Sigh... said it before, but most fourth generation designs including the one the US killed by John Kerry's ignorance burn nuclear waste as fuel. Russia continued, and their once through versions like the BN-600 burn 80% of their nuclear fuel and would burn nearly 100% if they used continuous reprocessing, but that is considered a proliferation risk. 80% - vs
In any case, one of the primary reasons nuclear experimentation was killed off was that it was corrupt and in the pocket of reactor owners - from the NRC site itself:
AEC to NRC
By 1974, the AEC's regulatory programs had come under such strong attack that Congress decided to abolish the agency. Supporters and critics of nuclear power agreed that the promotional and regulatory duties of the AEC should be assigned to different agencies. The Energy Reorganization Act of 1974 created the Nuclear Regulatory Commission; it began operations on January 19, 1975.
The NRC (like the AEC before it) focused its attention on several broad issues that were essential to protecting public health and safety.
The NRC rubber stamps everything too, so not much has changed.