The likelihood of the plant at Sellafield blowing up, while on the lower end of the scale, is not zero. Any engineer, technician or specialist who pretends the risk is zero is telling lies. He or she will be aware from his or her training that there is no such thing as absolute safety. An evaluation of the risk is, therefore, essential. The first factor to consider in undertaking such an evaluation is that the potential scale of the damage were something to go wrong is enormous. Moreover, in order to believe the risk is minimal, one must also believe, in the light of the likely scale of damage, that the probability of something going wrong is extremely low.