Taiwan on Tuesday unveiled plans to process nuclear waste abroad for the first time as its power plants reach capacity -- but environment groups slammed the proposal as "too risky".

The government is under growing public pressure over its unpopular nuclear policy as concerns over the safety of its plants have grown since the 2011 Fukushima disaster in Japan.

Authorities were forced in July to seal off a new power plant due to open next year, 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 state-owned Taipower supply 20 percent of the island's electricity.

The new proposals, announced on Tuesday by a special government task force, pave the way for used nuclear fuel rods stored at two plants to be shipped abroad to be processed.

A reduced amount of nuclear material would then be sent back to Taiwan and re-stored at the sites, which are due to come out of commission within the next few years and are reaching storage capacity.

"The storage sites of the two plants would run out of capacity next year and the plants would have to be shut down if these plans were not carried out," Bob Lee, spokesman for the task force, told AFP.

He added that open bidding was scheduled for next year to pick a contractor. One Taipower official said a French firm had already voiced interest in processing the waste.

The government and Taipower say the processing plan could significantly reduce the amount of used nuclear fuel and that only a few countries have the technology to carry it out.

But the plan sparked opposition from environmental protection groups who questioned the safety of shipping the fuel.

Activist Pan Han-shen of the Tree Party warned it was "too risky".

"Any risks in the process of transportation could be a huge disaster," he said.

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

Concerns about Taiwan's nuclear power facilities 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.