Participants raise banners with a slogan, "Good bye, nuclear power station," at a rally protesting against the usage of nuclear energy in Tokyo Saturday, May 5, 2012. Thousands of Japanese marched to celebrate the last of this nation's 50 nuclear reactors switching off Saturday, shaking banners shaped as giant fish that have become a potent anti-nuclear symbol. (AP Photo/Itsuo Inouye)

A traditional "Koinobori" carp-shaped banner for Children's Day flies at a rally protesting against the usage of nuclear energy in Tokyo, Saturday, May 5, 2012. Thousands of Japanese marched to celebrate the last of this nation's 50 nuclear reactors switching off Saturday, shaking banners shaped as giant fish that have become a potent anti-nuclear symbol. (AP Photo/Itsuo Inouye)

A participant wears an anti-nuclear sign at a rally protesting against the usage of nuclear energy in Tokyo Saturday, May 5, 2012. Thousands of Japanese marched to celebrate the last of this nation's 50 nuclear reactors switching off Saturday, shaking banners shaped as giant fish that have become a potent anti-nuclear symbol. (AP Photo/Itsuo Inouye)

Participants hold a traditional "Koinobori" carp-shaped banner for Children's Day during a march protesting against the usage of nuclear energy in Tokyo Saturday, May 5, 2012. Thousands of Japanese marched to celebrate the last of this nation's 50 nuclear reactors switching off Saturday, shaking banners shaped as giant fish that have become a potent anti-nuclear symbol. (AP Photo/Itsuo Inouye)

Participants gather at a rally protesting against the usage of nuclear energy in Tokyo Saturday, May 5, 2012. Thousands of Japanese marched to celebrate the last of this nation's 50 nuclear reactors switching off Saturday, shaking banners shaped as giant fish that have become a potent anti-nuclear symbol. (AP Photo/Itsuo Inouye)