Since the combustion system of coal-fired boiler in thermal power plant is characterized as time varying, strongly coupled, and nonlinear, it is hard to achieve a satisfactory performance by the conventional proportio...Since the combustion system of coal-fired boiler in thermal power plant is characterized as time varying, strongly coupled, and nonlinear, it is hard to achieve a satisfactory performance by the conventional proportional integral derivative (PID) control scheme. For the characteristics of the main steam pressure in coal-fired power plant boiler, the sliding mode control system with Smith predictive structure is proposed to look for performance and robustness improvement. First, internal model control (IMC) and Smith predictor (SP) is used to deal with the time delay, and sliding mode controller (SMCr) is designed to overcome the model mismatch. Simulation results show the effectiveness of the proposed controller compared with conventional ones.展开更多
The original internal flooding probabilistic safety analysis （PSA） study of Krsko Nuclear Power Plant （two-loop Pressurized Water Reactor （PWR） plant of Westinghouse design） was performed in mid nineties and lim...The original internal flooding probabilistic safety analysis （PSA） study of Krsko Nuclear Power Plant （two-loop Pressurized Water Reactor （PWR） plant of Westinghouse design） was performed in mid nineties and limited to reactor core damage risk （Level 1 PSA）. In 2003, it was, together with other safety and hazard analyses, subject to the Periodic Safety Review （PSR）. In the PSR, it was stated that methodological PSA approaches and guidelines have evoluted during the past decade and several observations were provided, concerning the area screening process, residual risk and treatment of plant damage states and risk from radioactivity releases （i.e., Level 2 PSA）. In order to address the PSR observations, upgrade ofKrsko NPP internal flooding PSA was undertaken. The area screening process was revisited in order to cover the areas without automatic reactor trip equipment. The model was extended to Level 2. Residual risk was estimated at both Level 1 and Level 2, in terms of core damage frequency （CDF） and large early release frequency （LERF）, respectively.展开更多
Objective:To investigate the activity concentration of tritium in urine of nuclear power plant(NPP)workers,in order to evaluate the occupational exposure levels.Methods:Three chosen NPPs were respectively located in s...Objective:To investigate the activity concentration of tritium in urine of nuclear power plant(NPP)workers,in order to evaluate the occupational exposure levels.Methods:Three chosen NPPs were respectively located in southern,southeastern and northeastern China.Workers involved in operating,service,nuclear cleaning,chemical analysis,health physics,technical support,among others were randomly selected as the research targets,and 69 urine samples of no less than 50 mL were collected.The oxidative distillation method was used to pretreat the urine samples,and the activity concentration of tritium in distillate was then measured using liquid scintillation counter.The formula for the committed effective dose was also applied used to estimate the internal doses.Results:The highest tritium activity concentrations in urine samples from three NPPs were 2412.7,6351.4,and 478.7 Bq/L,respectively.Correspondingly,the internal doses due to tritium intake were 1.8,4.8 and 0.4μSv,respectively.Conclusions:The urine tritium activity concentration of workers varied greatly dependent on their job categories.The values for urine tritium radioactivity concentrations of workers involved in health care,nuclear cleaning and maintenance were generally higher than those for other job categories.The difference in urine tritium activity concentration mainly came from the different exposure time and tritium concentrations.From the dose assessment results,the internal dose caused by tritium intake did not exceed the public annual effective dose limit.展开更多
基金Supported by the National Natural Science Foundation of China (61174059, 60934007, 61233004)the National Basic Research Program of China (2013CB035406)Shanghai Rising-Star Tracking Program (11QH1401300)
文摘Since the combustion system of coal-fired boiler in thermal power plant is characterized as time varying, strongly coupled, and nonlinear, it is hard to achieve a satisfactory performance by the conventional proportional integral derivative (PID) control scheme. For the characteristics of the main steam pressure in coal-fired power plant boiler, the sliding mode control system with Smith predictive structure is proposed to look for performance and robustness improvement. First, internal model control (IMC) and Smith predictor (SP) is used to deal with the time delay, and sliding mode controller (SMCr) is designed to overcome the model mismatch. Simulation results show the effectiveness of the proposed controller compared with conventional ones.
文摘The original internal flooding probabilistic safety analysis （PSA） study of Krsko Nuclear Power Plant （two-loop Pressurized Water Reactor （PWR） plant of Westinghouse design） was performed in mid nineties and limited to reactor core damage risk （Level 1 PSA）. In 2003, it was, together with other safety and hazard analyses, subject to the Periodic Safety Review （PSR）. In the PSR, it was stated that methodological PSA approaches and guidelines have evoluted during the past decade and several observations were provided, concerning the area screening process, residual risk and treatment of plant damage states and risk from radioactivity releases （i.e., Level 2 PSA）. In order to address the PSR observations, upgrade ofKrsko NPP internal flooding PSA was undertaken. The area screening process was revisited in order to cover the areas without automatic reactor trip equipment. The model was extended to Level 2. Residual risk was estimated at both Level 1 and Level 2, in terms of core damage frequency （CDF） and large early release frequency （LERF）, respectively.
基金This work was supported by Environmental Radioactivity Research Network Center(Japan,Grant Number:I-20-15)the Key Program of Tianjin Municipal Natural Science Foundation(China,Grant Number:19JCZDJC40500).
文摘Objective:To investigate the activity concentration of tritium in urine of nuclear power plant(NPP)workers,in order to evaluate the occupational exposure levels.Methods:Three chosen NPPs were respectively located in southern,southeastern and northeastern China.Workers involved in operating,service,nuclear cleaning,chemical analysis,health physics,technical support,among others were randomly selected as the research targets,and 69 urine samples of no less than 50 mL were collected.The oxidative distillation method was used to pretreat the urine samples,and the activity concentration of tritium in distillate was then measured using liquid scintillation counter.The formula for the committed effective dose was also applied used to estimate the internal doses.Results:The highest tritium activity concentrations in urine samples from three NPPs were 2412.7,6351.4,and 478.7 Bq/L,respectively.Correspondingly,the internal doses due to tritium intake were 1.8,4.8 and 0.4μSv,respectively.Conclusions:The urine tritium activity concentration of workers varied greatly dependent on their job categories.The values for urine tritium radioactivity concentrations of workers involved in health care,nuclear cleaning and maintenance were generally higher than those for other job categories.The difference in urine tritium activity concentration mainly came from the different exposure time and tritium concentrations.From the dose assessment results,the internal dose caused by tritium intake did not exceed the public annual effective dose limit.
