Understanding how the reactor power monitoring detection equipment works requires a working knowledge of basic terminology.
Signal-to-Noise Ratio
Signal-to-noise ratio is the ratio of the electrical output signal to the electrical noise generated in the cable run or in the instrumentation.
Discriminator
Discrimination in radiation detection circuits refers to the process of distinguishing between different types of radiation on the basis of pulse height. A discriminator circuit selects the minimum or maximum pulse height that is to be counted.
Analog
Analog is defined as a mechanism in which data is represented by continuously variable physical quantities. As it applies to the intermediate range, the output of the intermediate range is an analog current. Due to the wide range of the flux measured, use of logarithmic circuitry is required for indication on a single scale instrument. Analog is used in contrast to digital to refer to circuits in which the magnitude of the signal carries the information. Figure 30(A) illustrates an example of an analog display, and 30(B) illustrates a digital display.
Logarithm
Logarithm is defined as the exponent that indicates the power to which a number is raised to produce a given number (i.e., the logarithm of 100 to the base 10 is 2). When discussing nuclear instrumentation, this term refers to the electronic circuitry of the source and intermediate ranges. These ranges utilize logarithms due to the wide range of measured flux and the necessity to measure that flux on a single meter scale.
Reactor Period
Reactor period is defined as that amount of time, normally in seconds, required for neutron flux (power) to change by a factor of e, or 2.718.
Decades Per Minute (DPM)
Rate circuits are important in the source and intermediate ranges. Rate information is displayed on a meter in decades per minute. These meters indicate how fast reactor power is changing in decades (power of 10) in each minute.
Scalar
This term refers to a measurement or quantity that is capable of being represented on a scale (i.e., neutron flux on source range, intermediate range, and power range meters).
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