"Prototype Demonstration of Gamma Insensitive Centrifugally Tensioned Metastable Fluid Neutron/Alpha Detector,"
M.S. Thesis, Nuclear Engineering, Texas A&M University, College Station, TX (2015).
Tensioned metastable fluid detectors are a novel detector
concept with a wide array of potential uses. A particularly
interesting application is as a real-time alpha and neutron
detector that is also insensitive to gamma rays. This type of
detector could have many uses for safeguards and nonproliferation
including reprocessing facilities and border protection. For
safeguards facilities, the detector could be used to perform online
measurements of alpha-emitting nuclides such as uranium and
plutonium in the reprocessing fluids. The online measurements could
include dissolver tank fluids and products solution fluids where
conventional detector use is infeasible.
In this research, an initial characterization of one version of
the tensioned metastable fluid detector (TMFD) was performed. A
TMFD works by putting a fluid under negative pressure or tension.
Once under tension, small amounts of energy can cause the tensioned
molecules in the fluid to burst apart forming a visible bubble. The
small amount of energy can come from nuclear particles such as
alphas and neutrons. Another key concept of the TMFD is that the
amount of energy needed to form a bubble is dependent on the
negative pressure of the fluid. By varying the negative pressure,
only particles of a desired energy or higher would form bubbles in
the system allowing for a form of spectroscopy. The spectroscopy
could be used, along with a volume measurement, to quantify the
amount of uranium or plutonium in the reprocessing fluid.
The initial characterization was performed using gamma, neutron,
and alpha radiation. The gamma-ray tests were performed using an
external 137Cs source next to iii the system. Several
neutron tests were performed using an external 252Cf
source including a test to verify compliance with the inverse
square law and a test varying the pressure of the TMFD to test
spectroscopy uses. Last, alpha-radiation tests were conducted using
various amounts of depleted uranium dissolved in the working fluid
of the detector. This study confirmed that the detector system is
insensitive to low amounts of gamma-rays. It also confirmed that by
varying the negative pressure in the detector, different energy
neutrons could be detected. Last, the study confirmed that the
detector could be used to detect alpha particles in real time but
that additional work was needed on the design to ensure reliable
The TMFD can be used to detect alpha particles and
neutrons and is insensitive to gamma-rays. However, the current
design of the system is a prototype and must be redesigned in order
to be used in a reprocessing facility. Also, a lower negative
pressure is needed for neutron detection compared to alpha
detection. The pressure discrepancy would cause the detector to be
unable to detect alpha particles in a large neutron radiation field
making the detector unusable at the dissolver tank, but still
usable for the reprocessing product lines.