A primary research direction within the department is support of the continued role of nuclear power in meeting society's energy needs through currently used light-water fission reactors and through development of both fast breeder reactors and fusion reactors for future applications. Other directions being pursued are plasma applications to materials and radiation source development and utilization, including medical applications, advanced computational and analytical methods, thermal sciences, and nuclear materials.
Important contributions have been made recently by several research groups, including: inertial electrostatic confinement for fusion applications and for neutron, x-ray and gamma radiation sources; hydrogen cell performance for energy generation and material transmutations; thermal and epithermal neutron activation analysis in aerosol transport and environmental and other applications; nuclear-pumped lasers as space power sources and direct energy conversion; advanced computational techniques applied to stochastic radiation transport, smoke distribution in buildings, reactor physics and reactor safety, including Lie groups and group invariant difference schemes; perceptual displays and temporal pattern recognition applied to reactor control and operation; nuclear nonproliferation and safeguards; fusion blanket and diverter materials behavior and performance; plasma processing of electronic materials, plasma-induced sputtering and plasma measurements; nuclear radiation effects on materials and neutron scattering measurements; materials behavior under high-temperature corrosion and radiation bombardment environments, including nondestructive examination; combined neutron capture therapy and magnetic resonance imaging for cancer cell treatment; and thermal hydraulics including multi-phase flows, boiling in porous media, and molten jet breakup, and turbulent structure modeling.
In addition, departmental facilities include the Illinois Advanced TRIGA, an above-ground, tank-type reactor with maximum steady-state power of 1.5 MW and peak pulsing power up to 6000 MW.
Sea coasts, clouds, mountains, and the microstructure of surfaces can
all be described by fractal geometry--a geometry not limited to
integer dimensions. Present surface analysis computer models such as
TRIM and the "embedded atom method" treat surfaces as flat.
They calculate the reflection coefficient and sputtering coefficients
as a function of energy, angle of incidence, and material composition.
This study introduces realistic surface roughness and more complete
interaction physics into those codes by incorporating the fractal
geometry concept.
The next generation of microelectronic integrated circuits will have
submicron features whose depths are much greater than their width. To
fill such features with metal (which creates the "wires"
which connect various parts of the microchip), a new technology is
needed. Standard magnetron sputtering fails because the top closes
over before the trench (or via) is filled. By ionizing the metal atoms
before they reach the substrate, the ions can be drawn to the bottom
of the trenches filling the features. We are developing and testing
novel ionization techniques in a commercial-scale system.
When ions strike materials, electrons may be emitted, the ion
reflected or the material removed (sputtered). Magnetron sputtering is
used in all microelectronics and the production of video cassette
tapes. In a magnetron, plasma ions fall through the plasma sheath and
impact the target. The emitted electrons are accelerated away from the
target and sustain the plasma discharge, the sputtered material
deposits on the microelectronic device being fabricated. To understand
this system in detail, the emission coefficients for low-ion energy
must be known. These measurements are complicated by the presence of
real-life adsorbates and surface defects. Measurements of these
phenomena are under way in a UHV ion-surface interaction facility.
Modeling efforts are also underway.
Radio frequency power is used to heat and drive many industrial plasma
applications. The rf waves interact with the edge plasma of the device
and effect the waves' propagation. The details of this physical
process are poorly understood. The electron energy distribution has
not been measured and modeling of the system cannot be done without
knowing it. An experiment to measure this distribution and the time-
varying plasma potential using new electric and magnetic probe
techniques in an actual industrial application is underway.
The wires that connect the tiny transistors together in a computer
chip are produced using a magnetron sputtering plasma-processing
reactor. As chips have gotten smaller and smaller, the techniques for
making these wires have needed improvement and modification. Ionized
sputtering is the latest of these and we are producing an accurate
model of the metal atoms from their "creations" all the way
to their deposition site. This model includes the critical step of
turning the atoms into ions en route to the target.
The design of the National Spallation Neutron Source (NSNS) is
currently underway. If everything goes according to plan, construction
of this 1-MW neutron source will begin within a few years. The primary
purpose of the NSNS is to provide conditioned beams for a variety of
neutron scattering techniques. Our involvement in this project centers
on the optimized coupling of long-wavelength, elastic scattering
(small-angle and reflectometry instruments) to the target/moderator
system. We are simulating neutron moderation and transport within the
complex spatial geometry of the target/moderator system using MCNP. A
second Monte Carlo-based code will be used to optimize instrument
performance based on the target/moderator arrangement and coupling.
A relatively large proportion of fire-related deaths in large
buildings are caused by inhalation of combustion products away from
the combustion sites. Hence, accurate prediction of smoke movement is
important for improved building designs and for reliable evacuation
procedures. In order to extend the building size over which smoke
movement can be accurately predicted, we are developing advanced
computational methods for implementation on large multiprocessor
computers for a special set of equations specifically developed to
study smoke dynamics.
Large production codes (such as Commix) developed more than a decade
ago lack the efficiency of modern numerical methods. Hence, improving
the efficiency of such production codes by replacing the less
efficient modules is desirable. As a first step to exploring the
feasibility of such an exercise, we are developing a third-order nodal
integral method to solve the convection-diffusion equation. This is
being done by retaining up to the first-order term in the expansion
(in Legendre polynomial) of the pseudo-source terms, and without using
higher (beyond zeroth) Legendre moments of the dependent variables,
thus reducing the computational time significantly.
To demonstrate its feasibility in solving the Navier-Stokes equations,
the modified nodal integral method is being applied to solve the 2-D
Burgers equation at high Reynolds numbers. The resulting set of
algebraic equations will be solved using the multigrid iteration
scheme. Performance of the nodal method will be compared with other
competing methods.
The IEC fusion device uses 80% to 100% transparent spherical cathode
wire grid to accelerate deuterium plasma ions. The formation of deep
double potential wells in the IEC device is essential for achievement
of high fusion rates. IXL, a 1-D code that solves Poisson-Vlasov
equations, is used to simulate IEC double potential wells. Second
potential wells, which are 80% to 100% as deep as the first potential
well, are found at high perpendicular ion energy spread (3keV-14keV),
low perpendicular electron energy spread (3eV), and high ion and
electron currents (30A-60A). Fokker-Planck calculations are now in
progress to study collisional effects not included in IXL.
Electrolytic cell experiments with a packed bed of metal coated
microspheres manufactured at UIUC were analyzed using techniques such
as SIMS, EDX, AES, NAA, and ICP-MS. Quantification of isotopes by SIMS
in the metal films was possible by developing a calibration with NAA.
A distinct grouping of isotopes in four mass regions was observed in
all the runs. The RIFEX (Reaction In a Film-Exited CompleX) theory,
presently under development, attempts to explain this observation with
a proton-induced fission "complex" reaction.
In both geometries, a central cathode grid ionizes low-pressure gas
within a vacuum chamber. Ions are accelerated through the grid to high
energies where they collide with other particles and fuse. Experiments
have yielded 106 steady-state DD fusion neutrons per second in both
configurations. The focus of experimental IEC studies has been on:
pulsed high-current operation for greater fusion neutron yield,
investigation of forced and natural plasma oscillations for core
densification, measurement of spectral emission to characterize
different modes of operation, high-energy proton detection for
potential well measurements, electrode grid and insulator design for
ion confinement and lifetime studies, gas mixture separation for
plasma processing, and investigation of the IEC jet mode for space
thruster applications.
An approximate model has been developed to predict the plasma physics
behavior and the neutron generation rates in the cylindrical inertial
electrostatic confinement fusion device (IEC C-Device). This model is
being used in conjunction with experiments to optimize the design and
operating conditions of an IEC C-Device neutron generator. Several
simplifying approximations are employed in the model: local quasi-
neutrality, spatially one-dimensional variation of plasma properties,
a linear plasma potential profile, and a monoenergetic ion
distribution. The effects of collisions are included via a
recirculation parameter, h, which relates the plasma particle current
to the electric current measured.
A compact, tunable, x-ray source would have a wide range of
applications. The nature of synchroton radiation results in an
expensive and multiuser facility. A low-cost, small-scale, tunable x-
ray source, an electron-injected IEC, is proposed in which the
electron storage ring is replaced by recirculating focused electrons
accelerated by a spherical grid, and the bending magnets are replaced
by virtual cathode and the electron-electron collisions in the dense,
central plasma core region. Thus an IEC synchrotron source operates at
a much lower electron energy but still gives the same x-ray energy due
to the small-scale bending radius associated with electron-electron
interactions.
The development of a spherical inertial electrostatic confinement
(IEC) device for confining energetic ions arose in part from the
theoretical prediction of the existence of alternating potential wells
inside a spherical electrode into which ions or electrons are
injected. A new diagnostic technique, based on measuring the emission
of D-D fusion proton and analyzing these data, has been developed to
allow exploration of the well structure. The present research is
designed to study the formation of multiple well structure and at the
same time provide firmer experimental and diagnostic foundation for
the IEC concept.
The D-3He fusion reaction yields charged particles (minimizing
structural activation and allowing direct conversion) and a large
amount of energy. However, limited terrestrial resources of 3He would
inhibit worldwide commerical development of D-3He reactors. Here, 3He
breeding through D-D inertial electrostatic confinement (IEC) fusion
reactors is proposed. The analysis of D-D IEC breeder-D-3He reactor
systems reveals that IEC reactors are particularly suited for the
breeding step because 3He can be efficiently collected by direct
conversion. Moreover, low breeder gains (Q-values~5) are found
sufficient for efficient operation of the combined system and to allow
its competitiveness with respect to alternative 3He resources, such as
lunar mining.
Recycling is the process by which particles are returned to a plasma.
Recycling in magnetic fusion devices is dominated by the surfaces in
contact with the plasma--walls, limiters, and divertor plates. To
understand and possibly control recycling it is necessary to know the
ion and neutral atom energy and particle emission coefficients for a
variety of materials at the energy of the incident particles, 1-1000
eV. New models that include sputtering, reflection, and the transport
of these atoms in the plasma are being developed and applied to
current fusion research devices.
Russia, Japan, Western Europe, and the United States are jointly
designing a tokamak reactor that will achieve and sustain fusion
ignition. One region of particular concern is the edge region where
the plasma strikes the wall. The helium produced by the fusion events
needs to be exhausted, and the power load must not melt the wall and
contaminate the plasma. Complete modeling of this edge region,
including the detailed macroscopic and microscopic geometry and
neutral atom scattering, is of critical importance.
Tritium has been introduced into the TFTR tokamak over the last few
years. Because of on-site inventory restrictions, a complete model of
where the tritium will be retained and how much will recycle in each
discharge has been developed. A combined experimental and
computational approach has predicted inventory totals. The isotropic
exchange in the walls between will be measured using H and D instead
of T and D. Three-dimensional modeling of neutral atom transport and
plasma wall interactions has been checked against this experiment and
extended to the decommissioning phase of operation.
Simulation of results from the world's major tokamaks using current
transport theories with a Bayesian treatment of calibration and random
measurement variances gives confidence contours for the a priori
uncertain parameters in the theories. Fusion power production
probabilities for fusion reactor designs are computed using these
results. Epistemological implications of this methodology are also
analyzed. The collisional/collisionless transition flow to material
boundaries is also investigated using Mathematica and numerical
analysis.
Reason(s) for the fall of heart rate variability (HRV) during neonatal
illness is being investigated by analyzing the nature and amounts of
order in RR interval time series from 25 neonatal ICU patients with a
spectrum of clinical illness severity. We are measuring predictability
(deviation of predicted intervals from observed), and regularity
(measured as approximate entropy) of RR interval time series with
different degrees of HRV. We will use these measures to investigate
the nature of order in the data as HRV changes.
Advances in nonlinear dynamical analysis, bifurcation theory, and
deterministic chaos are allowing a return to the analysis of systems
that were so far "considered to be random." We are analyzing
the EKG signal from a baby with a transplanted heart. The signal shows
patterns of deterministic chaos. Supported by the existence of
inverted p-waves in the EKG signal, the dynamics of this heart is
hypothesized to be resulting from the interaction between the sinus
node and an ectopic focus. The transplanted heart has been modeled as
a coupled oscillator. The deterministic component in the EKG signal is
being analyzed using nonlinear prediction theory.
Neutron capture therapy (NCT) is a binary technique that delivers a
nonradioactive agent to the tumor followed by neutron irradiation and
conversion of the agent into a radioactive compound. To predict the
efficacy of the treatment, one must run dosimetic calculations. This
implies an a priori knowledge of the drug concentration. One technique
uses a method based on the tumor enhancement achieved with gadolinium
labeled derivatives and magnetic resonance imaging (MRI). This
requires an understanding of the magnetic properties of the agents
under physiological conditions. We are characterizing a gadolinium
labeled carbon derivative for dual MRI and NCt applications.
An interdisciplinary program based on neutron capture therapy (NCT) to
kill cancerous tumor cells using high-energy radiation from neutron
capture reactions in selected nuclei has been initiated. The Illinois
TRIGA reactor provides a high neutron flux necessary for NCT. Boron-10
is currently the popular choice of absorbing nuclei, but gadolinium,
with its higher neutron-capture cross section and tumor-to-blood
concentration, is being evaluated. The decay of Gd157 products Auger
electrons, internal conversion electrons, and g-rays which may
participate in and increase radiation-induced cell death during NCT.
Agents that bind to the tumor cells and induce cell death are under
development for diagnosis and treatment by magnetic resonance imaging
and NCT.
Ion-chelate complexes have many applications in tumor diagnosis and
therapy. Radioactive isotopes of technetium, yttrium, indium, and
samarium offer applications in radioscintography and radiotherapy.
Gadolinium has applications in magnetic resonance imaging and neutron
capture therapy. We have attached ion-chelate complexes to Starburst
dendrimers. Folic acid was attached to these polymers. They
specifically bind to tumor cells that express the high affinity folate
receptor. We are using these polymers to diagnose and treat tumors
that express this receptor in vivo. Tumors of epithelial origin
express this receptor. These include 90% of ovarian tumors,
ependymomas, and choroid plexus tumors.
Due to the poor economic state of the city of East St. Louis, Ill.,
there has been much effort in renewing the prosperity of the
community. This is the objective of the East St. Louis Action Research
Project. As a part of the project our focus is to assess the extent of
contamination that has resulted from years of heavy industrial
activity. Numerous soil cores have been analyzed for elevated levels
of heavy metals using neutron activation analysis and x-ray
fluorescence. The results indicate that, in general, there is moderate
soil contamination of most of the selected heavy metals. Future
efforts will focus on morphology and leachability studies to indicate
their mobility in the biota.
Small-angle neutron scattering (SANS) is being used to investigate
hydride (deuteride) precipitation in single-crystal palladium (Pd).
There are many aspects of Pd-H phase transformation behavior that are
not clearly understood. One example is the large hysteresis that
occurs during an absorption/desorption cycle. SANS is extremely
sensitive to the presence of hydrogen and deuterium in metals. An
initial set of experiments is planned to investigate deuteride
precipitation in single-crystal Pd, primarily to deduce the particle
morphology and give general characteristics of the SANS response.
These results will serve as a basis for future investigations in this
system.
Small-angle neutron scattering (SANS) is being used to study deuterium
trapping and diffusion in deformed, single-crystal Pd. The local
concentration and spatial profile of trapped deuterium at dislocations
can be determined from careful evaluation of the SANS response. The
effect of dislocation trapping on lattice diffusion can also be
investigated by analyzing the decay of the SANS response during
deuterium evolution. A study of the variation of the trapping
phenomena with dislocation morphology is possible with SANS as well.
This analysis, therefore, can be considered as a probe of the near-
dislocation environment.
Small-angle neutron scattering (SANS), TEM, and metallographical
analysis are employed to characterize deuterium precipitation in Nb.
The effect of lattice defects such as dislocations and grain
boundaries on the phase transformation characteristics are of interest
here. Lattice defects can result in a shift from homogenous nucleation
to heterogeneous nucleation, thereby significantly altering the
deuteride particle morphology and phase transformation temperature
dependence. These effects and others will be studied in this project.
Neutron reflectometry is used to characterize deuterium phase behavior
in thin-film Pd. In situ measurements simultaneously provide the phase
diagram, out-of-plane film expansion, and depth profile. We have found
that the phase diagram of the thin-film Pd-D system altered
significantly from that of the bulk, and that this is due to a
substrate clamping effect. This conclusion is based on the observed
exclusion of deuterium at the film-substrate interface (due to
clamping stresses) and from the out-of-plane expansion following a
clamped, isotropic behavior. More work on epitaxial layers is planned.
A temperature-controlled, high flux level, neutron irradiation
facility is being developed for installation and use in the central
core region of the TRIGA reactor. The facility will provide both
steady and cyclical temperature control of material specimens during
neutron irradiation. This will enable study of effects of specimen
temperature on the radiation damage and property changes resulting
from neutron bombardment. Specimen temperature control from near
liquid-nitrogen (~77 K) to relatively high levels (900 K) will be
provided in the facility. Out of core, electrically treated prototype
tests confirm thermal performance of the design.
The literature on controls on fissile materials and tritium is being
researched in connection with proposals for improved worldwide
agreements on the storage and use of these materials for weapons
programs. Implications for verification agreements and technologies
are being examined. Methods involving radiation transport and other
physical means for detection of land mines and their components have
also been examined in connection with a project on the technology of
peacekeeping.
Factors that control the fatigue behavior of welded components are
currently being studied. Analytical methods for estimating the total
fatigue life of butt and fillet welds subjected to variable-amplitude
loading histories are evaluated. Surface treatments, such as shot
peening and laser dressing of the weld toe, are investigated as
possible methods for improving the fatigue strength. A new model for
estimating the fatigue life of weldments has been proposed for butt,
T-joint, and cruciform weldments using the concepts of "crack
closure" for cracks emanating from a notch. Results compare
favorably with experimental data in the UIUC fatigue data bank and
with experimental work in the literature.
The aim of this study is to develop a life prediction methodology for
fatigue crack growth based on the changes in crack opening levels with
maximum stress level, crack length, geometry, mean stress, and
microstructure. The primary tool for the determination of opening
stress is an elastic-plastic finite-element simulation of fatigue
crack growth. Stress-strain behavior in the model accounts for slip at
the microlevel as well as elastic anisotrophy. Fatigue crack growth
data obtained under conditions of intermediate- and large-scale
yielding, including low-cycle fatigue and biaxial loading, are
successfully correlated only when closure-modified parameters are
employed.
To develop fatigue life prediction methods for notched components
subjected to nonproportional multiaxial fatigue, the local stresses
and strains must be related to the global stresses and strains by some
approximation procedure, such as Neuber's rule. Experimental tests on
notched shafts subjected to proportional and nonproportional loading
in tension and torsion are being performed. The results are being used
to develop and verify the approximation procedure. Fatigue life
estimates will then be made using an appropriate damage model that is
based upon observations made during the tests. A life prediction
scheme will be developed from the approximation procedure and the
appropriate damage model and will be verified from the results of the
tests.
Fiber-reinforced sheet molding compound is an attractive material used
in ground-vehicle structural applications. It experiences cyclic
loading in service, therefore, understanding the fatigue behavior as a
function of processing conditions, chemistry of constituents, and
loading conditions is important. The purpose of this work is to
analyze some of the available fatigue data on these materials and to
conduct experiments to identify the nature of damage mechanisms and to
study cumulative fatigue damage. Tension-compression testing will be
considered to gain insight into mean stress effects. In all these
cases the fiber orientation of the molded part affects the progression
of damage.
Recent developments in processing technology have resulted in advanced
materials with lower fabrication costs and improvements in
microstructural uniformity. To utilize the full potential of these
materials, new design tools have to be developed in collaboration with
industry. Examples of such materials include metal matrix composites
and short reinforcement fibers in epoxy matrices. The metal matrix
composites with higher elastic modulus, higher temperature
capabilities, and lower weight compared to their counterparts
represent excellent opportunities for engine, brake, and rotating
components in the ground vehicle industry.
A comprehensive fatigue damage model is being developed to address the
following issues: What governs the nucleation of a microcrack within a
single grain or other suitable microstructural unit cell? What governs
the growth of this microcrack into adjacent microstructural unit
cells? When does the microcrack develop enough plasticity to sustain
its growth? These elements will be combined into a model for the
entire fatigue damage process.
It is no longer possible to specify a material without first
considering its processing. In some applications, the so-called old
materials processed in new ways are often more cost effective than
some of the new advanced materials. Surface treatments such as
carburizing and nitriding have been used for many years. Flexible
manufacturing processes, such as those using lasers, now offer the
potential to modify surfaces selectively to produce superior
mechanical properties of traditional lower cost materials.
The major structural components of the International Tokamak
Experimental Reactor (ITER) are presently under development in the
program. The design and performance of a fusion plasma chamber are
being assessed and improved in the joint industrial program. The
thermal performance of the structure; materials selection, performance
and fabricability routes of the first wall-blanket-shield structure;
and nondestructive examination and in situ serviceability of the
structure are all being examined in this program.
This research project is aimed at developing an understanding of the
performance of copper and copper alloys for fabrication of high heat
flux components in nuclear fusion applications. Service performance
will be based on irradiation damage behavior and elevated temperature
mechanical properties. These features are being examined by testing
alloys that have been subjected to high fluences of neutrons in FFTF,
and performing room and elevated temperature mechanical properties
testing.
Surface and near-surface compositional modifications are being modeled
to take into account various computing processes due to energetic ion
bombardment of materials surfaces. This work is developing methods to
model complex alloys, three constituents, using techniques to take
full advantage of the present generation of supercomputers.
Experiments are being carried out on model alloy systems to further
elucidate the behavior of materials under surface ion bombardment.
This work is aimed at studying corrosion processes and the
capabilities of corrosion inhibitors to prevent corrosion in mixtures
of oil, water, and CO gas under full pipe and slug flow conditions.
The work is carried out in 4-in.-diameter horizontal pipes and studies
the corrosion and corrosion inhibition processes of multiphase flow in
pipelines. Corrosion rates are monitored as a function of wall shear
stress, turbulent intensity, Froude number, oil/water cut, and other
fluid and flow characteristics.
The goal of this work is to study multiphase flow in pipelines and to
identify and characterize the flow regimes and transitions. Oil,
water, and gas (CO) at various gas and liquid velocities are examined.
The effect of fluid viscosity and other flow variables are related to
the changes in flow characteristics in horizontal pipes. The flow
regimes covered in these studies range from smooth stratified flow at
both low liquid and gas velocities to horizontal annular flow at both
high liquid and gas velocities. Mechanistic modeling of the flow
regime transition is also being performed.
Tis work is to model the characteristics of slug flow and, in
particular, the flow in the slug body. The mixing zone and the slug
body are examined using high-speed video equipment and high-resolution
graphics software. From the results, models for the velocity
distribution and the slug length are being developed.
The high-pressure corrosion studies are to characterize the effects of
pressure on corrosion and corrosion inhibition in horizontal pipes
with either full pipe flow or slug flow. The influence of the
oil/water composition, fluid flow rates, wall shear stress, and
temperature are also studied for their effect on corrosion and control
of corrosion. Microstructural analysis of metal samples that have been
exposed in the flow is being performed using SEM, TEM, and a variety
of other microstructural analysis techniques.
Ferritic/martensitic steel alloys have been under investigation for
structural applications in fusion reactors. They are very appealing
because of adequate mechanical properties and extremely good
irradiation performance when compared to austenitic stainless steels.
The strength of the alloy comes from the complicated dislocation lath
structure that forms on heat treating. This imparts good initial
strength, but the strength can degrade under cyclic or fatigue loading
conditions. This program is studying the loss of strength of an
advanced ferritic/martensitic steel as a function of cyclic loading.
The development of accelerator-driven systems for the transmutation of
nuclear waste materials will consist of liquid metal-based targets and
processing systems, likely based on liquid lead or lead-bismuth
eutectic. The processing structure must be resilient at elevated
operating temperatures, consistent with the use of liquid metals, and
in an extremely aggressive irradiation environment. This work is
focused on the selection and use of structural materials compatible
with these aggressive environments where radiation damage and liquid
metal corrosion are important.
The use of bilayer materials is being studied to understand the
fracture behavior. This behavior depends strongly on the character of
the bond and the characteristics of the structural loads. In this
study, we are concentrating on Cu alloy to 316L SS bilayers where
joining has been accomplished by hot isostatic pressing. This develops
a strong bond layer where fracture seems to be controlled by the
differing materials properties near, but not precisely on, the
interface. The interdiffusion zone leaves a region in the copper alloy
side where the microstructure is altered from the starting
microstructure. The fracture process and a useful means to quantify
the bond strength are being studied using experimental techniques and
by finite-element modeling.
A direct perception interface (DPI) integrates information into a
unified animated diagram that supports fault diagnosis more strongly
than conventional displays. Building on our earlier work on a DPI for
nuclear thermal hydraulics, this project will lead to a complete suite
of DPI displays for an entire nuclear plant, from nucleonics to power
generation. It will also take into account the need for teams of
operators to extract different types of information from a DPI. A
special case of reactor start-up has been examined to demonstrate the
effectiveness of the display.
This multiyear project has supported departmental infrastructure
including: partial funding of the TRIGA digital console upgrade,
startup funding for three new professors to establish new experimental
facilities on the TRIGA reactor: a small-angle scattering and
reflectometry system for material studies, thermal/epithermal neutron
beam system for medical diagnosis and treatment, and a temperature-
controlled neutron irradiation facility in the central thimble
location in the TRIGA. Instrumentation and computational equipment
have also been acquired for upgrading existing and equipping new
undergraduate nuclear engineering laboratories, as well as the student
computing facilities in the department. Computational equipment to
provide startup for a new faculty member was also provided.
Exergetic efficiency analysis of a dual-purpose (DP) electricity and
water production plant is considered. The total system cycle
efficiency is the sum of the electrical power efficiency and the water
production efficiency weighted by the ratio of the heat addition
temperature of the water cycle to the heat addition temperature of the
electrical cycle. Analyses show that product streams represent
competing processes from the perspective of overall cycle efficiency--
i.e., improvement of one process occurs at the expense of the other.
Thus, thermoeconomic analysis of a DP plant is considered for
optimization of the water-electricity ratio under minimized water
costs.
This multidisciplinary research is aimed at developing neural network-
based power level control strategies for nuclear reactors. A 10th
order mathematical model of a PWR is simulated using the
MATLAB/Simulink environment. The model is formulated based on point
kinetics with six delayed neutron groups and feedback from lumped fuel
and coolant temperature calculations. The neural network controller is
structured in the form of a local output gamma feedback neural network
(LOGF-NN) which utilizes digital gamma memories to provide temporal
context in varying time scales. This novel feature lends the LOFG-NN
to modeling complex engineering systems where the system is composed
of disparate members with varying time constants.
A theory is introduced for a multilayered local output gamma feedback
neural network (LOGF-NN) within the locally recurrent globally
feedforward neural network paradigm. It is developed for the
classification and prediction tasks for spatiotemporal systems and
allows the representation of different time scales through the
incorporation of a digital gamma memory. As a demonstration, it is
applied to the benchmark problem of sunspot series prediction and is
compared to other neural network (weight elimination neural network)
and statistical (linear and threshold autoregressive) methods.
Overall, the proposed LOGF-NN approach's performance is comparable to
the TAR method and outperforms the WNET approach.
World and regional energy economics models are being studied for
incorporation of modules specific to examining the future evolution of
uranium markets and the commercial value of plutonium reprocessing.
The interaction of these issues with energy and international security
concerns is examined, with emphasis on Russia and other parts of Asia.
The security and economic implications of enhanced nuclear safeguards
and more stringent controls on holdings of nuclear explosives in
general are also being investigated.
One of the main concerns involved with the design of a high-level
waste repository is the leakage of radioactive contaminants to the
environment through groundwater flow. To examine the effects of such
leakage, a model which will simulate fluid flow through porous media
of varying heterogeneity is currently under development. A discretized
form of the convective-diffusion equation will be used to describe the
contaminant transport. Simulations using Monte Carlo renormalization
group methods will be performed.
Deposition of boron (negative reactivity) in crud formed on fuel
elements has been suggested to be the reason for the discrepancy
between the predicted and measured axial power distributions in
reactors cores. Formation of crud is directly related to the subcooled
boiling that occurs in the top portions of most pressurized water
reactor cores. This project aims at establishing the link among
subcooled boiling, crud formation, and the deviation between measured
and predicted axial flux distribution. Means of reducing the boron
deposition in crud will be explored in the second phase of the
project.
The time evolution of the neutron population in a fissile assembly
containing an insufficiently large enough number of neutrons to be
able to define a probable number of neutrons per unit volume of phase
space must be analyzed on the basis of stochastic formulations. New
methods for obtaining the generating functions from which dynamics
parameters and neutron fluctuations can be found are being developed.
Methods for multidimensional assemblies are being studied.
A nodal integral method is being developed and implemented to solve
the multigroup neutron diffusion equations. Two new features--lacking
in current implementations--will be added. First, the nodal method
will allow different node sizes in the axial direction to accurately
accommodate physically distinct regions in the axial direction.
Second, the iterative solution of the final set of equations will be
carried out using the multigrid algorithm.
Experimental and theoretical studies are being performed on the
spherical inertial electrostatic confinement (IEC) jet thruster to
better understand its plasma physics behavior and performance
characteristics in order to optimize its design and operational
conditions for use as a 500- to 800-W spacecraft thruster. The IEC jet
thruster creates and accelerates ions toward a central spot, which
then escape out through a single quasi-neutral jet with electrons,
creating thrust. Faraday cup and thermocouple measurements are being
taken to determine particle energy distributions and heating power of
the jet, and hence, the device thrust and efficiency.
Radiation-induced plasmas provide a nonlinear index of refraction
media for focusing or defocusing of laser beams (gas lensing). Two
laboratory techniques have been employed to date to create such
plasmas. One technique uses neutron-induced reactions in the medium or
in coatings on surrounding surfaces while the other uses a
radioisotope source. Experimental studies of the phenomenon for a
charged-particle source generated with neutrons from a pulsed fission
reactor have been performed. Issues examined include: physics of beam
propagation in a radiation-induced plasma and potential applications
of the lensing properties of a radiation-induced plasma.
Stress limitations constrain the launch velocity from a single
centrifugal rotor and limit the utility of rotary launchers for
propulsion. Spaceborne propulsion systems can overcome this limitation
by using mass launched from one centrifuge to propel a second
centrifuge. Mass from the second centrifuge can be used to propel a
third centrifuge, and so on. An application of this method for
attaining geosynchronous transfer orbits shows potentially large
advantages over conventional chemical rockets. Centrifugal launchers
also have potential uses for inserting earth-launched payloads into
low earth orbit. Research topics in this area include kinematics,
mechanical design, and guidance system studies.
Concepts from the transformation theory of ordinary and partial
differential equations have been applied to determine self-similar
solutions of the nonlinear partial differential equations of nonlinear
and linear diffusion phenomena, hydrodynamics, and plasma physics.
Invariance properties of turbulence models have been calculated
together with the corresponding solutions. An invariant source
iteration method for one- and two-dimensional multigroup neutronics
calculations has been developed. Exact difference equations for
transient heat conduction have been determined. The theory of Lie
group extensions in discretized jet spaces needed to construct
invariant difference schemes has been worked out in terms of grid
point values of dependent variables.
A numerical model of boiling heat transfer in heterogeneous porous
layers with and without chimneys has been conducted. Experimental
observations have provided qualitative modeling information and model
refinements. 1-D and 2-D models have been evaluated numerically with
nonlinear coupling between mass, momentum, energy, capillary pressure,
and evaporation rate. Good agreement with published data has been
obtained. Examination of artificially created layer performance
suggests broad potential application for controlled boiling heat
transfer, such as computer chip cooling via freon or other CFCs, with
heat fluxes in excess of 100 W/cm2, and in steam generator tube
performance.
The effects of interfacial mixing and contact area between two liquids
of differing densities and temperatures have been studied, which
result from a high-density, high-temperature liquid passing through a
lower density, low-temperature liquid. Heat transfer effects,
including the effects of vapor generation as well as break-up and
solidification, are modeled. Analytical modeling was carried out at
UIUC while simulant experimental studies of both single and multiple
injected columns were conducted at Argonne National Laboratory. Good
agreement between model predictions and experimental data is found.
Isothermal flow tests have been conducted to determine parametric flow
resistance characteristics of hypervapotron (i.e., boiling in single-
sided ribbed flow channels) configurations using low-pressure water
systems, with prototypic dimensions and flow rates. Experimental data
indicate friction factors significantly lower than previously
published correlations and are only slightly higher than smooth wall
values. For very small flow channel height, of the dimension of the
tooth pitch or smaller, the tests show a modest friction factor
increase, but this is very sensitive to channel height.
Nonlinear finite-amplitude flow and power oscillations are important
safety concerns for BWR operations. Though many large-scale
computational codes have been developed in recent years to study this
problem, for efficient parametric analyses, simple and accurate models
that can be studied using classical stability techniques and methods
from modern bifurcation theory are needed. We are developing such a
model that includes single- and two-phase thermal hydraulics and
coupled point kinetics or modal reactor kinetics equations. Recent
results obtained using modal reactor kinetics equations show that the
low-flow/high-power region is even less stable than previously
believed because of the important effect of the first harmonic.
Nonlinear dynamics of natural circulation BWRs is being analyzed. A
low-dimensional boiling water reactor (BWR) model is being implemented
in the Hopf-bifurcation code BifDD. This model describes the nonlinear
dynamics of a BWR in the vicinity of the linear stability boundary. A
bifurcation analysis and direct numerical simulations with and without
nuclear feedback effects are being investigated. Preliminary results
show both supercritical and subcritical bifurcations for an elementary
thermohydraulic system. The elementary thermohydraulic system is being
extended with an unheated riser on top of the heated section. Further
bifurcation studies with the complete BWR model, including nuclear
feedback effects, are scheduled.
Roy A. Axford
Everitt Award for Teaching Excellence, College of Engineering, UIUC, 1985
Nuclear Engineering Student's ANS Excellence in Undergraduate Teaching Award, UIUC, 1990, 1995, 1997
Distinguished Faculty Member, Alpha Nu Sigma, 1991
Daniel F. Hang, Emeritus
Honorary Member, Alpha Nu Sigma
Life Senior Member, Institute of Electrical and Electronics Engineers
Life Member, National Society of Professional Engineers
Life Member, Illinois Society of Professional Engineers
Stanley H. Pierce Award, College of Engineering, UIUC, 1981
Distinguished Service Award, Central Zone of NCEES, 1990
Distinguished Service Award, National Council of Examiners for Engineering and Surveying, 1990
Illinois Award, Illinois Society of Professional Engineers, 1997
Loyalty Award, University of Illinois Alumni Association, 1997
Barclay G. Jones
Athlone Fellow
Honorary Member, Alpha Nu Sigma
Fellow, American Nuclear Society
Power Engineering Educator Award, Edison Electric Institute, 1991
George H. Miley
Fellow, American Physical Society
Fellow, American Nuclear Society
Fellow, Institute of Electrical and Electronics Engineers
Exceptional Service Award, American Nuclear Society, 1980
J. S. Guggenheim Foundation Fellow, 1985
United Kingdom Research Fellow, 1987
Halliburton Engineering Education Leadership Award, College of Engineering, UIUC, 1990
Distinguished Faculty Member, Alpha Nu Sigma, 1991
Outstanding Achievement Award in Fusion Energy, American Nuclear Society, 1992
Senior Fellow, Japan Society for the Promotion of Science, 1994
NATO Senior Fellow, Eastern European Outreach, 1994
Edward Teller Medal, 1995
Outstanding Scientist Award, J. New Energy, 1996
David N. Ruzic
NSF Presidential Young Investigator Award, 1985
Xerox Award for Faculty Research, College of Engineering, UIUC, 1990
Andersen Consulting Award for Excellence in Advising, College of Engineering, UIUC, 1990, 1991, 1992, 1993, 1994
Everitt Award for Teaching Excellence, College of Engineering, UIUC, 1992
Stanley H. Pierce Award, College of Engineering, UIUC, 1992
Oakley-Kunde Award for Excellence in Undergraduate Instruction, UIUC, 1993
College of Engineering Teaching Excellence Award, 1996
Harriet and Charles Luckman Undergraduate Distinguished Teaching Award, UIUC, 1996
Honorary Knight of St. Pat, College of Engineering, UIUC, 1996
The Broadrick-Allen Award for Excellence in Honors Teaching, UIUC, 1997