Degrade would be a better word. In other words, break down organic material into simpler molecules and use them as a source of respiration, releasing radioactiv

Degrade would be a better word. In other words, break down organic material into simpler molecules and use them as a source of respiration, releasing radioactive carbon as CO2 and, potentially, radioactive isotopes as compounds that are gaseous or water soluble. This is the normal action of fungi.