No, Europa has a negligible atmosphere, so there won't be a re-entry burn. Sterilizing the probe will be one of the biggest challenges. (Earth) life is very hardy and has traveled with Apollo to the Moon and back (on the outside of the craft).
I also very much doubt a probe, even if it leaks, would damage the environment much, only very locally. Europa should have a vast ocean and Uranium doesn't dissolve that quickly. The oceans of Europa might contain some uranium already, just like Earth's ocean at 3 parts per billion (or 10^13 kg (2 × 10^13 lb) total). That's 10 with 13 zeroes.