Short answers, pulled from the story.
NERVA was a US Nuclear thermal rocket engine project that ran from 1956 to 1973. The program aimed to develop nuclear-powered upper stages for intercontinental ballistic missiles and later for space exploration missions.
The Armed Forces Special Weapons Project allocated $100 million over three years in March 1956 for feasibility studies and test facility construction. This funding marked the official start of the NERVA nuclear thermal rocket engine project timeline.
Work commenced on test facilities at Jackass Flats mid-1957 requiring all materials shipped from Las Vegas. Test Cell A featured concrete walls thick enough to protect electronic instrumentation from radiation produced by reactors.
Administration decided cancel anyway the 5th of January 1973 when NASA announced termination. Nixon spent just $29 million of allocated funds despite Congress supporting NERVA again 1972 bipartisan coalition headed by Smith and Cannon appropriated $100 million for small engine fitting inside shuttle cargo bay estimated costing about $250 million over decade.
Shorter flight duration estimated three to four months compared eight to nine months using chemical engines reduced crew exposure harmful cosmic rays. Engine studied March 2013 at Marshall Space Flight Center focusing on nuclear thermal rocket engines allowing quicker transfer times increasing cargo capacity.