WASHINGTON, Bulgaria has sent its remaining highly enriched uranium to Russia for safeguarding from terrorist or other potential misuse.

Nearly seven kilograms of the spent fuel were received Thursday at a Russian nuclear facility, the U.S. National Nuclear Security Administration announced. A first shipment of 17 kilograms of fresh uranium fuel was sent to Russia in December 2003.

``With this shipment there is no more highly enriched uranium in Bulgaria,' said Brian Wilkes, a spokesman for the U.S. agency, which was established by Congress in 2001.

``Bulgaria now joins Latvia in clearing out all Soviet-era dangerous nuclear fuel.'

Remaining in Bulgaria, he said, are small quantities of low-enriched uranium, which most civilian reactors run on.

In the 1970s the Soviet Union sent shipments of enriched uranium to Bulgaria, which was then part of the Soviet bloc.

The returned shipment was transported under guard in casks to the Danube River, loaded on a barge and shipped to Ukraine and then shipped by rail to the secure Russian facility near Chelyabinsk.

Spent and fresh uranium fuel has also been returned to Russia from Serbia, Romania, Libya, Uzbekistan, Poland, Germany, the Czech Republic and Vietnam.

At the same time, all highly enriched uranium spent fuel was returned to the United States by Argentina, Brazil, Chile, Colombia, Denmark, Greece, Italy, the Philippines, Slovenia, South Korea, Spain, Sweden and Thailand.