In 1967 two Magnox reactors producing 626 megawatts (MW) in total (enough electricity on a typical day to serve an urban area twice the size of Bristol) opened at Oldbury on the south bank of the river Severn.
The power station was due to cease operation in 2008, with decommissioning due to begin in 2009. An announcement on 18 December 2008 by the UK Nuclear Decommissioning Authority stated that the station will continue to operate for another two years. (Wikipedia - 2009 September 21st)
The sounds in this video were created by playing various ambient sounds of traffic and wind noise through tuned delay lines and comb filters with feedback. Some of the film was shot on a recent trip to the Forest of Dean, particularly the shots of the powerstation from the severn bridge.
An album (titled "Oldbury magnox powerstation") featuring many more slow moving ambient pieces like this is soon to be released on http://www.zenpho.co.uk