The amended bilateral nuclear energy agreement between the USA and South Korea, which removes some of the restrictions on enrichment of uranium and reprocessing of used nuclear fuel, took effect on 25 November.

The amendments to the agreement, first signed in 1973, were finally agreed in April, after a sometimes acrimonious negotiation process that lasted four and a half years. It was officially signed by authorities in June and the US Congress approved it in October.

The agreement came less than a year before the expiry of the existing pact, which had already been extended by two years to allow talks to continue.

The agreement promises extensive consultation on South Korean enrichment and reprocessing, but leaves open the question of whether these activities will ultimately be permitted. The deal mandates the establishment of a joint committee to consider how South Korea could treat uranium to produce nuclear fuel at a low grade of enrichment, meaning it could not be used for weapons.

South Korea says the ability to produce its own fuel would help its energy and building companies to win nuclear plant projects abroad.

During the negotiations, South Korea had also insisted on the need to reprocess used fuel from its nuclear power plants, now totalling 25 units, given that its storage sites for used fuel are rapidly approaching capacity. "It is increasingly urgent for us to find a way to reprocess used fuel," said Song Ki-chan at the Korea Atomic Energy Research Institute last April. "We can store used fuel only until 2024 with the existing facilities [and] it’s hard to build multiple storage facilities in a small nation."

The new agreement allows for future consultation through which South Korea could work on "pyroprocessing", a new technology that yields plutonium mixed with other elements and is therefore unsuitable for weapons development.

South Korean exporters of nuclear reactors welcomed a clause in the revised deal whereby the USA granted comprehensive, long-term consent. It exempts Seoul from getting Washington’s permission every time the nation exports a reactor technology.

Previously, South Korea needed US approval every time it exported nuclear materials or reactor equipment and parts produced in the USA to a third country. Under the new deal, South Korea only needs the consent of the recipient country to export provided that country has a nuclear accord with South Korea and the US.

South Korea began developing nuclear reactor technology in 1959 with US support and gradually adapted the reactor designs to its own specification. Progress was made towards becoming a nuclear exporter in 2009 when it received an order to build a research reactor for Jordan and then subsequently won a $40bn tender to construction four reactors for the UAE using domestic technology.

South Korea has since received orders from Thailand and Malaysia and is seeking to take part in nuclear reactor projects in Turkey, Argentina and Vietnam. In November last year, South Korea entered the European market with an order to renovate a research reactor in the Netherlands and build cold neutron research facilities.