Taiwan has unveiled a Tw$11.25 billion ($356 million) plan to process nuclear waste overseas for the first time as its power plants approach capacity, sparking criticism from environmental groups.

The state-run Taiwan Power Co. (Taipower) opened bidding on Tuesday for 1,200 used fuel rods used in the island's first and second nuclear plants to be processed abroad.

The two plants, which currently store the spent fuel rods, were launched in 1978 and 1981 and will each be decommissioned once they have been operational for 40 years.

But Taipower has said it may be forced to shut down or decommission the plants earlier than scheduled as they are reaching storage capacity for spent nuclear fuel.

Some environmental groups accused Taipower of trying to extend the operations of the two plants even though they are set to be decommissioned.

"We strongly protest the plan. It's absurd to send the fuel rods abroad to be reprocessed since Taiwan is no longer building nuclear power plants," said the National Nuclear Abolition Action Platform.

"It's clear that Taipower is in a rush to ship the nuclear waste abroad because the first nuclear power plant will be shut down if it fails to do so, which will mean that its plan to push for extended operation of the plant will fall through."

The government is under growing public pressure over its unpopular nuclear facilities as safety concerns have mounted since 2011, when Japan's Fukushima nuclear plant was hit by a tsunami which knocked out power to its cooling systems and sent reactors into meltdown.

Like Japan, Taiwan is regularly hit by earthquakes. In September 1999 a 7.6-magnitude quake killed around 2,400 people in the island's deadliest natural disaster in recent history.

Last year the authorities were forced to seal off a new power plant due to open in 2015, pending a referendum on its future.

But the government says Taiwan will run out of energy if it ditches nuclear power -- the three plants currently operated by Taipower supply about 20 percent of the island's electricity.

Taipower has said the technology to reprocess spent fuel is mature and that countries including Germany, Japan and Italy have shipped their nuclear waste overseas for reprocessing.

"We need to handle used nuclear fuel whether we are going to have nuclear power or extend nuclear plant's operation or not... We will be irresponsible if we don't deal with it. It is absurd to oppose overseas reprocessing," it said in a statement.

Companies from England, France and Russia have expressed interest in bidding for the proposal, local media reported.