After a 28-year lull, the United States seems ready to resume its flirtation with nuclear energy. Despite several high-profile incidents, including one that claimed two lives in 1999, Japan has never lost its interest in this power source. Europeans have gone back and forth on the issue: Green candidates have called on various governments to shut down their nuclear programs, but progress has been halting. Rising energy prices and California's woes have given the nuclear industry a fillip in recent months, and proponents of nuclear power have seized the initiative. Nuclear energy is a partial solution for what ails modern industrialized economies, but it raises important questions as well. They must be answered before the rush to build new nuclear plants resumes.

There has always been a strong case for nuclear energy. For a country like Japan, which has no energy supplies of its own, nuclear power was an indispensable part of national-security strategy: a means to safeguard independence. Proponents also claim that nuclear technology is more efficient than other energy sources, although close analysis shows that the numbers are not so solid. The alleged economies of nuclear power depend on accounting methods, and in particular how costs are distributed over time.

Nuclear power is more efficient if governments subsidize insurance costs, but that reasoning is circular when economic efficiency is the reason for building plants in the first place. In the U.S., in particular, where government subsidies are usually anathema -- there is little stomach for other forms of interference in the workings of the market -- the argument does not make sense.