Nuclear Facilities In The Surrounding Environment Radiation Continuous Monitoring System For The Screening Technology On The Natural Disturbance Factors

The aim of establishingγradiation monitoring system for nuclear facilities in the surrounding environment is to monitor and assess the impact of additional exposure caused byγrelease. The rapid and accurate screening methods of natural disturbance factors can distinguish whether the smoke plume or natural factors cause the increase of dose rate of surroundingγradiation near nuclear facilities. Meanwhile, the methods can monitor the release of abnormal emissions, which will provide proofs to evaluate the accident consequences and emergent decision-making.First of all, the paper introduces layout principles of surroundingγradiation monitoring network, equipment selection and performance, Completion of monitoring network for research work in the China Institute of Atomic Energy (CIAE). Five monitoring stations lay out around CIAE, respectively: total industrial water outfall (1#),615 (2#),new sources library (4#),the 20th Building (#5) and the reference point for the nuclear industry postgraduate Department (3#).Secondly, the paper studies the rules, how background values in CIAE change with. The two experimental nuclear reactors (101 heavy water reactor and 49-2 swimming pool reactor) are intermittent operated in CIAE. The background values are based on the monitoring data during the shutdown of the reactors. The cosmic rays dose rate in CIAE is 29.78 nGy/h calculated by the use of empirical formula, this empirical formula checked up by the measured cosmic rays in Miyun Reservoir. The radon concentration is measured in 1# monitoring points, and then radon variation curve is drawn. Finally, theγannual effective dose(2.27±0.47)×10^-2mSv radon progeny is calculated. As a result, theγradiation dose rate is increased in the impact of precipitation. The precipitation could lead to 30% increase ofγradiation dose rate than background values. In addition, precipitation intensity will also affect the surroundingγradiation dose rate, fitting the increase of dose rate and in the rate of precipitation.Thirdly, the paper investigate the plume emissions in CIAE. The increase in radiation dose rate in the monitoring stations caused by of plume reaches to 9～12nGy/ h (3# exceptions). However, the 4# monitoring station has much larger increasing dose rate due to the impacts of reactor operation. 49-2 # Swimming pool reactor also has a large surrounding radiation dose rate during mono-crystalline silicon operation. The dose rate of 4#, 2 # and 5# monitoring points increased at the same time. The dose rate of 1# monitoring point remains unchanged. 111 chimneys result in relatively higher radiation dose in surrounding environment due to the radioactive effects of the deposition in the bottom of the chimney during initial ventilation.By the analysis of background values in CIAE and plume emissions, the author finds a set of rapid and effective methods to screen natural disturbance factors by jointly using dose rate, the standard deviation, Wind direction, wind speed, precipitation and other meteorological conditions. This set of methods can accurately provideγ-radiation data for normal and incidents emissions of nuclear facilities.Adopting the atmospheric dispersion model of limited plume, the author calculates of additional absorbed dose in monitoring points caused by radioactive gaseous outflows, which are emitted by the chimneys of two nuclear reactors in CIAE. Compared the calculated data with the measured data, it is found that the deviations are±61%.