WylfaThe nuclear emergency at Fukushima Japan, brought about by the earthquake and tsunami has risen questions about the safety of nuclear plants throughout the world.
Here on Anglesey we have Wylfa A, which is programmed to be shut down and decommissioned from next year. So what lessons can we learn from the accident from Japan, and how safe is Wylfa A?
The first thing to note they are of a different design, the nuclear plants at Fukushima being boiled water reactors (BWR), whereas the two reactors at Wylfa A are gas cooled reactors (GCR).
Wylfa A was the last Magnox nuclear power plant to be built in this country and is the largest of its type. The reactors themselves operate at relatively low pressure in comparison with modern reactors. The reactor is cooled by C02, and are designed that should the pumping systems fail the reactors would still be kept cool (after shut down) by natural circualtion of the C02. As the coolant is already a gas, explosive pressure buildup from boiling is not a risk, as happened in the catastrophic steam explosion at the Chernobyl accident.
The main reason the Magnox design were abandoned was cost and the fact that they only operate at 28% efficiency.
The reactor fuel is unenriched uranium, which is encased in the alloy magnox (hence name for design) that is a mixture of magnesium and aluminium. Because of the low burn up rate of the fuel, on load refuelling was considered essential, as the cost of shutting down the reactor to refuel would have made them uneconomical.
In Fukshima we know that initially the emergency shut down of the reactors was going well and that the control rods had been inserted succesfully. What failed were the cooling systems required to remove the residual heat, at Wylfa A even in the event of the pumps failing cooling would still take place by natural circulation of C02.
The other major and potential greatest danger at Fukushima was the loss of water from the spent fuel ponds. As these ponds are outside the primary containment building, any fire or melting of the rods would have resulted in the radiation being realised directly into the atmosphere.
The system for storing spent fuel rods at Wylfa A are completely different in that they are kept in dry store cells, also cooled by carbon dioxide.
Here on Anglesey we have Wylfa A, which is programmed to be shut down and decommissioned from next year. So what lessons can we learn from the accident from Japan, and how safe is Wylfa A?
The first thing to note they are of a different design, the nuclear plants at Fukushima being boiled water reactors (BWR), whereas the two reactors at Wylfa A are gas cooled reactors (GCR).
Wylfa A was the last Magnox nuclear power plant to be built in this country and is the largest of its type. The reactors themselves operate at relatively low pressure in comparison with modern reactors. The reactor is cooled by C02, and are designed that should the pumping systems fail the reactors would still be kept cool (after shut down) by natural circualtion of the C02. As the coolant is already a gas, explosive pressure buildup from boiling is not a risk, as happened in the catastrophic steam explosion at the Chernobyl accident.
The main reason the Magnox design were abandoned was cost and the fact that they only operate at 28% efficiency.
The reactor fuel is unenriched uranium, which is encased in the alloy magnox (hence name for design) that is a mixture of magnesium and aluminium. Because of the low burn up rate of the fuel, on load refuelling was considered essential, as the cost of shutting down the reactor to refuel would have made them uneconomical.
In Fukshima we know that initially the emergency shut down of the reactors was going well and that the control rods had been inserted succesfully. What failed were the cooling systems required to remove the residual heat, at Wylfa A even in the event of the pumps failing cooling would still take place by natural circulation of C02.
The other major and potential greatest danger at Fukushima was the loss of water from the spent fuel ponds. As these ponds are outside the primary containment building, any fire or melting of the rods would have resulted in the radiation being realised directly into the atmosphere.
The system for storing spent fuel rods at Wylfa A are completely different in that they are kept in dry store cells, also cooled by carbon dioxide.
