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NuScale’s story of simulation

In the News

Nuclear Engineering International Magazine | 12 December 2017

Simulation played a major role in getting the 50MWe NuScale reactor ready for design certification in the United States. Caroline Peachey reports


In March 2017, the US Nuclear Regulatory Commission accepted the design certification application for NuScale Power’s small modular reactor, making it the first modern SMR to begin the licensing process in the West.

NuScale submitted its application to the NRC on 31 December 2016. By accepting the application, the NRC confirmed that NuScale’s submission addresses all US regulatory requirements and contains sufficient technical information for the NRC to carry out its review. NRC is expecting to complete the certification process in 46 months, or by January 2021.

“The uncommon fact that the NRC was able to accept our application during the 60-day docketing review period is validation of all of our hard work over the past eight years,” said NuScale CEO John Hopkins, upon acceptance of the application.

Simulation played a key role in this achievement. NuScale provided technical justification from the simulator to support its design certification application – the first time this approach has been used in the licensing of a US nuclear plant.

Simulation first

When simulator supervisor Ross Snuggerud joined NuScale in 2008, one of his first roles was looking at how many people would be needed to staff the NuScale control room. After reviewing the regulation, Snuggerud managed to convince management that a simulator would be needed to investigate staffing requirements.

Currently, in the United States regulations require a minimum number of operators per reactor and a maximum of two reactors are operated from a single control room. Operating 12 units from a single location was a “quantum leap” from anything the NRC had approved before. However, the attributes of the NuScale design – the passive nature of the safety systems, the fact it doesn’t need safety-related AC or DC power or operator action for design basis events – mean that it is different to operate than today’s conventional reactors.

After a request for proposals, US-based GSE Systems was chosen to develop simulation modules for the NuScale plant. The simulator was to be used in the design certification process, for analysis of the Human-System Interface design, controls system strategy and to develop operating procedures. “Before, simulators were built after the plant to train and license operators,” says Snuggerud. However, NuScale is using the simulator to investigate how the human- system interface will function.

“We are using the simulator to prove to the NRC that our staffing plan is safe and acceptable for the design,” adds Tim Tovar, plant operations manager at NuScale. “We originally talked about getting an exemption. But we worked through the processes with the NRC and it made sense to develop a staffing rule for the customers.”

In January 2016, the NRC described two options that NuScale could consider for addressing the 10 CFR 50.54(m) regulatory requirements related to control room staffing in the design certification application. NuScale decided to propose, as part of the rulemaking, certification of an alternative approach to control room staffing to be used in place of 10 CFR 50.54(m). This would require NuScale to provide the technical basis for rulemaking language that addresses control room staffing and control room configuration as part of the design certification. Any future combined operating license (COL) application that incorporates the NuScale design certification would, as such, not need an exemption from 10 CFR 50.54(m).

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Nuclear Engineering International magazine | 12 December 2017
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