Russia has one of the largest nuclear arsenals in the world, and Russian President Vladimir Putin and those in his inner circle have threatened to use nuclear weapons if Russian territory is threatened. Similar comments have been made before, but many experts are looking at these threats differently in light of the so-called referendums taking place across four regions of Ukraine.Cheryl Rofer worked for more than 30 years as a nuclear scientist at Los Alamos National Laboratory. Now, she writes about national security and about the war in Ukraine. She’ll explain what kind of nuclear weapons Russia has, and what it would mean if Putin decides to use them.Questions? Comments? Ideas? Email us at thedecibel@globeandmail.com