Isotopes of sodium

Acute neutron radiation exposure (e.g., from a nuclear criticality accident) converts some of the stable 23Na (in the form of Na+ ion) in human blood plasma to 24Na.

22Na is being investigated as an efficient generator of "cold positrons" (antimatter) to produce muons for catalyzing fusion of deuterium.

[8] Sodium-23 relaxation has applications in studying cation-biomolecule interactions, intracellular and extracellular sodium, ion transport in batteries, and quantum information processing.

Since the half-life is short, the 24Na portion of the coolant ceases to be radioactive within a few days after removal from the reactor.

Sodium has been proposed as a casing for a salted bomb, as it would convert to 24Na and produce intense gamma-ray emissions for a few days.