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
Another fine and dry day with long sunny spells.
Welsh acts Jamie Miller and Into The Ark have made it to the final of ITV's The Voice UK.
Mind Cymru is calling for specialist mother and baby units to be reinstated in Wales.