Chongyang Zhou

Atmospheric radioxenon isotope monitoring in Beijing after the Fukushima nuclear power plant accident.

A custom-made, on-site radioxenon sampling, separation and monitoring system was used to monitor atmospheric radioxenon concentrations in Beijing, released from the Fukushima Daiichi nuclear power plant after the earthquake of 11 March 2011. The results show that (133)Xe concentrations ranged from 393 to 26 mBq/m(3) from 12 to 27 April 2011, and those of (131 m)Xe were 84 and 40 mBq/m(3) on 13 and 15 April 2011, respectively. The highest dose rate caused by (133)Xe was 2 × 10(-5)mSv/yr, and the average (133)Xe/(131 m)Xe ratio was 3.8 ± 0.4.

The determination of trace amounts of natural 133Xe in gas under high radon activity concentration levels

Radioxenon monitoring has become one of the major concerns in both international monitoring systems and on-site inspection. The most important technical specifications for radioxenon system are the radon removal coefficient and the minimum detectable activity concentration. We have developed one kind of on-site radioxenon sampling, separation and measurement system, and have tested it under high radon activity concentration levels. The result shows the natural (133)Xe background activity concentration, the (133)Xe/(222)Rn ratio and the radon removal coefficient to be in the ranges 0.73-1.6 mBq/m(3), (1.5-3.5) × 10(-8) and (2.3-57) × 10(-8), respectively.

A Simple Method for Calculating the Overall Adsorption Rate Constant in the Wheeler-Jonas Equation

Use of the Wheeler–Jonas (WJ) equation to predict adsorbate breakthrough for a packed bed of granular activated carbon requires the calculation of the overall adsorption rate constant (kν) and the amount adsorbed. These quantities can be calculated from the intercept (A) and slope (B) of a linear fit to the elapsed time as a function of the logarithm of the ratio of the adsorbate concentration (C0 – Cx)/Cx based on the breakthrough curve. Because kν varies with the flow rate (F), numerous measurements at different values of F were performed to find the appropriate value of kν. One relatively simple method for calculating kν directly from the WJ equation is presented and the physical meaning of A and B revealed. The key factors that lead to a simplified calculation of kν are the ratio of the breakthrough time to the equilibrium time (t0.05/t0.50) and the ratio of the equilibrium time to the saturation time (t0.50/t0.95), both of which remain nearly constant for different values of F, concentration and temperature. Knowledge of kν, A and B, and their relationships, are very helpful for predicting the breakthrough behaviour of packed bed adsorbents using the WJ equation.