* Bomb-grade uranium exports would be for unprecedented 10 years
* U.S. has sought to reduce bomb-grade uranium supplies since 1978
* Belgian suicide bombers had planned to target nuclear plants
* Belgian research center working on using safer uranium
By Timothy Gardner and Robert-Jan Bartunek
WASHINGTON/BRUSSELS, Aug 15 (Reuters) - The U.S. nuclear regulator is considering long-term shipments of weapons-grade uranium to a medical research reactor in security-challenged Belgium, something critics say would set back global anti-proliferation efforts.
With a final decision still months away, the Belgian Nuclear Research Center is seeking permission from the U.S. Nuclear Regulatory Commission to receive 317 pounds (144 kilos) of highly enriched uranium, or HEU, fuel in a series of shipments over 10 years.
The United States has supplied the reactor, which produces radioisotopes for fighting cancer, with HEU for decades. But the long-term nature of the latest request is unprecedented; previous agreements have been for periods of one to three years.
The Belgian research center has told U.S. officials since at least 2005 that it is on the verge of converting to low-enriched uranium, or LEU, not suitable for bombs. But there is no definitive date set for that change.
"Now more than a decade has passed and they are asking for another 10 years - that seems to be a bit preposterous," said Armando Travelli, who until 2005 headed the U.S. Energy Department's program to convert research reactors to safer uranium and bring bomb-grade uranium back to the United States.
If the Belgian reactor closes before the end of the 10 years, it could leave the center with an HEU supply over which the United States would have little control, he said.
BOMBERS FILMED RESEARCHER
Belgium has beefed up protections at nuclear plants after being rocked with security problems at the facilities for years. In 2014, an unknown perpetrator drained turbine lubricant at the country's Doel 4 reactor, shutting the power plant and causing $200 million in damages.
This year police said bombers who blew themselves up in Brussels had secretly filmed movements of the head of Belgium's nuclear research program. Police said the bombers, who were part of coordinated attacks on March 22 that killed 32 civilians, had planned to target Belgium's nuclear research facilities before changing their minds. The Islamic State militant group claimed responsibility for the suicide bombings.
Alan Kuperman, coordinator of the Nuclear Proliferation Prevention Project at the University of Texas, said if the NRC approves the application it would undermine efforts to swiftly convert reactors and signal that the United States is not serious about retrieving HEU.
"In the wake of the recent terrorist threat to the Belgian site, we have a request for bomb-grade uranium that is unprecedented in both duration and amount," said Kuperman who has filed a brief with the NRC calling for a hearing into the matter.
ATOMS FOR PEACE
Former U.S. President Dwight Eisenhower's Atoms For Peace program launched a wave of global research reactors using HEU in the 1950s, but experts soon urged tightening controls. Since 1978, the United States has spent tens of millions of dollars trying to do so. Nearly 100 global research reactors have been shut down or converted to run on non-weapons grade uranium, but more than 70 plants still use HEU or plan to.
The application at the NRC, published this month in the Federal Register, is open for public comment until early September.
The NRC said there are no temporal restrictions on HEU shipments and that it approves exports only to users with "adequate physical security measures." It will likely rule in coming months after the Department of Energy and State Department weigh in.
The Belgian center says the reactor supplies about 25 percent of the world's radioisotopes used in detecting and treating cancers and more in peak demand periods.
In the past, some reactors have switched to safe fuels only after the NRC threatened to cut off supply of HEU. But one American working on converting the Belgian reactor said its special need for high-energy density fuel means no suitable substitute has yet been found.
The Belgians are asking for 10 years because "there's no other fuel they can use at the moment," said the source, who spoke on the condition of anonymity, adding that contracts for HEU exports shorter than 10 years "drive the costs way up."
The Belgian research center said in a statement it is committed to using only low-enriched uranium fuel in the reactor "as soon as a technical solution exists." It has the same security procedures as the country's nuclear power plants, with permanent military protection, it added. (Editing by Kevin Drawbaugh and Matthew Lewis)
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