Japan has announced it will soon require nuclear reactors to be shut down after 40 years of use to improve safety.

Concern about aging reactors has grown after the three units at the Fukushima Dai-ichi plant went into meltdown following the tsunami last March. They were built starting in 1967.

Many more of Japan's 54 reactors will reach the 40-year mark in the near future.

The government says it plans to propose the idea to legislation in the coming months.

Japanese media reported the law may include loopholes to allow some old nuclear reactors to keep running if their safety is confirmed with tests.

The government has already decided to scrap six reactors at Fukushima Dai-ichi, where backup generators were destroyed.