Mission: Impossible - Season 1 Episode 21 : Snowball in Hell 1973

A former prison guard, Sefra, has got hold of a supply of cesium 138, which explodes at temperatures above 70 degrees. Sefra plans to sell the sample and the formula from the closed-down prison base where he once worked. Rollin and Barney go in as a photographer and model respectively, and Sefra ""learns"" that Barney is a former prisoner returning for revenge. The team fakes a generator break down while Sefra beats Barney, and the cesium starts to heat up. Sefra has it taken to a nearby hospital refrigerator, where the IMF makes the switch. When Sefra discovers the missing jar, he forces Barney to show him the escape route which he supposedly used to escape. As Sefra makes his own escape, the IMF send the cesium sample toward him on a remote-controlled mini-tank, and it blows up, killing Sefra and making sure no one gets the formula or the sample.