目的在移动式反应堆现有研发水平无法满足《放射性物品安全运输规程》(GB 11806—2019)的背景下,本研究提出通过风险评价的方法对移动式反应堆运输的安全性进行研究。方法风险评价的内容主要包括计算移动式反应堆在运输中遇到假想事故的概率和事故后果,本研究根据美国联邦法规10CFR71中§12条款的相关要求对移动式反应堆在运输中可能遇到的事故种类进行梳理,并以事故后果最为严重的与油罐车发生撞击作为极端的假想事故,通过五因子计算公式的方法对假定热功率为20 MWt的移动式反应堆在假想事故下的事故后果进行计算。结果计算得出移动式反应堆在每年运输1次的条件下假想事故的发生概率为9.7×10^(–6)次/年,反应堆冷却1年后在假想事故下对工作人员的辐照剂量为810 mSv;冷却5年后在假想事故下对工作人员的辐照剂量为590 mSv。结论假想事故下移动式反应堆的事故后果远超过Advisory Material for the IAEA Regulations for the Safe Transport of Radioactive Ma-terial(SSG-26)和《电离辐射防护与辐射源安全标准》(GB 18871—2002)中工作人员受到的辐照剂量限值,并且假想事故的发生概率没有满足我国核安全导则对超设计基准事故10–7次/年的筛选要求。因此有必要在移动式反应堆运输过程中采取包括武装押运和路线规划在内的管理措施以降低假想事故的概率并采取相应的应急措施减轻假想事故的事故后果以满足核安全部门的监管要求。
Micromixing efficiency is an important parameter for evaluating the multiphase mass transfer performance and reaction efficiency of microreactors.In this work,the novel curved capillary reactor with different shapes was designed to generate Dean flow,which was used to enhance the liquid-liquid micromixing performance.The Villermaux-Dushman probe reaction was employed to characterize the micromixing performance in different curved capillary microreactors.The effects of experiment parameters such as liquid flow rate,inner diameter,tube length,and curve diameter on micromixing performance were systematically investigated.Under the optimal conditions,the minimum value of the segmentation factor XS was 0.008.It was worth noting that at the low Reynolds number(Re<30),the change of curved shape on the capillary microreactor can significantly improve the micromixing performance with XS reduced by 37.5%.Further,the correlations of segment index XS with dimensionless factor such as Reynolds number or Dean number were developed,which can be used to predict the liquid-liquid micromixing performance in capillary microreactors.
Microchannels enable the fast and efficient mixing of multiphase fluids.In this study, a millimeter-scale three-dimensional(3D) circular cyclone-type microreactor was designed for the mixing.The flow characteristics and mixing intensity were simulated by computational fluid dynamics simulations at a flow rate range of 12–96 m L/min using a water/ethyl acetate system.In the 3D variable-diameter structure,the microreactor induced paired opposite vortices and abruptly changed the local pressure to achieve a stable turbulent effect within the theoretical range of laminar flow.Tracer injection simulations indicated that sufficient mixing units successfully promote fluid dispersion.Diazo-coupling experiments showed a segregation index of X_S= 0.00,039 within a residence time of 9 s.Extraction experiments on the nbutanol/succinic acid/water system showed that the 3D circular cyclone-type microreactor achieved 100%extraction efficiency(E) in 4.25 s, and the overall volume mass transfer coefficient(K_La) reached 0.05–1.5s^(-1) in 12–96 m L/min.The isolated yield of the phase transfer alkylation and oxidation reactions in the 3D circular cyclone-type microreactor achieved 99% within 36 s, which was superior to the coil microreactor and batch reactor.
A sustainable and practical process is presented for the direct synthesis of sodium tanshinone IIA sulfonate(STS).Our approach was inspired by the well-established and industrially applied batch synthetic route for STS production.We constructed a telescoped two-step continuous flow platform.This involved a continuous tanshinone IIA sulfonation and in-line salt formation.For the setup,we constructed a 3D circular cyclone-type microreactor using femtosecond laser micromachining.Compared to the 68%yield for 2 h in batch,the two-step continuous flow had an STS yield of 90%,achieved for a total residence time of<3.0 min under optimal conditions.The proposed continuous flow method vastly simplified the operation and improved procedural safety,while significantly reducing the required acid content and wastewater production.
The development of efficient systems for the catalytic oxidation of 2-nitro-4-methylsulfonyltoluene(NMST)to 2-nitro-4-methylsulfonyl benzoic acid(NMSBA)with atmospheric air or molecular oxygen in alkaline medium presents a significant challenge for the chemical industry.Here,we report the synthesis of FeOOH/Fe_(3)O_(4)/metal-organic framework(MOF)polygonal mesopores microflower templated from a MIL-88B(Fe)at room temperature,which exposes polygonal mesopores with atomistic edge steps and lattice defects.The obtained FeOOH/Fe_(3)O_(4)/MOF catalyst was adsorbed onto glass beads and then introduced into the microchannel reactor.In the alkaline environment,oxygen was used as oxidant to catalyze the oxidation of NMST to NMSBA,showing impressive performance.This sustainable system utilizes oxygen as a clean oxidant in an inexpensive and environmentally friendly NaOH/methanol mixture.The position and type of substituent critically affect the products.Additionally,this sustainable protocol enabled gram-scale preparation of carboxylic acid and benzyl alcohol derivatives with high chemoselectivities.Finally,the reactions can be conducted in a pressure reactor,which can conserve oxygen and prevent solvent loss.Moreover,compared with the traditional batch reactor,the self-built microchannel reactor can accelerate the reaction rate,shorten the reaction time,and enhance the selectivity of catalytic oxidation reactions.This approach contributes to environmental protection and holds potential for industrial applications.
