NUCLEAR ARCHEOLOGY ON THE 5 MWE GRAPHITE REACTOR AT YONGBYON

On June 26, 2008, the DPRK submitted to China a declaration of its nuclear activities. The IAEA and the five countries that are negotiating with North Korea will want to verify how much plutonium it originally produced. The graphite isotope ratio method (GIRM) can give an accurate estimate of the total plutonium production in a graphite-moderated reactor without detailed information on the reactor's operating history. The Pacific Northwest National Laboratory (PNNL) developed the GIRM concept into a practical plutonium production verification tool for graphite moderated reactors in the early 1990s. The basic idea of GIRM is that the transmutation of trace impurities in the graphite is directly related to the cumulative plutonium production in the nuclear fuel. This study explains how the total amount of plutonium produced in the 5 MWe graphite reactor at Yongbyon could be accurately estimated using the GIRM technique without operational history, if a number of samples from graphite moderator can be obtained. The neutronics of the reactor is modeled, based on the physical core characteristics of the 5 MWe reactor, and the distribution of transmutation products is modeled as a function of cumulative plutonium production, using the MCNPX Monte Carlo radiation transport depletion computer code.