Engineer lauded by nuclear group

The man who designed and implemented a new technique for uranium tailings disposal has been recognized by the Canadian Nuclear Society.

Wing Tao, president of PVS Technologies, was named winner of the society’s Innovative Achievement Award for his work at the Rabbit Lake uranium mine of Cameco (TSE) in Saskatchewan, where the disposal system had its debut. The new system, called the Pervious Surround Method, is earmarked for use at two other Saskatchewan uranium deposits, Key Lake and McClean Lake. Conceived in 1980, it has addressed many of the problems associated with conventional contaminant storage.

In the past, disposal of uranium tailings involved placing them in natural lakes, in surface facilities or above the water table in constructed ponds as at Rabbit Lake.

The new method, rather than relying on barriers to prevent the spread of contaminants, eliminates the process which causes contaminants to escape from the tailings.

Using “pervious surround,” the tailings are placed in a mined-out pit which is lined with a highly permeable envelope of crushed rock. To remove excess pore-water pressure and allow the tailings to consolidate, they are drained by pumping. At closure, when pumping stops and the water table re-establishes itself, the ground water will take the path of least resistance and flow through the envelope around the tailings.

Thus, the only way that contaminants can spread is through molecular diffusion over thousands of years.

Cameco says field data from the Rabbit Lake mine shows the system is consolidating faster and draining better than originally predicted. Tao has been involved in geotechnical and hydrological projects since 1965. Based in Islington, Ont., he specializes in consulting services in the field of waste disposal.