A cargo of reprocessed nuclear fuel containing highly radioactive plutonium left the French port of Cherbourg for Japan under heavy security on Wednesday as demonstrators protested against the transport.

The controversial shipment from a plant of the French nuclear group Areva located some 20 kilometres (12 miles) away arrived at the port before dawn aboard two trucks escorted by dozens of security vehicles as a helicopter flew overhead.

Around 20 Greenpeace activists carried protest banners and threw smoke bombs at the convoy shortly before it arrived at the port.

It is the sixth shipment of mixed oxide (MOX), a blend of plutonium and uranium, from France to Japan since 1999.

"We are warning of how dangerous this shipment is and especially the risk of nuclear proliferation and the possible diversion for military purposes," Greenpeace France activist Yannick Rousselet told AFP.

Areva spokesman Alexandre Marinot described the cargo as being of "a maximum safety level."

Uranium reactors produce a mixture of depleted uranium and plutonium as a by-product of fission. These can be re-processed into MOX fuel, which can then be used in other reactors to generate more power.

Japan has few energy resources of its own and relied on nuclear power for nearly one-third of its domestic electricity needs until the 2011 meltdowns at the tsunami-crippled Fukushima plant.

On Tuesday, the Reseau Sortir du Nucleaire (Nuclear Phase-Out) said in a statement: "Areva profits from selling this dangerous fuel to a country devastated by a nuclear accident to supply reactors whose resumption the Japanese people reject."

There are currently five reactors in operation in Japan compared with 54 before the Fukushima accident.

source: AFP