There are trace amounts, but not in the quantities seen after the 1900s. It's like the radio got turned from 1 or 2 to 10. it's actually part of radiocarbon dating. It's why they can't accurately date things near blast sites, or near other areas with high radioactivity, like coal ash dump sites. Microcracks and such will not matter. they're testing the paint itself. they also test from several points. typically all 4 corners. if the paint is legit, a dust level of contamination can be seen. But if the paint itself is fake, it shows up easily. It's actually one of the interesting things about the Shroud of Tourin. We know for a fact that it's old based on written accounts. But when they test it, the radioactivity counts are off the charts. Some blame it on a fire it was in and survived. But based on the levels that exist, that doesn't account for what we see in it. It's very fascinating.