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UK SMR design filings must focus on back-up systems, spent fuel to curb approval costs
Significant UK licencing challenges remain for Small Modular Reactor developers as the lower output capacities of modular-built units will offer limited scope for streamlining the Generic Design Assessment process and new safety mechanisms will require backup systems to meet the current standards, academic experts said.
SMR developers have received increasing support from UK government and industry and as focus turns towards the commerciality of the new plant designs, projects will need to focus on critical design licence requirements to minimise costs.
Design applications will need to concentrate in particular on passive safety systems, spent fuel pool design and emergency planning zones to achieve an efficient Generic Design Assessment (GDA) process, according to academic experts speaking at Nuclear Energy Insider's Small Modular Reactor UK Summit last month.
EDF-Areva's 1.6 GW EPR is thus far the only third-generation reactor to have received a design acceptance confirmation from UK's Office for Nuclear Regulation (ONR).
The GDA took five years to complete, and the ONR charged the developers around GBP35 million ($53.5 million) for the entire process. EDF plans to use this reactor type for its planned 3.2 GW Hinkley point C plant which will be the first nuclear plant in the UK in over 20 years.
UK's GDA timeline for EPR
Source: UK Office for Nuclear Regulation
According to Keith Ardron, Energy Consultant and Senior Research Fellow in the Nuclear Engineering Department at Imperial College London, the smaller size of SMR plants does not significantly increase the licensability of the design.
Ardron is leading a study on the licensability of SMRs in the UK and worked on the GDA for the EPR reactor when he was UK Licensing Manager, Areva NP UK.
The radiological consequences of an accident at SMR plants "are still well above the thresholds at which we could justify perhaps a reduction in the deterministic design requirements which are laid down by our regulators," Ardron said.
"We think these reactors would face the same issues and challenges of the larger reactors," he said.
SMR developers must also take into account the high-level detail and design completeness required by the UK's GDA as this can have a significant impact on the timescale of the assessment process, Ardron warned.
The current detail offered by SMR developers is below the level of detail produced for the EPR assessment, he said.
"We were expected to provide design information at the same level as you would put in in a procurement specification that you send a supplier to purchase equipment... My impression at this stage is the design status of the SMRs is more limited than the larger reactors which have gone through GDA so far, I think that has a potential impact on timescales of GDA."
A key area for the GDA of SMR designs will be the passive cooling concepts which have been built into the plants, as they often do not have active systems to backup this passive safety system.
UK regulations require two nuclear-grade means of performing each safety function and this had a significant impact on the GDA for the EPR and also impacted the GDA for the Westinghouse AP 1000 design, which is yet to be completed, Ardron said.
"The UK requirements tend to drive them into installing extra nuclear grade systems to back up the main line of protection...this I think is going to be a significant challenge for the SMR concepts that we have seen," he said.
The need for more extensive analysis of spent fuel pool vaults could also lead to other design upgrades. Changes to inspection technologies for spent fuel pools were made during the GDA for the EPR, Ardron said.
"We also had to make significant changes to the geometry of the primary cooling system, the huge forgings within the primary system, in order to facilitate, allow access for inspection-- these were big issues," he said.
SMR plants built up of multiple units may require a number of spent fuel wells and Ardron said that, according to the SMR designs, "It’s not completely clear we could get access."
Backed by federal government funding, US firms have been leading proponents of SMR technology.
Oregon based NuScale has said it plans to submit design certification application for its SMR to the US Nuclear Regulatory Commission (NRC) next year ahead of the first US plant by 2023, and believes it could follow up its first US plant with its first UK plant by the mid-2020s.
Industry interest was heightened last month when Westinghouse proposed to partner the UK government in the licensing and deployment of SMR technology, by contributing its conceptual design partnering with UK government and industry to complete, license and deploy the design.
The outcome of SMR design licensing in the US will provide a key indicator for the potential deployment in the UK, experts told attendees at the Small Modular Reactor UK Summit.
Tony Roulston, Lecturer Nuclear Energy at University of Cambridge, said US NRC Design Approval process will be the first real test for SMR technology maturity and this will start in 2016 with NuScale's SMR application.
Issues yet to be fully addressed include the control and monitoring of multiple reactors on one site, instrumentation and control systems for multiple reactors, and the expectation of much smaller Emergency Planning Zones (EPZ) than for larger capacity nuclear power plants, Roulston said.
"The encounter between the deciding team and the regulator, whether it's the US or UK, will throw up quite a lot of light about the prospects of these things," he said.
More scientific evidence needs to be presented on size requirements for EPZs, as the case for smaller emergency planning zones has been made on probability rather than source term (radioactive release) data, he said.
The license application requires significant preparation ahead of its submission. NuScale began work on its NRC design certification pre-application project back in 2008 and expects to submit it in late 2016 after receiving $217 million from the DoE in 2014 towards the design certification application and other commercialization engineering, analysis and testing.
Giorgio Locatelli, Lecturer in infrastructure procurement and management at the University of Leeds, noted the considerable work on EPZs already undertaken by NuScale ahead of its application submission next year.
"It is a discussion that takes a long time and takes money," he said.
Expected global SMR demand by 2035
Source: UK National Nuclear Laboratory's 2014 Small Modular Reactors Feasibility Study. The UK forecast of 7 GW is based on deployment limited to current nuclear licensed sites and limited deployment at government owned sites such as former military zones.
As developers move closer towards the design application phases, service providers such as engineering consultancy Amec Foster Wheeler have been looking at ways to optimise the GDA assessment process.
"We're been talking to a number of potential vendors about undertaking assessment before GDA," Simon Franklin, Head of Licensing and Regulatory Support for Amec Foster Wheeler, said.
Pre-GDA assessment procedures can ensure the completeness of the proposal to speed the early steps pf the GDA process, and this can shave off half a year from the designated six-year timeframe, he said.
By supporting the development of SMR reactors, the UK regulatory authorities could offer a springboard for SMR development globally, Franklin noted.
"The UK is often referred to as having a kitemark for regulatory assessment of reactors," he said.
The UK's safety assessment procedures closely follow International Atomic Energy Agency guidelines and SMR design approvals would provide a strong benchmark for application in new entrant countries around the world, he said.