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UK DM project: radioactivity test results
The table below gives a, b, and g count rates for the principal natural sources of radioactivity, assuming isotopes are present in their `natural' concentrations, and that U and Th chains are in equilibrium. The g activity is separated into that which is `coincident' with a or b (half-lives for g emission from excited states left by a, b decay are typically below 1ns) and `other', resulting from either electron capture or decay of long-lived excited states. A significant proportion of some (usually low energy) nuclear de-excitations proceed by emission of a `conversion electron' rather than a photon; since, in target materials, the former contribute to total background, these are also listed.
|U||1.11 × 103||8.88 × 103||6.60 × 103||155
c.e.: 1.19 × 103
|2.30 × 103
c.e.: 1.68 × 103
|Th||351||2.10 × 103||1.40 × 103||28.5
Units are tru for 1 ppb of source, where: 1 tru = 1 a, b, g per day per kg, and 1 ppb = 1 part per (US) billion by weight, ie a concentration of 10-9;
c.e.: `conversion electrons'.
An Excel spreadsheet which also gives rates for elements at their mean crustal abundances is here.