<prompt> Half-life of radium is:14 day27 day1626 years5.25 yr  <response>: Ans: C 1626 years Ref: Grainger Allison Radiology 6th118; Harrison 17th1360; Dutta Gynaecology 5th484, 4th465 ; Merdith Radiation Physics Nuclear Medicine28T12 of Ra-226 : 1626 years 1602yr- Harrison 17th1369; 1620- Dutta Gynaecology 5th484; 1622- Merdith Radiation physics nuclear medicine28. On various internet sites T12 of Ra-226 range from 1599-1626Table 223-1Harrison: Internal Contaminant Radionuclides: Properties and TreatmentIsotope NameSymbolRadiation Type t 12 Radiologic t 12 Biologic, daysCobaltCo-60b, g 5.26 y 9.5RadiumRa-226a, b, g 1602 g 16,400Table : Merdith Radiation phvsics nuclear medicine28RaysRadioactive elementst 12 bP-32Sr-90Y-90PhosphorousStrontiumYttrium14.3 days28 years2.54 daysb, gRa-226Au-198I -131RadiumGoldIodine mainly b1622 years2.7 days8 daysgIr-192Co-60Cs-137Xe-133I-123I-132Tc-99Ga-70Tl-201Rn-222Cr-51K-81SeIridiumCobaltCesiumXenonIodineIodineTechnitiumGallium citrateThallous chlorideRadonChromiumKryptonSelenium74.5 days5.2years30 years5.2 days13 hours2.3 hours6 hours3.2 days3.1 days3-6 daysN, gCf- 252Ta-182CaliforniumTantalum2.6 years4 months 