Radiation Detectors
CIRCUITRY AND CIRCUIT ELEMENTS
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).
Components
Three ranges are used to monitor the power level of a reactor throughout the full range of reactor
operation: source range, intermediate range, and power range. The source range normally uses
a proportional counter, while the intermediate and power ranges use ionization chambers. A
compensated ion chamber is used for the intermediate range. The power range uses an
uncompensated ion chamber. Each of the three different ranges makes use of some or all of the
following types of components.
Preamplifiers and Amplifiers
Radiation detector output signals are usually weak and require amplification before they
can be used.
In radiation detection circuits, the nature of the input pulse and
discriminator determines the characteristics that the preamplifier and amplifier must have.
Two stages of amplification are used in most detection circuits to increase the signal-to-
noise ratio.
Rev. 0
Page 57
IC-06
