The Lockheed U2 had one of these and the pilots were assured that;-
1 it was only powerful enough to destroy the sensitive bits.
and
2 it had a good long time delay from point of activation to going bang

When Garry Powers found himself in the unfortunate position to have to press the button he declined…….. I think his reasoning went something like “he himself was probably was the sensitive ‘bit’ and in that case they would say there was a good delay”