Nuclear energy can complement tidal
SIR – I would like to support David Dunbar (Letters, November 13) in his view that Britain should exploit the small-scale modular reactor designs that are under development, using thorium as a fuel.
This would be more plentiful and environmentally acceptable than uranium, which is to be used in our future large-scale nuclear plants.
However, I disagree with Mr Dunbar on tidal power. A suitably positioned Severn Barrage could generate about 5 per cent of our electricity. It would last more than 120 years – as opposed to 20 years for wind turbines – and would not present the decommissioning problems of uranium-powered facilities. Tides are also predictable, unlike wind and sun. Liz Eales Swansea SIR – With a tidal range of 15 metres and currents of up to five knots, the Severn is a vast reserve of energy. It is easy, however, to become seduced by the potential of this “free” energy and overlook the estuary’s Achilles’ heel: the very high sediment levels.
The twice-daily ebb and flood of the tide is enough to keep high amounts of sediment in suspension. While suspended, it scours the deep-water channels essential for safe navigation, and limits the deposition of silt to areas where the currents slow naturally.
The estuary has a history of intolerance to developers, responding unpredictably to structural incursions. When Royal Portbury Dock was built in the Seventies, it was thought water depths could be maintained without dredging. The reality is that we have to dredge three million tons of silt each year from within the dock and remove similar quantities from the harbour entrance, where it builds up at a rate of 10cm per week.
Should the Swansea Bay lagoon go ahead, let us see how that performs and then create others incrementally. This way, the effects of lagoons on tidal regimes will be understood more fully, as will the rates of wear on underwater machinery from the highly abrasive silt particles. We will then have the opportunity to live in harmony with the estuary while extracting energy effectively. Jerry Stanford Harbour Master, Port of Bristol