| residence time [`rez·ǝ·dǝns ´tīm] CHEMICAL ENGINEERING The average length of time a particle of reactant spends within a process vessel or in contact with a catalyst. NUCLEONICS The time during which radioactive material remains in the atmosphere following the detonation of a nuclear explosive; it is usually expressed as a half-time, since the time for all material to leave the atmosphere is not well known. |