Almost since the first nuclear power plant started generating electricity in the 1950s, critics have pointed out the difficulty of safely disposing of highly radioactive spent fuel. In those days, radiation was among the few carcinogens that were recognized and could be measured easily. Cold-war anxieties amplified public fear of nuclear technologies and radiation. As a result, spent fuel — often referred to as nuclear waste — came to be treated as uniquely hazardous, requiring exceptionally stringent isolation over long timescales.