TerraPower

Using Simulation to Improve Reactor Design and Operation

Designing a new, next generation nuclear reactor like the traveling wave reactor (TWR) isn’t easy. Our work is a massive undertaking and requires significant and extensive innovative thinking. That’s why we’ve taken a whole-system approach to designing the TWR, to ensure that it works and works well.

Operating a complicated, first of a kind TWR nuclear plant demands a proactive approach to understanding the interplay between design and operations. Our first phase system-level simulator represents a significant, exciting step forward in our path to constructing the prototype TWR. This impressive piece of technology puts us in the control room of a virtual TWR, allowing us an in-depth study of the reactor’s operation from start-up to full power.

TerraPower's first phase system-level simulator in operation.
TerraPower’s first phase system-level simulator in operation.

“Systems” in a nuclear reactor refer to the various components that comprise the total design; for simplicity’s sake, they are often broken into categories. For example: the “Nuclear Island” system includes the reactor core, safety measures and steam generation mechanisms; the “Balance of Plant” system includes operational and maintenance buildings, turbines and the plant’s electrical system. With the simulator as a design tool, we’re able to study the detailed response of the TWR’s actual design parameters for individual systems to ensure its safety and efficiency. Our phase one simulator examines eight systems important for the operation of the prototype TWR.

For the TWR, such a simulator had to be developed essentially from scratch. Working with AD Technology of Taiwan, we paired RELAP5, a widely used modeling tool developed at Idaho National Laboratory, with TerraPower’s in-house neutronics capabilities. This allows us to model the plant’s nuclear and thermal response to changes in operating conditions. Everything from control rod positions to turbine speed is incorporated in this first phase modeling effort, helping us understand the operational aspects of our present design. This type of modeling also provides us the opportunity to improve the design of particular components and systems and streamline the plant’s response, making life easier for future TWR operators.

But this is only the first step. As you read this post, TerraPower’s engineers are building a whole-system engineering simulator to study the behaviors of all 40+ systems in the TWR. And, in conjunction with Idaho National Laboratory and the University of Tennessee, we are developing advanced control algorithms. Once both of these elements are complete, our simulator will be able to run in parallel with the prototype TWR and provide on-line monitoring of the plant’s status. This will include, for example, providing alarms for out-of-specification conditions, and simulating casualties such as emergency reactor shutdowns and loss of turbines.

Eventually, our engineering simulator will function as both a tool for training and as a means of investigating the anticipated plant response in case of an unusual combination of events. Both provide the necessary foundation for designing and operating a safe and efficient TWR.