Today's scenario is an incident involving the transportation of radioactive materials.
"It's extremely unlikely that an event like this could happen for real" said a spokesman for Magnox.
"However we can't allow ourselves to be complacent and need to be prepare for such eventualities".
More top news
The Royal London One-Day Cup match being played in Cardiff has been abandoned due to a 'dangerous pitch'.
A series of crashes on the A470 have led to traffic disruption
A largely dry and warm afternoon, but a muggy night to come with showery outbreaks.