Abstract
The Molten Salt Reactors (MSR) are an innovative kind of nuclear reactors and are presently considered in the framework of the Generation IV International Forum (GIF-IV) for their promising performances in terms of low resource utilization, waste minimization and enhanced safety. A unique feature of MSRs is that molten fluoride salts play the distinctive role of both fuel (heat source) and coolant. The presence of an internal heat generation perturbs the temperature field and consequences are to be expected on the heat transfer characteristics of the molten salts. In this paper, the problem of heat transfer for internally heated fluids in a straight circular channel is first faced on a theoretical ground. The effect of internal heat generation is demonstrated to be described by a corrective factor applied to traditional correlations for the Nusselt number. It is shown that the corrective factor can be fully characterized by making explicit the dependency on Reynolds and Prandtl numbers. On this basis, a preliminary correlation is proposed for the case of molten fluoride salts by interpolating the results provided by an analytic approach previously developed at the Politecnico di Milano. The experimental facility and the related measuring procedure for testing the proposed correlation are then presented. Finally, the developed correlation is used to carry out a parametric investigation on the effect of internal heat generation on the main out-of-core components of the Molten Salt Fast Reactor (MSFR), the reference circulating-fuel MSR design in the GIF-IV. The volumetric power determines higher temperatures at the channel wall, but the effect is significant only in case of large diameters and/or low velocities.
Highlights
In recent years, there has been a growing interest in the Molten Salt Reactor (MSR) technology, one of the six nuclear reactor concepts considered in the framework of the Generation IV International Forum as promising candidates for an increasingly sustainable, safe and secure nuclear energy production
Equation (3) implies that the Nusselt number (Nu) in case of internally heated fluids and constant wall heat flux NuQ+jw can be computed by means of traditional correlations for the value of Nujw with the introduction of the corrective factor: (4)
It has been shown that the effect of internal heat generation can be described by means of a corrective factor to be applied to traditional correlations for the Nusselt number
Summary
There has been a growing interest in the Molten Salt Reactor (MSR) technology, one of the six nuclear reactor concepts considered in the framework of the Generation IV International Forum as promising candidates for an increasingly sustainable, safe and secure nuclear energy production. A main and characterizing feature of MSRs is the dual role of the molten salts, acting as both fuel and coolant. This requires investigation in view of the little information available in the open literature regarding the thermal-hydraulics of internally heated fluids.
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