The accidents of TMI-2 and Chernobyl showed the risk of severe accident can not be ignored although its frequency is very low.

• 美国三里岛事故、前苏联切尔诺贝利事故表明尽管核电厂发电严重事故的频率极低，由于其后果相当严重，仍然不能忽视它的风险。