In any future war, electricity-generating power stations are likely to be primary targets of attack, because their destruction could paralyse the whole war effort of a country. The trend towards ever larger power stations, arising from economy of scale, makes each such station a highly attractive target. These installations will no doubt be strongly defended, but the greatly improved performance of modern missiles - in terms of (even non-nuclear) explosive power, range, payload and accuracy - ensures a high degree of success in such attacks. All this applies especially to nuclear power stations which contain reactors of very high output - sometimes two or more in one station - and which may provide a significant proportion of the energy needs of a country. Putting them out of action could have a devastating effect on the economy, particularly in countries which plan to obtain most of their electricity from nuclear reactors, quite apart from the huge material loss, since reactors represent a very large concentration of capital investment.
There may be another important reason for making a nuclear power station a primary target, namely the release into the biosphere of an immense quantity of radioactivity. Such a release, with the consequent contamination of a large area and the panic that this would cause among the population, might indeed be the main purpose of the attack.