cesio137

Cesium-137 (Cs-137) is a radioactive isotope of the element cesium (atomic number 55) with a mass number of 137. It is a fission product produced in nuclear reactors and nuclear weapons, commonly appearing in the fallout from nuclear accidents. Cs-137 is typically encountered as sealed sources used in industry and medicine, or as a contaminant in the environment after releases of radioactive material.

Radioactive decay and gamma emission: Cs-137 decays via beta minus emission to metastable barium-137m (Ba-137m), which then promptly decays to the ground state of Ba-137 while emitting a characteristic gamma ray with an energy of about 662 keV. The half-life of Cs-137 is approximately 30 years, making it relatively long‑lived in the environment and requiring long-term containment and monitoring when released.

Production and handling: As a fission product, Cs-137 is generated in nuclear reactors and can be extracted and manufactured into sealed radioactive sources for industrial radiography, moisture-density gauges, and calibration equipment. Due to its gamma emission, Cs-137 sources are shielded and regulated to minimize exposure to workers and the public.

Applications and hazards: In industry, Cs-137 provides a strong gamma beam useful for nondestructive testing, sterilization, and material processing, as well as for instrument calibration. Environmentally, Cs-137 can be absorbed by soils and waters and tends to accumulate in biological systems, posing long-term radiological hazards after contamination. Major incidents such as nuclear accidents have distributed Cs-137 over large areas, necessitating monitoring and remediation efforts. Regulatory controls govern its possession, use, and disposal.