Isotope 07 : Any of two or more forms of an element having the same atomic number and similar chemical properties but differing in mass number and radioactive behavior
NFPA 801 Standard for Fire Protection for Facilities Handling Radioactive Materials, 2008 ed. https://www.nfpa.org/Assets/files/AboutTheCodes/80 1/FIF-AAA_ROPagenda_6-11.pdf, (Std: Fr Prac for Faclty Hndlg Radioactive Mtrls - Amer) {348 NFC}