NASA, in cooperation with the DOE, is moving ahead with technology testing under NASA's Surface Nuclear Power program. This is intended to produce a relatively small, low-maintenance, durable, and safe fission reactor to power a lunar base. NASA Glenn Research Center engineers are using a Stirling engine generating electricity from the heat provided by a liquid metal working fluid, which will be heated by the fission reactor.
COMMENT: Long-term space exploration, especially human exploration, doesn't work without nuclear energy. Some form of fission or (eventually) fusion reactors must provide stable power where solar energy is insufficient (that is, for any sizable base or spacecraft on Mars or beyond) or unreliable (lunar darkness lasts two weeks, and Martian dust storms are nasty). I understand concerns about nuclear power, but this isn't the 1960s. Our ability to build, launch, and operate nuclear systems safely has advanced enormously, and we have to deal with the fact that there just isn't an equivalent source of power for these kinds of missions.
THANKS TO Larry Klaes for sending this link via the fpspace email group.