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
Figures show Wales has the lowest percentage homes estimated to be worth at least £1 million - in the whole of the UK.
All very autumnal today with a mixture of sunshine, showers and fresher feeling temperatures!
Wales Manager Chris Coleman has criticised alleged corruption in football, believing that anyone found guilty should be banned for life.