The HML's new field deployable, high-resolution whole body counter

Area of Science:

• Nuclear instrumentation
• Radiation detection and measurement
• Health physics

Background:

• The Human Monitoring Laboratory (HML) sought alternative applications for a hyperpure germanium field instrument, the Ortec Detective.
• Originally designed for detecting radioactive contraband, its potential as a portable whole body counter was explored.

Purpose of the Study:

• To evaluate the Ortec Detective's suitability as a high-resolution portable whole body counter for emergency response.
• To determine the instrument's sensitivity for various radioactive isotopes, including fission products, activation products, and actinides.
• To develop calibration methods for accurate measurements based on photon energy and subject size.

Main Methods:

• Repurposing the Ortec Detective instrument by connecting it to a laptop to function as a spectroscopy system.
• Utilizing Monte Carlo simulations for instrument calibration and optimization of counting geometry.
• Developing empirical functions to relate counting efficiency to photon energy, subject size, and height.

Main Results:

• The instrument demonstrated adequate sensitivity for detecting fission and activation products but not actinides in emergency scenarios.
• Calibration curves were established as a function of photon energy and subject size for whole body counting.
• A function correlating counting efficiency with subject height was developed for thyroid counting.
• Minimum Detectable Activities (MDAs) were found to be in the low kilo Becquerel range for fission and activation products with a 5-minute count.

Conclusions:

• The Ortec Detective, when configured as a portable whole body counter, is a viable tool for emergency response concerning fission and activation products.
• Monte Carlo simulations and empirical functions provide effective calibration strategies for this repurposed instrument.
• Further investigation is needed to assess its utility for actinide detection.