Speakers
Description
The Waste Management Department (SEGRR) in the Nuclear and Energy Research Institute (IPEN), São Paulo, Brazil, is responsible for managing radioactive waste produced in its facilities and also in the southeastern region of Brazil. Among those wastes are the compactable solid waste, stored in 200-liter drums at IPEN interim storage site. It is estimated that the content of 256 of those drums had reached their clearance potential, being able to be discarded. The drums were catalogued among one thousand more by Dellamano. From the data gathered then, it is possible to calculate the present activity and compare it to ANSN 3.01 Standard, which establishes the maximum activity for solid radioactive waste clearance.
Each one of the 256 drums needs to be analysed by gamma spectrometry, confirming or denying its clearance potential. At the same time, this analysis has the objective to update the data collected due to measuring errors or inaccurate information input at the time the old library of stored drums was digitized.
The main instrument for this procedure is a liquid nitrogen-cooled high-purity germanium (HPGe) detector, with 16,384 channels, ranging from 0 to 2050 keV, approximately. The process is run by the Genie 2000 software, paired with its auxiliary calibration software, Geometry Composer. The software uses Monte Carlo method to calculate the efficiency under the curves of the number of counts per energy in a graphic. The calibration requires the modelling of the spatial disposition of the radiation source in reference to the detector, as well as the radiation source shape, material constitution and mass.
So far, some analysed drums show low radiation levels, while some have shown still high Cesium-137 or Radium-226 activity. There is also inconsistency in the mass of some drums, due to imprecision in old measurements. Data is continuously updated as this work proceeds.