UK ABWR executives chart path ahead for Horizon

15 December 2017

Successful completion of the Generic Design Assessment (GDA) process for Hitachi-GE's UK Advanced Boiling Water Reactor (UK ABWR) is a "huge step forward" for Hitachi's UK subsidiary Horizon Nuclear Power, two senior executives said this week.

Hitachi-GE Regulatory Advisor Dave Watson and Horizon Technical Director Mark Lunn spoke to World Nuclear News as the Office for Nuclear Regulation (ONR) and the Environment Agency and Natural Resources Wales announced yesterday they had awarded the UK ABWR a Design Acceptance Confirmation (DAC) and a Statement of Design Acceptability (SoDA).

Lunn said: "It's a huge step forwards for us with the project because it shows an ability to deliver to schedule. The number of the assessment findings that we'd consider to be technically challenging is also significantly lower than what previous GDAs have seen. That shows how mature the ABWR design is and so this will show the market what a good product we have in the ABWR. To achieve a clean DAC with minimal assessment findings is a testament to the quality of the design that we have."

Straight to full DAC

Hitachi-GE is the third company to complete the GDA process, which it began in April 2013. The first reactor design to receive a DAC and SoDA was Areva's European Pressurised Reactor in December 2012. This was followed by the Westinghouse AP1000 in March this year. The Hualong One design that General Nuclear Services - a subsidiary of EDF and China General Nuclear - began the GDA process in January.

Watson highlighted that Hitachi-GE is the only company to date that did not require an interim DAC and interim SoDA stage during the GDA process, thanks to regulatory confidence in the reactor design and the company's approach to its GDA application.

He said: "What a significant achievement it is to have completed GDA and to get the regulatory approvals on schedule and as planned. It's the third reactor to achieve GDA and the first one to have achieved it straight to a full DAC and SoDA, without the interim stage, which demonstrates that the regulator has confidence in the ABWR design for the UK. It brings the reality of a nuclear power plant in the UK one step closer which will create thousands of jobs in north Wales, where it will produce enough electricity for five million homes. It is a huge step for Hitachi globally and also for Wylfa Newydd in particular."

GDA is "clearly the critical milestone" for the UK ABWR this year, Lunn said.

"The next major milestone will be the submission of the development consent order applications. We have already made the EPRSR [environmental permit radioactive substances regulation] application this year. We also have in parallel the Article 37 and Article 41 terminations, which are part of the Euratom Treaty submissions that the government makes to support the DCO [development consent order]," he said.

Watson added: "Delivery of the GDA on top of the completion of the licence application shows really strong progress for the Horizon project, and builds on the fact that these reactors have been successfully delivered before, and this creates a huge opportunity for Anglesey and the wider region in Wales."

Different cultures

The ABWR design is already licensed in Japan and the USA. Four units have been built in Japan, where there more are under construction. Horizon Nuclear Power hopes to build two ABWR units at Wylfa Newydd site on the island of Anglesey in north Wales and start them up in around 2025. The units would be the first commercial boiling water reactors in the UK. Horizon also plans two UK ABWR units for its site in Oldbury, South Gloucestershire.

Watson noted the challenge for Hitachi-GE to adapt from the prescriptive approach to reactor design regulation in Japan to the non-prescriptive approach in the UK.

He said: "Demonstration of ALARP (As Low As Reasonably Practicable) was very challenging. So, Hitachi-GE had to listen, learn and adapt, and receiving the positive GDA result shows that we were successful in doing that. Having the right people in the right roles was important as well; Hitachi has world-class nuclear knowhow and is famous for the quality of its engineering and on-time delivery. UK project management capability and the UK safety case expertise helped guide that Hitachi knowledge and expertise in the right direction."

Hitachi has a reputation for delivery on schedule for ABWRs built in Japan, but the GDA is a tough and rigorous process, he added.

"We had to submit about 6000 documents and there were thousands of questions from the regulator and there were technical meetings. It was about taking the expertise and Hitachi engineering style and adding UK project management and safety experts to help manage this process across different continents and time zones, and also getting input from Horizon on operational experience."

The UK regulatory process is "quite tough", he said, and Hitachi-GE "had to have humility" to understand some weaknesses in how it had needed to change the way it presented information on the reactor design for a UK, rather than Japanese regulator.

On the relationships between Hitachi-GE and Horizon, Lunn said they had been working very closely together since the start of GDA, in particular since the start of Step 3.

"My team have been working very closely and attending all of the GDA meetings with respect to licensing. Initially, helping very much with our knowledge transfer from the Hitachi-GE team to the Horizon team, but also to make sure the licensing experience of my team was able to support and influence GDA discussions. The design team from Hitachi-GE and the Horizon team are fairly well connected and work well together, and we've also looked for a number of Hitachi-GE staff to augment us, particularly in the project management safety case, so the same project managers who delivered the instrumentation and control throughout GDA will deliver that for the site-specific solution," he said.

Regulatory Issues

Hitachi-GE received two Regulatory Issues during the GDA process.

Watson said: "The UK regulation has a tiered approach to questioning. At the lower level, there are Regulatory Queries and we received 1519 of those. At the next level are Regulatory Observations and we had 82. And then, at the highest level, there are Regulatory Issues and we had two - the first related to reactor chemistry and source terms (the radioactivity that's present potentially within the reactor design); and the other one was about the probabilistic safety analysis. These issues were really about how this information was being presented and not about weaknesses in the design. Hitachi had to adapt in how they presented that information. The regulator said that what had been put together originally was not adequate and so Hitachi put together some targeted and specific teams in the UK and Japan, as well as have input from GE-Hitachi in the US, to target those particular topics to understand what the shortfalls were and how they could be addressed."

For example, with the probabilistic safety analysis (PSA), Hitachi-GE had to demonstrate how it calculated risks.

"A modern standard PSA to the best international standards now has to be very wide ranging and include all the operational stages, from operation, shutdowns and outages, and refuelling," Watson said. "It also has to consider normal operations, plus internal hazards, like fire, and external hazards, like seismic events, and to pull together all of that information in a very transparent way, so that the regulator gets the confidence that all these aspects have been considered appropriately. In the original PSA, the regulator felt that transparency was not sufficient or of a wide enough range of events and different scenarios."

Design changes

Asked about the design changes agreed in GDA versus the reference design, Watson stressed that the ABWR is a "well-established Gen III+ reactor that is already in operation".

He said: "It's evolved and will continue to do so. As part of that process, changes had been made to the design, from lessons learned from Fukushima, general international improvements in good practice and standards over time, and then some UK-specific changes.

"The Fukushima changes included additional electrical systems and cooling systems to provide diversity, and the back-up building, which is located in a separate area at elevation on the site. On international standards, for example, there’s been a process since 9/11 for aircraft protection.

"The UK-specific changes were introduced because of a specific regulatory expectation in the UK, relating, for example, to diversity and segregation in the Control & Instrumentation system; to provide clear evidence of that and modifications were made to the C&I system at a very early stage in the GDA. Equally, the approach to protection against hazards -internal barriers against fire; the emergency diesel generators were relocated from inside the reactor building to a separate building outside of the reactor building. Some of the UK-specific changes were introduced at an early stage in the GDA process, so there was some degree of learning from the previous GDAs [on other reactors designs]."


In terms of a project timeline, Lunn noted that Horizon had already made its EPRSR [environmental permit radioactive substances regulation] and Nuclear Site Licence applications and is now preparing its DCO. This will be “our next major application", he said. "The other permits are associated with that; so, we are preparing those as well. We're looking at the end of the first quarter of next year to make those submissions."

The next steps in permits and permissions for the Wylfa Newydd site are, Lunn said, "to go through all of the assessment findings and agree resolution plans of how we plan to resolve those with regulators."

He added: "We've already agreed with the regulators our programme for developing site-specific chapters that aren't in GDA and we'll go through a number of changes and developments to the site-specific PCSR [Pre-Construction Safety Report] to support our construction schedule. At the same time, we made our site licence application. We’re looking at how we maximise value in the PCSR. We're very pleased with the quality of the documentation coming out of GDA; there are 4000 documents that make up a significant element of the site-specific case, along with the Resolution Findings and our site-specific programme, which will enable a very clear scope of work in the project delivery team to follow what we’ve learned in GDA into site-specific delivery, so we have the certainty of delivering to schedule."

On translating the Generic PCSR into a site-specific PCSR, Lunn said: "We've looked at each of chapters in the GDA and graded them into which are unchanged through to the other extreme where, for example, the construction elements, which aren't included in the GDA. We've graded each of the chapters as to how much of PCSR is unchanged and the same with the supporting documents for the safety case and topic reports."

He added: "We're looking at which can be used in their entirety, which don't exist or need to be completely revisited, which are a relatively small amount. The aim is to use the GDA as a corner-stone for the site-specific safety case. An example of a chapter that needs to be established is the operation and maintenance section doesn’t cover the maintenance justification to a very high level. Also, the construction chapter is to a very high level in the GDA than in the PCSR."


Asked about attracting investment to the project, Lunn said the GDA demonstrated that the ABWR is a "mature design".

"Whilst we've modified it for the UK market, it's not first-of-a-kind, but is an nth-of-a-kind, design, which I think gives a lot of assurance that the product is a first- class reactor design that has stood the test of GDA and come out of it very strongly," he said.

Asked about the strike price Horizon would seek to agree with the government for the Wylfa Newydd project, Lunn said: "We are actively developing our project for the lowest strike price that we can, but that's subject to negotiation."

Researched and written
by World Nuclear News