Demonstration of equipment: Ultra sensitive sea water radioactivity monitoring system autonomous low power consumption equipped with wireless data communication

Abstract

Since the beginning of the 60's, the very first nuclear facilities were applying a full environmental monitoring survey program: water, air, releases,... At that time, very few on-line measurements were carried out because of the technical limitation. Sampling and later laboratory analysis was of common practice. Only stacks, fences and liquid storage pools were equipped with a continuous monitoring system. Only alarm signals were transmitted remotely. In 1975: the National Institute for Radioelements (I.R.E.) had a new challenge: prove permanently to the authorities that the environmental impact of the institute was negligible. It was the beginning of a new era: the nuclear industry started to be criticised, new telecommunication and computer technologies were emerging. At the same time, radiation detectors reached a sufficient level of performance and reliability. The scientific community could benefit from this evolution. Since 1982, I.R.E became a pioneer when it sets-up automatic intelligent monitoring network with an availability better than 99.9% and able to give alarm and to be operated remotely. They were installed in the neighbourhood of Fleurus, Tihange and Chooz and were able to measure continuously the radioactivity in air and river water. They were coupled to a sampler where water was collected on a weekly basis to be able to detect short-lived radioisotopes like 1 3 1 1 , 9 9 m T c or p -emitters. 20 measuring points were installed (15 air and 5 water); they are still in operation with availability of 99.9%. The air probes measured the radioactive irradiation around the nuclear sites or at the fences; the river was monitored by Nal detectors (2 x 2) connected to a Single Channel Analyser. The principle of those was based on the overflow-shielded tub. They may be also based on the principle of the diving probe without pump more reliable. The use of SCA has the disadvantage that isotope identification is almost impossible and that the energy calibration is difficult. Operation of the continuous monitoring of rivers has revealed several unexpected aspects of the radioactivity of water, such as effects related to Rn and its progeny during thunderstorms: alarms due to the increase of radioactivity, difficult to confirm, to understand and to manage. Routine releases from hospitals 9 9 m T c and 1 3 1 I more easily to detect than the releases coming from the nuclear facilities. Finally, it's important to underline that those networks were operational before the Chernobyl accident and that their interest for the Authorities was at that time very limited. After the accident, the probes sensitivity, reliability and interest was recognised and the concept was adopted.