, and can be handled easily.</p>
</p> 相似文献
12.
The vertical distribution of85Sr and137Cs in undisturbed single-contaminated agricultural soils have been studied during their irrigation with wet atmospheric precipitation
in dependence on time under laboratory conditions for about one year. The soil samples were collected from several localities
in the environment of nuclear power plants at Dukovany and Jaslovské Bohunice using a special auger. The samples were placed
into polyethylene columns of 9 cm in diameter and 20 cm in height. The activity of radionuclides in soil profiles after their
separation into single layers were counted by Ge(Li) semiconductor gamma-spectrometry. Based on the exponential depth distribution
of radionuclides, the values of their migration parameters as relaxation depth, migration rate and retardation factor were
calculated. The influence of the permanent grass cover and of the applied zeolite on the migration parameters of these radionuclides
was also investigated.
Presented at the Conference “Nukleonika '98”, Prague, Czech Republic, 9–10 September 1998, dedicated to late Professor František
Běhounek in honour of his 100th birthday. 相似文献
13.
N. M. Antovic V. Popovic I. Antovic N. Svrkota P. Vukotic 《Journal of Radioanalytical and Nuclear Chemistry》2011,290(1):81-88
A coincidence method for measuring 137Cs, 40K, 226Ra and 232Th decay products activity in soil, vegetation and fish samples, was applied to the six-crystal gamma-coincidence spectrometer
PRIPYAT-2M. In this way, some problems appeared in simultaneous measurement of 137Cs, 226Ra and 232Th by NaI(Tl) detectors and the PRIPYAT-2M spectrometer were solved. The obtained results were agreeable with the HPGe spectrometer
ones. 相似文献
14.
The aim of this paper was to determine the extent of contamination by anthropogeneous radionuclides 137Cs and 90Sr in the bottom sediments from the Barents Sea based on the radioactive activity of the samples taken up in August 1991,
among others, from the area close to New Land Island and Francis Joseph Archipelago. The results are based on the phenomenon
of vertical migration, in the bottom sediments which is of significant importance from the natural environment point of view. 相似文献
15.
M. M. El-Dessouky A. N. Sharaf El-Deen 《Journal of Radioanalytical and Nuclear Chemistry》1988,125(2):481-484
Separation of Cs, Sr and Ca from their mixture was studied using solvent extraction and ion exchange techniques. More than 90% separation efficiency was achieved for Ca–Sr separation using ion exchange resin (Doulite C-20) while solvent extraction amounted to 88%. A proposed technique for determination of137Cs and89Sr in milk (after removal of organic matter) showed more than 80% accuracy for89Sr determination and more than 90% for137Cs determination. 相似文献
16.
K. M. Abd El-Rahman A. M. El-Kamash M. R. El-Sourougy N. M. Abdel-Moniem 《Journal of Radioanalytical and Nuclear Chemistry》2006,268(2):221-230
Summary The
batch removal ofCs+, Sr2+, Ca2+and Mg2+ions from aqueous solutions using synthetic
zeolite A was investigated. The influence of the initial ion concentration, pH
and temperature was studied. The obtained isotherm data have been correlated
with Langumir, Freundlich, and Dubinin-Radushkevich(D-R) isotherm models. The effect of the temperature on the equilibrium
distribution values has been utilized to evaluate the standard thermodynamic
parameters such as free energy (DG), enthalpy (DH) and entropy (DS). Based on the D-R
isotherm expression, the maximum ion-exchange capacity and the mean free energy
of each studied ion has been determined. The selectivity sequence, deduced from
the equilibrium isotherm data is: Sr2+>Ca2+>Mg2+>Cs+>Na+.</p>
</p> 相似文献
17.
A. S. Al-Hobaib K. M. Al-Sulaiman D. M. Al-Dhayan A. A. Al-Suhybani 《Journal of Radioanalytical and Nuclear Chemistry》2006,268(2):425-431
Summary Sand
filters are used in water treatment stations to remove particulate matter from
underground water, where iron and manganese are collected forming thin oxide
films. These oxides of iron and manganese adsorb radium from underground water.
Radium concentration increases in time on the filters, and consequently the
level of radioactivity increases in the station. The removal of adsorbed radium
on sand using inorganic acids was studied. Good efficiency of radium removal
was obtained by controlling different parameters like temperature, time, pH,
addition of competitive cations and anions. It was found that hydrochloric acid
is the best for radium removal from sand filters. Maximum removal obtained was
about 60% at 5M BaCl2 and 2M HCl at 50 °C for 180-minute contact
time. Kinetic parameters of the removal process were studied and compared with
literature data.</p>
</p> 相似文献
18.
<Superscript>226</Superscript>Ra and <Superscript>228</Superscript>Ra determination in environmental samples by alpha-particle spectrometry 总被引:1,自引:1,他引:0
J. L. Aguado J. P. Bolivar R. García-Tenorio 《Journal of Radioanalytical and Nuclear Chemistry》2008,278(1):191-199
A complete methodology for 226Ra and 228Ra determination by alpha-particle spectrometry in environmental samples is being applied in our laboratory using 225Ra as an isotopic tracer. This methodology can be considered highly suitable for the determination of these nuclides when
very low absolute limits of detection need to be achieved. The 226Ra determination can be performed at any time after the isolation of the radium isotopes from the analyzed samples while the
228Ra determination needs to be carried out at least six months later through the measurement of one of its grand-daughters.
The method has been validated by its application to samples with known concentrations of these Ra nuclides, and by comparison
with other radiometric methods. 相似文献
19.
M. D. Engelmann L. A. Metz N. E. Ballou 《Journal of Radioanalytical and Nuclear Chemistry》2006,268(2):201-204
Two
methods capable of near complete recovery of technetium adsorbed on charcoal
are presented. The first involves liquid extraction of the technetium from the
charcoal by hot 4M nitric acid. An average recovery of 98% (n=3) is
obtained after three rounds of extraction. The second method involves dry
ashing with air in a quartz combustion tube at 400-450 °C. This method yields
an average recovery of 96% (n=5). Other thermal methods were attempted, but
resulted in reduced recovery and incomplete material balance.</p>
</p> 相似文献
20.
A. Bhattacharyya P. K. Mohapatra P. N. Pathak V. K. Manchanda 《Journal of Radioanalytical and Nuclear Chemistry》2006,268(2):323-328
Summary Sorption
behavior of Th and U on cation-exchange resins was investigated from nitric
acid medium by both batch and column methods. The cation-exchange studies
involved the sorption of UO22+ and Th4+ and
their cationic complexes onto Dowex 50Wx8 and Dowex 50Wx4 resins (50-100 mesh).
The batch data yielded a separation factor (Kd,Th/Kd,U)
value of >100 for the cation-exchanger, Dowex 50Wx4 at 1-2M HNO3.
Separation of uranium from thorium was also carried out by column method in
nitric acid medium using cation-exchangers, Dowex 50Wx4 as well as Dowex 50Wx8.
While uranium elution was possible at 1M HNO3, Th could be eluted
only at higher concentration of nitric acid (>6M). The stripped solution
emanating from a mixer settler employing di-2-ethyl hexyl isobutyramide as
extractant and feed solution similar to THOREX process comprising 350 mg/l U
and 380 mg/l Th in 0.75M HNO3 was loaded on the column and the
decontamination factor value for U in the product was >1000.</p>
</p> 相似文献