Nuclear waste management and migration of radiocontaminants.

The production of radioactive wastes is perceived as one of the major problems facing the nuclear industry. There are three general categories of radioactive wastes: high level (spent fuel), inter-mediate, and low-level radioactive wastes. The philosophy of any type of waste disposal is to minimize the potential of migration of radioactive substances to the environment. My overall research strategy is to provide scientifically sound data that would help predict the movement and impact of radiocontaminants in the environment. The intended end use of this research is to solve problems currently facing the nuclear industry and policy makers.

Geochemical data are needed to calculate the migration of radiocontaminants between the source of contamination and the point of impact. Calculations rely on transport and geochemical data that are often difficult to obtain, or that are inexistant for some radionuclides. In this work, we are developing the methodology to measure the parameters that affect the migration of the radiocontaminants in soils: chemical stability at the source, solubility, speciation, sorption, interactions with dissolved organics, etc.

We have a unique expertise on the behaviour of Carbon-14, from reactors to waste management areas, and to contaminated air and groundwater. Our expertise extends to other radionuclides and other aspects of radiochemistry in contaminated areas.

Major topics of work:

1. Behaviour of Carbon-14 on ion exchange resins.
Ion exchange resins are used in nuclear reactors to keep a high level of purity in the heavy water. The resins remove, and hence concentrate, the radio-contaminants, including especially Carbon-14. These resins, now contaminated, are discarded to become a major type of intermediate-level radioactive wastes. This research topic deals with the effectiveness of resins to retain Carbon-14 and other contaminants in this type of wastes. We are developing methods to predict the chemical properties of resins, and the factors affecting the Carbon-14 equilibria on resins.

2. Fate of Carbon-14 from waste storage sites.
The major chemical form of Carbon-14 is as 14CO2 (in gaseous form) and carbonic acid (in solution, depending upon the pH). Because of its long half-life (5730 years) and its potential incorporation in the food chain (Carbon is essential for life), management of this radionuclide from wastes is very difficult. Our work consists of field sampling and to improve existing analytical techniques for determining the quantities of this contaminant released from wastes.

3. Radionuclide speciation in degrading wastes.
Low-level radioactive wastes are composed mostly of contaminated laboratory refuse (paper wipes, used clothing, mop heads, etc.). Water will eventually contact the wastes and help degrade this matrix, which, in turn, will affect the speciation and mobility of the radionuclides contained in the wastes. This involves analytical method development and the use of geochemical computer codes (e.g., MINTEQ, PHREEQC, WHAM, etc.).

Selected publications: