Radiation Detectors
INTERMEDIATE RANGE NUCLEAR INSTRUMENTATION
Figure 36 shows a typical intermediate-range channel.
Figure 36 Intermediate Range Channel
Typically, the compensated ion chamber output is an analog current ranging from 10-11 to 10-3
amperes, but varies with reactor design. The log n amplifier is a logarithmic current amplifier
that converts the detector output to a signal proportional to the logarithm of the detector current.
This logarithmic output is proportional to the logarithm of the neutron level.
The determination of rate change of the logarithm of the neutron level, as in the source range,
is accomplished by the differentiator. The differentiator measures reactor period or startup rate.
Startup rate in the intermediate range is more stable because the neutron level signal is subject
to less sudden large variations. For this reason, intermediate-range startup rate is often used as
an input to the reactor protection system.
The reactor protective interface provides signals for protective actions. Examples of protective
actions include control rod withdrawal interlocks and startup rate reactor trips.
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