Taking advantage of the potential benefits of a combined electricity production and district heating nuclear power plant requires the integration of the plant into two grids: the electrical grid and the thermal grid. The integration of a CANDU reactor of the Pickering type into the grids has been assessed, and some preliminary conclusions have been reached. For a given system size and fractional nuclear capacity, the practical optimum extraction point for steam from the turbines for the district heating system has been established. With steam from the practical optimum extraction point, there is considerable economic incentive to maximize the fractional nuclear capacity of the system. As a system grows, the unit thermal costs of heat at the plant boundary are reduced significantly by adding nuclear capacity. This conclusion suggests that advantage be taken of the characteristic flexibility of extraction-condensing turbines to accelerate the growth of the nuclear contribution to the system.