 CHRIS HUHNE, the energy secretary, will this week unveil the most radical overhaul of the energy industry since privatisation two decades ago.  The government wants to slash Britain's reliance on fossil fuels by switching to new nuclear reactors and offshore wind farms. The move will cost ?200 billion and could see household energy bills double.  On Tuesday, Huhne will lay out a regime of penalties on old coal- and oil-fired plants and subsidies for low-carbon alternatives.  The white paper is a key step towards putting the new framework into law, probably next year.  It follows 