What is the half-life of the Cobalt-57 isotope used in XRF devices?

The half-life of the Cobalt-57 isotope, which is utilized in X-ray fluorescence (XRF) devices for measuring lead and other heavy metals, is approximately 271.8 days, which translates to about 9 months. This property is essential for understanding how long the isotope remains active and effective for measurements before it decays to half its original activity. XRF devices benefit from this relatively short half-life because it allows for more controlled and accurate measurements over time, ensuring the readings are consistent and relevant for assessing lead exposure or contamination.

While other options suggest different durations, they do not align with the scientifically established half-life of Cobalt-57. A half-life shorter than 9 months would not suffice for the applications in which Cobalt-57 is typically employed, as the isotope needs to provide reliable readings over a reasonable period without significant loss of activity. Conversely, a longer half-life would mean that it remains active longer than necessary for typical assessments in environments like homes or schools where quick results are often preferred.