Radium

²²⁶Ra and ²²⁸Ra can be used for dating materials up to a few thousand years in age because the half-lives of ²²⁶Ra and ²²⁸Ra are 1600 years and 5.75 years, respectively, even though the long-lived ²²⁶Ra is found in nature as a result of its continuous production by the decay of ²³⁸U. For example, long-lived ²²⁶Ra has been used to date a limestone cave in central Switzerland, corals in the Indian Ocean, and Pleistocene gravel terraces [580]. The activity ratio A(²²⁴Ra)/A(²²³Ra) is a potential age calculator for old lake water because the low ²²³Ra and ²²⁴Ra activities in old lake water are relatively unaffected by mixing [579].

²²⁶Ra is used in brachytherapy (Fig. IUPAC.88.1), which is a method of localized treatment of various types of cancer. A sealed implant (such as a rod, seed, or needle) containing the radioactive isotope ²²⁶Ra is inserted into or near a patient’s tumor to apply a high dose of radiation to the tumor. The sealed implant is inserted by a physician or by an automated device (called a remote afterloader), and it is removed from the patient once the tumor is destroyed [75], [581].