Energy Secretary Edward Davey said the announcement was "a vote of confidence" in the Government's energy policy.
He told BBC Radio 4's Today programme:
This will show that international investors looking at our energy policy have a huge amount of confidence in it.
This will provide energy for 14 million homes, it will provide huge jobs, and I think it will put the UK in a fantastic position for exporting nuclear expertise.
What has been pushing up people's energy bills in recent years has been the increasing price of global gas.
We are having to import far more gas now as the gas in the North Sea declines in volume. That is very expensive.
Part of our whole energy policy is to diversify - a more balanced approach - so we are not over-dependent on one fuel supply.