Autonomous and portable radioactivity mapping system for environmental survey (SOCRATE).

P. Richon Actes du congrès ECORAD, 3-7 sept 2001, Aix en Provence, France Radioprotection - Colloques, volume 37, C1-999/ C1-1004.

SOCRATE is a cartographic tool for natural and artificial radioactivity survey, developed for implementation in contaminated sites and natural environments. The comprehensive mapping of a contaminated surface (10.000 square meters, with a grid as small as one meter across) is possible in one day by two surveyors only. The system uses a differential GPS (DGPS NovatelTM) and a gamma probe (SaphymoTM AD6128), making it possible to obtain in real time the dose rate and the geographical position (latitude, longitude and elevation) with an accuracy of 0.2 meter. It is made up of two distinct parts: the sensor and its ancillary equipment, including GPS, packed in a rucksack (10 kg), and the reference GPS station located on a tripod in the site. The GPS receivers are radio linked (range 12 km) in order to make differential corrections available in real time at the mobile station. The mobile station is equipped with a computer and a LCD screen, allowing the simultaneous visualization of path and dose rate. The data file includes geographical position, elevation, and dose rate in nSv.h-1. These parameters are directly processed by ARCVIEWTM (a Geographical Information System), which produces dose rate contours. These maps can be superimposed to topographic maps, aerial photographs or digital terrain modelling. The SOCRATE system has already been implemented on several sites, including Saint Jean d'Ormont (Vosges), the Mercantour natural park (Alpes-Maritimes), and the village of Gif-sur-Yvette (Essonne).