By the end of the century, over half our electricity will probably be generated by nuclear reactors. As our dependence on atomic energy grows, scientists are becoming increasingly disturbed by the evidence that this technology, created to aid man, may become one of the greatest dangers to his survival. There are two major fears: first, that the constant release of low-level radiation may eventually cause a massive increase in leukaemia and cancer of all kinds; secondly, that a nuclear reactor could ' melt down ' - releasing large amounts of radioactive fall-out, causing certain death to anyone in its path. Without nuclear energy, we may lack the power on which we are increasingly dependent. With it, we may be putting the world at risk. Tonight's programme analyses the danger. Chairman James Burke Narrated by IAN HOLM Written by JOHN LLOYD Producer MICHAEL BLAKSTAD