The ANTECH G3600 Series of instruments are a range of non-destructive assay machines which operate in line with the ISO 19017 Open Detector methodology for the high resolution assay of waste drums in both 200L (55 US Gallon) and 340L (85 US Gallon) drums. This methodology is optimised for the assay of relatively homogenous drums, both in matrix composition and activity distribution, resulting in a highly efficient drum assay. Drawing the from the ANTECH modular Universal Drum Gamma Design set, the G3600 series of instruments can be easily customised and configured for a range of different installations and applications, and for both low and high activity.
The G3600 series of systems encompass a range of machines for the non-destructive assay of waste drums using the Far Field or Open Detector methodology. The core of all G3600 systems are based around two main sub-assemblies; a Detector Column and a Rotary Platform.
The Detector Column provides a mounting position for the High Purity Germanium (HPGe) detector and its shielding, at the optimum height for the drum when mounted on the rotary platform. For standard applications of 200L (55 US Gallon) and 340L (85 US Gallon), the detector pillar is fixed in a single vertical position. In applications where a range of container types, including non-standard containers, are to be measured, a vertical axis of motion with configurable height positions for different container sizes can be incorporated to ensure the optimum measurement position for all container types. The HPGe detector is mounted in a cylindrical lead shield, at least 50mm (2″) thick, including lead back shields to provide high background shielding for the detector. This ensures only contributions from the drum being measured are analysed, with background subtraction being incorporated in the analysis software.
The detector field of view is optimised using an MCNP designed, fixed steel collimator with a conical-trapezoidal profile to both reduce the effects of background radiation and optimised the field of view of the drum. Through this, the entire sample container is in the field of view of the detector at all times. In front of the collimator, optional filter sets can be automatically deployed, with a range of thicknesses selected to suit the measurement range. When deployed, the tungsten filters cover the detector crystal, to reduce the counts and detector dead time of the system. This, in combination with the optional horizontal motion, allows the G3600 range to be used to measure high activity drums.
The Rotary Platform provides a measuring position for the drum, which is rotated about its axis during to scan to minimise the effect of any radial inhomogeneity. The assembly consists of a Turntable, with centralising rings to allow for easy loading of the drum, mounted on top of a low friction bearing and driveshaft, driven by a low backlash, multi-turn encoded servo motor controlled by the system electronics. 0-degree position sensors, combined with the motor encoding ensure consistent radial start positions for rotation counting. The assembly is mounted on a network of high-precision load cells to provide gross and net mass values for the container, used for density correction of the scan.
The Far Field Gamma Monitor systems operate utilising three software packages;
The Assay System is controlled by the ANTECH GammaScan+ software package, which is used for manual motion control, measurement setup, automated calibration, QA measurements, background measurements etc. ANTECH GammaScan+ is the User Interface package, and automatically communicates and controls the Ortec® GammaVision software suite.
GammaScan+ has been designed in collaboration with customers all over the globe over many years to ensure an intuitive and easy software package to operate and configure. Featuring a customisable language file, the package can easily be displayed in any language for optimum customisation to end user requirement. A hierarchical security access system of User, Supervisor and Administrator, ensures that configurations critical to the analysis cannot be accessed or modified by operators. A traffic-light display system is deployed throughout the software, particularly on the ‘System Status’ screen (as shown below), providing easy visibility to the operator regarding the connectivity status and validity status.
ANTECH GammaScan+ Status Screen
The GammaScan+ assay software is used for total control and operation of the system, including;
GammaScan+ features configurable time-limited validity for both Background and Quality Assurance “measurement control” measurements, to ensure the highest accuracy results possible. Each Sample Measurement is saved in a unique file directory, with all raw data and copies of calibration, background and configuration files to allow for remote off-line analysis at any time in the future, maintaining the parameters and calibrations used in the actual measurement.
For higher activity applications, the G3600 series can incorporate a horizontal axis of motion to move the detector column further from the drum, utilising the 1/r² rule to reduce the signal at the detector. This, in combination with the tungsten filters allow for accurate measurements of high activity drums.
Furthermore, the G3600 series can be integrated with a loading axis of motion, to move the drum turntable away from the sensitive detection electronics, and also can be incorporated with in-feed and out-feed conveyors for batch mode operation. This incorporates a roller-top turntable which integrates with and is parasitically driven by the conveyor, allowing safe operation and loading.
For inhomogeneous/heterogeneous waste, either in matrix composition or activity distribution, it is recommended that a segmented assay technique from the ANTECH G3200 or G3250 series of instruments is utilised, due to the large measurement errors and uncertainties that result from measuring heterogenous waste with the Open Detector/Far Field methodology. ANTECH has produced a Technical Paper, available in the Resources page, detailing the errors found in these measurements (see Ma15b, Measurement Issues with Radioactive Waste Drums Containing Heterogeneous Matrices and Non-Uniform Activity Distributions, Proceedings of INMM15, Indian Wells, CA, USA, July 2015).