Monte Carlo simulation of an HPGe detector for detection of 239 Pu in waste assay system

• Published in: Applied radiation and isotopes 2019-10, Vol.152, p.127
• Main Authors: Pavan Narayanam, Sujatha, Manohari, M, Ramar, R, Subramanian, V, Mathiyarasu, R, Srinivas, C V, Baskaran, R
• Format: Article
• Language: English
• ISSN: 1872-9800
• DOI: 10.1016/j.apradiso.2019.07.003

This paper discusses the modeling of HPGe detector used in waste assay system using Monte Carlo code FLUKA to determine its detection limits. The modeled detector is validated using experimental point sources efficiencies in the energy range 60 keV-2000 keV. The numerical estimation of efficiency values for Pu present inside a 230 L cotton filled waste drum at various locations along the axis of the detector is discussed. Estimation of the minimum detectable activity (MDA) for Pu at these locations in the presence of 1 MBq of Cs/ Co again along the axis of the detector is examined. The efficiency of Pu decreases from 6.1 × 10 to 7.5 × 10 cps/Bq as the location of Pu moves away from the detector. MDA of Pu increases as the position of Pu and Cs/ Co in the waste drum shifts away from the detector while it decreases as the location of Cs/ CO moves away from Pu along measurement axis. It is observed that for all locations of Cs/ Co with Pu located up to 200 mm from the edge of the drum, the detection limit is within 140.3 mg (allowed limit).