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1.
For the disposal of the high efficiency particulate air (HEPA) glass filter to environment, the glass fiber should be leached
to lower its radioactive concentration. To derive the optimum method for removal of Co and Cs from HEPA glass fiber, four
methods were applied in this study. Results of electrochemical leaching of glass fiber by 4.0 M HNO 3–0.1 M Ce(IV) solution showed that the removal efficiency of 134Cs, 137Cs, and 60Cs from glass fiber after 5 h was 96.4, 93.6, and 93.8%, respectively. Results by 5 wt% NaOH solution showed that the removal
efficiency of 134Cs, 137Cs, and 60Cs after 30 h was 81.7, 82.1, and 10.0%, respectively. Results by repeat 2.0 M HNO 3 solution showed that the removal efficiencies of 134Cs, 137Cs, and 60Cs after 2 h of three repetitions were 96.2, 99.4, and 99.1%, respectively. Finally, results by repeat 4.0 M HNO 3 solution showed that the removal efficiencies of 134Cs, 137Cs, and 60Cs after 4 h of three repetitions were 100, 99.9, and 99.9%, respectively, and their radioactivities were below 0.1 Bq/g.
Therefore, the chemical leaching method by 4.0 M HNO 3 solution was considered as an optimum one for removal of cesium and cobalt from HEPA glass fiber for self disposal. Also
the removal efficiencies of 60Co, 134Cs, and 137Cs from the waste-solution after its precipitation-filtration treatment for reuse of 4.0 M HNO 3 waste-solution were 88.0, 95.0, and 99.8%. 相似文献
2.
β-Xylosidases are critical for complete degradation of xylan, the second main constituent of plant cell walls. A minor β-xylosidase (BXYL II) from Penicillium janczewskii was purified by ammonium sulfate precipitation (30% saturation) followed by DEAE-Sephadex chromatography in pH 6.5 and elution with KCl. The enzyme presented molecular weight (MW) of 301 kDa estimated by size exclusion chromatography. Optimal activity was observed in pH 3.0 and 70–75 °C, with higher stability in pH 3.0–4.5 and half-lives of 11, 5, and 2 min at 65, 70, and 75 °C, respectively. Inhibition was moderate with Pb+2 and citrate and total with Cu+2, Hg+2, and Co+2. Partially purified BXYL II and BXYL I (the main β-xylosidase from this fungus) were individually immobilized and stabilized in glyoxyl agarose gels. At 65 °C, immobilized BXYL I and BXYL II presented half-lives of 4.9 and 23.1 h, respectively, therefore being 12.3-fold and 33-fold more stable than their unipuntual CNBr derivatives (reference mimicking soluble enzyme behaviors). During long-term incubation in pH 5.0 at 50 °C, BXYL I and BXYL II glyoxyl derivatives preserved 85 and 35% activity after 25 and 7 days, respectively. Immobilized BXYL I retained 70% activity after 10 reuse cycles of p-nitrophenyl-β-D-xylopyranoside hydrolysis. 相似文献
3.
Vertical distributions of global fallout 137Cs and 14C were investigated in a Japanese forest soil in 2001. Even 38 years after the fallout, 137Cs was still observed mostly in the uppermost 5 cm. A preferential accumulation of 137Cs was found in a 1-cm-thick transition layer between organic-rich A and underlying B horizons. This unique observation indicated that 137Cs migrated through the A horizon at a rate of 0.20 % year−1 and the transition layer acted as a barrier for 137Cs migration to deeper layers. The vertical distributions of 137Cs and 14C were significantly correlated, suggesting a coupled downward migration of 137Cs and organic matter on a time scale of decades, along the same physical pathways. 相似文献
4.
Radioactivity measurements were performed, at the east (Georgia) and west (Romania) part of the Black Sea, for natural radionuclides and 137Cs in collected water and sediment samples using lab-based and in situ gamma-ray spectrometry. The activity concentrations of 137Cs at Georgian area in the sediment and seawater ranged between 20 to 50 Bq kg−1 and 8 to 25 Bq m−3, respectively while at the Romanian area the activity concentration ranged from 10 to 30 Bq kg−1 and 3 to 15 Bq m−3, respectively. The activity concentration values of 7Be at the Georgian area reached values up to (30 ± 4) Bq kg−1. The induced dose rates to marine organisms in both areas estimated by the ERICA assessment tool were much lower than the screening value of 10 μGy h−1. 相似文献
5.
Sulfonated ion irradiated (H+ and He2+) PEEK films were synthesized with a range of cross-linking density and a variety of sulfonation degrees. Batch adsorption experiments were carried out at an initial pH of 6.0 ± 0.2, initial concentrations of Pb2+ and 137Cs ions of 10.0 mg L−1 and 5500 Bq L−1, respectively. The maximum adsorption capacity was 60 mg g−1 for Pb2+, and the distribution coefficient reached 6200 cm3 g−1 for 137Cs. The results indicated that sulfonation could be used to recycle low cross-linked PEEK and prepare efficient adsorbents to remove toxic Pb2+ and 137Cs from polluted aqueous solutions. 相似文献
6.
The mineral extraction activities may disturb the natural radioactivity, therefore current study aims to generate baseline data of natural radionuclides and anthropogenic 137Cs before the start of industrial activities. Gamma spectrometry and gross alpha and beta counting systems were used for activity measurement in environmental samples. In soil, the mean activity of 232Th, 226Ra, 40K and 137Cs were determined as 79 (66–117), 47 (34–80), 823 (602–1159) and 1.3 (1.1–4.5) Bq kg?1, respectively. The average annual effective dose rate (128.7 µSv h?1) in the study area was twice higher than world’s average value. Indoor hazard index was greater than unity at two places; therefore, proper ventilation is proposed during construction. 相似文献
7.
Zirconyl tungstate ceramic-supported membranes were developed and characterized. The transport process of Cs(I), Sr(II) and La(III) from the anode compartment to the cathode was investigated. The cationic fluxes for Cs(I), Sr(II) and La(III) were found to be 9·10 –10, 2.7·10 –9 and 2.4·10 –9 g·eq·cm –2·s –1, respectively. The transport numbers of these cations were found to be 0.12, 0.07 and 0.09, respectively. Separation of Cs(I), Sr(II) and La(III) was achieved using EDTA as a chelating agent in the anode compartment. Cs(I) was successfully separated with a decontamination factor of 97% from simulated intermediate level liquid waste (ILLW) containing Cs(I) and Sr(II). 相似文献
8.
The uptake behavior of long-lived radionuclides such as 134Cs (2.06 years), 137Cs (30 years) or 133Ba (10.54 years) on calcium alginate (CA) beads have been investigated. The CA beads are able to remove 133Ba (92%) at pH 7 after 90 min of exposure from the binary mixture of two. The separation method of short-lived daughter 137Ba (2.55 min) from its long-lived parent 137Cs (30 years) using this CA beads have also been developed. 相似文献
9.
Cesium-137 concentrations in red, brown and green algae have been studied for the calculation of natural depuration rates. The algae species were collected from the same population of the Black Sea stations during the period of 1986–1995. The natural depuration rates are estimated as biological half-lives. The pattern of depuration results represented by a single component for each algae division. The biological half-lives of 137Cs in red (Phyllophora nervosa), green (Chaetomorpha linum) and brown (Cystoceira barbata) algae are estimated to be 18.5, 21.6 and 29.3 months, respectively. 137Cs and 40K activity levels and their ratios in algae species in two stations in Black Sea region of Turkey have been determined during the period of 1990–1995. The results showed that the Sinop region was more contaminated than the ile region on the Black Sea coast of Turkey from the Chernobyl accident. 相似文献
10.
Crystalline silicotitanate inorganic ion exchanger, with a sitinakite structure is candidate material for remediation of aqueous
nuclear waste streams. The syntheses of crystalline silicotitanate (CST) and Nb-substituted crystalline silcotitanate (Nb-CST)
were carried out under hydrothermal conditions and the products were characterized using techniques viz., XRD, SEM/EDS, DTA/TGA,
surface area respectively. Batch experiments were carried out to study the kinetics of uptake of 137Cs and 90Sr, to estimate the decontamination factor (DF) values and distribution coefficients ( K
d) for the above synthesized CST and Nb-CST samples from actual radioactive waste solutions. The DF values for uptake of Cs
and Sr by Nb-CST after 24 h of equilibration was 355 and 136 whereas for CST it was found to be 40 and 176 respectively. The
K
d values for uptake of Cs and Sr for Nb-CST after 24 h of equilibration was found to be 35,490 and 13,500 mL/g respectively
whereas the K
d values for uptake of Cs and Sr for CST was found to be 4,025 and 17,525 mL/g respectively. The ion exchange capacity of Nb-CST
towards 90Sr and 137Cs was estimated to be 11.8 and 3.2 meq/g respectively whereas the ion exchange capacity of CST towards 90Sr and 137Cs was estimated to be 14.6 and 4.4 meq/g respectively. 相似文献
11.
UiO-66 and chitosan/UiO-66 composites were successfully synthesized by varying the mass addition of chitosan which were 0%, 2.5%, 5%, 10%, and 20% of the mass of UiO-66, denoted as UiO-66, Cs(2.5)/UiO-66, Cs(5)/UiO-66, Cs(10)/UiO-66, and Cs(20)/UiO-66, respectively. UiO-66 was modified with chitosan using the impregnation process. The X-ray diffraction patterns of the synthesized materials showed characteristic peaks at 2θ of 7.25° and 8.39°, which matched to that of the reported UiO-66. In addition, the Fourier transform infrared spectroscopy spectra of the materials showed absorption bands at the same wavenumber as UiO-66 and chitosan previously reported. The surface morphology of UiO-66 observed from scanning electron microscopy images was in the form of agglomerated small cube particles, where the smaller particles were observed for Cs(10)/UiO-66. From the N 2 adsorption isotherms, it was found that the Brunauer-Emmett-Teller surface areas of UiO-66, Cs(5)/UiO-66, and Cs(10)/UiO-66 materials were 825.7 m 2/g, 835.4 m 2/g, and 882.2 m 2/g, respectively. The results of the study on adsorption of methyl orange in aqueous solutions showed that Cs(5)/UiO-66 had the highest adsorption capacity of 370.37 mg/g and followed the pseudo–second-order adsorption kinetic with a Langmuir isotherm model. 相似文献
12.
Fluvial export of particulate and dissolved 137Cs was investigated to reveal its sources and transfer mechanisms in a broadleaved forest catchment using a continuous collection system. The finest size fraction (<75 µm), consisting of decomposed litter and surface mineral soil, was the dominant fraction in the particulate 137Cs load, although the contribution of coarser size fractions increased during high water discharge in 2014. The dissolved 137Cs originated from the decomposition of 137Cs-contaminated litter. Temporal changes in 137Cs distribution in the litter–mineral soil system indicated that the dissolved 137Cs load will be moderated in several years, while particulate 137Cs load has the potential to continue for a long time. 相似文献
13.
The evolution of Chernobyl 103Ru, 134Cs and 137Cs in accumulated fallout is rigorously followed. The 103Ru activity of about 12 kBq.m –2 in the middle of May 1986 became insignificant at the end of 1986, while the levels of 134Cs and 137Cs have changed during 3 years from 2.5 kBq.m –2, respectively, 5 kBq.m –2 to about 0.9 kBq.m –2, respectively 4.7 kBq.m –2 according to their proper half-lives. 相似文献
14.
Concentrations of 134+137Cs and 133Cs in aquatic macrophytes, water, and sediment were measured in samples collected from Fukushima Prefecture, Japan. The concentrations of 137Cs in submerged and floating-leaved plants were higher than the values for emergent plants according to their main Cs uptake mode. The geometric mean water-to-plant concentration ratio for 137Cs and 133Cs was comparable observed in submerged and floating-leaved plants, while the geometric mean sediment-to-plant concentration ratio for 137Cs in emergent plants was higher than that of 133Cs, which suggest that the mobility of Fukushima accident-derived 137Cs is not in steady state 4–5 years after the accident. 相似文献
15.
The dairy processing industry in India, on an average basis, involves an extensive amount of thermal and electrical energy consumption, i.e. 2.51 × 105 kW MT−1 and 1.44 × 105 kW MT−1, respectively, for an installed milk food processing capacity of 1.21 × 105 TPD. However, energy consumption spectrum depends upon the level of automation along with better utilisation of utility resources. The global ultra-high-temperature (UHT) pasteurised milk trade was valued at € 52.29 billion in 2012 and is expected to reach € 114.38 billion by 2019–2020. In the present work energy, exergy and exergoeconomic evaluation of ultra-high-temperature milk pasteurisation plant have been considered. The overall energy efficiency and efficiency pertaining to executable potential of energy in UHT Milk Processing Unit were reported to be 86.36% and 53.02%. The specific exergy destruction and specific exergy improvement potential were estimated to be 219.23 kJ kg−1 and 137.60 kJ kg−1, respectively. The highest possible retrievable exergy potential of the plant was associated with heating coil, i.e. 158.98 kW, followed by homogeniser (54.62 kW), which pinpointed towards the possibility of huge technical improvement. The processing cost was enumerated to be highest for heating coil (rk: 38.35%) followed by regeneration-1 (rk: 23.40%). Further, the total operating cost rate associated with thermodynamic deficiencies of subunits was estimated to be highest for heating coil (4859.82 € H−1) followed by regenerator-2 (1264.88 € H−1) and homogeniser (1187.14 € H−1). The broad survey of thermoeconomic indices of subunits indicated that the level of exergetic destruction was far more on higher side. 相似文献
16.
137Cs activity concentrations were determined in samples of macrophytes Polysiphonia fucoides (red algae) and Zostera marina (vascular plant) collected during the entire vegetation season in the Gulf of Gdańsk in the southern Baltic Sea. The measurements
showed considerable seasonality of 137Cs activity in both species; an increase of cesium concentrations was observed from spring to autumn with maximal levels 49.1 ± 1.4 Bq kg d.w.−1 ( P. fucoides) and 14.5 ± 1.0 Bq kg d.w.−1 ( Z. marina) in late autumn. 137Cs concentrations observed in a given season are the result of a number of processes, the intensity of which can differ depending
on external environmental conditions. The effects of these processes can differ and their directions can frequently be opposite
to one another. The examined macrophytobenthic plant species could serve as bioindicators of radionuclide pollution for monitoring
purposes on condition that the samples of plants are taken within a strictly defined period of the year to give comparable
results and to supply realistic information about pollution levels. 相似文献
17.
The paper deals with the transfer factors (TF) generated for a few varieties of leafy vegetables (spinach, fenugreek, and
amaranths) consumed by the locals around Tarapur atomic power station environment in India. The soil and leafy vegetable samples
collected from the ambient environment of nuclear site were used for the determination of the TFs and they were compared with
TFs generated from pot experiments under controlled conditions for 137Cs. The activity of 137Cs in soil and each vegetable was determined by gamma spectrometry using HPGe detector (35 and 160% relative efficiency) and
was reported on dry weight basis for both ambient environment and pot samples. The radioactive effluent containing 137Cs (pH ~7) from nuclear power station was used to spike the soil for pot (size 90 cm × 45 cm × 42 cm) experiment. The TFs
obtained for ambient environment and pot experiment were found to be in the range of 0.035–0.592 and 0.0054–0.29, respectively.
It is observed that TFs of ambient environment are in good agreement with those obtained in the pot experiment conducted under
controlled conditions. Further, the observed TF values at Tarapur nuclear site are comparable with the range of typical IAEA
transfer factor values for general leafy vegetation (0.11–2.9) for tropical environment. 相似文献
18.
This study with sampling expeditions of marine sediment, seawater and biota were performed at 30 stations within Malaysian
Exclusive Economic Zone (EEZ). A total of >400 samples were collected to determine the activity concentration of anthropogenic
radionuclides ( 239+240Pu, 137Cs) and their activity ratio ( 239+240Pu/ 137Cs) in sediments, seawater and biota. The purpose of this study was to determine the concentration levels for these radionuclides
and to evaluate any occurrence of radioactive contamination. Sediment cores were obtained using multicorer device, while water
samples via co-precipitation techniques and biota was purchased from local fishermen. The activity concentrations of 239+240Pu in sediment, seawater and biota were ranged 0.21–0.45 Bq/kg dry wt., 2.33–7.95 mBq/m 3 and <0.008 Bq/kg fresh wt., respectively. Meanwhile, the values of 137Cs were ranged <1.00–2.71 Bq/kg dry wt. in sediment, 3.40–5.89 Bq/m 3 in seawater and <0.05–0.41 Bq/kg fresh wt. in biota, respectively. Activity ratios of 239+240Pu to 137Cs obtained seem to confirm that these artificial radioactivities were mainly due to global nuclear fallout. 相似文献
19.
Results of determination of 137Cs, 90Sr, 40K, 239+240Pu, and heavy metals: Mn, Zn, Pb, Cd, Ni, Cr, Co, and Cu in skeletons of 15 species of birds of prey from Eastern Poland were
presented. The greatest amounts of 137Cs and 90Sr (70 Bq/kg and 33 Bq/kg, respectively) were found in rough-legged buzzards ( Buteo lagopus), winter visitors, coming from former soviet nuclear test places. Concentrations of 239+240Pu in raptors were negligible, only lesser-spotted eagles ( Aquila pomarina) revealed slightly higher values. Median concentrations of 137Cs and 90Sr in raptors which feed predominantly on small mammals were higher in comparison to concentrations found in other ones preferring
different trophy. The most noticeable was a very high lead concentration (reaching above 600 mg/kg) in birds which utilize
un-retrieved hunting casualties as their prey. 相似文献
20.
For this study, ion-eroded cement was prepared from the cement required for construction of middle- and low-level radioactive waste repositories in caves. The properties for adsorption of 137Cs on cement before and after ion erosion were investigated. XRF, XRD, SEM–EDS and BET were used to analyse various cement materials. The effects of reaction time, solid–liquid ratio, initial radioactivity and different ions on adsorption were studied by static batch experiments. When the initial radioactivity was 1114.5 Bq L?1 and the solid–liquid ratio was 5 g L?1, the adsorption equilibrium time was 12 h. Adsorption of 137Cs on ion-eroded cement was more effective than that on untreated cement. The adsorption process was consistent with the pseudosecond-order kinetic model and the Freundlich isotherm model, and the process involved multilayer chemisorption. This study provides basic research data for construction of a disposal repository. 相似文献
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