What are the preventative measures that countries now take since the Chernobyl accident?

Answer 1

The main thing to realise is that the Russian RBMK design reactor has only been built in Russia and former Soviet Bloc countries, so the lessons learned are not on the whole applicable. I know that various design changes were made and incorporated in reactors of that type which were still operating subsequent to Chernobyl, but it is still not a design that would be built in the future. The main lesson in general terms is to consider very carefully any experiment to be carried out on a reactor, to make sure the procedure is written up carefully and thoroughly, to make sure the operators understand what is going to be done, and to have a team standing by to advise the operators as it is carried out.

Needless to say, the overriding of safety systems which was part of the reason for the Chernobyl failure must not be allowed. I know for a fact that this would not be allowed in the UK, but of course can't vouch for every country that uses nuclear power. This is one of the unknowns- in countries where the rule of law is somewhat flexible and liable to be broken by over powerful politicians, one can't have full confidence that scientist's advice will always be listened to.

As far as other reactor designs go, certainly Chernobyl would have caused scientists and engineers to think through their safety analysis again, but I doubt if anything positive came out. Diversity of safety shutdown systems for instance was already part of the AGR design and not added after Chernobyl. For the PWR design in the US and elsewhere it was the Three Mile Island incident in 1979 that made people sit up and realise that some aspects of the design needed strengthening, rather than the Chernobyl experience.