Instead, the allies agreed to extend the current agreement by two more years until March 2016, said a senior official at Seoul's foreign ministry who is privy to the highly sensitive talks with the U.S., following the latest round of negotiations in Washington last week.
"The two sides agreed to extend the current nuclear cooperation agreement by two years to avoid a lapse in the agreement, and the next round of the talks will be held in June," the official said on condition of anonymity.
Extending the pact will "give Korea and the U.S. more time for close consultations and lay the ground for the two sides to achieve good results in smoothly revising the agreement," the official said.
Since October 2010, South Korea and the U.S. have negotiated to revise the 1974 agreement under which South Korea has been banned from reprocessing its spent nuclear fuel or enriching uranium for its commercial nuclear power plants, but Washington has been reluctant to do so apparently out of proliferation concerns.
This is one of the most sensitive issues for South Korean President Park Geun-hye and U.S. President Barack Obama as Seoul officials want to gain a "peaceful nuclear sovereignty" for the South Korean nuclear energy industry.
The decision to hold more talks on revising the nuclear cooperation agreement came about two weeks before Park visits the U.S. for her first summit talks with Obama.
Foreign ministry spokesman Cho Tai-young announces the results of negotiations with the U.S. aimed at revising a bilateral nuclear cooperation agreement on April 24. (Yonhap)
In a press briefing Wednesday, Seoul's foreign ministry spokesman Cho Tai-young said that there has been "meaningful progress" in the negotiations in terms of "management of spent nuclear fuel, stable supply of nuclear fuel and Korea's exports of nuclear reactors."
Nevertheless, Seoul and Washington decided to extend the accord because "much more technical and specific issues still remain to be resolved," Cho said.
"The Korean government will continue to make efforts to revise the accord in an advanced and mutually beneficial manner," Cho said.
The current pact requires South Korea to win U.S. permission before South Korea can reprocess U.S.-origin spent fuel, including spent fuel from U.S.-designed reactors in South Korea.
But the U.S. has been reluctant to grant such permission because it would be contradictory to Obama's broader non-proliferation agenda and North Korea's nuclear ambition.
Time has been running short because the two sides must conclude negotiations, which began in October 2010, by this summer for a revised accord to be approved by the U.S. Congress before the current accord expires in March next year.
One point of disagreement in the negotiations is whether the U.S. will permit South Korea to include a provision that allows it to reprocess its spent fuel and enrich uranium.
For years, South Korea has called for the U.S. to allow it to reprocess spent nuclear fuel to forestall a looming crisis of nuclear waste storage.
Scientists in South Korea, which runs 23 reactors and relies on nuclear energy for nearly 40 percent of its electricity needs, have estimated that spent fuel pools will run out of space beginning in 2016.
In the face of growing nuclear waste stockpiles and its ambition to become a global power in the civilian nuclear industry, South Korea hopes to adopt the so-called pyroprocessing technology, which leaves separated plutonium, the main ingredient in making atomic bombs, mixed with other elements.
South Korea wants the U.S. to allow it to use the new technology because it has to deal with more than 10,000 tons of nuclear waste at storage facilities that are expected to reach capacity by 2016.
Some nonproliferation experts say pyroprocessing is not significantly different from reprocessing, and the plutonium could be quickly turned into weapons-grade material.