Discussion of Water Quality Factors Affecting 137Cs Adsorption and the Relationship Between 137Cs-Kd and Flow Rate in Freshwater

Abstract

Abstract The discharge water of Inland Nuclear Power Plant (INPP) is freshwater. Freshwater has a lower environment capacity and more complex environmental impacts comparing with the salt water (oceans), which makes the public more sensitive and stricter. 137Cs, with a long half-life of 30.17 years, is likely to exist as particle form in freshwater, which increases the difficulty to be removed and also becomes a long-term potential radiation hazard. The factors affecting the behavior of 137Cs in freshwater could be divided into water quality factors and hydraulic factors. For water quality factors, the paper summarizes factors that have significantly influence on the adsorption of 137Cs: size and concentration of suspended particles, competing cations, pH, concentration of organic matters and another two environmental factors, time and extreme meteorological events such as floods, heavy rain. We describe the qualitative relationship that tells how the factors take effect on adsorption process. In terms of hydraulic factors, this paper focuses on a representative factor, flow rate, and takes the original measured distribution factor (137Cs-Kd) and flow rate data of 9 freshwaters from Asia and Europe for analysis. The study finds that there are two segmented index relationships between 137Cs-Kd and flow rate above the threshold of 1 m3/s, the experiences of other five rivers that had not participated in data fitting verify the accuracy and generic character of the index relationships. The qualitative summary of water quality factors and the quantitative conclusions between 137Cs-Kd and flow rate can provide advice for evaluating the behavior of 137Cs in freshwater, and then help in the site selection process for INPP.