SPECIAL REPORT | WATER WORLD
Water balance for new build nuclear
Arrangements around water supplies and discharges are critical for the UK’s next planned EPR at Sizewell which is being built in Suffolk, an area described as water stressed
AT THE END OF MARCH a water discharge permit was granted by the UK’s Environment Agency for the planned new EPR at Sizewell C (along with two others covering radiological discharges and the operation of power generators). The consent is required in addition to the development consent granted by the Secretary of State in July last year and approvals for the reactor design granted by the Office for Nuclear Regulation (ONR). Planning for water supply and discharge at the site have
Janet Wood
Expert author on energy issues
proved to be a complex challenge for the project company, NNB Generation Company (Sizewell C) Limited (NNB), both for the huge volumes of cooling water required during the site operation, but also for the much smaller volumes of potable water required during operation and for the water required during construction. The Sizewell C (SZC) site is adjacent to that of the operating plant at Sizewell B on the Suffolk coast, which gives ready access to cooling water – albeit the eventual arrangements may have marked differences from both Sizewell B and from the EPR now under construction at Hinkley Point in Somerset. But the Suffolk region in the eastern UK is an area defined by the Environment Agency as under ‘water stress’, so there is little access to fresh water supplies on land to meet the site’s short- and long-term needs and questions remain over securing the water supply in the long-term.
Cooling water The twin 1630 MWe reactors planned for Sizewell C will be direct-cooled. Each of the units will have its own dedicated
cooling water intake tunnel 3-3.5km offshore. Seawater will then be abstracted from the Greater Sizewell Bay in the North Sea via the two dedicated intake heads and tunnels, one for each reactor, around 500m apart. In its operational phase, the plant will require a continuous supply of cooling water at a rate of 132 m3
per
second at the mid-tide level of seawater. Flow rates will vary between 125 and 140m3
/s. The cooling water (waste stream
A) represents approximately 99% by volume of the total overall daily discharges of non-radioactive effluent from SZC. The maximum daily discharge volume of cooling water would be approximately 11.4 million m³. During standard operation, cooling water would be returned to the Greater Sizewell Bay at a maximum temperature of 11.6°C above the ambient seawater temperature, having passed through the steam turbine condensers. The outfalls also include six much smaller waste streams. The water discharge activity permit includes 19 pre-
operational conditions which need Environment Agency approval before the proposed power station can be commissioned or begin to operate. Many of them arise because of the lengthy design process and construction period associated with Sizewell C, which means aspects of the detailed design are evolving. Contaminants are of course of particular concern and
the Environment Agency (EA) requires a priority hazardous substances management plan before hot functional testing begins. It must show how the operator intends phase out discharging priority hazardous substances,
Above: Sizewell C has been granted a water discharge permit 16 | May 2023 |
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