Application of the Pathline Method to the Aircraft Reactor Experiment

TL;DR

This paper introduces a novel numerical pathline method based on the Method of Characteristics for modeling delayed neutron precursors in nuclear reactors, applied here to the Aircraft Reactor Experiment, demonstrating its effectiveness in real-world MSR simulations.

Contribution

The paper presents the first application of the pathline method to a real-world Molten Salt Reactor, integrating it with neutron transport and CFD codes for improved DNPs transport modeling.

Findings

Pathline method accurately modeled DNPs in ARE.

Recirculation of fission products significantly affects DNPs distribution.

Method successfully replicated the L-7 experiment results.

Abstract

In this work, a new numerical method for the transport of Delayed Neutron Precursors (DNPs) is applied to the Aircraft Reactor Experiment (ARE). The pathline method is based on the Method of Characteristics (MOC) and leverages the pathlines of the liquid nuclear fuel to derive an integral form of the DNPs balance equation. The method has previously been tested on the CNRS benchmark and in a simplified 2D geometry where turbulent diffusivity was significant compared to advection. Here, the pathline method is applied to a real-world Molten Salt Reactor (MSR), the ARE. DNPs transport is implemented in the framework of the coupling between neutron transport solver APOLLO3\textregistered{} and computational fluid dynamics code TrioCFD, both developed at the French Atomic and Energy Commission (CEA). The DNPs concentration obtained with the pathline method were compared with those previously computed by TrioCFD, highlighting the importance of recirculation of fission products. The L-7 experiment was also replicated to demonstrate the method's capability.