PUR-1 goes fully digital

14 November 2019

At Purdue University in Indiana, Reactor Number One (PUR-1) has been licensed by the US Nuclear Regulatory Commission as the first entirely digital nuclear reactor instrumentation and control system in the USA.

TRADITIONAL ANALOGUE CONSOLES IMPEDE THE accurate and rapid acquisition of research data, while a digital system allows values to be measured instantly. This allows more data to be processed and analysed, making possible capabilities such as predictive analytics, machine learning and artificial intelligence.

Digital technology also allows reactor facilities to identify performance interruptions which may occur before the scheduled maintenance time, making them safer and extending their lifetime. Moreover, replacing digital components is far less expensive than analogue parts, and they are more commercially available.

The upgraded reactor and facility, originally built in 1962 (see box), paves the way for widespread implementation of digital technology in research and industry reactors. PUR-1 supervisor Clive Townsend says modern control technology in the nuclear sector “will allow for big data applications and increased reliability”. He adds: “We’re going from the vacuum tubes and hand-soldered wires of the 1960s, to LEDs, ethernet cables and advanced electronics.”

PUR-1 now has digital capabilities that make possible preventive maintenance, a longer lifespan and big-data applications. It provides a platform for research in a wider range of fields, from understanding how heavy metals affect mental health, to identifying the origins of 1000-year-old artifacts or even predicting how well pilots will fly new planes.

The digital conversion of PUR-1 began in 2012, when the US Department of Energy awarded Purdue a grant to replace the instrumentation and control system with a state-of-the- art version through its Nuclear Energy University Program. Purdue developed and built the fully digital system in collaboration with Mirion Technologies and Curtiss-Wright Corp. PUR-1 now includes a 150-square-foot video wall, which enhances data display and engages prospective nuclear engineering students.

“The reactor’s use in recent years had shifted from fundamental reactor physics research to serving primarily as an educational support facility,” says Seungjin Kim, head of the School of Nuclear Engineering at Purdue. “Now, we can return to that impactful research while also significantly expanding the reactor’s teaching capabilities.”

Mung Chiang, the John A Edwardson dean of Purdue’s College of Engineering says the upgraded reactor is a milestone for Purdue’s School of Nuclear Engineering: “The research and teaching enabled by the new PUR-1 will also contribute to the next chapter of nuclear energy, safety and security in the country”.

Licensing approach

NRC licensing of the PUR-1 system is unprecedented in that some of the parts are certified under the German Nuclear Safety Standards Commission (Kerntechnischer Ausschuss or KTA), rather than under domestic standards.

Previously NRC accepted only parts certified under domestic standards, which are generally too expensive to use. Townsend says it accepted the parts in PUR-1 “through the agency’s initiative for a risk-informed and performance- based regulatory process”. He adds, “The fact that the NRC is accepting a digital console for a small research reactor, with parts certified under the KTA standards, signals the regulatory body moving toward approval in a large industry reactor”.

As a cyberphysical test bed, PUR-1 can now offer benefits to industry as well as in education. Collaborators and corporate partners will be able to evaluate simulations of industry reactors using Purdue’s facility as a model. They can apply lessons learned and best-practice improvements to their own reactors. According to Robert Bean, PUR-1 facility director and an assistant professor of nuclear engineering at Purdue, “Testing code and simulations in smaller university facilities allows more flexibility, ease of access and quicker development cycles than would be available at larger industrial partners. At low cost, researchers will be able to quickly evaluate their work and achieve full-scale deployment.”

PUR-I can now send live data to remote locations, helping researchers to match reactor status to their experimental results in real time, and allowing students to see from their monitors how a reactor responds. “We can send signals to areas, such as schools in developing countries, that do not have the luxury of their own nuclear reactor facility and the associated educational infrastructure. As long as they have internet and this partnership with Purdue, they can see and study how the reactor works,” says Kim.

Playing catch-up?

The USA lags behind Japan, France, China, South Korea, Russia and the UK in the use of digital I&C systems for its reactors, largely because very few new reactors have been built in the USA since the 1970s. In Japan, the first fully digitalised I&C system was integrated into the advanced boiling water reactor (ABWR) at Kashiwazaki-Kariwa 6 in 1996, followed by Kashiwazaki-Kariwa 7. France, the UK, South Korea, Sweden and other countries have also implemented digital I&C systems in their nuclear plants.

Framatome’s Teleperm XS digital safety I&C system is in use at China’s Tianwan plant and in 2018 Framatome upgraded I&C at Borssele in the Netherlands. The latter project, which began in 2014, included installation of a new reactor control and limitation system, to monitor the operation of the plant and interfere shut down the reactor safely in case of any deviations.

In February this year, an agreement to jointly participate in overseas nuclear digital I&C projects was signed between Korea Hydro & Nuclear Power (KHNP) and Doosan Heavy Industries & Construction. Both companies were involved in the development of the Korean digital I&C system. Doosan began development of Korean digital I&C in 2001, in cooperation with KHNP and Korean research institutions. The validation and verification process started in 2007 and was completed in 2010. The domestically- developed I&C system is being installed at Shin-Hanul 1&2.

Until recently NRC regulations did not encourage such upgrades. However, NRC has now issued an endorsement of industry guidance on upgrading to digital I&C systems. NRC’s updated regulatory issue summary (RIS) outlines how reactor owners can use “qualitative assessments” to show that digital I&C modifications to safety-related systems will not increase possible system malfunctions due to software or other issues. “Digital I&C shows it can enhance safety, reliability, and efficiency while addressing the issue of obsolescence of analogue components,” Bill Pitesa, chief nuclear officer at the Nuclear Energy Institute, said in 2018. NEI is now setting up information and training workshops among industry and NRC inspectors on digital upgrades to these systems.

US nuclear plant operators may now consider retrofitting digital I&C systems that have been approved by the NRC, and all new nuclear power plants in the USA are being designed with integrated digital I&C systems, according to NRC information.

Duke Energy’s Oconee plant was given a licence in 2010 to replace its 1970s-era analogue reactor protection system and engineered safeguard protection system with new digital systems. It was the first US plant to take this action. Several fuel cycle facilities also use digital technology in their process control and safety control systems.

In 2018, NRC approved the use of Mitsubishi Electric Total Advanced Control (Meltac) Nplus S digital safety system controllers in US plants. Mitsubishi said Meltac is already deployed in 38 nuclear power plants around the world, primarily in Japan and China. Meltac is a control and monitoring system developed from the ground up specifically for nuclear applications. It was built around a common controller for safety- and non-safety-related plant control functions.

Mitsubishi claims the system has operated for more than 30 million hours with no plant trips due to software or hardware failures. Meltac-N has been utilised in non-safety applications since 2001 and for safety critical control applications since 2009.

According to an equipment qualification summary document available on the NRC’s website, to gain NRC acceptance, equipment must demonstrate that it is capable of successfully performing its intended safety functions after exposure to all normal and abnormal environmental stressors. Performance under new atmospheric conditions, radiation exposure, seismic disruption and electromagnetic and radio frequency interference had to be evaluated.

Mitsubishi intends to promote the Mektac Nplus S controller as a solution for ageing and obsolete analogue or digital controllers in the US market. The platform is suitable for system applications in reactor protection, engineered safety features actuation, reactor control, control rod drive mechanism control, digital rod position indication, turbine protection, turbine electro-hydraulic governor control, nuclear instrumentation, in-core instrumentation and radiation monitoring.

To offset climate change, the nuclear energy sector must extend the lifetime of existing nuclear facilities and build new ones. They must follow the example of Purdue University and switch from traditional analogue technology to the latest advances in digital technology, as long advocated by the Nuclear Energy Institute.

Most US nuclear utilities have extended their reactors’ operating lifetimes to 60 years and in some cases 80 years, making the need for digital upgrades even more critical. “If we can’t innovate, we can’t continue to operate,” said Pitesa.

About PUR-1

University Reactor Number 1 (PUR-1) at Indiana’s Purdue University is a pool-type 12kWt materials test reactor that runs at 1kWt.

The reactor was built in 1962 by Lockheed Nuclear Corporation and it is a materials test reactor with plate-type uranium/aluminium fuel. Its primary purpose is to teach Purdue’s nuclear engineering students about the fundamentals of reactor physics and operation. The university also uses the reactor as a neutron source for activation to support the engineering, health science, chemistry, pharmacy, agriculture, biology and nanotechnology departments. There are three full time employees that perform day-to-day operations.

The core is about 2 cubic feet and rests at the bottom of a 17ft deep pool which acts as both moderator and coolant. The maximum thermal flux is 2.1×1010n/cm2·s.

An amendment to its licence authorised Purdue University to upgrade the instrumentation and control systems by replacing them with new digital versions that include the neutron flux monitoring system and detectors (fission chamber, compensated ionisation chamber and two uncompensated ionisation chambers), associated cabling, safety channels, equipment racks and the control console.

Approximately 1500 people visit the facility each year including university students, high school students and the general public. The facility welcomes the public to arrange a tour.

Digital version of core layout
PUR-1 has become the USA’s first all-digital reactor
Purdue’s nuclear reactor now has digital capabilities
New digital instrumental and control panels
New digital instrumental and control panels in the PUR-1 reactor
New digital instrumental and control panels
David Storz, nuclear electronics technician (left) with Clive Townsend, reactor supervisor and assistant lab director
Analogue version of reactor core structure

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