Chesapeake Nuclear Services, Inc.

- Compton Ratio Analysis for Testing Environmental Radioactivity Software


Chesnuc, in collaboration with Radiation Safety Associated, developed an innovative technology for measuring environmental levels of radioactive contamination. CRATER was designed to support remediation and decommission activities. The system integrates Nal(TI) detectors with specially developed gamma spectral analytical techniques to provide a unique method for screening bulk materials for elevated levels of radioactive materials.


Designed to support large area soil remediation and bulk material scanning projects, CRATER goes far beyond simple rate measurements. With spectral capabilities, it is able to analyze specific gamma energies of interest to enhance detection capability and allows sorting and segregating in varying background levels and material compositions. Utilizing real-time data collection, analysis, and Bluetooth communication, CRATER is fully capable of supporting automated material processing and handling mechanisms. Significant improvements in throughput and reduced personnel exposures can be realized by implementing CRATER.

Rugged and weather-tight, CRATER can be configured as an excavator or conveyor system for soil and bulk material remediation or as a vehicle mounted system for large area surveys. Data can be integrated with real-time GPS and incorporated into mapping applications such as ArcPad. CRATER has been used successfully at the Hanford Reservation site for remediation of waste burial trenches. Used to identify high dose rate items and locate spent fuel fragments in an excavator-mounted monitoring system, the system has been credited with saving millions of dollars in project remediation costs.

CRATER - Compton Ratio Analysis for Testing Environmental Radioactivity is a specialized radiation detection system, specifically developed for realtime screening of materials (e.g., excavated soils) for radioactive contamination. The system utilizes a methodology specifically developed for this application, which analyzes the spectral characteristics of the radionuclide(s) of concern using the Compton-to-photopeak ratio to quantify radioactivity. A background spectral stripping technique is added for enhanced detection under varying background conditions.

Application of CRATER for large area soil remediation projects will improve operations by providing real-time screening of materials - reducing personnel exposures by minimizing hands-on surveys, and improving throughput to reduce resource costs.

Radiation Detectors

  • Low-Range Scintillation Detector
  • Make/Model: REXON NAI 1.0X1.0/1.12IV
  • Crystal Type: NaI(Tl)
  • Crystal Diameter: 1”
  • Crystal Length: 1”
  • Resolution: 7.71% @ 662 keV
  • Enclosure Length: 9.5” (excluding jack)
  • Enclosure Width: 1.375”
  • Useful Spectroscopic Range: < 20 mR/h

  • High-Range Scintillation Detector
  • Make/Model: REXON NAI 0.25X1.0/1.12IV
  • Crystal Type: NaI(Tl)
  • Crystal Diameter: 0.25”
  • Crystal Length: 1”
  • Resolution: 7.51% @ 662 keV
  • Enclosure Length: 9.5” (excluding jack)
  • Enclosure Width: 1.375”
  • Useful Spectroscopic Range: < 200 mR/h
  • Exposure Rate Detector
  • Make and Model: LND 7149
  • Type: Energy Compensated Geiger-Mueller
  • Effective Length: 0.63”
  • Maximum Diameter: 0.38”
  • Minimum Dead Time: 15 µsec
  • Gamma Sensitivity: 1.5 cps-per-mR/h Co-60
  • Multi-Channel Analyzers (two, one for each NaI detector)
  • Make and Model: customized Radiation Alert® URSA-II
  • Maximum Resolution: 256 channels, customized
  • HV Supply: Variable, to +2000VDC @ 0.5mA
  • Gain: Variable, to X250
  • Shaping Time: Adjustable, 0.25 to 10 µsec
  • Power
  • Input Voltage Range: 9 to 36VDC
  • Maximum Current: 3A
  • Control/Display Unit
  • Make and Model: TDS Recon
  • Operating System: Windows Mobile 6
  • Processor: 400MHz Intel PXA255 XScale Processor
  • Memory: 64 MB high-speed SDRAM
  • Storage: 256 MB nonvolatile Flash storage
  • Communication
  • Protocol: RS232, 115200 baud, 8,N,1
  • Link: Bluetooth, FCC-Compliant, Dipole Antenna

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