Unicom, the parent of Commonwealth Edison, and Peco Energy, the parent of Philadelphia Electric, have proposed a merger. The new company, which would be named at a later stage, would own 20 per cent of US nuclear generating capacity.

The merger has yet to be approved by the US Nuclear Regulatory Commission, the Federal Energy Regulatory Commission, and the Pennsylvania Public Utilities Commission. The regulatory processes should be completed within 12 months.

Unicom, which is already the largest operator of nuclear plants in the US, owns Braidwood, Byron, Dresden, LaSalle and Quad Cities nuclear stations. Peco Energy owns two units at Limerick nuclear plant, and shares of the two unit Peach Bottom and Salem plants. Peco has also been trying to acquire more US nuclear plants through its participation in AmerGen Energy, a joint venture with British Energy.

While Unicom has not yet sought to acquire more nuclear plants, it has vastly improved capacity utilization at its 10 units.

The new joint company will be based in Chicago, but its generation and power marketing operations will have Philadelphia headquarters.