[en] Using powders prepared by a high-gravity reactive precipitation process, grain-controlled barium titanate ceramics were obtained under conventional sintering conditions. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, as well as dielectric measurements were used to characterize the samples. The powder was densified to >95% of theoretical density when sintered at 1200 deg. C (K1200), and the average grain size of the resulting ceramics was <0.5 μm. Increasing sintering temperature increased the grain size and did not arise the exaggerated grain growth. The grain size significantly affects the permittivity of the resulting ceramics. Room temperature permittivity of the sample K1200 showed relatively low values (2800) compared with those (typically 4143) for ceramics sintered at 1250 deg. C, consisting of larger grains (∼1 μm). The lower permittivity was attributed to an incomplete development of the tetragonal structure

[en] Barium titanate powders have been prepared using a low temperature aqueous synthesis method in both conventional batch stirred tank reactor (BSTR) and continuous high-gravity reactive precipitation (HGRP) technique. The powders synthesized with HGRP technique show much smaller average particle size and exhibit higher specific surface area as compared to those prepared by conventional BSTR method

[en] Isodose curves for ¹²⁵I ophthalmic application in different geometry and activity can be obtained using the empirical formula based on suitable geometric model. The results of surface dose rate determined with lithium fluoride (LiF) thermoluminescent dosimeter (TLD's) chips in water-organic glass phantom and air had no obvious difference and the surface dose rate and its uniformity, (3.46 +- 0.011) and (0.178 +- 0.15) nGy/h·10⁷Bq were obtained. Count measurements and dose determinations for the front and back etc. of the ophthalmic applicator with BaF₂ scintillation detector and LiF TLD's had revealed the space distribution of dose for ¹²⁵I ophthalmic applicator in which dose on the back was less than 0.1% of that on the front. The distribution of the absorbed dose rate along the eye axis had been measured using LiF TLD's in water-organic glass phantom. The measured and calculated dose data indicated that when measuring distances were larger than about 5 mm the experimental results agreed with those from calculation within the range of error, otherwise the measured values were lower, still it could be explained by experimental conditions

[en] Objective: To test the performance of air condensation method for collection and measurement of tritiated water vapor in air, to provide technical support for monitoring of tritiated water vapor in the surrounding environment of nuclear power plants. Methods: The water vapor in air was condensed to liquid water, and the liquid water sample was distilled and purified, and the activity concentration of tritium in water was measured with a low background of liquid scintillation counter. The precision, accuracy and detection limit of the method are tested, and the applicability of the method were verified. Results: The test results of several groups of samples in the laboratory show that, the average relative standard deviation was 14.2%, the relative error ranged from-9.8% to 5.2%, and the lower detection limit was 13.7 m Bq/m³, which was suitable for the collection and measurement of tritiated water vapor samples in air under humid environment. Conclusion: This method can be used to collect and measure the samples of tritiated water vapor in the air around nuclear power plants in wet seasons. (authors)

[en] Eu³⁺ activated M′-type LuTaO₄ phosphors were successfully prepared by using inorganic salts, citric acid and PEG400 via the Pechini sol–gel technique. Their crystallization, morphology, photoluminescence (PL) and X-ray excited luminescence (XEL) characteristics were investigated in detail. The results indicated that the M′-type LuTaO₄ phase appeared at about 850 °C, which was much lower than the crystallization temperature of the solid-state reaction. And the grain size of the phosphor was controlled from nano- to micron-scale by adjusting the sintering temperature. The optimal doping concentration of Lu_1−xEu_xTaO₄ phosphors was at x=0.10. With the sintering temperature increasing, PL intensity of the phosphor was improved remarkably, whereas its decay time was decreased. It is worth to notice that the sol–gel derived M′-type LuTaO₄:Eu³⁺ phosphors reveal excellent XEL performance and easily controlled grain size, which implies that they will have promising applications in high-spatial-resolution X-ray imaging. -- Highlights: • M′-type LuTaO₄:Eu³⁺ phosphors were firstly synthesized by the Pechini sol–gel technique. • The crystallization temperature 850 °C was much low than that required for classical solid-state reaction. • The grain size was controlled from nano- to micron-scale. • The luminescent properties of the sol–gel derived M′-type LuTaO₄:Eu³⁺ phosphors were investigated in detail

[en] Graphical abstract: Emission spectra of LuTaO₄:Ln (Ln = Pr, Sm and Dy) phosphors under X-ray excitation. The insets illustrate their SEM micrographs. - Highlights: • M′-type LuTaO₄:Ln³⁺ (Ln = Pr, Sm, Dy) phosphors were synthesized by sol–gel technique. • The phosphors exhibited an efficient energy transfer from the host to activators. • High intensity of activator emission was achieved under X-ray excitation. • The phosphors are encouraging for application in high-spatial-resolution X-ray CT imaging. - Abstract: M′-type Lu_1−xLn_xTaO₄ (Ln = Pr, Sm, Dy) phosphors have been successfully synthesized by sol–gel technique, their crystallization, morphology, photoluminescence and X-ray excited luminescence properties were investigated in detail. The phosphors had good crystallization behavior. The optimum doping concentrations of Pr³⁺, Sm³⁺ and Dy³⁺ in LuTaO₄ were at x = 0.003, 0.025, 0.02, respectively. They exhibited a more efficient host excitation relative to the 4f–4f excitations of the rare-earth ions, and a dominant ¹D₂ → ³H₄, ⁴G_5/2 → ⁶H_7/2 or ⁴F_9/2 → ⁶H_13/2 emission for Pr³⁺, Sm³⁺ or Dy³⁺, respectively, which corresponds to the average decay time of 21.7, 745.7 or 10.0 μs, respectively. It is expected that Pr³⁺- or Dy³⁺-doped LuTaO₄ phosphors with a microsecond level decay time are very encouraging for applications in X-ray computerized tomographic imaging with high spatial resolution

[en] The two-group competition model with non-local diffusion in a class of classic Lotka-Volterra system is studied. First, turning it into a collaborative system, under the condition that the monostable condition is satisfied, by constructing various new upper and lower solutions, it obtains new results that the minimum wave velocity of the system is linear or nonlinear, and the relationship between the parameters under the linear and nonlinear selection. (authors)

[en] The residue of spent fuel assembly after shearing and leaching in the reprocessing plant is called Leached Hull. The measurement of the U and Pu content will be an important reference for judging the level of spent fuel dissolution process, or as a judgment standard for whether it is necessary to re-dissolve the Leached Hull. In this paper, based on the analysis of the radioactive composition of the Leached Hull, and in view of the difficulty in analyzing the quality of U and Pu in the Leached Hull by directly by measuring the U and Pu characteristic particles, a method of indirectly measuring the residual U and Pu content in the Leached Hull is proposed, and the preliminary research work is carried out. In this method, a measuring device based on ³He proportional counter is designed. The content of ²⁴⁴Cm in the Leached Hull is measured and analyzed by neutron coincidence method. Aiming at the possibility of inhomogeneous distribution of radioactivity in the measured object, the simulation calculation of spatial detection efficiency distribution in the measuring device is carried out, and the limit error analysis of measurement is given. The nuclide composition information simulator of spent fuel assembly is established in the calculation program, the concerned nuclide content of the same type of spent fuel assembly in Japan is analyzed and calculated, then compared with the destructive analysis(DA)analysis result of this assembly, the uncertainty of the calculation result is given, and the ²⁴⁴Cm/U (Pu) value in the spent fuel assembly corresponding to the Leached Hull is calculated by the above program. Combined with the measured data and calculated data, the mass of U and Pu in the Leached Hull can be deduced. In addition, this paper also analyzes the error composition of this measurement analysis method, evaluates the uncertainty of the final analysis results to meet the needs of process judgment, and points out the direction of the next research work. (authors)

[en] A new method for the determination of hydrogen isotopes by cryogenic gas chromatography was established. The analysis was carried out by cryogenic gas chromatography with pulsed discharge helium ionization detector on the capillary column of 5A molecular sieve. H₂, HD and D₂ mixtures was separated at -95 degree C. The detection limit is 1 x 10^-6, and the precision of method is less than 15% for H₂, HD and D₂. (authors)

[en] Leached hull is the most important high-level radioactive solid waste in spent fuel PUREX process. Non-destructive assay technique and instruments are widely used for uranium and plutonium and other nuclides content analysis in leached hull. Average burnup of spent fuel assembly is quoted as initial parameter in traditional algorithm. According to reactor operation experience, spent fuel assembly burnup and fission product in spent fuel rods are inhomogeneity. So it contributes uncertainty to non-destructive analysis results of leached hull. Based on simulated reconstruction techniques, the key nuclides distribution along radius of spent fuel rods was got. The results show that the key nuclides concentration deviation between leached hull and fuel rod can be up to 100%. Several correction factors were added to establish fitting curves for correcting inhomogeneity affects. (authors)