The Chinese Academy of Sci-ences (CAS) has begun introducingthe trial implementation of theKnowledge Innovation Program(KIP)in an all-round manner just as,at the beginning of the new century,the state is about to impl...The Chinese Academy of Sci-ences (CAS) has begun introducingthe trial implementation of theKnowledge Innovation Program(KIP)in an all-round manner just as,at the beginning of the new century,the state is about to implement itsTenth Five-Year Plan for thecountry’s ongoing economic andsocial development. This will展开更多
The China Spallation Neutron Source（CSNS） is driven by protons whose energies are about 1.6 GeV.At such high energies, the spallation neutrons lead to the formation of large amounts of helium, hydrogen and new heavi...The China Spallation Neutron Source（CSNS） is driven by protons whose energies are about 1.6 GeV.At such high energies, the spallation neutrons lead to the formation of large amounts of helium, hydrogen and new heavier species in the form of transmutation products. These hydrogen, helium and transmutation products have a critical effect on the mechanical properties on the one hand and exacerbate the displacement radiation damage on the other hand. In this paper, the background hydrogen/helium concentrations and the maximum hydrogen/helium concentrations near cracks in a tungsten target for CSNS have been calculated at temperatures of 100 and 300 by applying a theoretical model. For the CSNS tungsten target plate, we find the maximum hydrogen concentration near the tips of cracks ranges from 3.0×10^（-2）–2×10^（-1）, which exceeds the hydrogen background concentration by 1.2–1.8 times; the maximum helium concentration near the tips of cracks ranges from 3.0×10^（-4）- 1.2×10^（-3）, which exceeds the helium background concentration by 2- 4 times; the maximum hydrogen/helium concentration increases with the increase of the transfer length across the surfaces of the target and it decreases with the increase of temperature.展开更多
Objective:To demonstrate the versatility of the natural soil gas harvesting technique,coupled with a semi-dynamic injection algorithm,as an efficient and reliable source for continuous ^(222)Rn delivery to a large-vol...Objective:To demonstrate the versatility of the natural soil gas harvesting technique,coupled with a semi-dynamic injection algorithm,as an efficient and reliable source for continuous ^(222)Rn delivery to a large-volume calibration chamber across different soil conditions and climatic conditions.Methods:Long-term experiments were performed during three seasons of a year in a tropical monsoonal climatic region with high rainfall on the Southwest Coast of India.Soil gas extraction was performed using soil-gas probes,inserted to 1 m deep into the ground.Soil gas was harvested at a flow rate of 60 L/min,passed through a moisture trap,a ^(222)Rn progeny filter,and a delay volume and pumped into a ^(222)Rn calibration chamber of volume 22.7 m^(3).Continuous monitoring of ^(222)Rn concentration in the chamber was performed using ionization chamber-based reference monitors.To achieve and maintain the desired ^(222)Rn concentration values in the calibration chamber,the semi-dynamic injection method was adopted,in which the ^(222)Rn concentration in the soil gas was monitored periodically,and injection into the chamber was controlled using a well-defined pumping algorithm.Three ranges of ^(222)Rn concentration values were chosen as the target values to be maintained in the calibration chamber for long-term experiments(15 d):low concentration(500-1,000 Bq/m3),medium concentration(1,000-10,000 Bq/m^(3)),and high concentration(10,000-25,000 Bq/m^(3)).Results:The achieved ^(222)Rn concentration values were in good agreement with the target values,with deviations of 12%,8% and 5% for the low,medium and high concentration exposures,respectively,during the summer season.During the monsoon season,the deviations between the target and the achieved concentration values were 12%,10% and 5% for low,medium and high concentration exposures,respectively,and the corresponding deviations were 12%,4%,and 5% for the winter season.These deviations are well within the cumulative uncertainty associated with the measurements.Conclusions:The results of this study conclusively demonstrate that the soil gas harvesting method,when coupled with the semi-dynamic injection approach,is a reliable method for generating and maintaining the desired ^(222)Rn concentration in the large volume calibration chamber during different seasons and environmental conditions.展开更多
文摘The Chinese Academy of Sci-ences (CAS) has begun introducingthe trial implementation of theKnowledge Innovation Program(KIP)in an all-round manner just as,at the beginning of the new century,the state is about to implement itsTenth Five-Year Plan for thecountry’s ongoing economic andsocial development. This will
基金Supported by National Science Foundation of China(51371195,11174358)
文摘The China Spallation Neutron Source（CSNS） is driven by protons whose energies are about 1.6 GeV.At such high energies, the spallation neutrons lead to the formation of large amounts of helium, hydrogen and new heavier species in the form of transmutation products. These hydrogen, helium and transmutation products have a critical effect on the mechanical properties on the one hand and exacerbate the displacement radiation damage on the other hand. In this paper, the background hydrogen/helium concentrations and the maximum hydrogen/helium concentrations near cracks in a tungsten target for CSNS have been calculated at temperatures of 100 and 300 by applying a theoretical model. For the CSNS tungsten target plate, we find the maximum hydrogen concentration near the tips of cracks ranges from 3.0×10^（-2）–2×10^（-1）, which exceeds the hydrogen background concentration by 1.2–1.8 times; the maximum helium concentration near the tips of cracks ranges from 3.0×10^（-4）- 1.2×10^（-3）, which exceeds the helium background concentration by 2- 4 times; the maximum hydrogen/helium concentration increases with the increase of the transfer length across the surfaces of the target and it decreases with the increase of temperature.
文摘Objective:To demonstrate the versatility of the natural soil gas harvesting technique,coupled with a semi-dynamic injection algorithm,as an efficient and reliable source for continuous ^(222)Rn delivery to a large-volume calibration chamber across different soil conditions and climatic conditions.Methods:Long-term experiments were performed during three seasons of a year in a tropical monsoonal climatic region with high rainfall on the Southwest Coast of India.Soil gas extraction was performed using soil-gas probes,inserted to 1 m deep into the ground.Soil gas was harvested at a flow rate of 60 L/min,passed through a moisture trap,a ^(222)Rn progeny filter,and a delay volume and pumped into a ^(222)Rn calibration chamber of volume 22.7 m^(3).Continuous monitoring of ^(222)Rn concentration in the chamber was performed using ionization chamber-based reference monitors.To achieve and maintain the desired ^(222)Rn concentration values in the calibration chamber,the semi-dynamic injection method was adopted,in which the ^(222)Rn concentration in the soil gas was monitored periodically,and injection into the chamber was controlled using a well-defined pumping algorithm.Three ranges of ^(222)Rn concentration values were chosen as the target values to be maintained in the calibration chamber for long-term experiments(15 d):low concentration(500-1,000 Bq/m3),medium concentration(1,000-10,000 Bq/m^(3)),and high concentration(10,000-25,000 Bq/m^(3)).Results:The achieved ^(222)Rn concentration values were in good agreement with the target values,with deviations of 12%,8% and 5% for the low,medium and high concentration exposures,respectively,during the summer season.During the monsoon season,the deviations between the target and the achieved concentration values were 12%,10% and 5% for low,medium and high concentration exposures,respectively,and the corresponding deviations were 12%,4%,and 5% for the winter season.These deviations are well within the cumulative uncertainty associated with the measurements.Conclusions:The results of this study conclusively demonstrate that the soil gas harvesting method,when coupled with the semi-dynamic injection approach,is a reliable method for generating and maintaining the desired ^(222)Rn concentration in the large volume calibration chamber during different seasons and environmental conditions.
