Noyade is correct. Well done all.
The atomic powered B-36 was called the NB-36H, so if the XB-60 had actually flown powered by a nuclear reactor, perhaps Convair and the USAF would have designated it XB-60H, as per
con-pilot's thought. According to declassified documents, the project was called X-6.
Ridge Runner was first to identify the powerplant(s).
Noyade has control.