Theory of operation The vapor core reactor (VCR), also called a gas core reactor (GCR), has been studied for some time. It would have a gas or vapor core composed of uranium tetrafluoride (UF4) with some helium (4He) added to increase the electrical conductivity, the vapor core may also have tiny UF4 droplets in it. It has both terrestrial and space based applications. Since the space concept doesn't necessarily have to be economical in the traditional sense, it allows the enrichment to exceed what would be acceptable for a terrestrial system. It also allows for a higher ratio of UF4 to helium, which in the terrestrial version would be kept just high enough to ensure criticality in order to increase the efficiency of direct conversion. The terrestrial version is designed for a vapor core inlet temperature of about 1,500 K and exit temperature of 2,500 K and a UF4 to helium ratio of around 20% to 60%. It is thought that the outlet temperature could be raised to that of the 8,000 K to 15,000 K range where the exhaust would be a fission-generated non-equilibrium electron gas, which would be of much more importance for a rocket design. A terrestrial version of the VCR's flow schematic can be found in reference 2 and in the summary of non-classical nuclear systems in the second external link. The space based concept would be cut off at the end of the MHD channel.
tHeory of opEratiOn tHE vapor core rEAcToR (vCR), Also CALled a gAs core ReActor (gCR), has Been studied For Some time. iT Would HAVe a gas oR vApOR cOre ComPosED Of urAnium TEtraFluOrIde (uf4) wiTh SoMe hElIum (4he) aDDed TO incReaSe the Electrical coNDuCtivitY, tHe VapoR corE mAy alSo havE TIny uf4 DroPleTs In It. it Has boTh tERreStrIAl and space bAsEd aPPlIcaTions. sincE the SpaCe CoNCept doesn't necessarily Have to be economical in tHE TraditiONAl senSe, iT alloWS the ENricHment tO exceed whAt wOulD be acCeptable for A Terrestrial sysTem. It also alLows fOr a higHEr ratiO of uf4 to HeliuM, which IN tHE terReSTrIal versIon would BE kept JusT HIGh enouGh To eNsURe crItiCaLIty iN OrdER tO INcrease THe effiCIency Of direct cOnvErSion. THE teRResTrial versiOn is desIgNed For a vaPor corE Inlet teMpeRatUre OF aboUT 1,500 K aND exit tempERaturE oF 2,500 K anD a uf4 to HEliuM raTio Of ArouNd 20% tO 60%. IT is thoUgHt THAT the outleT temPErAtUrE cOUld bE raised to tHAt of tHe 8000 k to 15,000 K range where the exHaust woUlD be A fissiOn-GenerAteD NoN-EquiliBriuM elEcTRon gas, whiCh woULd be of MuCh moRE iMportaNce fOr A ROcket desiGN. a terrEsTrIAl verSion of tHE vCr's flOw scHEmAtiC Can be Found iN refErenCe 2 aND iN The SumMary Of noN-clAsSICaL nucLEAr systeMs in the sEConD external lInk. the Space bAsed concept woULd be cut oFf at tHe enD of ThE MhD cHanNEl.