This is the sixth in a series of six blogs looking at a nuclear crisis at North Korea’s Yongbyon nuclear facility. Other pieces will look at the prospective issues of a nuclear crisis in North Korea from the perspective of North Korea, Russia, Japan, China, and the United States.

By Duyeon Kim

South Korea’s response to a nuclear reactor crisis at North Korea’s Yongbyon complex depends heavily on many assessments and factors. Was it its 5 megawatt-electric (MWe) graphite reactor or experimental light-water reactor (ELWR) that experienced a meltdown? Was the ELWR operational at the time? Was it caused by an accident or an attack? How big is the damage and how much radiation has leaked? While answers to these questions are important when devising appropriate response measures and North’s nuclear safety standards are of grave concern, it is believed that the radiological consequences of a reactor accident or incident would be minimal and isolated.

Before assessments can be made based on the above scenarios, a quick review of standard reactor safety is necessary to help understand whether North Korea’s nuclear facilities are in fact safely constructed.

Nuclear Safety

Modern safety standards for nuclear power plants are built in throughout the entire lifespan of the facilities from (land) siting, design, construction, operations, and decommissioning. Nuclear power plants are designed with a concept called defense-in-depth, which are multiple layers of protection to reduce risks to both the workers and the public. The priority to the defense-in-depth strategy is to prevent accidents, and if they cannot be prevented, to then mitigate their consequences. The layering of protection—including, for example, placing reactors inside containment structures to keep radiation from reaching the environment—allows modern nuclear power plants less prone to accidents than many industrial facilities, although sometimes human error may cause accidents.

Over time, the 1979 Three Mile Island accident and the 1986 Chernobyl disaster helped identify weaknesses in defense-in-depth and the need for a safety culture. However, even the 2011 Fukushima Dai-ichi meltdown showed that nuclear power plants that are designed with defense-in-depth principles can still fail if they are subject to system failures and multiple traumas from forces greater than what they were built to withstand. Fukushima also illustrated that the same conditions can be created by humans with malicious intent.

In North Korea’s case, it is unclear whether its reactors are built according to international safety standards, and the quality of its safety culture, if it exists, continues to be a critical question. The North’s isolation, potential safety vulnerabilities with an unverified safety culture, and questions surrounding Pyongyang’s ability to respond in a timely manner to contain a nuclear accident from becoming a catastrophic disaster all raise serious concerns.

North Korea’s gas-cooled graphite-moderated reactors originated from the research reactor, IRT-2000, built by the Soviets in the 1960s. Then, under the 1994 Geneva Agreed Framework between the United States and North Korea on Pyongyang’s nuclear program, the international consortium called the Korea Peninsula Energy Development Organization (KEDO) began building two, commercial-scale (1000 MW) light-water reactors (LWR) at the Kumho site to help meet the North’s energy needs in return for dismantling its plutonium-production facilities. The KEDO project, however, was terminated under the George W. Bush administration.

In 2010, Pyongyang showed Siegfried Hecker and Robert Carlin its 25-30 MWe experimental light-water reactor (ELWR) under construction using with what they were told “strictly indigenous resources and talent.” They also saw a reactor containment vessel being built, which according to the North’s chief engineer, was expected to be 22 meters in diameter, 0.9 meters thick, and 40 meters high, later confirmed by commercial satellite imagery, but interlocutors have questioned the quality of the vessel, particularly the quality of the concrete used for the containment structure. Another unknown is whether the North used the reactor components and designs left onsite after the KEDO project’s termination to fabricate or use for its ELWR.

A design-basis accident is a “postulated accident that a nuclear facility must be designed and built to withstand without loss to the systems, structures and components necessary to ensure public health and safety.” In other words, they are the most severe circumstances a nuclear power plant is likely to face and the minimum considerations that go into the construction of the plants.

However, Fukushima illustrated that the long electricity cut-off actually went beyond the design-basis accident of most nuclear plants in most countries and that most backup power generators are not enough to restore power to cool the reactor core and spent fuel ponds. In other words, critical safety components are an adequate onsite power source to provide a functioning cooling system to prevent a reactor core meltdown, the reactor operators’ ability to immediately shut down the reactor if the core overheated or address any accidents in a timely manner, and an emergency backup cooling system in case of a station blackout, which includes a generator to provide electricity to cool the reactor core or the means to transport water from a nearby river.

As for North Korea’s ELWR, Hecker and Carlin saw a sign that read “Safety first – not one accident can occur!” Due to the prominence of anything nuclear in North Korea’s national objectives, it is imaginable that their scientists and engineers would put their lives on the line to construct safe nuclear power plants and not allow a reactor core meltdown, but it is unclear whether Pyongyang has used adequate siting, reactor safety designs, quality construction, and beyond design-basis accident considerations for its ELWR, which they claim will eventually be scaled up once they mastered the nuclear technology. In early 2016, satellite imagery showed the ELWR’s cooling system, via river water supply channels from the adjacent Kuryong River, has become functional. Satellite imagery also indicates that the construction of the ELWR is complete, but as of April2016, there is no evidence yet of operations. Nuclear safety concerns will continue after the ELWR becomes operational for the reasons mentioned above, but also because it is widely believed that North Korean personnel lack experience in operating this type of reactor. The Three Mile Island nuclear disaster occurred about two months after the reactor became operational.

South Korean Interests and Response

As David von Hippel and Peter Hayes astutely point out in 2014, a reactor meltdown could occur at the North’s experimental light-water reactor either by accident or attack, but the radiological release would be modest in scale and scope. Some scenarios include: an ELWR accident, an attack by the U.S. (or jointly with South Korea), or a terrorist attack by an external actor or an insider threat. The following assessment will focus on a potential crisis at the North’s ELWR, which is of more concern to international experts.

South Korean interests and concerns would depend on which of the above scenarios is the cause and status of a reactor meltdown as well as its scale and scope. The following assessment is based on the assumptions illustrated above.

In the event of an accident (by nature, system failure, or human error) at North Korea’s ELWR, conventional expert wisdom is that the radiological fallout would be local, only contaminating neighboring agricultural areas within North Korea and perhaps even spread to the Kuryong River if the accident is not successfully managed. The isolated impact may calm South Korean fears in the short-term, but the South would still worry about the environmental damages in the North when thinking about life after the reunification of Korean Peninsula.

Currently, scientists believe the radiological effects of an accident at or even attack on the Yongbyon ELWR would not be consequential to South Korea because the radiological exposure would be so small and source materials would dilute to near undetectable amounts by air, rain, and water systems. The caveat and concern is possible retaliation by Pyongyang against South Korean nuclear facilities if its reactors were attacked by the U.S. or by the U.S. and South Korea. The radiological exposure and damage—economic, health, environmental—from an attack on South Korean nuclear facilities would be far more catastrophic and devastating.

One major concern, however, would be Pyongyang’s lack of transparency in the event of a reactor accident, which could pose greater risks if the regime is unable to contain it. The international community would also need to rely on its own means to detect the radionuclides released from the accident with the Comprehensive Test Ban Treaty Organization’s International Monitoring System and with South Korea’s extensive and real-time radiation monitoring network. The most problematic consequence with Pyongyang withholding information from the international community would likely be the induction of panic in South Korea because of the uncertainty about the accident’s impact and potentially harmful effects of radiation exposure.

A nuclear accident of or attack on the North’s ELWR would technically constitute a public health and safety issue, not a national security issue, for South Korea. Its Ministry of Public Safety and Security and particularly the Disaster Relief Headquarters would be first to address the situation and cooperate with the Korea Institute of Nuclear Safety (KINS) to make a probabilistic (radiation) risk assessment to help devise necessary measures because of the possibility of the southwestern down-winds that could carry radiation to the South. South Korean nuclear experts worry about Seoul, which is about 200 km away from Yongbyon. About 70 percent of the radioactive fallout from the Chernobyl nuclear catastrophe traveled 200 km way to Belarus, although one key flaw with the Chernobyl reactor was the absence of a containment structure.

Still, public fear is expected upon news of an incident at Yongbyon. Thus, depending on its assessment based on the scale and scope of the North’s nuclear accident or attack, Seoul may advise the public to, for example, temporarily avoid the outdoors or use umbrellas during rainfall to calm fears even in the absence of a downwind with radiation. If public fear peaks to panic and terrified levels, Seoul might even consider convening a National Security Council meeting to reassure public concerns even though the accident would be a public health and safety issue.

Duyeon Kim is a Visiting Senior Fellow at the Korean Peninsula Future Forum, a non-partisan think tank in Seoul founded and headed by former ROK National Security Advisor Chun Yung-woo aimed at devising practical policy solutions. The views expressed are the author’s own.

Photo from the Republic of Korea’s photostream on flickr Creative Commons.