Japan will allow nuclear reactors to operate for up to 60 years in revised regulations on power plant operators.
The decision marks the first time Japan has set a limit on a reactor's maximum lifespan.
The government said it aims to introduce the 60-year limit a year from now as part of a revision of laws regulating nuclear plant operators after the 11 March earthquake and tsunami crippled reactor cooling systems in the Fukushima Daiichi complex, triggering meltdowns and radiation leaks.
Chief cabinet secretary Osamu Fujimura told reporters details were still under consideration but the lifespan of a reactor would in principle be 40 years.
The government will allow plant operators to apply for one extension of up to 20 years for each reactor, in line with US standards.
Public anxiety sparked by the disaster has prevented the restart of many reactors shut for routine checks.
Only five of the nation's 54 reactors remain online, prompting utilities to import more fossil fuels to bridge the gap.
Stress tests are being carried out on idled reactors to reassure the public and persuade local governments to allow them to be restarted.
In a rare protest, a group of citizen observers delayed a hearing at the trade ministry in which experts were expected to approve the nuclear watchdog's review of stress test results on two reactors in Fukui prefecture.
Later, a meeting was held without any observers. Experts made final comments on the draft report on the two reactors, virtually ending the assessment process, but no details were immediately available.