Hitachi-GE's UK reactor enters final assessment stage

Hitachi-GE Nuclear Energy has reached a regulatory milestone in its progress towards deployment of the UK Advanced Boiling Water Reactor, following confirmation that British regulators will move to the final step of the Generic Design Assessment (GDA). The GDA process for the UK ABWR is on schedule for completion by the end of 2017.

Horizon plans to deploy the UK ABWR at two sites - Wylfa Newydd on the Isle of Anglesey and Oldbury-on-Severn in South Gloucestershire. 

The Office for Nuclear Regulation (ONR) announced on 30 October it had completed Step 3 of the GDA process of the design. This stage looked at the safety and security arguments Hitachi-GE presented to underpin the safety and security claims.

Jane Bowie, ONR's Head of GDA said that, throughout Step 3, interactions with Hitachi-GE had been positive. The company had been "responsive and open to constructive challenge and engagement", she said.

The next milestone in the GDA process will be the start of the Environment Agency's and Natural Resources Wales (NRW) consultation on the environmental part of the assessment, which is planned to start in October 2016.

Once the overall assessment is complete, ONR, the Environment Agency and NRW, will use the work to help inform any subsequent assessments for site specific proposals that use this reactor design – such as Horizon Nuclear Power's proposed developments at Wylfa Newydd and Oldbury. Before any site specific development could proceed, the operator would have to secure all relevant permissions for the site including a Nuclear Site Licence and environmental permits.

At the regulators' request Hitachi-GE has set up a comments process that enables people to see and comment on the submissions made to the regulators. This process is open throughout GDA until about four months before final decisions are made about the reactor design.

Rigorous assessment

Ken Sato, general manager for licensing at Hitachi Europe said that reaching Step 4 in around two-and-a-half years is a sign of the strong progress the company had made.

"GDA is rightly a thorough and rigorous assessment - challenging scrutiny from the regulators is to be expected and welcomed. This will continue through Step 4, and we remain focused on providing detailed submissions, and addressing the regulators' questions," Sato said. Hitachi-GE has a team of more than 300 experts working on GDA, he added.

Mark Lunn, engineering director at Horizon Nuclear Power - the eventual owner operator of the UK ABWR - said completion of Step 3 "keeps us firmly on track to start generating in the first half of the 2020s".

In the summary report of Step 3, Richard Savage, acting chief nuclear inspector, said that, during Step 3, there had been "a number of changes affecting the nuclear build landscape". These include a change in the British government, in 2010, "with the intent to push forward nuclear new build"; and increasing confidence in the UK market for new nuclear.

"As a result I continue to take steps to ensure that ONR is ready to respond to what we expect will be a significant growth in the industry. This is vital in continuing to provide confidence to our stakeholders that ONR as the independent safety and security regulator is well positioned to support such growth and innovation, and maintain public trust in our robust regulation," Savage said. "To this end ONR continues to examine options for recruitment, retention and technical support in an increasingly challenging labour market."

Savage noted that it is usual for design modifications to be required when a technology is assessed in a new regulatory environment, adding that "early identification allows them to be addressed swiftly which reduces impacts later on in the overall program".

Savage said he supports the early release of two Regulatory Issues for the UK ABWR, "which is beneficial to Hitachi-GE as Step 4 can be used effectively to address these challenges, which will improve the overall UK ABWR safety case".

In June, ONR and the Environment Agency raised a Regulatory Issue for their concerns about reactor chemistry matters related to the UK ABWR. Hitachi-GE was required to provide a "suitable and sufficient definition and justification for the radioactive source terms in UK ABWR during normal operation".

Then, in July, they asked Hitachi-GE to address a series of "shortfalls" in the probabilistic safety analysis PSA of the design. The request took the form of a Regulatory Issue.

Four-stage process

GDA is the UK nuclear regulators' (ONR and Environment Agency) process for assessing new nuclear power plant designs proposed for construction in the UK. GDA Step 1 is the preparatory phase, and does not involve technical assessment work. It involves the setting up of formal agreements between the regulators and the Requesting Party, and discussions on the requirements for GDA.

GDA Step 2 is an overview of the fundamental acceptability of the reactor design within the nuclear regulatory regime of Great Britain. It aims to identify design or safety shortfalls that could prevent the design from being acceptable for construction in Great Britain. It is focused on understanding the key assertions about the safety of the reactor.

GDA Step 3 progresses the Step 2 work and moves into assessment of the reasoning (safety arguments) supporting the safety claims. For security, the focus is on the arrangements for developing the conceptual security plan.

GDA Step 4 is the detailed assessment phase where regulators analyse the evidence provided to support the safety claims and arguments. At the end of Step 4, they determine whether sufficient evidence has been submitted by the RP to issue a Design Acceptance Confirmation (DAC) by ONR, and a Statement of Design Acceptability (SoDA) by the Environment Agency.

Completion of GDA alone does not enable a reactor design to be constructed on a site within Great Britain, but must be viewed along with nuclear site licensing and eventual regulation of the construction phase.

Following completion of GDA Step 2 for the UK ABWR, in August 2014, ONR published a series of reports summarising its work and concluded that there were no fundamental safety shortfalls that would prevent the UK ABWR from being constructed in Great Britain.

Its report on Step 3 of GDA covers the period from September 2014 to October 2015. The specific objectives of ONR's work during this period were to: improve its knowledge of the design; assess the safety arguments underpinning the fundamental safety claims assessed in Step 2 of GDA; assess security proposals for the UK ABWR; identify significant issues and whether any design changes or safety case changes may be required; identify major issues that may prevent the issue of a DAC/SoDA; and significantly reduce regulatory uncertainty.

ONR said the report is "essentially an interim statement" on the progress of its assessment since starting in 2013.

Researched and written
by World Nuclear News