$46.$ Plutonium$-239$ is producedas basic raw materialby neutron irradiation of IT$*$by neutron irradiation of thoriumartificiallyin high capacity furnaces$\mathrm{.}47.$ Pressurised water reactor isdesignedfor boiling pi water in the coreto use liquid sodium metal as coolantto use intermediate coolantto prevent the water coolant from boiling in the coreto eliminate the coolant loop of the pressurised water$\mathrm{.}48.$ Reactors designed for propulsion applications are designed fornatural uraniumenriched uraniumpure uraniumany type of uraniumnone of the above$\mathrm{.}49.$ Reactors for propulsion applications usenatural uraniummolten leadany form of uraniumthoriumplutonium$\mathrm{.}50.$ Reflector in nuclear plants is used toreturn the neutrons back into the coreshield the radioactivity completelycheck polllutionconserve energyis not used.