Leak detection in water reactors

An example of the requirements for detection systems is the one represented by the NRC Regulatory Guide 1.45 which is also adopted in many other countries. The principal requirements of the guide are summarized in the following. 

First of all it is required that identified leaks and non-identified leaks must be distinguished. For the latter, the admissible limit is 3.8 1 min (1 USgal min ). 

at least three separated detection systems must be available two systems out of the three have to be chosen among the following ones sump level measurement, flow rates measurement and radioactivity level in air. Each system must comply with the sensitivity limit of 3.8 1 min in one hour. 

These systems must be designed to resist earthquakes and their instrumentation must be loeated in the control room. 

The most commonly used systems are the following ones, with their corresponding sensitivities  

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