NRX Reactor Spent Fuel Study

Abstract:

In safeguards and nonproliferation, we routinely need the ability to estimate isotopic inventories of spent fuel. However, those estimates are usually produced without reporting uncertainties which limit their usability. In this work, we describe a method for generating uncertainty estimates from Monte Carlo based reactor physics codes. We use the NRX reactor as an example. The Canadian NRX research reactor was operated for more than 50 years and produced vast amounts of plutonium in spent fuel before its shutdown in 1993. The NRX reactor was a heavy-water moderated, light-water cooled, and natural uranium fueled 40 MWth research reactor with an average core burnup of 1300 MWd/MTU. In recent history, a small number of countries have built test reactors similar to the NRX. In this research we quantify, with uncertainty estimates, the amount of plutonium produced in a typical refueling cycle of the NRX with an average burnup of 1300 MWd/MTU. Details of the construction and execution of a simulation to calculate the isotopic inventory of spent fuel from the NRX reactor and to estimate uncertainties in those inventories due to modeling precision are given. The simulation was performed using the MONTEBURNS code package from Los Alamos National Laboratory.