South Korea and the U.S. officially signed a revised civil atomic energy cooperation agreement in Washington on Monday, wrapping up government-level finalization procedures some 50 days after the deal’s preliminary signing.

South Korean Foreign Minister Yun Byung-se and U.S. Energy Secretary Ernest Moniz signed the revision to the 1974 agreement, which was first signed in 1956. The preliminary signing was done in Seoul on April 22, ending four and a half years of tough negotiations.

After the deliberation process in the U.S. Congress, the agreement is expected to take effect at the end of this year, at the earliest, or early next year. Seoul does not need parliamentary ratification to implement the revision.

Seoul’s Foreign Ministry said Yun and Moniz recognized that the revision would help the allies elevate their cooperative relationship in the atomic energy sector to a “strategic and future-oriented” partnership and that the agreement would be “another milestone” in the alliance.

“Yun evaluated the revision as an expansion of the ‘modern and mutually beneficial’ cooperation between the allies as this is to allow (South Korea) to efficiently manage spent fuel, stably supply nuclear fuel and bolster exports of nuclear reactors,” said the ministry in a press release.

“He also said the revision is another example of South Korea and the U.S. strengthening strategic cooperation in an innovative, future-oriented way, and will serve as another core pillar of the alliance.”

During the signing, Moniz underscored that the allies are staunch supporters of nonproliferation goals, and that the deal will allow them to enter a “new phase of cooperation.”

Under the previous 1974 agreement, South Korea was barred from reprocessing spent fuel and enriching uranium in exchange for technological assistance from the U.S.

The revision, however, opens the possibilities for Seoul to produce low-enriched uranium with Washington’s consent. It also allows South Korean scientists to conduct early-stage research into a new type of technology to reprocess spent fuel, called “pyroprocessing,” which is thought to have a lower chance of being used to build nuclear bombs.

By Song Sang-ho (sshluck@heraldcorp.com)