Wi Sung-lac, head of the presidential Office of National Security, said in a KBS interview on the 26th that discussions between Korea and the United States are underway to give Korea more authority than now in the areas of uranium enrichment and nuclear fuel reprocessing. He said, Japan has both enrichment and reprocessing authority, adding, We asked the United States to allow the same level as Japan, and there was a positive response from the United States.
As the United States positively reviews Korea's request to expand authority for uranium enrichment and spent nuclear fuel reprocessing, signs are emerging that the Korea-U.S. nuclear cooperation agreement will be revised. If the agreement is revised, observers say Korea could secure fuel self-sufficiency at the level of Japan. However, due to trade negotiation variables, it is uncertain whether it will be formalized at the Korea-U.S. summit to be held in Gyeongju on the 29th.
The "Japan-style model" refers to a system that allows a country to carry out uranium enrichment and spent nuclear fuel reprocessing at home without prior U.S. approval. Among U.S. allies, Japan alone currently has such authority. Under the current agreement, Korea may produce low-enriched uranium of under 20% only with U.S. consent, and spent fuel reprocessing is prohibited.
◇ Domestic spent fuel storage facilities to reach capacity starting next year
The Korea-U.S. nuclear cooperation agreement was first signed in 1956 and is set to expire in June 2035. U.S. President Donald Trump issued an executive order in May allowing renegotiations to begin 10 years before expiration.
Korea is seeking to revise the agreement out of a practical need to directly manage the entire nuclear fuel cycle. In particular, storage space for spent fuel at major nuclear plants such as Hanbit, Hanul, Kori, and Wolsong is expected to become saturated in sequence within 10 years starting next year, strengthening the case for revising the agreement.
The nuclear fuel cycle is divided into the front-end cycle before fuel is loaded into the reactor and the back-end cycle after use, when it is removed for storage and treatment. The front end includes the enrichment process that turns uranium into fuel for power generation.
Reactors generate electricity from the energy released when neutrons collide with uranium and cause fission. In domestic reactors, slow neutrons can induce fission only in uranium-235, the isotope with an atomic mass of 235. Because uranium-235 accounts for just 0.7% of natural uranium, enrichment is essential.
Under the current Korea-U.S. agreement, Korea is allowed only low enrichment under 20% for power generation. For weapons, enrichment of 90% or more is required. However, since the 2015 revision, Korea has not carried out its own enrichment. The government is seeking to secure practical access not only to clearly stated authority but also to the procedures and all pre-fuel-fabrication steps of enrichment.
The back-end cycle refers to the stage of recovering materials capable of fission from spent fuel (spent fuel rods) that has completed fission in a reactor. It is like collecting the unburned parts from coal briquette ash to make new briquettes. Korea and the United States are jointly developing a new back-end reprocessing technology: pyroprocessing.
Aqueous reprocessing, which dissolves spent fuel rods in nitric acid, has been strictly regulated internationally because it easily separates pure plutonium usable for nuclear weapons. Pyroprocessing, by contrast, is a dry reprocessing technology that electrolyzes spent fuel rods after heating them to 550 degrees Celsius. This allows separation of uranium-235 and uranium-238. Heavier elements such as plutonium, neptunium, americium, and curium are extracted together as a mixed metal. Because there is no way to extract only pure plutonium from this, it is assessed as having no concern for direct weapons use.
If pyroprocessing is commercialized, part of the spent fuel can be reused to generate electricity. According to the Korea Atomic Energy Research Institute (KAERI), the volume of highly radioactive high-level waste can be reduced to about 5%, and the half-life of radiotoxicity can be shortened from thousands of years to hundreds of years.
◇ Expectations for pyroprocessing and fast breeder reactor development
In particular, if pyroprocessing is combined with a new reactor, the level of resource recycling could advance dramatically. It means recycled briquettes burn in existing stoves but are more efficient in dedicated stoves.
Here, fast breeder reactors are cited as a solution. A fast breeder reactor is a reactor that "breeds" fuel by using "fast" neutrons whose speed is not moderated to convert uranium-238, which makes up most of natural uranium but cannot undergo fission, into plutonium-239, a fissile material.
Fast breeder reactors use liquid metals such as sodium as a coolant instead of water. Neutrons are not slowed in liquid metal. When such fast neutrons hit uranium-238, it becomes plutonium-239, which can undergo fission. Spent fuel rods from nuclear plants contain uranium-238 and plutonium-239. Fast breeder reactors can burn these again to generate electricity.
The nuclear community believes that combining pyroprocessing with fast breeder reactors can realize a closed fuel cycle that enables waste reduction and resource recirculation. Current research indicates that operating pyroprocessing together with a sodium-cooled fast reactor (SFR) can increase fuel-use efficiency by more than 60% to 70% compared to existing nuclear systems.
The problem is that plutonium-239 bred in fast reactors becomes a raw material for nuclear weapons. A mechanism is needed to remove concerns about weapons diversion. Safety is also a concern because sodium can explode on contact with water or air. Japan's Monju fast reactor halted operations after a sodium leak caused a fire in 1995, the year it entered full operation.
However, there are recent assessments that advances in materials, fabrication, and operations have lowered the risk. Russia, India, and China are already operating or building fast breeder reactors. In Korea, KAERI has been developing pyroprocessing and SFR technologies since 1997. The goal is to commercialize SFR by 2030.
The decisive variable is the outcome of trade negotiations. Korea and the United States currently maintain that there will be no separate settlements on individual items, so if trade issues are not resolved, the revision of the nuclear agreement is likely to be delayed. An official in the nuclear industry said, The broad direction has already been set, but the details remain opaque, adding, There is also a possibility that the revision talks could fall through, so we need to watch the outcome a bit longer.