Detection of Fast Neutrons by Individual Dosimetry Using Stimulated Exoelectron Emissions. Final Report for the Period 15 November 1979 - 31 May 1982

摘要

Since 1979 studies were carried out at the French Atomic Energy Commission under an IAEA research contract on the detection of fast neutrons for personal dosimetry using thermally stimulated exoelectron emission (TSEE). Initially, alpha-alumina, which is alumina crystallizing in the alpha -phase, was used as the dosimeter. The exodosimeters were prepared by the pulverization technique using plasma arc and chemical flame deposition technique; the former was the better technique. With the plasma arc technique the alumina layers became indestructible, the surface of the layer was very homogeneous and the crystalline structure remained undisturbed. Later, the study was extended to other exoelectron emitting materials, namely, beryllium oxide and lithium fluoride. The response of the three types of exoelectron dosimeters was studied by exposing them to unidirectional neutron beams of fluences varying between 10 exp 8 and 10 exp 9 neutrons per cm exp 2 from sup 7 Li (n,p) reaction for the energy range 75-500keV and from sup 3 H (n,p) reaction for 1MeV. With the three exoelectron dosimeters studied, the sensitivity for neutron detection, Rn, was found to be rather poor as compared to the sensitivity to gamma rays, R gamma . The Rn/R gamma ratio obtained by using the glow peak at 360 deg. C was not more than 6%. However, by taking into account the two peaks at 360 deg. C and 470 deg. C the average Rn/R gamma ratio was found to be 60%. Although this could be used for neutron dosimetry, it had two major drawbacks, namely (a) the resolution was very poor as compared to that obtained by using the peak at 360 deg. C alone and (b) thermoionic background at high temperature reduced the reproducibility of measurements. Simultaneously, a TSEE reading device was developed and this was an engineering success. The results of the study have been of scientific interest, but the use of this technique for practical neutron dosimetry has not yet proved to be a success. (Atomindex citation 15:052595)