NEUTRON DETECTION | INSTRUMENTATION AND CONTROL
Neutron detection made easy for SMRs
With a huge variety of different SMR designs on the drawing board the supply chain is taking the initiative to keep costs to a minimum. Reuter-Stokes talks to NEI about its phased approach to design and qualification
THE EMERGENCE OF SMALL MODULAR reactor (SMR) sector is prompting capacity ramp ups across the supply chain as well as new designs for key equipment areas such as neutron detection. Reuter-Stokes, which has been designing and manufacturing neutron detection devices since the 1950s, is embracing these new opportunities. Rod Martinez, Reuter-Stokes Vice President, says: “in 1986 we became the OEM manufacturer of neutron sensors for boiling water reactors. Since then, we’ve been making neutron detectors for BWRs and PWRs and our company has expanded to not only provide neutron detection but auxiliary equipment. We’ve made the sensors that these companies need. With the emergence of SMR we’re helping these companies that are new names in the industry to design sensors too.” Reuter-Stokes has already made market in-roads,
recently signing a contract with NuScale to design and manufacture unique neutron detectors for the company’s SMR design. Although currently the NuScale’s is the only SMR with design approval from the U.S. Nuclear Regulatory Commission, Reuter-Stokes is clear in its ambition to become the go-to supplier for neutron detectors right across the SMR industry by leveraging the company’s experience. Daniel Schreiner, Nuclear Product Manager, for Reuter-Stokes, explains: “From a Reuter-Stokes perspective we want to work right across the sector. Our detectors are essentially reactor technology agnostic. They can work with any kind of reactor, just as long as it generates neutrons.”
The first NuScale project to use the detectors, which
are being developed in partnership with Paragon Energy Solutions, will be the Carbon Free Power Project (CFPP) in Idaho Falls, Idaho, which will see the first VOYGR SMR power plant installed. It is scheduled to begin generating power in 2029. Reuter-Stokes’ detector assemblies will be responsible for monitoring the fission rate while Paragon will develop the signal processing electronics and also the associated reactor protection system. “Our partnership with Paragon, where customers can realise our combined offering of detection technology and control system technology is unique,” says Martinez.
Detector decisions For neutron detection, the major difference between large- scale boiling water reactors and pressurized water reactors (BWRs and PWRs) is the physical location of the neutron detector. That location drives the geometry and the size. “For the boiling water reactor fleet our detectors are
located inside the nuclear core right next to the fuel bundles. Since they’re very close to the fissioning fuel the detectors can be quite small. On a pressurized water reactor our detectors are located outside of the nuclear core, maybe one or two meters away so they see significantly less neutron flux. Therefore, the neutron detectors are substantially larger and could be up to, say, 40 inches (100 cm),” says Schreiner. For small modular reactors, companies are developing
reactors based on both PWR and, less frequently, BWR technologies. “While the majority of the market is going the PWR route there are some boiling water reactors currently being designed,” says Martinez, adding: “Just about everything else is a pressurised water reactor, such as NuScale, Holtech and Rolls Royce but there’s also some others that are being developed. While they’re well understood and have been theoretically worked on for decades we’re getting to the point where we’re going to construct new fourth generation plants like high-temperature gas reactors or liquid metal reactors so there’s quite a bit of variation out there. Every one has their own pros and cons.” As Schreiner observes: “We would love to make just
Above: A local power range monitoring (LPRM) system measures neutron flux
a generic detector that worked for everyone but what we’re seeing is that the different SMR developers are different enough that we are going to have to develop bespoke detector designs for each developer. A NuScale reactor detector design is not going to work for an X-Energy reactor detector design and so on. Each one of these reactors is different and is going to require a little U
www.neimagazine.com | February 2023 | 19
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