Page 59 - bukuneutron

below the root zone.

7. Maintenance: Neutron gauges is robust and its
require only little maintenance to ensure proper
operation. Permanent access tubes should be
checked regularly to ensure water or foreign ma-
terials are not in them. Since the usage of long
cable between the detector and data acquisition
device, the most common failure in this technique
is a broken or worn cable. Checking the cable
integrity is a must. Every changes in the ac-
cessories is require recalibration. The source
strength will reduce with time, so some situation
where the sources is passed over two or more
half life will require devices to recalibration.

8. Access Tubes: Selection of access tubing ma-
terial is crucial since some materials capable to
adsorb and scatter large amount of neutron. This
will affect counting rates. Highest counting rates
are achieved with aluminum because it is trans-
parent to neutron while PVC is the lowest be-
cause its contain clorine and hydrogen as they
are neutron absorbent materials.

9. Standard Counts: The performance of neutron
gauge is evaluated based on the count ratio of
actual with a standard count. Standard count is
obtained periodically since the source strength is
reduced with time. Standard count is collected

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