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
Wales have qualified for the Euro 2016 quarter finals after beating Northern Ireland 1-0 in Paris.
A rally has been held in Cardiff following the EU referendum to show support to migrant communities.
It's 0-0 at half time in Paris as Wales face Northern Ireland in the last 16 of Euro 2016.