"one purpose of nuclear energy is to avoid entanglements in energy wars".

Less Generous reading:

"Having had both, it is our opinion that nuclear accidents are vastly less painful than nuclear warheads.
 The future is uncertain, and thus we judge that maintaining a large nuclear energy sector so that we can quickly  Just-in-Time  manufacture some warheads in the event politics in China/US/ECT goes seriously non-linear is a nessesary insurance policy/deterrent, while being much less costly and problematic than being an actual nuclear weapons state".

It is possible they actually intend both readings, too.

Japan's Former Leader Urges Political Debate on Nuclear Ban - Bloomberg

Former Prime Minister Naoto Kan, who last year presided over the initial response to Japan's biggest crisis since World War II, today urged the nation's political leaders to debate banning nuclear power generation.

Submission of legislation on a nuclear-free mix of energy sources would mean each party, or even individual members of the Diet, would have to show support or opposition, Kan, 65, said in Tokyo.

"Forming a green party may be one option," Kan said at a symposium at International Christian University. "We could have significant influence through a political force in which every single member supports a nuclear-free Japan."