Spokesperson for #Russia Exterior Maria Zakharova in an official statement named the substance in question. They claim that Ukraine is smuggling the radioactive material “Californium-252” into Transnistria
This is purely a trope for the poorly educated Russian audiences. Total world reserves of Californium-252 are estimated at 10 grams globally by 2022. Price per 1 g can reach $250 million. A container would be enough to buy all of Moldova
Californium was chosen for its American sounding name
While preparing this official statement Zakharova probably googled for radioactive materials in general and chose the meanest, scariest sounding name for the average Ivan. Had there been an element called Americanium, she’d have chosen that for sure