The United States is unlikely to allow South Korea to use the "pyroprocessing" technology to recycle spent nuclear fuel even after a joint study is completed in

2021 because the technology will make no economic sense at all for decades, a U.S. expert said Thursday.

Pyroprocessing refers to a new type of technology for reprocessing spent nuclear fuel. It poses fewer proliferation risks than the conventional reprocessing technology because it does not involve producing pure plutonium that can be used in nuclear weapons.

It was a key contentious point in negotiations between South Korea and the U.S. to revise their civil nuclear cooperation agreement, with Seoul insisting on using the technology and the U.S. balking at the idea over proliferation concerns.

As a compromise, the U.S. agreed to allow South Korea to conduct research only into the first stage of the technology.

Whether Seoul will be able to fully use the technology is expected to be determined after the sides complete a 10-year joint study into the technology in 2021.

Gary Samore, a former top nonproliferation adviser for President Barack Obama, said that even after the study is over, the U.S. is unlikely to allow South Korea to use pyroprocessing to recycle spent fuel because even if it's technically feasible, it's economically unfeasible.

"I think it's very likely that the study will conclude that commercial-sale pyroprocessing really doesn't have any economic utility at this time," he said during a discussion at the Center for Strategic and International Studies about the Korea-U.S. nuclear cooperation agreement signed in June.

Samore said pyroprocessing is designed to produce fuel only for a new type of reactor, called "fast reactors" or "sodium-cooled fast reactors," and the likelihood of such reactors replacing traditional ones is "many decades away, if ever."

"So, it's good to have the technology for pyroprocessing available if it ever becomes necessary, but I think we're many, many years away from any commercial requirement for those types of reactors and therefore for pyroprocessing," he said.

Samore, executive director for research of Harvard University's Belfer Center for Science and International Affairs, said that the U.S. and South Korea could disagree over the economic feasibility of pyroprocessing, but disagreement means there won't be any U.S. consent to South Korea using the technology.

"I wouldn't be at all surprised if the two parties can't come to an agreement on whether pyroprocessing is economically viable or attractive. But if they disagree, then there won't be an agreement on advance consent," he said.

He emphatically stressed the economic non-feasibility of fast reactors and pyrocprocessing.

"I think we're further away today than we were in the 1960s to actually building those types of reactors as power reactors as opposed to research models. I think it will be decades. It will be long past my lifetime before anybody ever runs a fast reactor for power," he said.

The civil nuclear cooperation deal, known as "123 Agreement" is now before Congress for approval.

Should there be no opposition raised during a 90-day review process, the pact will go into effect. Widespread views are that no objections will be raised as shown in two resolutions introduced in the Senate and the House that call for approving the agreement.

No legislative approval is necessary in South Korea.

Jodi Lieberman, a nonproliferation expert well versed in congressional affairs, said she believes the agreement was "very ably negotiated" to address any proliferation concerns.

"It's my prediction ... that this agreement will enter into force without any problems on the congressional side," she said. (Yonhap)