Uranium Mine Tailings have relatively low concentrations of radioactive materials.

 

These wastes have long half-lives, which means that they will break down faster and thus do not pose such a serious threat as high-level wastes.

 

Uranium mine tailings are composed of radium (which, through radioactive decay, becomes radon), thorium, and small residual amounts of uranium left over from the collection and milling process.

 

(United States Nuclear Regulatory Commission 2015)