关键词：
光学期刊,光学期刊联盟,光学论文,光电资讯,光电社区,光学人物,光学专家,光学实验室,光学文献,编辑出版,光学权威,光学前沿,光学会议,微信智能应答服务,光学资源库,DOI代理注册,高功率激光,High Power Laser Science and Engineer,光子学研究,Photonics Research,中国光学快报,COL,Chinese Optics Letters,光学学报,中国激光,激光与光电子学进展
摘要：
A compact broadband Compton spectrometer with high spectral resolution has been designed to detect spectra of laser-driven high-flux gamma rays. The primary detection range of the gamma-ray spectrum is 0.5 MeV–13 MeV, although a secondary harder gamma-ray region of 13 MeV–30 MeV can also be covered. The Compton-scattered electrons are spectrally resolved using a curved surface detector and a nonuniform magnetic field produced by a pair of step-like magnets. This design allows a compact structure, a wider bandwidth, especially in the lower-energy region of 0.5 MeV–2 MeV, and optimum spectral resolution. The spectral resolution is 5%–10% in the range 4 MeV–13 MeV and better than 25% in the range 0.5 MeV–4 MeV (with an Al converter of 0.25 mm thickness and a collimator of 1 cm inner diameter). Low-Z plastic materials are used on the inner surface of the spectrometer to suppress noise due to secondary X-ray fluorescence. The spectrometer can be adjusted flexibly via a specially designed mechanical component. An algorithm based on a regularization method has also been developed to reconstruct the gamma-ray spectrum from the scattered electrons.
摘要：
Two fusion methods were established for rapid determination of Pu in soil and sediment samples. The methods consisted of NH4HSO4 or NH4HF2 fusion procedures incorporated with procedures for CaF2/LaF3 co-precipitation, extraction chromatography and SF-ICP-MS measurement. The fusion procedures were done on a portable hot plate instead of in a cumbersome muffle furnace and took only 15min heating-up time from room temperature to 250 degrees C and 15min fusion time at 250 degrees C. Chemical recoveries of Pu after completing the NH4HSO4 and NH4HF2 fusion methods for 0.5-1g sample were approximately 70% and more than 90%, respectively, and decreased with the increase of sample weight from 0.5g to 5g. Sediment samples were pre-ignited at different temperatures ranging from 450 degrees C to 1000 degrees C to form refractory fractions of Pu, with which the dissolution rates of Pu by the NH4HSO4 and NH4HF2 fusion were investigated. With the increase of pre-ignition temperature of the sediment samples, the dissolution rates of Pu from the samples prepared by NH4HSO4 fusion declined dramatically from near 100% for 450 degrees C to 8% for 1000 degrees C. In contrast, the NH4HF2 fusion was capable of completely releasing Pu from samples that were pre-ignited at temperatures over 450 degrees C to 1000 degrees C, which was comparable to releases obtained by the hazardous and time-consuming HNO3-HF digestion, and was superior to the conventional HNO3 digestion. Additionally, because HF is not used in any procedure of the NH4HF2 fusion, a safer and greener alternative to NH4HSO4 fusion and HNO3-HF digestion is realized for rapid Pu determination in environmental samples for nuclear emergency response and application in environmental studies.
摘要：
This work presents a method developed for simultaneous analysis of ultra-trace level Np-237 and Pu isotopes in soil and sediment samples by sector field inductively coupled plasma mass spectrometry (SF-ICP-MS). Pu-242 was used as a yield tracer for Np-237 as well as for Pu isotopes. A simple single chromatographic column packed with anion exchange resin (AG MP-1M) was used for the separation of Np-237 and Pu isotopes from the matrix elements and other potential interferences. The SF-ICP-MS measurement precision of the Np-237/Pu-242 atom ratio for sub-fg/mL level Np-237 and (PU)-P-242 was 0.97%, and the overall fractionation between Np-237 and (PU)-P-242 for the whole analysis procedure was 1.010 +/- 0.038. Besides, the single column chromatographic separation realized high decontamination factor of U (1.8 x 10(6) to 1.7 x 10(7)), and that ensured the interference effect of U-238 to the Np-237, Pu-239 and Pu-240 measurements was negligible or could be easily corrected. Four standard reference materials were analyzed for method validation, and the results illustrated Pu-242 was an effective non-isotopic tracer for Np-237 determination. Finally, the developed method was successfully employed in the analysis of the global fallout level of Np-237 and Pu isotopes in Japanese paddy soil samples to study their environmental behaviors.
关键词：
(239+240)Pu;(240)Pu/(239)Pu atom ratio;Fukushima accident;ICP-MS;Seawater
摘要：
The marine environment is complex, and it is desirable to have measurements for seawater samples collected at the early stage after the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident to determine the impact of Fukushima-derived radionuclides on this environment. Here Pu isotopes in seawater collected 33-163 km from the FDNPP site at the very early stage after the accident were determined (May 2011, within two months after the accident). The distribution and temporal variation of Pu-239 and Pu-240 were studied. The results indicated that both (239+24) PU activity concentrations (from 0.81 +/- 0.16 to 11.18 +/- 1.28 mBq/m(3)) and Pu-240/Pu-239 atom ratios (from 0.216 +/- 0.032 to 0.308 +/- 0.036) in these seawater samples were within the corresponding background ranges before the accident, and this suggested that Fukushima-derived Pu isotopes, if any, were in too limited amount to be distinguished from the background level in the seawater. The analysis of Pu isotopic composition indicated that the major sources of Pu in the seawater after the accident were still global fallout and the Pacific Proving Ground close-in fallout. The contribution analysis showed that the contributions of the Pacific Proving Ground close-in fallout in the water column of the study area ranged from 26% to 77% with the average being 48%. (C) 2018 Elsevier Ltd. All rights reserved.
摘要：
In order to assess the impact of the Fukushima derived Pu isotopes on seawater, a new analytical method to rapidly determine Pu isotopes in seawater by SF-ICP-MS including Fe(OH)(2) primary co-precipitation, CaF2/LaF3 secondary co-precipitation and TEVA+UTEVA+DGA extraction chromatographic separation was established. High concentration efficiency (similar to 100%) and high U decontamination factor (similar to 10(7)) were achieved. The plutonium chemical recoveries were 74-88% with the mean of 83 +/- 5%. The precisions for both Pu-240/Pu-239 atom ratios and Pu239+240 activity concentrations were less than 5% when 15 L of seawater samples with the typical Pu239+240 activity of the Northwest Pacific were measured. It just needs 12 hours to determine plutonium using this new method. The limit of detection (LOD) for Pu-239 and Pu-240 were both 0.08 fg/mL, corresponding to 0.01 mBq/m(3) for Pu-239 and 0.05 mBq/m3 for Pu-240 when a 15 L volume of seawater was measured. This method was applied to determine the seawater samples collected 446-1316 km off the FDNPP accident site in the Northwest Pacific in July of 2013. The obtained Pu239+240 activity concentrations of 1.21-2.19 mBq/m(3) and the Pu-240/Pu-239 atom ratios of 0.198-0.322 suggested that there was no significant Pu contamination from the accident to the Northwest Pacific.
