6 Months to Produce Fissile Materials, 6-9 Months to Develop a Detonation Device...South Korea Could Arm Itself With a Nuclear Weapon in 1.5 Years
Lee Young-Wan, Science reporter
Following North Korea's nuclear test and the subsequent long-range missile launch, there have been voices calling for South Korea to develop a nuclear weapon of its own. According to experts, "the question of whether South Korea could do so is not a question of technology or capability, but only a question of [political] will." They added that South Korea could "deploy a nuclear weapon in only 1.5 years once the decision is made, and in no longer than 2 years."
Fuel Reprocessing Possible in Laboratories
In order to create a nuclear weapon, it is necessary to obtain fissile materials, such as uranium or plutonium. Furthermore, there needs to be a detonation device that can set off a high-grade explosive with a precision of less than a millionth of a second. This is necessary to initiate the nuclear fission chain reaction. Lastly, it is also important to have materials that can safely encase the fissile material.
Of these requirements, obtaining fissile material is the most important. Nuclear bombs can be made from both uranium or plutonium. Under the Nuclear Non-proliferation Treaty (NPT) and the U.S.-ROK Nuclear Agreement, South Korea is prohibited from obtaining fissile material. However, this does not mean that it lacks the requisite capability or technology to do so. We currently operate twenty-four nuclear power plants, incuding the Gori-1 plant, which is set to be shut down.
During the course of their operation, nuclear power plants produce spent nuclear fuel rods that contain small amounts of plutonium. In particular, the four Wolsong power plants (#1-4), which are heavy water reactors, produce spent fuel that is of higher plutonium content than that produced by light water reactors. On average, the spent fuel from the Wolsong plants consists of 1% plutonium. At the end of 2014, the Wolsong plants stored 7,414 metric tons of spent fuel rods. If this reprocessed, it is possible, in theory, to obtain 74 metric tons of plutonium. Only 4kg of plutonium is necessary for a single nuclear bomb, which means that up to 18,500 bombs could be made from this amount.
Kim Seung-Pyong, a professor of nuclear engineering at Chosun University, said that "there are multiple ways of extracting plutonium from spent fuel rods, including electrolysis (dry method) and liquid-liquid extraction, but none of them present technical challenges." He added that "it would take time to construct a large-scale reprocessing facility, but it can be done [at a smaller scale] even now in laboratories." South Korea is prohibited from reprocessing fuel, but Japan has a reprocessing facility in Rokkasho, Aomori county. This facility is used to separate plutonium from spent fuel for the purpose of re-using it in power plants, but the facility could potentially be used to produce fissile material for nuclear bombs.
South Korea also has advanced reprocessing technology. One professor of nuclear engineering said that "our capabilities when it comes to pyroprocessing, which involves reprocessing by using electolysis, are world-class." He noted that "if spent fuel is first reprocessed using pyroprocessing and then dissolved using nitric acid-which is the typical method-then it is possible to obtain more fissile material in a shorter amount of time." Experts estimated that it would take a total of 6 months to build a reprocessing facility and then obtain the necessary fissile material for a nuclear bomb.
South Korea also has new laser enrichment technology
To obtain fissile material for a uranium bomb, naturally occurring uranium must be enriched. This is because uranium, when found in nature, is a mix of the two isotopes U-238 and U-235. Natural uranium only contains 0.7% of U-235, which is the fissile isotope. It is necessary to cross the 90% threshold to be used in a nuclear weapon, and U-235 of such high purity can only be produced through an enrichment process using centrifuges. To obtain 1kg of uranium of such high concentration, one needs 1,000 metric tons of naturally-occurring uranium. Because of this, North Korea has been unable to construct large-scale enrichment facilities even though it has pursued nuclear weapons for several decades.
South Korea could develop uranium bombs faster than North Korea. In 2000, the Korea Atomic Energy Research Institute tested a sophisticated laser enrichment technology. It is said that 1kg of highly enriched U-235 can be produced in around 4 hours if this technology is used.
It is also straightforward to obtain the technology to construct a nuclear bomb. Most of the requisite technology was developed in the 1940s and 1950s, and blueprints can even be easily found online. One professor at a private university in Seoul said that "we teach some elements of nuclear weapon design to students taking classes in nuclear design, so that they can understand the power of nuclear bombs." Seo Gyoon-Ryeol, a professor in the Nuclear Engineering Department at Seoul National University, said that "alloys and precision manufacturing are necessary to develop the materials to encase fissile material, but this technology is already commonly used for industrial purposes in South Korea." South Korea's
civil engineering capabilities, which are necessary in preparing for nuclear tests, are also world-class.
According to experts, it would take 6 months to obtain fissile material, 6-9 months to develop a detonation device, and 3-6 months to conduct a nuclear test. This means that a nuclear bomb could be made in 1.5-2 years. Lim Man-Seong, a professor of Nuclear and Quantum Engineering at KAIST, said that "the time needed to create a nuclear bomb would vary depending on how much financial and human resources are invested into the project."
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: Time Estimated to Produce a Nuclear Weapon, as estimated by experts
Stage 1 (light brown, far left)
Obtaining Manpower (3 months)
Interviewing & selecting personnel in relevant fields
Designing a nuclear weapon
Stage 2 (light brown)
Producing Fissile Material (6 months)
Construction of reprocessing factory or a reprocessing system relying on laboratories
Collecting spent fuel rods from Wolsong 1-4 nuclear power plants
Primary extraction of plutonium using electrolysis
Liquid-liquid extraction using nitrates and other substances to obtain weapons-grade plutonium
Stage 3 (light brown
Developing a detonation device (6-9 months)
Testing a detonation device
Building a nuclear test site
Stage 4 (light brown, far right)
Nuclear testing (3-6 months)
Complete production of nuclear warheads
Deployment on missiles