The on-site monitoring technique for carborne radioactive waste container

This paper presents an on-site monitoring technique for carborne radioactive waste container, including theoretic model and efficiency calibration method. Three portable HPGe detectors are used to scan three surfaces of the carborne waste container. And then the weighted average is performed to get the average specific activity of the interested nuclides. The experiments which turned out the necessity of scanning three surfaces successfully were completed with uniform and non-uniform volumetric sources on the ideal condition. When the measurement time is 1000 s, the MDAs of ²⁴¹Am, ¹³⁷Cs, ⁶⁰Co and ¹⁵²Eu are 170 Bq/kg, 1 Bq/kg , 1 Bq/kg and 5 Bq/kg, respectively. And the uncertainty is less than 40%(1σ) for ²⁴¹Am, 35%(1σ) for ¹³⁷Cs,⁶⁰Co and ¹⁵²Eu. Compared with the other techniques, transmission source device and collimators are not required, and the assay time is shorter. However, the limitations of this technique are that measurement results are not radionuclide activity for every voxel but specific activity for the whole container, and that it is difficult to measure for the low energy gamma emitters (e.g. ²⁴¹Am) in the waste with high density matrix based on gamma-assay method. (authors)