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Protactinium also has two nuclear isomers, 217m Pa (half-life 1.2 milliseconds) and 234m Pa (half-life 1.16 minutes). [ 34 ] The primary decay mode for the most stable isotope 231 Pa and lighter ( 211 Pa to 231 Pa) is alpha decay , producing isotopes of actinium .
Protactinium-231 is the longest-lived isotope of protactinium, with a half-life of 32,760 years. In nature, it is found in trace amounts as part of the actinium series , which starts with the primordial isotope uranium-235 ; the equilibrium concentration in uranium ore is 46.55 231 Pa per million 235 U.
They planned to separate and store protactinium-233, so it could decay to uranium-233 without being destroyed by neutron capture in the reactor. With a half-life of 27 days, 2 months of storage would assure that 75% of the 233 Pa decays to 233 U fuel. The protactinium removal step is not required per se for a LFTR.
Thorium-233 decays into protactinium-233 through beta decay. Protactinium-233 has a half-life of 27 days and beta decays into uranium-233; some proposed molten salt reactor designs attempt to physically isolate the protactinium from further neutron capture before beta decay can occur, to maintain the neutron economy (if it misses the 233 U ...
5f 2 6d 1 7s 2: Electrons per shell: 2, 8, 18, 32, 20, 9, 2 ... Spectral lines of protactinium: Other properties; Natural occurrence: ... Decay; abundance half-life ...
Although thorium-232 mainly decays by alpha decay, it also undergoes spontaneous fission 1.1 × 10 −9 % of the time. [3] In addition, it is capable of cluster decay , splitting into ytterbium-182 , neon-24 , and neon-26 ; the upper limit for the branching ratio of this decay mode is 2.78 × 10 −10 %.
More modern designs propose to use a lower specific power or a separate thorium breeding blanket. This dilutes the protactinium to such an extent that few protactinium atoms absorb a second neutron or, via a (n, 2n) reaction (in which an incident neutron is not absorbed but instead knocks a neutron out of the nucleus), generate 232 U. Because 232
The thorium fuel cycle has several potential advantages over a uranium fuel cycle, including thorium's greater abundance, superior physical and nuclear properties, reduced plutonium and actinide production, [1] and better resistance to nuclear weapons proliferation when used in a traditional light water reactor [1] [2] though not in a molten ...