Ionization Chamber Intercomparison in Mixed Neutron and Gamma-Ray Radiation Fields by National Bureau of Standards and Armed Forces Radiobiology Research Institute

摘要

This report describes a dosimetry intercomparison conducted between the Armed Forces Radiobiology Research Institute (AFRRI) and the National Bureau of Standards (NBS). The project was undertaken as part of an overall program to validate the reliability and credibility of the neutron dosimetry system used with the AFRRI TRIGA reactor in support of radiobiology research. The intercomparison included adsorbed dose measurements with ionization chambers by the AFRRI Radiological Physics Division and the NBS Nuclear Radiation Division. Measurements were made at the NBS californium-252 facility using unmoderated and heavy-water-moderated configurations. At the AFRRI TRIGA reactor, measurements were done in four radiation fields, including unshielded, lead-shielded, and water-shielded configurations. All data were collected during the period July 1983 to March 1984. The agreement between results obtained by the two groups was good in the NBS californium-252 fields and excellent in the AFRRI reactor fields. Through the course of the study, the calibration procedures used at AFRRI were validated, and valuable data were collected on ionization chamber characteristics and the spatial variation of tissue kerma rates in the AFRRI reactor exposure room. This report includes descriptions of the radiation sources, dosimetry methods, dosimetry result, and special dosimetry problems encountered during the work.