MEASUREMENTS OF LOW RADIOACTIVE CONTAMINATIONS IN LEAD USING BOLOMETRIC DETECTORS

Bolometric detectors made with samples of crystalline and polycrystall ine lead have been operated to measure their internal radioactivity du e to Pb-210. It has been found that contaminations of hundreds of becq uerels per kilogram are present in commercial low radioactivity lead a nd that these contaminations can be reduced by an order of magnitude b y crystallisation. A low activity of a few hundreds of millibecquerels per kilogram still persists in specially prepared low radioactivity l ead. No evidence for contamination is on the contrary found in a 2000 year old lead sample from a sunk Roman ship, at a level of less than 2 0 millibecquerel per kilogram.