프로택티늄

shiny, malleable metal; readily tarnishes in air; α: tetr, a = 0.3929 nm, c = 0.3241 nm, stable from room temp up to 1170°C; β: bcc, a = 0.381 nm, stable from 1170°C–1575°C; first discovered in 1917; enthalpy of fusion 12.34 kJ/mol; can be produced by nuclear reaction 230Th + n → 231Th + γ 231Th → 231Pa, however, Pa is also found in natural sources; t1/2 231Pa is 3.25 × 10+4 years [KIR78] [MER06] [CRC10]

역사In 1913 Fajans and Gohring identified the first isotope of this element, a metastable isotope having a mass 234, Pa-234m, a short-lived member of uranium-238 decay series. They named it brevium. In 1918, two independent groups, namely Hahn and Meitner and Soddy, Cranston, and Fleck simultaneously identified a longer-lived isotope Pa-231, a member of the uranium-235 decay series. The isotope Pa-234 in its ground state was discovered by Hahn and Meitner in 1921. The element derived its name from the Greek word protos, which means ‘first.’ Protactinium 231 occurs in the ore pitchblende at about 0.1ppm abundance. Certain ores of pitchblende have a higher abundance of this isotope, about 3ppm. Pa-231 also is found naturally in uranium and radium wastes. No commercial application of protactinium isotopes is known.

용도233Pa as intermediate in production of fissile 233U in thorium breeder reactors.