The High Fidelity Modeling of the Modular Helium-cooled Reactor

Francesco Venneri¹, Alan Baxter¹, Yonghee Kim², Jerzy Cetnar³, Alberto Talamo⁴, Carl-Magnus Persson⁵, Di Yun⁶, Bei Yi⁶, Wen Wu⁶

The accurate modeling of the Modular Helium-Cooled Reactor (MHR) presents difficult challenges related to the diverse scale lengths present in the reactor (six orders of magnitude from the size of the core to the size of a TRISO fuel particle kernel). Neutron slowing down in the graphite moderator is also very gradual, allowing the fuel to see a large spectrum of neutron energies.

Traditional approaches are based on extensive cross section averaging and are necessarily approximate. The High Fidelity Model (HFM) of the MHR aims at removing these approximations as much as possible, so as to become a predictive design tool for new applications of the gas cooled reactor, such as those envisioned for the nascent GNEP.

HFM uses Monte Carlo transport methods and a multi-zone depletion model, with geometric detail of the individual TRISO particle down to several layers in the kernel. The core neutronics are interfaced with a thermohydraulics model and with a particle fuel model, to calculate neutron fluxes, fluences, burnups, temperatures and fuel-failure rates, down to the individual TRISO particle, anywhere in the core.

Initial results of the HFM will be presented, based on the current implementation using simplified thermohydraulics and fuel behavior models that model the MHR in the Deep Burn mode with fully transuranic fuel loads. The modular architecture of the HFM will allow the incorporation of increasingly sophisticated models for fuel performance, thermal and structural analysis as they become available.

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