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
After a chilly start it will be a blustery day with some decent sunny spells for most and isolated, locally heavy, showers.
Mosques from across Wales are taking part in an open day today. Their aim is to let the public discover more about the Islamic faith.
Wales second-row Alun-Wyn Jones believes his side are in "an exciting place" as they target a post-World Cup Six Nations title.