Local dose monitoring in nuclear plant surroundings - having compensation of zero effect on scale for increasing background radiation

摘要

An activity measuring point for a flowing medium, e.g. gas or air in a nuclear power station, comprises a scintillation counter or counting tube with a given calibration factor K, which can vary slowly (e.g. over months) with changes in background radition. A dose meter integrates the count in a specific period and provides a logarithmic indication on a scale. The beginning of the scale can be adjusted by at least one decade. A pulse generating device is used for supplying a count adjustable through the range 10-3 to 102 impulses per second; this count is subtracted from the count given by the detector, to give a residual zero effect (N1); thus the product of N and K, which determines the scale, can be adapted to the background radiation by setting it to a desired value. Pref. the measuring instrument comprises a decadic scaling-down unit giving infinite adjustment of the start of the scale over two decades. Typically, for monitoring circulating air inside the secondary shield of a nuclear power plant. The scales of a number of different instruments can be easily adjusted from time to as the background reactivity increases.