This paper deals with the determination of location, time and quantity of the release of heavy metals in a pilot-scale grate system by means of short-lived radioactive isotopes during the incineration of municipal waste. The isotopes Zn-69m (half life: 13.8 hours) and Cu-64 (half life: 12.7 hours) were used to represent heavy metals which can be released relatively well and more difficultly, respectively. Due to the implementation of isotopes which emit gamma rays, all measured values could be acquired without direct contact and without the need to take samples. The location of release was determined by means of NaI(Tl)-scintillation detectors positioned alongside the outer walls of the grate. The time and the quantity of the release were measured with a detector located in a special absorption vessel for the purification of a partial flow of the exhaust gases.