Feasibility Study of the Conversion of IRT Research Reactor in the Democratic People’s Republic of Korea (DPRK) from Highly Enriched Uranium (HEU) to Low Enriched Uranium (LEU) Fuel

Abstract

Democratic People’s Republic of Korea (DPRK) currently uses highly enriched uranium (HEU) with 80 wt% 235U fuel in their research reactor (8MWth-IRT). This 8MWth-IRT reactor of DPRK is not under the International Atomic Energy Agency (IAEA) safeguards since its withdrawal from the Treaty on the Non-Proliferation of Nuclear Weapons (NPT). Conversion of fuel in nuclear research reactors from HEU to low enriched uranium (LEU) is a global trend for meeting the objectives of nuclear non-proliferation. A computational feasibility study was conducted to convert DPRK’s 8MWth-IRT reactor fuel from HEU to LEU. Comparisons were made of the reactor performance, such as neutron flux, effective neutron multiplication factor, neutron reactivity, temperature reactivity coefficients, fuel life-time, etc., with the current 80 wt% 235U enriched HEU fuel type (UAl: uranium aluminum alloy) and potential 19.9 wt% 235U tubular LEU fuel (UAl) and 19.75wt% 235U HANARO LEU fuel (uranium silicide). Potential proliferation risk of plutonium was assessed and compared by performing fuel burnup simulations for these three types of fuel. The neutronics simulation of fuel burnup in the reactor, buildup of fission products and other actinides, including plutonium were carried out using the Monte Carlo radiation transport code, MCNP6.2. The MCNP6.2 code was selected because it is suitable to model complex geometry of the reactor fuel as well as it uses very accurate energy dependent neutron interaction point cross sections. Two potential LEU fuels showed suitable performance with sufficient excess reactivity and the thermal neutron flux to replace the HEU fuel from a neutronics perspective. The results of the study can form the basis for further discussions on the nuclear weapons denuclearization of DPRK and can contribute to global nuclear non-proliferation regime.