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National Radioactivity Monitoring Network (LMR) Data Report 1993-1995

Landelijk Meetnet voor Radioactiviteit (LMR): Data rapportage 1993-1995


In March 1990, the Dutch National Radioactivity Monitoring network (LMR) was put into operation. The tasks were early detection of major nuclear incidents and collection of radiation data during such an event. By integrating with a network more directed at the requirements of local authorities, the LMR was succeeded by the National Monitoring Network Radioactivity (NMR) early in 1996. This report evaluates the performance of the LMR over the years 1993-1995 and presents a data review over this period. The technical properties are described of the two field monitors used, the Bitt Technology RS02/RM10E proportional counter device and the FAG FHT59S airborne gross-alpha/beta-activity monitor. Measurements of external radiation, expressed in ambient dose-equivalent rate contain a systematic error for the correction of which a conversion formula is presented. The natural alpha-activity concentration as determined by the aerosol monitor is (during non-emergency situations) proportional to the equilibrium-equivalent decay product concentration of 222Rn progeny in air, EEDC. In the period 1993-1995 nuclear accidents with any impact for the Netherlands did not occur. However, automatic warning messages indicating that radiological data were recorded above one of the warning levels were received many times. Some of these warnings were due to natural causes or industrial activities, but most were false, for instance, because of malfunctioning equipment. In 1994, but especially in 1995 the number of 'false' messages was relatively large, partly due to the ageing of the instruments and partly due to the extreme weather conditions of 1995. Nevertheless, the availability of LMR data in the period 1993-1995 was higher than in previous years: dose-rate on average some 96%, air activity approximately 91%. The monitoring results of the LMR have increased the knowledge of the variations in the natural background radiation and the determining parameters. This report contains a reference to the results of an extended LMR data analysis.

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