This follows on from what Mark Whitby said at the talk on Friday, particularly about the Fuel in the ponds.

A fire from spent fuel stored at a U.S. nuclear power plant could have catastrophic consequences, according to new simulations of such an event. A major fire “could dwarf the horrific consequences of the Fukushima accident,” says Edwin Lyman, a physicist at the Union of Concerned Scientists, a nonprofit in Washington, D.C. “We’re talking about trillion-dollar consequences,” says Frank von Hippel, a nuclear security expert at Princeton University, who teamed with Princeton’s Michael Schoeppner on the modeling exercise. The revelations come on the heels of a report last week from the U.S. National Academies of Sciences, Engineering, and Medicine on the aftermath of the 11 March 2011 earthquake and tsunami in northern Japan. The report details how a spent fuel fire at the Fukushima Daiichi Nuclear Power Plant that was crippled by the twin disasters could have released far more radioactivity into the environment.

Further detail can be found here:

 

At present we do not know what fuel will be used at Sizewell C/D however if it is high burn up or MOX, we have been told it would need to be kept in the pond for a longer period than that of SZB (which was a minimum of 5years).

There have been grave concerns since the Weightman report about the safety/security of ponds and the cooling water and it has been pointed out
by some that it is their Achilles heel. Mark Whitby made it quite clear that the loss of cooling water at Fukushimas 4th reactor which was in shut down at the time and therefore had all the reactor fuel within the pond meant it was in serious trouble after the eartquake and following tsunami. In Marks' words there could have been a disastrous fire, luckily a drone was able to confirm the low water level and water was immediately diverted to the site.
We also had a situation with A station when the pond there leaked and was only discovered by chance. We were given lots of reassurances, but their
alarm system did not work and only by chance was the potential disaster managed. It took a year and a half to prise out the real story .