In February 2025, a team led by the University of Surrey discovered an oblate spheroid nucleus for one of this element’s isotopes. For 10 points each:
[10m] Name this element whose 208-isotope is molten and mixed with bismuth as a neutron moderator material. That isotope of this element has a doubly magic nucleus and ends the thorium and actinium decay series.
ANSWER: lead [or Pb; accept lead-208 or Pb-208]
[10e] Lead-bismuth mixtures are also used as coolants in the fast type of these devices. Elevated temperatures in these devices can generate steam voids, which resulted in a meltdown of its RMBK type at Chernobyl.
ANSWER: nuclear reactor [or fission reactor; accept fast breeders; prompt on nuclear power plant or fission power plant]
[10h] A drawback of using bismuth-209 is that it can spontaneously undergo this process then beta-minus decay to form alpha-emitting polonium-210. A sensitive elemental analysis technique uses energy-dispersive XRS to induce this process.
ANSWER: neutron activation [accept neutron activation analysis or NAA; accept neutron capture or neutron absorption; prompt on activation or capture or absorption]
<Oxford A/Columbia C, Chemistry>