In a landmark decision, the US has approved South Korea’s plan to build nuclear–powered submarines (SSNs). The decision was announced following a meeting between the presidents of the two countries on the sidelines of the Asia-Pacific Economic Cooperation (APEC) summit in South Korea. The move will allow South Korea to join a small club of countries possessing SSNs, that is, the US, Russia, China, France, the UK, and India.
However, the decision to allow South Korea to build SSNs will set a dangerous precedent for potential proliferators and put a strain on the global nuclear non-proliferation regime.
North Korea’s growing nuclear arsenal, exemplified by its declaration as an “irreversible nuclear weapons state”, has intensified demands for South Korea’s own nuclear deterrent. While more than 70% of the South Korean public favours nuclear armament, the majority of elites still do not support that option. However, a substantial number of elites favour the option of acquiring nuclear latency.
Nuclear latency is referred to as a condition in which a country possesses all the means (technology, infrastructure, and expertise) to build nuclear weapons, but has not yet done so. It can also be called a nuclear threshold state, as the country possesses the ability to develop nuclear weapons within a matter of months.
South Korea could take years to build nuclear weapons for now. But, acquiring nuclear latency will enable it to build nuclear weapons within months, thus reducing costs associated with it (economic sanctions, international isolation, and the US withdrawing its security guarantee) and presenting a fait accompli. However, South Korea possesses all the means to achieve nuclear latency, except for nuclear fissile material, and the move to build SSNs provides it with an opportunity to obtain the fissile material.
Only declared nuclear-weapon states under the Nuclear Non-Proliferation Treaty (NPT), the P5 countries, and India (a non-signatory of the NPT) possess SSNs. But South Korea is a non-nuclear-weapon state signatory to the NPT, and it can exploit a loophole in the NPT to build nuclear weapons. The NPT allows non-nuclear-weapon states to remove nuclear fissile material used in “non-proscribed military activity”, such as naval reactors, from the International Atomic Energy Agency’s (IAEA) inspection mechanism. Therefore, South Korea can utilise the fissile material from the SSNs to build nuclear weapons.
Although, Australia is also set to build SSNs as part of the AUKUS deal, however, it possesses neither the means nor the motives to build nuclear weapons. From a non-proliferation perspective, this explains the US and UK’s decision to help Australia construct its SSNs. But, South Korea have intentions to develop nuclear weapons, and with the SSNs, it will obtain the only remaining means (that is, fissile material) to develop that.
There are two ways through which the US can help South Korea build the SSNs: either supply it with enriched uranium for a naval reactor or amend its nuclear cooperation agreement (the 123 Agreement) with South Korea to allow it to enrich and reprocess the US-supplied nuclear fuel. Through both ways, South Korea can divert the fissile material of the naval reactor to build nuclear weapons.
Firstly, the US can supply low-enriched uranium (20%) fuel to South Korea’s SSN naval reactor. This will be independent of their 123 agreement, as the US is also helping Australia build SSNs, without any amendment to its nuclear cooperation agreement with Australia. However, the problem lies in the fact that a reactor with low-enriched uranium requires periodic refuelling, which increases the probability of diversion of fissile material to produce nuclear weapons-grade uranium (90%) through further enrichment.
Secondly, if the US amends its nuclear cooperation agreement with South Korea to provide it with advanced consent to enrich and reprocess the US-supplied nuclear fuel. In that case, it will enable South Korea to divert some of the fissile material for building nuclear weapons. The US has bestowed this privilege only on Japan. This is due to Japan’s strict adherence to international non-proliferation safeguards and its three non-nuclear principles (not possessing, not producing, and not permitting the introduction of nuclear weapons). That is why Japan is said to have “bomb in the basement”, as it can build nuclear weapons within a matter of months, but because of its strong commitment to non-proliferation, it does not provoke substantial resistance.
Thus, in both cases, the US will allow South Korea the means to achieve nuclear weapons. Although South Korea may just intend to reach a nuclear threshold state (nuclear latency), and not actually develop nuclear weapons. But, this sets a dangerous precedent for potential proliferators to build nuclear weapons under the guise of constructing SSNs. Several countries, such as Brazil (Alvaro Alberto) and Turkey (NUKDEN), are actively pursuing plans to construct SSNs. Furthermore, Iranian officials have on several occasions revealed their intentions to develop SSNs, although the country does not have an active SSN construction plan in place. Additionally, it will put a strain on the US-led global nuclear non-proliferation regime, which has so far been highly successful in constraining the non-nuclear-weapon states from building nuclear weapons.
