Critical mass is the minimum mass of a fissionable material (235U or 239Pu) that will initiate an uncontrolled chain reaction as in an atomic bomb. The critical mass of pure 239Pu is about 4.5 kg, and of 235U about 15 kg.
Generalic, Eni. "Critical mass." Croatian-English Chemistry Dictionary & Glossary. 29 June 2022. KTF-Split. {Date of access}. <https://glossary.periodni.com>.
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