The Multi-Module Challenge:
As NuScale Power moves forward, we typically find ourselves talking about the NuScale Power Module in terms of size, simplicity, reliability, cost and constructability. While all of these are important areas where we have made major advancements, one area where we are leaping ahead is in our control room and simulator design. Here, I’d like to highlight some of the industry-leading work we are doing in digital Instrumentation and Controls (I&C), Human Factors Engineering (HFE) and Human Systems Interface (HSI).
The typical NuScale Power SMR power plant employs 12 NuScale Power Modules at 50 MW each, powering steam turbine generators that produce the electricity. In contrast, a conventional nuclear plant today has a single large reactor. So one of many major differences with NuScale is a configuration with multiple, smaller power modules producing the steam. This means we needed to optimize the number of control room staff needed to monitor up to 12 operating units simultaneously.
A Deep-Rooted Issue:
Reactor operator controls and challenges are long-standing and personal issues for me. In 1979, I was a young staff at the U.S. Nuclear Regulatory Commission. I became one among a five-person team asked to gather information for a Department of Justice investigation into the accident at Three Mile Island (TMI). As part of that effort, I had to review the TMI operator log books.
"Today, what may be the most surprising thing is that control rooms in nuclear power plants have changed very little in nearly 40 years"
What have stayed with me throughout my career were the enormous challenges the operators faced. The control room has hundreds of lights, dials, meters and controls. As the accident progressed, the operators were trying to understand and respond to more than 100 alarms and annunciators simultaneously. At one point, they were trying to do all of this while wearing breathing apparatus. The result was an impossibly complex and stressful environment for decision making.
Today, what may be the most surprising thing is, that control rooms in nuclear power plants have changed very little in nearly 40 years.
The Progress-Adoption Disconnect:
There have been major advancements in nuclear energy plant design, including communications, centralized plant diagnostic computers, control room simulators, HFE and HSI studies, and the ability to monitor and automate processes and procedures. The Human System Simulation Laboratory (HSSL) at the Idaho National Laboratory is a complete virtual nuclear control room created specifically to test how human factors engineering informs intuitive control room design. We see examples every day in other settings, from our smart phones to the dashboards in our cars. One key finding reflected in the NuScale simulator is digital displays that condense information from several gauges into visual, at-a-glance overviews of what is happening.
Still, control rooms at today’s nuclear generating stations bear a striking resemblance to TMI. Duke Energy, for example, has made a number of technology upgrades to their Oconee Nuclear Station in Seneca, South Carolina. Some upgrades, including reactor protection systems, engineered safeguards, main turbine controls, control rod drives and the plant’s main generator voltage regulation, were among the first moves “from paper to electrons” in reactor control systems.
But most of the processors and capabilities are hidden behind panels which look pretty much the same as before, except for a few extra digital readouts and indicator lights.
An attempt at designing a control room or simulator for the NuScale plant in an analog world would be impossible. It is the remarkable simplicity and robustness of the NuScale Power Module design that makes this digital I&C solution particularly safe and elegant. In addition, USNRC regulatory requirements for digital instrumentation and controls called for new approaches to improve safety as well as reactor operator effectiveness.
The heart of our solution is the Highly Integrated Protection System (HIPS) platform. The HIPS platform is a logic based platform that does not utilize software or microprocessors for operation. It is composed of logic implementation using discrete components and field programmable gate array technology. HIPS is based on the fundamental design principles of independence, redundancy, predictability and repeatability, diversity, and defense-in-depth. It was developed to provide a simple and reliable solution for nuclear power plant safety-related and important-to-safety applications.
The NuScale Power control room simulator design takes full advantage of today’s technologies, including large screen displays, soft controls, online computerized procedures, advanced alarm processing and presentation techniques, computerized operator support systems and decision aids.
Empowering the Operators of Tomorrow:
The reactor operators who will run future NuScale power plants are 13 year-old today. Ask any parent and they will tell you that our young people are growing up with a very different relationship with digital technology. As a result, they take in information and process it in different ways. At a recent NuScale family day, I was amazed at how easily the kids could “click along” with the Senior Reactor Operator at the simulator panel.
Young and future operators look at traditional analog displays and they see just a number, with no context. A temperature or pressure reading with no instant recognition of whether it is rising or falling and what that says about the state of the plant. Is the number good or bad? How do we know?
When visitors come to our simulator facility in Corvallis, they see first-hand the impact and power of easily recognizable trending information on the configurable displays. The central displays show the major indicators for 14 performance characteristics of all 12 operating reactors. Chevrons show the direction of the trend and the brightness shows the rate of the trend. The number now has context to enable rapid and confident decision making by the operator.
Bringing Ideas and Insights to Reality:
One of the most satisfying parts of my work with NuScale continues to be taking visitors around our prototype facilities. It never gets old seeing seasoned executives and operators reach that “aha moment.” They watch a simulation of a Fukushima-like scenario and they see how the NuScale Power Modules behave. They see the richness and clarity of information available to operators. They see a 12 reactor plant achieve safe shutdown with absolutely no operator action, no AC or DC power, and no additional water needed.
They see all of this unfold, knowing full well what they expect to see. They ask a few challenging and informed questions. Then the room goes quiet. The faces all register the same thought. “Oh my gosh.”
And it happens every time. As a nuclear engineer, that’s pretty cool.