Conference Agenda

In molten-salt-fuelled reactor systems, the fluid may experience substantial volumetric heat generation in addition to heat removal from surrounding structures. To quantify these effects, we investigate developed channel flow with internal heating using a systematic multi-scale approach comprising Direct Numerical Simulation (DNS), Large Eddy Simulation (LES), and a semi-analytical solver (SAS). First, DNS and LES are compared in a turbulent parallel-plate configuration at different Prandtl and Reynolds numbers, demonstrating excellent agreement in flow and thermal fields, with the SAS method showing acceptable accuracy. Building on this benchmarking, the SAS tool is then employed to explore a broad parameter space, offering insights into how internal heat deposition modifies the temperature distribution across Reynolds and Prandtl numbers. Comparisons are also drawn against the canonical wall-heating scenario, revealing that volumetric heating often remains a secondary effect in turbulent regimes but can become more pronounced at lower Reynolds numbers, higher Prandtl numbers, or when nearly all heat is deposited in the fluid. These findings establish guidelines for reduced-order modeling in liquid-fuel reactor analyses and highlight conditions under which internal heating warrants particular attention. The paper concludes by outlining ongoing and future research directions, including refinements for variable fluid properties and complex geometry extensions.

Moltex Energy is developing the technology and design for a stable salt reactor-waste burner (SSR-W). It is a static fueled chloride molten salt reactor (MSR) with a fast neutron spectrum and is designed to be fueled with transuranic elements recovered from spent fuel of CANDU and light-water reactors. Argonne, University of Michigan, and Moltex are developing three multi-physics plant digital twins (DT) which leverage advanced computational methods to achieve reactor performance optimization and enable predictive maintenance to reduce the plant operation and maintenance (O&M) costs. DT-1 provides methods for long-term fuel cycle modeling and optimization and provides the operator with an indication of refueling time and position. DT-2 comprises of an integrated system plant model that can be utilized in simulating normal operation as well as in assessing the safety performance of SSR-W during postulated and bounding accident conditions. DT-3 develops a conceptual structural health monitoring strategy for an innovative matrix heat exchanger, which involves machine learning-based classification of distributed temperature sensing for detection and localization of faults. Additionally, a separate effects loop (SEL) is being constructed at Argonne to support the SSR-W in three technical areas: (1) thermal-hydraulic heat transfer in MSR, (2) natural circulation phenomenon pertinent to passive decay heat removal, and (3) redox control in salt to minimize corrosion of structural materials. This paper describes the methodologies implemented in the three DTs and shows some illustrative results and outputs. The paper also describes the SEL, the test campaign and presents some preliminary thermal hydraulic and heat transfer data.

Aqueous homogeneous reactor is a new type of reactor that dissolves nuclear fuel in a liquid. The aqueous homogeneous reactor have significant advantages in extracting medical isotopes such as I-125 and Sr-89 due to their liquid fuel characteristics. However, during the operation of the aqueous homogeneous reactor, water molecules in the fuel aqueous homogeneous will collide with fission fragments, decompose to produce hydrogen and oxygen. Under accident conditions, the rapidly increasing nuclear power of the reactor will exacerbate this phenomenon. The generated hydrogen will accumulate in the gas space of reactor, posing a threat to the structural integrity of the reactor. Therefore, the system design of an aqueous homogenous reactor needs to take the hydrogen elimination into consideration.This article considers a gas recombination system(GRS) , a nitrogen blow system(NBS) and constructs a 200kW aqueous homogeneous reactor model in RELAP5.The impact of the gas Recombination system on the volume fraction of hydrogen produced by the aqueous homogeneous reactor in a typical reactivity introduction accident was analyzed under different working conditions. The results indicate that the presence of a gas recombination system can significantly reduce the volume fraction of hydrogen during a reactive accident in a aqueous homogeneous reactor. The hydrogen volume fraction can be guaranteed to be less than 4% during the accident , which make sure meets the requirement of hydrogen risk guideline. This study contributes to the design and construction of medical aqueous homogeneous reactor.

Due to the high-temperature operation expected from Molten Salt Reactors (MSRs), thermal radiation can significantly influence the thermal-hydraulic evaluation of these systems, and the intricate coupling of multiple physical phenomena in this kind of reactor necessitates the development of high-fidelity simulation codes. This work presents a new library, developed in OpenFOAM using C++ object-oriented programming, to model thermal radiation coupled with fluid mechanics and other physical phenomena. This library employs the SP₃ method to solve the Radiative Transfer Equation (RTE) and is compatible with all OpenFOAM sub-models for absorption, emission, and scattering, thanks to its inheritance from the default radiationModel library. Additionally, an innovative boundary condition is implemented to model metals such as Stainless Steel and Hastelloy, which are commonly used in the reflector of MSRs. This code can accurately calculate the power density distribution within the system through the strong coupling between neutronics and thermal-hydraulics calculations. This work considers two case studies: the 2D axisymmetric EVOL geometry and the 3D one-sixteenth MSFR geometry. In both cases, the effects of the thermal radiation on the temperature fields are evaluated. Additionally, the effects of temperature, fluid flow type (laminar or transient), and radiation properties (emission and absorption coefficients) on incident radiation are analyzed.

Kairos power is developing a pebble fuel based molten salt reactor. As a part of development, pressure drop through the pebble bed is tested, and a converging and diverging conical part of the core is experimentally studied in current scope. Test facility is scaled down with pebble’s Reynolds number. Test results are compared to KTA correlation, which is widely used correlation in cylindrical pebble bed pressure drop. Since KTA correlation is based on cylindrical geometry, parameters are taken at inlet or outlet of each truncated conical interval. For converging cone, there are four measurement intervals along flow direction. Most of the test results show good accordance with KTA correlation based on parameters from outlet of the truncated cone. However, the last interval, which has the smallest cross section, KTA underestimates the pressure drop. The difference between KTA and test at the last interval increases with Rep. For diverging cone, there are three measurement intervals along the cone. For the middle interval, KTA and test result match well. However, for the other two intervals, KTA shows significant overestimation. Considering manifold like geometry of the two cones and interval-sensitive predictability of KTA, a new correlation is needed.