Investigation of Alternate Droplet Material Bubble Dosimeters

Abstract

Past theoretical research involving superheated liquid droplet (bubble) neutron dosimeters has shown the possibility of using alternate droplet materials in order to give the dosimeter improved temperature stability. Based on that research testing was conducted on HFC-134a, propylene, propane, and hexafluoropropylene to determine (1) the compatibility of the novel superheated liquid material with the detector gel matrix material; (2) the gamma sensitivity of the detector droplets; (3) the response of the dosimeters as a function of neutron energy; and (4) the response of the dosimeters as a function of temperature. These tests were conducted at the Armed Forces Radiobiology Research Institute using a 60Co source, the Naval Surface Warfare Center using a tandem neutron accelerator, and the United States Naval Academy using an unmoderated 252Cf source. The response of the alternate droplet material dosimeters was compared to the response of the original Freon 12 droplet material dosimeter. The data indicated that the propane and propylene materials were chemically incompatible with the gel material and that the hexafluoropropylene dosimeters were sensitive to gamma radiation, thus making these types of dosimeters unsuitable. However, the HFC-134a superheated liquid droplets were stable in the gel material, responded uniformly over varying neutron energies, and had a predictable temperature response.