WM2200 Series Segmented Assay System
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Features
- Complete quantitative gamma analysis for fission products or TRU (alpha) radionuclides.
- Modular design permits system to be optimized for customer's measurement application.
- Non-Destructive Assay Software (NDA-2000) provides extensive setup analysis, calibration, and QA capabilities
- PLC based electromechanical control system.
- Many optional capabilities available including:
- Automatic weighing system.
- Surface dose rate measurement.
- Inline Automated Conveyor System.
Introduction
CANBERRA's WM2200 Segmented Assay System is designed to perform accurate quantitative assays on gamma emitting nuclides found in fission product, activation product, and Transuranic (TRU) waste. With the optional ASTM algorithms it is also designed for use in safeguards applications. The system provides very accurate assays through the use of a collimated high purity germanium detector. The container is divided into a number of vertical segments and the activity is quantified in each vertical segment using matrix correction techniques which calculate the average matrix density for each segment.
The system is designed to assay drums with volumes up to 320 L (85 gal) and weights up to 900 kg (2000 lb) in its standard configuration. Optional configurations have been provided for larger or heavier containers.
The standard system is designed to assay radionuclides such as 60Co or 137Cs with drum activities ranging from approximately 100 nCi up to approximately 20 mCi. For transuranic waste the system is optimized for assaying drums containing 0.1 gram up to 1000 grams of 235U or 239Pu. Detector size and collimation can be used to modify the dynamic range of the system.
The following sections describe the system hardware and software as well as the typical system performance.
Description
The waste assay system utilizes CANBERRA's modular mechanism design. This design provides the flexibility to easily add features such as transmission correction or to upgrade from a manual to an automatic system. This design can also be adapted for a variety of container sizes and weights.
Model 2442 Mechanism
The mechanism is a modular design and consists of one or more of the following modules: 2442 detector vertical drive module, 2442R-24 turntable rotation module or optional inline conveyor rotator, 2442T transmission vertical drive module, 2442S single transmission source shield and shutter. These are described in detail on the following page.
The 2442 detector vertical drive unit is a stepper motor driven vertical drive platform which will raise and lower the germanium detector, collimator, and optional dose measurement system over a vertical range of 114 cm (45 in.). The unit is designed to handle operational weights up to 680 kg (1500 lb). This permits use of large collimators if necessary when measuring high activity containers. A variety of collimators and detector shields are available. The drive is designed for use with any of the following detector cryostats: horizontal integral, cryolectric, or 7935-7 Big MAC cryostats.
The 2442R is the manual turntable module. This module can be equipped with a variety of turntable sizes depending on the measurement requirements. The turntable module is designed to handle a maximum diameter of 76 cm (30 in.) and weight of 900 kg (2000 lb). The turntable uses a dc motor which can be set up to rotate at speeds from 1 to 10 rpm.
The inline conveyor/rotator (shown in picture) is an optional drum rotator module which can be used to automatically load, assay, and unload drums from infeed and outfeed conveyors.
An optional digital scale can be interfaced into the PLC system to automatically weigh the drum and enter this weight into the application software during the assay. The accuracy of the weighing system is ±1 kg for the manual turntable and ±2 kg for the conveyor/rotator.
Transmission Correction (optional)
If transmission correction is specified, the transmission vertical drive and transmission source shield and shutter must be added to the system. This option is also shown in the picture above. The vertical drive is similar in design to the detector vertical drive.
The transmission source shield and shutter is designed to shield a transmission source with activities up to 370 MBq (10 mCi) to minimize worker radiation exposures.
Model 2445 Control System
The Model 2445 control system is a PLC-based controller with associated contactors, stepper motor controllers, I/O modules, drivers, etc. The PLC utilized is a GE/Fanuc Series 90 PLC. The PLC interfaces to the application software through an RS-485 interface. The flexibility of this design permits it to be easily modified to interface to a customer's process line. The control system is mounted in a locking NEMA 12 enclosure to ensure security, safety, and environmental control.
Detector and Electronics
A high purity germanium detector is used for detection of the gamma emitting nuclides from the drums. The detector provided with the standard WM2200 system is a 30% relative efficiency "P" type coaxial detector with a resolution of 1.9 keV at 1332 keV. The detector is housed in a horizontal integral cryostat. As an option, an electrically cooled detector can be provided. Other detector sizes can be specified to improve low level sensitivity or to improve the high activity performance.
The counting electronics utilizes CANBERRA's high count rate Instrument Control Bus (ICB) NIM electronics. This is necessary to handle the wide dynamic range of activities which are typically found in waste measurements.
Waste Assay Application Software
CANBERRA’s Genie 2000 based Non-Destructive Assay Software (NDA-2000) is used for WM2200 applications. The application software is designed to run under Windows® NT®/2000 and utilizes all of the standard Genie 2000 high resolution gamma spectroscopy techniques. In addition, some of the features included in the software are:
- A high level menu structure for ease of use.
- Multiple matrix correction techniques including:
- Average density.
- Differential peak absorption.
- Transmission correction.
- Extensive QA and measurement control routines.
- Automated calibration routines.
- Archiving capabilities.
- User editable report templates.
- Compliant with NQA2 and ISO9001.
- And much more.
A more detailed description is included in the NDA-2000 spec sheet.
Performance
System performance will depend on actual measurement conditions. Under the following conditions the standard WM2200 waste assay system has an MDA of approximately 0.1 µCi for 137Cs or 0.2 gm for 239Pu:
- Standard 200 L (55 gal) drum.
- Density less than 0.3 gm/cc.
- Background less than 0.02 mR/hr.
- No other significant nuclides present.
- 30 minute assay time.
This sensitivity can be modified by detector size, assay time, and geometry.
The typical dynamic range is five to six orders of magnitude.
The accuracy of the measurement is based on the uniformity of the activity distribution and the density and homogeneity of the waste material. Typical accuracies are ±20% with maximum errors being in the range of 50% for drums with densities up to 1 gm/cc.
Table 1.
| Nuclide | Daughter | Energy (MeV) | LLD (µCi) | LLD (kBq) | LLD (g) |
| 137Cs | 137Ba | 0.662 | 0.1 | 3.7 | |
| 134Cs | 0.796 | 0.1 | 3.7 | ||
| 60Co | 1.173 | 0.1 | 3.7 | ||
| 152Eu | 1.408 | 0.4 | 14.8 | ||
| 235U | 0.185 | 0.2 | 7.4 | 0.1 | |
| 238U | 234mPa | 1.001 | 20.0 | 740.0 | 59.0 |
| 239Pu | 0.414 | 12,000 | 4.4E5 | 0.2 |
Table 2.
Physical Specifications
| MODULE WEIGHTS (approximate) | |
| Detector Drive Module | 550 kg (1200 lb) |
| Detector and Drive Collimator Add | 365 kg (800 lb) |
| Rotator Module | 160 kg (350 lb) |
| Conveyor/Rotator Module | 230 kg (500 lb) |
| Transmission Drive Module | 230 kg (500 lb) |
| FOOTPRINT | |
| Detector Drive Module | 81 cm (32 in.) x 137 cm (54 in.) |
| Rotator Module | 81 cm (32 in.) x 81 cm (32 in.) |
| Transmission Drive Module | 81 cm (32 in.) x 81 cm (32 in.) |
| POWER REQUIREMENTS | |
| Counting Electronics | 15A at 110 V |
| Mechanical System | |
| Manual | 30 A at 110 V |
| Automated | 60 A at 110 V |
Related Systems
- Segmented Can Scanner - Segmented Gamma Assay System (SGS) assay system optimized for waste and scrap materials in containers less than 30 cm in diameter.
- High Activity SGS - SGS assay of Intermediate Level Wastes in 200 liter and larger drums with surface exposure rates in excess of 100 R/hr.
- High Throughput SGS - SGS assay of drums using multiple HPGe detectors for increased throughput.
- Shielded Multi-Detector SGS - Segmented Gamma Analysis system using multiple HPGe detectors and a 4¦µ low background steel shield provides both the accuracy of the SGS analysis and low detection levels.
- Tomographic Gamma Scanner (TGS) - Provides improved accuracy over the standard SGS along with images of the drum contents.
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