Nuclear power plants around the world utilize the Rankine cycle to generate electricity. In this thermodynamic cycle water is turned to steam, and that steam is used to drive a turbine to produce power. The cycle is completed in a condenser where the exhaust steam is cooled and the resulting water is returned to a heat exchanger to start the process over. That cooling results in the exhaust of waste heat through a cooling tower:
The cloud you see from a typical cooling tower is carrying away the waste heat from the plant's condenser.
How much waste heat? An awful lot! The typical Rankine cycle is only about 30% efficient, most of the energy from fuel consumed in a power plant is simply wasted. With energy prices on the rise, fuel efficiency is a significant concern.
Gas-powered turbines are typically driven via much hotter exhaust gasses, allowing them to run on the Brayton cycle. The Brayton cycle is more efficient, closer to 55% or higher depending on the design of the turbine and the gas which drives the turbine. At the HT3R facility, readily available nitrogen (78% of the atmosphere is nitrogen) is currently the working gas of choice. Engineering studies of the Brayton cycle will take place in the power generation lab of the HT3R, putting UTPB at the forefront of energy generation engineering research.
This Brayton Cycle can be adapted to run on a nuclear heat source, or in combination with a second cycle to recover the waste heat and further increase the efficiency of the system.
In fact, engineering research opportunities have already been created by the HT3R project for students at UT Austin's College of Engineering. The senior thesis project for 13 students was to help flesh out the pre-conceptual design of the secondary systems and primary heat exchanger for the reactor. They came up with solutions to questions such as "How do you exhaust the waste heat (even the Brayton cycle will have some waste heat) from the reactor in west Texas, where a significant source of water for a cooling tower would be a real problem?" Their answers to this question (nitrogen-to-air heat exchanger) and others will help give us a starting point for future engineering of the reactor project, and allowed the students to tackle the very real challenges of engineering a cutting-edge research facility.