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hole for irradiation also locate within the fuel element
in the reactor core. The sample is sent to the irradiation
hole using pneumatic transfer system. The function of
this system is to carry sample before irradiation into the
hole and get the irradiated sample back to the shielding
area. The PTS is installed in the NAA laboratory con-
structed adjacent to the reactor building. The sample
irradiated using PTS only within 20.0 minute maximum
and can be around 1.o second the minimum.

Third irradiation channel use for NAA is the rotary-
rack which also known as ”lacysusan”. The rotary-rack
consists of 40 tubes hanging on the rotating rail in the
surrounded alumonum cover. Samples are placed in
the tubes. There is a systematic mechanical device
that control the rotating of tube to ensure it is meet
exactly the tranfer pipe. The design of rotary-rack is
shown in Figure 3.5.

The rotary-rack is located in between the reactor
core and the grahite reflector so that it is a slight far
from the core center, Comparing with other two chan-
nels, RR is considered the lowest thermal neutron flux.
It is useful for irradiating many samples. Maximum
number of samples can be irradiated using RR is 40.
The rack is being rotated during the exposure, so the
effective flux of thermal neutron interacted with the sam-
ple is homogenous.The sample is sent into each tube
via pipe inlet located at the platform of reactor top.

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