Underground radioactivity measurements of meteorites: Development of methods suitable to determine precise...

The L6 chondritic meteorite, HaH-346, fell in Libya. However, neither the exact date of the fall nor the exact size of the original meteoroid or asteroid is known. A specimen of the meteorite, weighing 488 g, was measured using ultra low-background gamma-ray spectrometry in the 225 m deep underground facility HADES. Activation products ²²Na, ²⁶Al, ⁶⁰Co, ⁵⁷Co, ⁵⁴Mn and ⁴⁴Ti were detected. The detection efficiency was determined by 3D scanning the meteorite and introducing this in the computer model of the detector and sample implemented in the MCNP6.2 Monte Carlo code. The activities of ²²Na and ²⁶Al support the hypothesis that the fall took place on 26 August 2018. Furthermore, the ⁶⁰Co and ²⁶Al activities indicate that the original radius of meteoroid was between 50 and 80 cm, which suggests the mass prior to atmospheric entry was between 2400 and 7300 kg.