Editing Protactinium (section)

==Preparation==
[[File:Uraninite-39029.jpg|thumb|right|upright|Protactinium occurs in [[uraninite]] ores.]]
Before the advent of nuclear reactors, protactinium was separated for scientific experiments from uranium ores. Since reactors have become more common, it is mostly produced as an intermediate product of [[nuclear fission]] in [[thorium fuel cycle]] reactors as an intermediate in the production of the fissile <sup>233</sup>U:

:<chem>^{232}_{90}Th + ^{1}_{0}n -> ^{233}_{90}Th ->[\beta^-][22.3\ \ce{min}] ^{233}_{91}Pa ->[\beta^-][26.967\ \ce{d}] ^{233}_{92}U.</chem>

The isotope <sup>231</sup>Pa can be prepared by irradiating <sup>230</sup>Th with [[Neutron temperature#Cold (slow) neutrons | slow neutrons]], converting it to the beta-decaying <sup>231</sup>Th; or, by irradiating <sup>232</sup>Th with fast neutrons, generating <sup>231</sup>Th and 2 neutrons.

Protactinium metal can be prepared by reduction of its [[fluoride]] with [[calcium]],<ref name="exp">{{cite journal|last1=Marples|first1=J. A. C.|title=On the thermal expansion of protactinium metal|journal=[[Acta Crystallographica]]|volume=18|pages=815–817|date=1965|doi=10.1107/S0365110X65001871|issue=4|bibcode=1965AcCry..18..815M }}</ref> [[lithium]], or [[barium]] at a temperature of 1300–1400&nbsp;°C.<ref name="super" /><ref name="pao2" />