A Designers View of Nuclear Energy - Department of Materials ...

Nuclear Safety PhilosophyIn the real world things can go wrong:• Three Mile Island - minor leak withconfusing signals led to core beinguncovered and major damage but littleexternal radiation;• Chernobyl - prompt criticality followed bya core fire in 1986 – major externalradiation in Ukraine and across Europe.Safety Strategies:1. Preclude the event/accident by design;2. Provide defence in depth to ensure theeffects are protected, contained, orminimised;3. Independent evaluation of all design andoperating practices.Developed world safety approach:• Design base events which are always protected with asignificant margin of safety;• Large scale events rendered very unlikely by:o providing defence in depth/multiple barriers torelease;o including features and best practise in the design toextent that is As Low As Reasonably Practicable.Frequencypa10 -4Area ofacceptance ofdesign10 -7Complete Protection withhigh degree of certaintyLarger releases - bydesign made mostunlikelyALARP – best practice iscontinually being challengedProbabilisticsafety targetRelease10