Abstract:
This thesis focuses on designing, building, and analyzing a neutron detection system to
measure neutron fluxes of a TRIGA reactor at Texas A&M University to verify newly
developed simulation codes. Such a system must be designed to cover a wide range of
neutron fluxes in transient power surges (up to 1015 neutrons/cm2/s, lasting 20 to 50 ms)
and in steady-state operations (1013 neutrons/cm2/s at full power of one megawatt). The
size of the detector is limited to a maximum of 9.525 mm outer diameter including
housing.
The detection system consisted of slow neutron detectors, associated electronics, data
acquisition and storage equipment, and an analysis software. The detector used boron-
10 to capture slow neutrons, generating charged particles within an ionization chamber
filled with air. Due to the low Q-value of the reaction, a high gain charge-sensitive
preamplifier, which was a part of a miniature 16.9 mm x 298.5 mm electronic package,
was placed within 1.7 m of the detector to minimize noise level. The preamplifier was
designed to offer pulse mode, current mode, and high voltage current mode of operation.
Experimental data were acquired at 20 MHz using a solid-state drive for data storage
and were subjected to 250 MHz for up to eight-hour continuous operation using an array
of five three-TB hard drives. Data analysis software was programmed using MATLAB. In
addition to analysis using the shaping amplifier’s output, an algorithm to generate a
radiation pulse from the directly digitized preamplifier signal was proposed and tested with test pulses simulating neutron events. The detection system was tested with isotopic sources and in a dry tube located near the
TRIGA reactor. The latter showed an increase in the number of gamma events with the
reactor power, whereas the number of neutron events was also proportional to the
power. In addition, a trial run of in-core measurements was performed. The results
suggested that high gamma radiation present in the core interfered with the neutron
signal. Suggestions was made for modification of the mechanical assembly of the
system, compensation for gamma signals, and additional tests to improve analysis of the
neutron signal.
Description:
A Thesis
Submitted to the Faculty of Graduate Studies and Research
In Partial Fulfillment of the Requirements
For the Degree of
Doctor of Philosophy
in
Electronic Systems Engineering
University of Regina. xiv, 141 p.