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UK advances underground nuclear facilities 23 Oct 2013
Peter Kenyon, TunnelTalk
Agreement on key investment terms between the UK Government and French electricity company EDF paves the way for construction of the UK's first nuclear power reactors in nearly two decades.
New nuclear plant will have two pressurised water reactors

New nuclear plant will have two pressurised water reactors

An announcement earlier this week reconfirms the Bouygues/Laing O'Rourke JV as preferred bidder for a £2 billion civil works package and Costain as the delivery and design partner for marine work that includes construction of extensive underground water intake and outfall infrastructure.
The marine package will include two cool water intake tunnels, one for each of the two pressurised water reactors (PWRs) that are planned for construction. These will extend 3.3km into the Bristol Channel and will be 6m in diameter. A shared 7m diameter outfall tunnel will extend 2km from the shoreline. All three tunnels will be excavated by TBM. Construction also comprises a forebay, an underground cooling water pumping station plus two concrete outfall ponds that will link with the shared outfall tunnel.
Hinckley Point C primary structures and tunnels

Hinckley Point C primary structures and tunnels

Planning permission for the £14 billion project is already in place, and this week's agreement between the UK Government and EDF over a wholesale "strike price" ceiling for electricity that will be generated when the reactors come online in 10 years time means that one of the final hurdles for the huge development has been overcome. Agreement is also reached over future decommissioning, and confirmation is made that the project will benefit from the government's Infrastructure Guarantee, under which up to 65% of project costs prior to operations starting will be underwritten by public debt. A final investment decision will be made by EDF in July next year (2014), but the latest agreements and confirmation that a significant Chinese investment of up to 40% of total project cost will be acceptable, paves the way for a final financing deal to be reached.
Hinckley Point C design plans and intake/outfall structures

Hinckley Point C design plans and intake/outfall structures

The strike price agreed is £89.50/MWh to rise in line with the Consumer Price Index, or £93.50 if EDF's plans to construct two new Sizewell C reactors do not go ahead. The current wholesale price is £45/MWh.
Under the current financing structure, spread over 35 years, EDF will be the majority equity partner with a 45-50% stake, AREVA (an international nuclear supply industry company) 10%, and the China General Nuclear Corporation (CGN) and China National Nuclear Corporation (CNNC) 30-40% between them. Discussions are also taking place with a shortlist of other investors who could take an investment stake of up to 15%. EDF has been in an industrial partnership with CNNC and CGN for the last 30 years, including involvement in a joint venture with CGN to build two EPR reactors at Taishan, China.
Current and future nuclear reactor facilities in the UK

Current and future nuclear reactor facilities in the UK

The two EPR type reactors planned for the UK, design for which is already approved by regulators, will be built at Hinckley Point in Somerset. Project scope also includes construction of temporary spent fuel storage facilities. There are also plans that are less well advanced for two identical reactors to be built at the existing nuclear facility at Sizewell (Sizewell C), as well as proposals for similar constructions in the future that would have a "series benefit" from shared design, supply chain and engineering work.
"We are delighted that Costain will play a key role in delivering the secure, low carbon energy the UK needs for the future through our role as a Tier One contractor in the Hinkley Point C project", said Andrew Wyllie, Chief Executive of Costain. "The project will also help ensure Costain can play its part in building the skills of the UK and showcasing them to the world in a way which will help us to compete for other such contracts. We estimate that this contract will lead to the creation of hundreds of new jobs at Costain alone, including apprentices, specialist technical and engineering roles and programme management. We are very much looking forward to working with all our partners in this project to design and deliver a world class power station at Hinkley Point."
Construction of Hinkley Point C will create up to 25,000 jobs, including 400 apprentices, as well as a further 900 jobs once fully operational. Hinckley Point B, which comprises two gas-cooled type reactors, took eight years to build and began its operational life in 1976. It is scheduled for decommissioning in 2023, and since 2006, owing to its age, has been operating at only 70% capacity.
Pressurised water reactor design
In a Pressurised Water Reactor (PWR) like the EPR (European Pressurised Reactor) to be constructed at Hinckley Point, ordinary (light) water is utilised to remove the heat produced inside the reactor core by nuclear fission.
Water pressurised reactor schematic

Water pressurised reactor schematic

This water also slows down (or moderates) neutrons (constituents of atomic nuclei that are released in the nuclear fission process). Slowing down neutrons is necessary to sustain the nuclear chain reaction (neutrons have to be moderated to be able to break down the fissile atom nuclei).
The heat produced inside the reactor core is transferred to the turbine through the steam generators. Only heat is exchanged between the reactor cooling circuit (primary circuit) and the steam circuit used to feed the turbine (secondary circuit).
No exchange of cooling water takes place. The primary water is pumped through the reactor core and the primary side of the steam generators, in four parallel closed loops, by coolant pumps powered by electric motors. Each loop is equipped with a steam generator and a coolant pump. The reactor operating pressure and temperature are such that the cooling water does not evaporate and remains in the liquid state, which increases its cooling effectiveness. A pressuriser connected to one of the coolant loops is used to control the pressure in the primary circuit. Feedwater entering the secondary side of the steam generators absorbs the heat transferred from the primary side and evaporates to produce saturated steam. The steam is dried in the steam generators then delivered to the turbine. After exiting the turbine, the steam is condensed and returns as feedwater to the steam generators. The generator, driven by the turbine, generates electricity.
References
Excavation advances nuclear research - TunnelTalk, May 2013
Move to bury Yucca nuclear waste repository - TunnelTalk, March 2010
Short sighted Yucca Mountain shutdown - TunnelTalk, June 2011

           

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