Carbonic composite materials and ceramics appear to be excellent structural materials for parts subjected to very high temperatures in molten salt reactors(MSRs), in which the reactor core outlet temperature is normal...Carbonic composite materials and ceramics appear to be excellent structural materials for parts subjected to very high temperatures in molten salt reactors(MSRs), in which the reactor core outlet temperature is normally above 700℃. Because of the high temperature,there are major challenges in the sealing of flanged connections for tubes made of alloys and nonmetallic materials. In this study, an improved method for sealing bolted flange connections for tubes made of dissimilar materials at high temperature is analyzed. The study focuses on the compensation mechanism for the difference in thermal expansion between the bolts and the flanges. An angle is introduced for the sealing surface in the flanged connection to provide effective sealing. The arctangent of the angle is the ratio of the thickness between the theoretical core of the sealing surface and the outside end face of the flange to the distances between the axis of the flanged joint and the theoretical core of the sealing surface of the flange; the sealing surface of the flange, which is made of the same material as the fastening assemblies, faces the fastening assemblies. To ensure effective sealing, the frictional coefficient between the two sealing surfaces should not exceed the tangent of the angle. This result does not agree well with the solution given by previous researchers. Further, in the modified flanged connection, the compression of each bolt in the clamped condition is increased to maintain the compaction force unchanged without increasing the number of bolts on the flanged joint.展开更多
The molten salt leakage accident is an important issue in the nuclear safety analysis of molten salt reactors.While the molten salt leaks from the pipeline or storage tank,it will contact the insulation layer outside;...The molten salt leakage accident is an important issue in the nuclear safety analysis of molten salt reactors.While the molten salt leaks from the pipeline or storage tank,it will contact the insulation layer outside;hence,the processes of penetration and spreading play an important role in the development of leakage accidents.In this study,the penetration and diffusion of leaking molten salt(LMS)in an aluminum silicate fiber(ASF)thermal insulation layer were studied experimentally.A molten salt tank with an adjustable outlet was designed to simulate the leakage of molten salt,and the subsequent behavior in the thermal insulation layer was evaluated by measuring the penetra-tion time and penetration mass of the LMS.The results show that when the molten salt discharges from the outlet and reaches the thermal insulation layer,the LMS will penetrate and seep out from the ASF,and a higher flow rate of LMS requires less penetration time and leaked mass of LMS.As the temperature of the LMS and thickness of the ASF increased,the penetration time became longer and the leaked mass became greater at a lower LMS flow rate;when the LMS flow rate increased,the penetration time and leaked mass decreased rapidly and tended to flatten.展开更多
A proton therapy(PT)facility with multiple treatment rooms based on the superconducting cyclotron scheme is under development at Huazhong University of Science and Technology(HUST).This paper attempts to describe the ...A proton therapy(PT)facility with multiple treatment rooms based on the superconducting cyclotron scheme is under development at Huazhong University of Science and Technology(HUST).This paper attempts to describe the design considerations and implementation of the PT beamline from a systematic viewpoint.Design considerations covering beam optics and the influence of high-order aberrations,beam energy/intensity modulation,and beam orbit correction are described.In addition to the technical implementation of the main beamline components and subsystems,including the energy degrader,fast kicker,beamline magnets,beam diagnostic system,and beamline control system are introduced.展开更多
To investigate the relationship between food insecurity(FI)and overweight/obesity(OW/OB)or corresponding chronic diseases in adolescents,33 studies with 181135 individuals were included in this meta-analysis.Six studi...To investigate the relationship between food insecurity(FI)and overweight/obesity(OW/OB)or corresponding chronic diseases in adolescents,33 studies with 181135 individuals were included in this meta-analysis.Six studies and 10 studies,reported a higher risk of overweight and obesity in adolescents experiencing FI,respectively(OR 1.38,95%CI 1.20‒1.58,P<0.0001;OR 1.11,95%CI 1.01‒1.22,P=0.035,respectively).Based on the pooled results,adolescents with severe FI had the highest risk of OW/OB(OR 1.45,95%CI 1.20‒1.75,P<0.0001).The pooled OR indicated no signifi cant association between FI and OW/OB,when the adolescents were stratifi ed into those under 6 years old and those between 6 and 18 years old.Eleven studies assessed the relationship between FI and the risk of chronic diseases.The anemia subgroup was significantly associated with FI(OR 1.67,95%CI 1.30‒2.13,P<0.0001).Severe FI was reported to increase the risk of hypertension(OR 1.59,95%CI 1.28‒1.98,P<0.0001).Furthermore,a pooled analysis revealed a signifi cant association between FI and the risk of chronic diseases in both 6 and 6-18-year-old subgroups.展开更多
基金supported by the Chinese TMSR Strategic Pioneer Science and Technology Project(No.XDA02010000)the Frontier Science Key Program of Chinese Academy of Sciences(No.QYZDY-SSW-JSC016)
文摘Carbonic composite materials and ceramics appear to be excellent structural materials for parts subjected to very high temperatures in molten salt reactors(MSRs), in which the reactor core outlet temperature is normally above 700℃. Because of the high temperature,there are major challenges in the sealing of flanged connections for tubes made of alloys and nonmetallic materials. In this study, an improved method for sealing bolted flange connections for tubes made of dissimilar materials at high temperature is analyzed. The study focuses on the compensation mechanism for the difference in thermal expansion between the bolts and the flanges. An angle is introduced for the sealing surface in the flanged connection to provide effective sealing. The arctangent of the angle is the ratio of the thickness between the theoretical core of the sealing surface and the outside end face of the flange to the distances between the axis of the flanged joint and the theoretical core of the sealing surface of the flange; the sealing surface of the flange, which is made of the same material as the fastening assemblies, faces the fastening assemblies. To ensure effective sealing, the frictional coefficient between the two sealing surfaces should not exceed the tangent of the angle. This result does not agree well with the solution given by previous researchers. Further, in the modified flanged connection, the compression of each bolt in the clamped condition is increased to maintain the compaction force unchanged without increasing the number of bolts on the flanged joint.
基金supported by the“Strategic Priority Research Program”of the Chinese Academy of Sciences(No.XDA0201002)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.2018301).
文摘The molten salt leakage accident is an important issue in the nuclear safety analysis of molten salt reactors.While the molten salt leaks from the pipeline or storage tank,it will contact the insulation layer outside;hence,the processes of penetration and spreading play an important role in the development of leakage accidents.In this study,the penetration and diffusion of leaking molten salt(LMS)in an aluminum silicate fiber(ASF)thermal insulation layer were studied experimentally.A molten salt tank with an adjustable outlet was designed to simulate the leakage of molten salt,and the subsequent behavior in the thermal insulation layer was evaluated by measuring the penetra-tion time and penetration mass of the LMS.The results show that when the molten salt discharges from the outlet and reaches the thermal insulation layer,the LMS will penetrate and seep out from the ASF,and a higher flow rate of LMS requires less penetration time and leaked mass of LMS.As the temperature of the LMS and thickness of the ASF increased,the penetration time became longer and the leaked mass became greater at a lower LMS flow rate;when the LMS flow rate increased,the penetration time and leaked mass decreased rapidly and tended to flatten.
基金the National Key Research and Development Program of China(No.2016YFC0105305)the National Natural Science Foundation of China(11975107)the Program for HUST Academic Frontier Youth Team.
文摘A proton therapy(PT)facility with multiple treatment rooms based on the superconducting cyclotron scheme is under development at Huazhong University of Science and Technology(HUST).This paper attempts to describe the design considerations and implementation of the PT beamline from a systematic viewpoint.Design considerations covering beam optics and the influence of high-order aberrations,beam energy/intensity modulation,and beam orbit correction are described.In addition to the technical implementation of the main beamline components and subsystems,including the energy degrader,fast kicker,beamline magnets,beam diagnostic system,and beamline control system are introduced.
文摘To investigate the relationship between food insecurity(FI)and overweight/obesity(OW/OB)or corresponding chronic diseases in adolescents,33 studies with 181135 individuals were included in this meta-analysis.Six studies and 10 studies,reported a higher risk of overweight and obesity in adolescents experiencing FI,respectively(OR 1.38,95%CI 1.20‒1.58,P<0.0001;OR 1.11,95%CI 1.01‒1.22,P=0.035,respectively).Based on the pooled results,adolescents with severe FI had the highest risk of OW/OB(OR 1.45,95%CI 1.20‒1.75,P<0.0001).The pooled OR indicated no signifi cant association between FI and OW/OB,when the adolescents were stratifi ed into those under 6 years old and those between 6 and 18 years old.Eleven studies assessed the relationship between FI and the risk of chronic diseases.The anemia subgroup was significantly associated with FI(OR 1.67,95%CI 1.30‒2.13,P<0.0001).Severe FI was reported to increase the risk of hypertension(OR 1.59,95%CI 1.28‒1.98,P<0.0001).Furthermore,a pooled analysis revealed a signifi cant association between FI and the risk of chronic diseases in both 6 and 6-18-year-old subgroups.
