Twenty-five years after the Chernobyl disaster, the Fukushima catastrophe once again brings into sharp focus the risks imposed on all of humanity by certain technologies. An earthquake, followed by a tsunami, triggered a major international crisis, arousing fears of an unprecedented technological disaster. The nuclear explosion ultimately did not take place, and the worst seems to have been avoided. But significant quantities of radioactive material, iodine 131 and caesium 137 in particular, were released into the atmosphere by three of the six reactors that partially melted. Moreover, large quantities of seawater that had served to cool down the reactors were