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
Drizzle gives way to more substantial rain which will push in to western areas during the second half of tonight!
Geraint 'Busker' Jones, from Llandysul, has been entertaining the crowds since the 1960s.
Wales will not bid for the 2026 Commonwealth Games. Ken Skates said the Welsh Government had concluded it is not in a position to do so.