Abstract

North Korea produced weapon-grade plutonium in its graphite-moderated 5-MWe reactor. Estimating the total production of fissile materials provides an important baseline for denuclearization efforts. Nuclear archaeology can improve such production estimates by measuring isotope ratios in the graphite moderator of the reactor. The accumulation of certain trace isotopes in the graphite enables to accurately estimate life-time reactor fluence which can then be related to plutonium production. This article uses the open-source reactor physics software ONIX to simulate the operation of the 5-MWe reactor. It discusses consolidated estimates of plutonium production from 1986 to 2020 based on publicly available operation history data. An updated mathematical framework to relate isotope ratio uncertainties to fluence uncertainties and its implementation in a special ONIX module for nuclear archaeology are also presented. The module is used to identify which isotope ratios should be measured in the 5-MWe reactor to minimize uncertainties on plutonium estimation.

摘要

朝鲜在其石墨慢化 5 兆瓦反应堆中生产了武器级钚。估算裂变材料的总产量为无核化工作提供了重要的基线。核考古学可以通过测量反应堆石墨慢化剂中的同位素比率来改进这种产量估计。石墨中某些痕量同位素的积累能够准确估计反应堆寿命期间的注量，然后可以将其与钚生产相关联。本文使用开源的反应堆物理软件ONIX来模拟5-MWe反应堆的运行。它讨论了基于公开可用操作历史数据的 1986 年至 2020 年钚产量的综合估计。还介绍了将同位素比不确定性与注量不确定性相关联的更新数学框架及其在用于核考古的特殊 ONIX 模块中的实现。该模块用于确定应在 5-MWe 反应堆中测量哪些同位素比率，以最大限度地减少钚估算的不确定性。