Performance Characteristics Of Neutron Personnel Dosemeters Used In The Oak Ridge Intercomparison Studies PDF Download

The third Personnel Dosimetery Intercomparison Study was held at the Oak Ridge National Laboratory Dosimetry Applications Research Facility during March 15--16, 1977. The Health Physics Research Reactor (HPRR), used unshielded, with a 12-cm-thick Lucite shield or a 13-cm-thick steel shield, provided three neutron and gamma-ray spectra. The characteristics of these fields such as neutron energy spectra, intensity, and uniformity had been measured previously during nuclear accident dosimetry studies. Exposures were made to simulate total exposures likely to be encountered in personnel dosimetry. Neutron dose equivalents of the order of 500 millirem were produced by controlling the reactor power level and exposure time. Dosimeters were mounted on the trunk section of water-filled phantoms, the front edges of which were located 3 m from the reactor center. When shields were used they were placed at 2 m from the core. Sulfur pellets exposed at a standard location on the reactor during the intercomparison were used to calculate values of tissue kerma for neutrons at the 3-m position based on previous measurements. Using the fission yield and the calculated leakage of the HPRR, the neutron fluence was calculated for each reactor run. Then the dose was calculated based on the HPRR neutron spectra and the dose conversion factors, which had been calculated previously for the three spectra. The results of these personnel dosimetry intercomparison studies reveal that estimates of dose equivalent vary over a wide range. The standard deviation of the mean of participants data was in the range of 25 to 50%.