Research activities in the NuEST lab focus on understanding micro to macro scale transport of matter and radiation. The fundamental and applied research in the Nu-EST lab are conducted with the aide of novel experimental and computational tools.
I. High temperature thermal-hydraulics
Graphite-fuel matrix in VHTRs or HTGRs can come in direct contact with air at high temperature during air ingress as associated with severe accidents, which can affect their passive heat removal capabilities. Nuclear grade graphite material has been shown to undergo oxidation reaction during air ingress resulting in degradation of its thermal conductivity and emissivity. A new machine learning based technique is devised to characterize and classify thermographic images of graphite surfaces during transient heat transfer experiments.
II. Air ingress in HTGRs
The Air Ingress experiment simulates a situation in which natural convection occurs in HTGR during a double guillotine break in the main cooling system. During this process, atmospheric air will begin to diffuse into the helium coolant system located at the point of the break, creating a boyancy difference between the inner plenum and the outer leg.
After a considerable ammount of time, the ammount of air diffused into the system will create a boyancy difference between the legs, causing Onset Natural Convection (ONC).
This ONC results in the intake of more air into the system than before, which can increase the oxidation rate of various elements within the reactor itself.
The time in which ONC will occur can be extended or diminished by injecting helium at certain flow rates into the cooling system at specific points. Through this injection method, the total ammount of helium within the system will decrease at a slower rate than before, decreasing the diffusion rate of air and consequently increasing or decreasing ONC times.
The goal of this experiment is to test which injection rates are optimal for the system and to find out which locations the injections should occur in order to optimise ONC time.
III. Thermal Energy Storage
The serious economic challenge faced by the existing NPPs is their inability to follow the grid load demand. Due to this reason, they are economically less competitive as compared to their fossil counterparts which can supply peak-loads and thus generate far more revenue during those peak hours. The technical challenge behind this economic disposition is that reactor power cannot be allowed to follow the grid and fluctuate in order to avoid unsafe conditions inside the reactor. Thus, only way NPPs can accommodate grid demand is if the reactor thermal power or plant electrical power is stored in an integrated device when in surplus. We develop methods to store exergetically efficient thermal energy storage devices. The novel design of these methods is based on manipulating thermal anisotropies in materials at micro or macro-scale.
IV. The Gallium Thermal-hydraulic Experiment (GaTE)
The Gallium Thermal-hydraulic Experiment (GaTE) facility is intended to experimentally obtain novel information on the thermal-hydraulic characteristics of liquid metals via the use of high fidelity instrumentation. As an example, the thermal stratification seen in liquid metal pool type reactors can be recreated in the lab experiment. By limiting the temperature, the scaled model of a liquid metal hot plenum can be affixed with instrumentation capability not previously used in this manner to study nuclear thermal-hydraulics.