RÉSUMÉLes auteurs se sont intéressés à la réaction nucléaire 32 S(n, p) 32 P qui a lieu entre autres dans les phanères de l'homme (cheveux et poils) lors d'accident de criticité ou de surexposition aux neutrons d'énergie supérieure à 2,5 MeV. La présence de 32 P dans les cheveux ou les poils est un signe indiscutable d'une exposition aux neutrons rapides. L'activité du 32 P décelée est directement proportionnelle à la fluence neutronique. Elle permet une estimation précise de la dose absorbée dès lors que l'on connaît la nature du spectre incident. La connaissance du rapport neutron/gamma autorise même l'estimation de la dose totale absorbée (neutron + gamma). ABSTRACT The nuclear reaction 32 S(n, p) 32 P occurring in human hair has been studied in the case of criticality accident or overexposure to neutrons with energy above 2.5 MeV. The occurrence of 32 P is an obvious sign of exposure to fast neutrons. The detected activity of 32 P is directly proportional to the neutron fluence. It allows an accurate assessment of the absorbed dose provided the nature of the incident spectrum is known. The total absorbed dose can even be assessed if the neutron/gamma ratio is known.
Les petites quantités de phanères nécessaires aux mesures (quelques dizainesBecause very small amounts of hair are required for the measurements (a few ten milligrams) samples can be taken in various parts of the body of an average hairy individual. The direct incident fluence vector and the heterogeneity of the exposure can be then derived. This operational method requires no difficult radiochemistry. The physicians are supplied with very reliable dosimetric data within 24 h. The detection threshold is about a few ten centrigrays.
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