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Objective To establishment a process of monitoring waste resin clearance in nuclear power plants, and to meet clearance requirements and simplify the monitoring work. Methods In accordance with the requirements specified in current laws, regulations, and standards in China, as well as the practice of slightly polluted waste resins generated during the operation of nuclear power plants, in-depth discussion was conducted on sampling methods, sample uniformity and representativeness tests, radiation monitoring contents and methods, and simplified monitoring processes, in order to accurately monitor the radionuclide activity of waste resins to be cleared. Results A process was established to monitor waste resin clearance in nuclear power plants. A total of 55 barrels of waste resins were cleared and the radiation levels met the requirements. Conclusion An effective clearance process can facilitate the sampling of representative resins, improve the accuracy of monitoring data, differentiate radioactive waste from cleared waste, and simplify the monitoring process. Our results provide a basis and reference for future waste resin clearance.
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Objective Nowadays, radioactive xenon isotopes, including 131mXe, 133mXe, 133Xe, and 135Xe, are primarily released into the atmosphere through various reactor operation and major accidents of reactors. To improve the online monitoring capability of xenon in nuclear facilities and their gaseous effluents, a highly sensitive online xenon monitoring system was developed to monitor, warn, and alarm the activity concentration of radioactive xenon. Methods The online monitoring system for radioactive xenon gas in nuclear facilities was established using xenon membrane separation and concentration, xenon high-efficiency selective adsorption, and low-background gamma-ray spectrometry analysis methods. Results Under the operation mode of one-hour sampling and one-hour measuring, the minimum detectable activity concentration of the radioactive xenon online monitoring system for 133Xe was approximately (1.43 ± 0.03) Bq/m3. Conclusion This system can be effectively used for online monitoring of xenon activity concentration in nuclear facilities such as nuclear power plants and isotope production reactors, as well as in gaseous effluents. It helps improve the safety level of personnel, the environment, and nuclear facilities.
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Objective To evaluate the migration of plutonium aerosol caused by α recoil. Methods In this paper, the recoil deposition and Brownian motion of plutonium-containing nanoaerosols were simulated by Monte Carlo method. The recoil angle and the vertical first landing time of Brownian motion in the process of settling were sampled, and then the lateral displacements of Brownian motion were sampled to determine the final settling position of aerosol. Results For aerosols with particle sizes of 10-50 nm, the maximum migration distance of a single recoil settling was 1.39 μm. Brownian motion increased the migration capacity. Although there was a high likelihood that aerosols settled within 100 μm, there remained a slight probability of long-term suspension in the air. Conclusion The α recoil is one of the mechanisms of plutonium aerosol migration. An important mechanism for long-distance migration of nanoaerosols is that Brownian motion after recoil may cause them to suspend for a long time.
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Objective To establish a method for measurement of 239Pu in fecal samples based on inductively coupled plasma-mass spectrometry (ICP-MS), and to provide a novel method for assessing the internal exposure of workers. Methods Fecal samples were collected from workers and labeled. The samples were pretreated with carbonization ashing and microwave digestion devices, purified on TEVA resin, and measured using ICP-MS. Results The detection limit of 239Pu in fecal samples based on ICP-MS was 1.91 × 10−4 Bq. Conclusion In the routine monitoring of class S substances characterized by a 5 μm aerodynamic diameter during 12 months, the committed effective dose corresponding to the detection limit is 0.17 mSv. This value meets the requirements of relevant national standards and ICP-MS can be used as a novel means for accurate evaluation of internal exposure for workers.
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@#<b>Objective</b> To preliminarily study and establish a method for measurement of the transuranic nuclide <sup>241</sup>Am in fecal samples, and to provide technical support for internal radiation monitoring of staff. <b>Methods</b> Fecal samples were collected with a self-made stool sampler and treated with a self-made carbonization and ashing furnace. DGA resin was used to separate and purify <sup>241</sup>Am from fecal samples. With <sup>243</sup>Am as the tracer, the orthogonal method was used for condition optimization. <b>Results</b> The optimum conditions for separation and purification were: the acidity of HNO<sub>3</sub> added into the column, 6 mol/L; column flow rate, 0.6 mL/min; and the volume of analytical solution,12 mL. The method based on inductively coupled plasma mass spectrometry showed a detection limit of 9.79×10<sup>−4</sup> Bq for <sup>241</sup>Am in fecal samples, which was satisfactory and feasible. <b>Conclusion</b> This method fills the vacancy of <sup>241</sup>Am measurement in fecal samples to some extent, which is of practical significance for internal radiation monitoring and protection for analysts.
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Objective To investigate the biological effects of 12C heavy ions with different LETs,and to construct the dose-effect curves of chromosomal aberrations and micronucleus.Methods Human peripheral blood lymphocytes were irradiated with 0.5 - 5.0 Gy of 60Co γ-rays,29 and 148 keV/μm 12C with a dose rate of 0.5 Gy/min,respectively.The colchicine method and cytokinesis-blocking method were applied to measure chromosome aberrations and micronuclei formation,respectively. Results The chromosomal aberrations induced by 29 and 148 keV/μm of 12C ion had a linear dose response,while the dose-response of micronucleus induction followed to a linear-quadratic model.Chromosome aberration and micronucleus frequency increased with the LET of 12C ions. However, the micronucleus frequency increased slowly when the radiation doses exceeded 3.0 Gy..Chromosomal aberrations induced by 148 keV/μm 12C ions increased significantly when the time of colchicine treatment was prolonged.Conclusions Chromosome aberration and micronucleus induced by 12C ions increased with the LET,and the micronucleus frequency increased with dose less than 3 Gy.The biological effects of 12C ions were stronger than those of low LET irradiation of γ-rays.
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Objective To establish the dose-effect curves of chromosome aberrations in human peripheral blood lymphocytes induced by different LET rays,including 60Co γ-rays,252Cf neutrons,14MeV neutrons and 12C heavy ions at low doses,respectively,in order to assess radiation-induced damages after occupational and accidental exposure.Methods Heparinized whole blood samples were irradiated with the various radiation devices and doses ranged from 0 to 1 Gy with the interval of 0.25 Gy.Conventional chromosome culture method was applied with adding colchicines at the beginning and chromosome specimens were prepared after 48 h incubation.The Metafer scanning system was used for automatical finder of chromosome metaphases.The mathematic models were fitted according to aberration data obtained.Results At the dose range of 0 - 1 Gy,the math models of dic + r were linear for 60 Co γrays and linear-quadratics for 252 Cf neutrons,14 MeV neutrons and 12 C heavy ions.The models of ace were linear-quadratic for 60Co γ-rays and 12C heavy ion beams,and linear for 252Cf and 14 MeV neutrons.The models of total aberrations were linear-quadratic for all types of radiation.Conclusions High LET rays have higher biological effects in inducing chromosome aberrations yields compared with low LET rays.Moreover,the severity of damage is 252Cf ＞ 14 MeV neutrons ＞ 12C heavy ions ＞ 60Co γ-rays in turn.Therefore,in the range of low doses,the dic + r may be a better target of radiation damage for high LET radiation.
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Objective To study the protection of vanillin derivative VND3207 on the cytogenetic damage of mouse bone marrow cell induced by ionizing radiation.Methods BALB/c mice were randomly divided into five groups:normal control group,2 Gy dose irradiation group,and three groups of 2 Gy irradiaiton with VND3207 protection at doses of 10,50 and 100 mg/kg,respectively.VND3207 was given by intragastric administration once a day for five days.Two hours after the last drug administration,the mice were irradiated with 2 Gy γ-rays.The changes of polychromatophilic erythroblasts micronuclei (MN),chromosome aberration (CA) and mitosis index (MI) of mouse bone marrow cells were observed at 24 and 48 h after irradiation.Results Under the protection of VND3207 at the dosages 10,50,100 mg/kg,the yields of poly-chromatophilic erythroblasts MN and CA of bone marrow cells were significantly decreased(t = 2.36-4.26,P ＜ 0.05),and the marrow cells MI remained much higher level compared with the irradiated mice without drug protection (t = 2.58,2.01,P ＜ 0.05).The radiological protection effect was drug dose-dependent,and the administration of VND3207 at the dosage of 100 mg/kg resulted in reduction by 50% and 65% in the yields of MN and CA,respectively.Conclusions VND3207 had a good protection effect of on γ-ray induced cytogentic damage of mouse bone marrow cells.