North Korea’s New Light Water Nuclear Reactor: A Proliferation Risk?

Posted on September 5, 2012 by


North Korea has recommenced construction of an experimental light water nuclear reactor (LWR) at its nuclear facility at Yongbyon, with completion slated for late 2013. 

The Kim regime has previously stated that the new LWR and its already operational uranium enrichment facility at Yongbyon are intended for electric power generation and not for production of fissile material for nuclear weapons.

While energy security is a laudable and necessary objective for a country with real resource constraints, North Korea’s consistent nuclear proliferation effort over the past two decades gives pause for scepticism.

North Korea was promised two light water nuclear reactors (LWRs) for civilian energy generation under the 1994 Agreed Framework in exchange for suspending operations as Yongbyon and re-opening the site to International Atomic Energy Agency (IAEA) inspections.  LWRs were said to be more nuclear weapon proliferation-resistant because less plutonium can be reprocessed from their spent reactor fuel. 

Why then might a North Korean LWR pose a proliferation problem now?  To answer this question we need to understand the nuclear fuel cycle and locate Pyongyang’s new LWR in the context of the uranium enrichment and plutonium reprocessing stages of the cycle that are pathways to nuclear weapons production.

The Nuclear Fuel Cycle

Despite of its anaemic economy, North Korea has established an entirely indigenous nuclear fuel cycle, consisting of a number of complex industrial processes through eight specific stages at sites at Yongbyon and elsewhere around the country

North Korea is endowed with extensive uranium ore deposits, the prerequisite feedstock of the nuclear fuel cycle.  The extracted uranium ore must be milled into a uranium oxide concentrate called yellowcake.

Yellowcake is converted into uranium hexafluoride and fed into a uranium enrichment process in which gas centrifuges separate the different uranium isotopes out by weight to increase the proportion of the uranium-235 isotope to a concentration of 2-4 percent for reactor fuel and over 90 percent for nuclear weapons application. 

A cascade of only ten centrifuges is all that is required to produce low enriched reactor-grade uranium, or about 35 centrifuges for highly-enriched weapons-grade uranium.  As the capacity of each centrifuge is very small, thousands of centrifuges are required to produce highly enriched uranium on an industrial scale. 

Highly enriched uranium does not need to pass through a reactor to be used in nuclear weapons, however low enriched uranium does have to undergo reactor burn to produce plutonium.  Low enriched uranium is fabricated into metallic ingots, which are melted into an aluminium alloy and then machined into cladded fuel rods for insertion into a nuclear reactor. 

Inside the reactor, the fuel rods sustain a controlled nuclear reaction within a liquid cooling fluid (water in the case of LWRs).  The nuclear reaction serves two possible functions: (1) to pass the heated water through a turbine for electricity generation; and (2) to produce radioactive isotopes for industrial and medical applications or plutonium for nuclear weapons.

Spent reactor fuel must then be unloaded into a storage pond where the water traps remaining volatile radiation and heat from the fuel rods, after which it is removed and reprocessed to separate remnant uranium and plutonium from other waste products.  Separated uranium is recyclable at the conversion stage of the fuel cycle, while the plutonium can be used for nuclear weapon production.

A Growing Nuclear Stockpile?

In June 2008, the cooling tower of Yongbyon’s old 5MW(e) was demolished in compliance with agreements reached in the Six Party talks and by early 2009 approximately 90 percent of disablement work was complete.  A new cooling system would have to be built for the reactor to resume production at optimal levels, which means that North Korea’s plutonium stockpile remains capped, enough for 6-18 nuclear weapons in the absence of a functioning nuclear reactor.

In November 2010, American scientists Sigfried Hecker, John Lewis and Robert Carlin were taken on a tour of an industrial scale uranium enrichment facility at Yongbyon where they saw over 2,000 fully operational centrifuges.  Recent estimates place North Korea’s current inventory of highly enriched uranium between 0-13 nuclear weapons, giving a total stockpile of fissile material capable of producing 6-31 nuclear weapons, with the likely number lying in the mid-range of 16-19.

David Albright and Christina Walrond offer three scenarios for potential for growth in North Korea’s nuclear stockpile utilising the completed LWR and uranium enrichment facility in an August 2012 report for the Institute of Science and International Security (ISIS). 

If uranium enrichment is dedicated to producing low enriched reactor-grade uranium for electricity generation in the LWR as the regime claims, the centrifuge facility could only produce enough highly enriched uranium for 14-29 nuclear weapons by 2016, a slight increase on its present inventory. 

If the reactor core of the LWR is optimised for weapons-grade plutonium production, as described in the ISIS report, and uranium enrichment is geared toward producing low enriched uranium reactor fuel for this purpose, North Korea’s fissile material stockpile may be large enough for 28-39 nuclear weapons by 2016.  Standard LWR designs produce lower grade plutonium that can also be used in nuclear weapons but for technical reasons is less desirable.

In the scenario that uranium enrichment is optimised to produce highly enriched weapons-grade uranium, with no diversion of low-enriched uranium to the LWR, the stockpile could produce 21-32 nuclear weapons by 2016.  This third scenario seems less likely unless North Korea has an additional clandestine enrichment facility to supply reactor fuel to the LWR.  In this case North Korea could have the best of both worlds, producing highly enriched uranium and plutonium for nuclear weapons application.



Dr. Benjamin Habib is a Lecturer in Politics and International Relations at La Trobe University, Albury-Wodonga. Ben is an internationally published scholar with research and teaching interests including the political economy of North Korea’s nuclear program, East Asian security, international politics of climate change. He also teaches in Australian politics and Chinese studies.  Ben undertook his PhD candidature at Flinders University in Adelaide, Australia.  He is an Asia Literacy Ambassador for the Asia Education Foundation and has worked previously for Flinders University, the University of South Australia, and the Australian Department of Immigration and Citizenship.  He has spent time teaching English in Dandong, China, and has also studied at Keimyung University in Daegu, South Korea.  Ben is involved with local community groups Wodonga and Albury Toward Climate Health (WATCH) and Albury-Wodonga Ecoportal.