In nuclear energy: radioactive material that emits ionizing radiation, typically in the form of alpha and beta particles, gamma rays or neutron radiation. The following are types of radioactive sources: (1) sealed source is a radioactive source in which the radioactive material is (i) permanently sealed in a capsule or (ii) closely bonded and in a solid form and which is not exempt from regulatory control; (2) unsealed source is a radioactive source in which the radioactive material is neither (i) permanently sealed in a capsule nor (ii) closely bonded and in a solid form [Section 5(ll), Philippine National Nuclear Energy Safety Act of 2025]; also includes any radioactive material released if the radioactive source is leaking or broken, but does not include material encapsulated for disposal, or nuclear material within the nuclear fuel cycles of research and power reactors [ibid.]
