Radiological Survey Measurement Approaches for Direct Readout of Effective Dose Rate, 20-R9724

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Principal Investigator
Roland R. Benke

Inclusive Dates:  07/01/07 – Current

Background -  External radiation dose is a primary consideration for the operation and regulation of many facilities with licenses to possess radioactive material or radiation-generating machines. For example, radiation area designation (i.e., radiation area, high radiation area, and very high radiation area) is based on dose rate measurements. Effective dose is an improved, internationally adopted dosimetric quantity and represents a more realistic metric for human exposure to external radiation than alternative operational quantities, which can be overly conservative. Proposed changes in United States policy on radiological dosimetry have recently specified effective dose (equivalent) as the new primary quantity for external radiation protection. The effective dose concept, however, has been limited to calculations because methods for measuring this quantity directly have not been developed or demonstrated. Because current survey instrumentation cannot read out effective dose rate, the simplified operational quantities continue to be used as proxies for external dose. Successful survey measurement of effective dose, therefore, implies that routine radiation surveys, radiation area designations, and operational facility decisions can be based on best estimates for external radiation risk. This increased realism has the potential to reduce regulatory burden and operational costs.

Approach - This project focuses on the development of a survey measurement approach that relies on existing, commonly used detection equipment rather than development of a completely new detection system. The objectives of this work are twofold: develop and demonstrate survey measurement approaches to characterize features of gamma-ray radiation fields that are necessary for determining effective dose and develop numerical algorithms for converting measured spectral data into direct readout of effective dose rate.

Accomplishments - This project has been active for three months. Calibration measurements were performed in the laboratory with a portable gamma-ray spectrometry system. The experimental setup was designed, and its construction began.

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