‘Unfortunately, this process of nuclear fission produces a lot of by-products which are known collectively by a name which has a sinister connotation these days: radioactivity. Certainly, radioactivity has a lot of nasty things in it that have got to be controlled and kept well away from human beings, except in areas of medicine, which I’ll come on to later. You’ve got neutron particles, which aren’t going to do you a whole lot of good coming through you at twenty-five thousand miles a second; there’s Cobalt 60 and Iodine 131, Krypton 85, Strontium 90, Plutonium 239, with alpha rays, beta rays, gamma rays – none of which are going to do you any good. Alpha rays are damaging if breathed in, gamma rays and beta rays do damage if they hit human tissue.

‘A lot of them have a short life-span – we measure their life-spans in what we call half-life. That means the length of time it takes for a radioactive substance to lose half its strength. Some have a very short half-life – a matter of seconds only – but others, such as Krypton, have long half-lives – Krypton’s is nine and a half years, Strontium 90 is twenty-eight years, and Plutonium 239 is twenty-four thousand three hundred years – so we have to take a great many precautions to make sure mankind is shielded from this radioactivity, and is going to remain shielded for ever.

‘The first stage is the reactor core itself. The containment wall around that is two-metre-thick reinforced concrete; it is dome-shaped for maximum structural strength, and it will withstand very great stress. In tests on this type of dome, a simulation of a fully laden jumbo jet crashing into it at six hundred miles an hour was done – and the aircraft lost the fight. It didn’t even make a noticeable dent.

‘But even in the event of the containment dome being fractured, we have a fall-back here at Huntspill Head. The containment is connected to a second building, with the same internal capacity, which is kept permanently as a vacuum. If there were any crack in the core containment, a series of valves between the two buildings would automatically open, and all the steam would be sucked straight through.’ His eyes were running from the glare of the lights, his throat was parched, and he badly wanted to scratch his balls.

‘Apart from all the security which all of you have witnessed on coming to this station, there is a great deal more hidden security here as well. The entire station is monitored by no less than three completely separate computers. If at any stage the three do not tally, they are all programmed to automatically start shut-down procedures until the reason for the difference is known and corrected.’