Radium-228 () is a radioactive isotope of Radium and a key member of the Thorium Decay Chain. Unlike Radium-226 (which comes from the Uranium-238 chain, also known as the Uranium Decay Series), Radium-228 has a relatively short half-life of 5.75 years.
Radium-228 decays via beta-minus emission into Actinium-228 (). Because it is a beta emitter, it does not pose a major external hazard in small quantities, but its decay chain quickly leads to high-energy gamma emitters like Thallium-208.
In the oil and gas industry, Radium-228 is a critical component of Naturally Occurring Radioactive Material (NORM). It is often co-mingled with Radium-226 in produced water. In thorium-rich geological environments, Radium-228 can become the dominant contributor to radioactive scale buildup in separators and piping.
Because its half-life is 5.75 years, Radium-228 concentrations in industrial scale can reach secular equilibrium with its parent Thorium-232 over the life of a well. Managing this isotope requires specific laboratory analysis as its beta emissions are harder to detect in the field than the gamma emissions of its progeny.