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UK DM project: radioactivity test results

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Count rates for principal natural radioactivity sources

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.

Source parent
decays
a b g coincident
with a
g coincident
with b
other g
U 1.11 103 8.88 103 6.60 103 155
c.e.: 1.19 103
2.30 103
c.e.: 1.68 103
0.1
Th 351 2.10 103 1.40 103 28.5
c.e.: 276
901
c.e.: 844
0
Rb 78 0 78 0 0 0
(87Rb 280 0 280 0 0 0)
Lu 4.5 0 4.5 0 8.6
c.e.: 4.1
0
Sm 10.8 10.8 0 0 0 0
K 2.67 0 2.39 0 0 0.286
La 0.070 0 0.023 0 0.023 0.046
In 0.022 0 0.022 0 0 0

Notes:
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.