The government evaluated Japan's 54 reactors for quake and tsunami vulnerability after the March 11 disasters that heavily damaged the Fukushima Dai-ichi plant in northeast Japan.
Currently, officials have shuttered the Hamaoka power plant in central Japan while seawalls and backup systems are set up to protect its reactors from major earthquakes.
Nuclear energy provides more than one-third of Japan's electricity, and shutting the three reactors would likely worsen power shortages expected this summer. Already, buildings have reduced lighting, stores have trimmed service hours and subway operators have shut air conditioning in a conservation effort in the capital region since the March disasters.
The Associated Press contributed to this report.