An overview of the geophysics activity within the canadian nuclear fuel waste management program

Abstract

The concept of disposal of nuclear fuel wastes in igneous plutonic rocks is being assessed in the Canadian Nuclear Fuel Waste Management Program. The decision on whether to implement this concept will be made only sometime after 1991. Geophysical techniques are being assessed and developed, in order to map igneous plutons, the fractures within them, and also the overburden. Field tests at research areas have shown that gravity and magnetic methods can in most cases map the boundaries of plutons. Airborne EM and surface VLF-EM methods have been particularly useful in mapping near-surface vertical trending fractures. Deeper horizontal trending fractures have been located by reflection seismic and magnetotelluric methods. Shallow seismic, VLF-EM resistivity, radar and, to a certain extent, airborne EM methods can determine the nature of surficial materials. The sonar method provides information on lake bottoms. Several downhole logging methods can detect fractures that intersect a borehole; however, tracing the continuity of fracture zones between holes and determining their hydrogeological characteristics by geophysical means is considerably more difficult. In an underground research laboratory, currently under construction in a granitic batholith, several geophysical methods will be assessed, including radar for mapping fractures and ultrasonics for testing rock quality.