Assertion: cosmic ray's source | /r/HasProperty | radioactive material
Facets:
Source sentences:
text: If the source of the ionizing radiation is a radioactive material or a nuclear process such as fission or fusion, there is particle radiation to consider.
text: A common source of ionizing radiation is radioactive materials that emit α, β, or γ radiation, consisting of helium nuclei, electrons or positrons, and photons, respectively.