Determination of ¹³⁷Cs half-life with an ionization chamber

The half-life of ¹³⁷Cs was measured with an ionization chamber by following the decay of 5 sources over a 30 years period between 1983 and 2013. The ratio between the ionization chamber current for the cesium sources and ²²⁶Ra source was used for the half-life calculation. The value found for the ¹³⁷Cs half-life is 10,955.2±10.7 days, where the uncertainty evaluation combines type A and B for one standard deviation. - Highlights: • Decay measurements of ¹³⁷Cs for a period of 30 years. • Uncertainty estimation for measurements of the ionization chamber current. • Fitting procedure for half-life determination. • Comparison of ¹³⁷Cs half-life with the recommended DDEP value and with previous measurements.