Lead may form as a degradation product from uranium. Various isotopes of lead may emit alpha particles for some time. High emission of alpha particles may damage electronics made with lead solder.
Lead
Uranium Source
Lead Isotope Source
lead-204
uranium-238
lead-206
lead-210
lead-207
uranium-235
lead-208
thorium-232
Lead-210 degrades to lead-206 via intermediary isotopes.
Degradation of lead-210
half-life
Particle Emitted
lead-210
22.3 years
beta
bismuth-210
5 days
beta
polonium-210
138 days
alpha
lead 206
stable
none
For electronic circuits alpha particles must be less than 0.01 alpha particles per hour per square cm (cph/cm^2), with levels less than 0.002 cph/cm^2 required for the most demanding products.
Naturally occurring lead emits alpha particles in the range of 1 to 30 cph/cm^2.
After lead has been mined and cast, it takes time for alpha emission to drop to a levels suitable for high-level electronics. The alpha emission of a lead can be measured by taking slices of the lead and measuring alpha particle emissions.
Pure lead-206 is associated with very low alpha emissions (“low alpha”) and is more valuable than freshly mined lead. This makes lead ingots that are greater than 120 years old relatively valuable. The older the lead the more valuable it is.
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