The half-life of ^235^U is hundreds of millions of years so it is not a concern. However, it will literally become a nuke if too much (a few liters or 60 kg) get too close together.

The half-life of plutonium-239 is tens of thousands of years so only a thousandth will get a chance to hurt Theodore over his lifetime. However, it is probably chemically toxic so it might cause non-radiation poisoning.

Radium-225 will decay in days, and will quickly go through 7 more radioactive reactions, both alpha and beta, before becoming essentially stable bismuth. It is the worst by far.