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About HFIR
The ORNL High Flux Isotope Reactor
(HFIR) is the highest
flux reactor-based source of neutrons
for condensed matter research in
the United States. Thermal and
cold neutrons produced by HFIR are
used to study physics, chemistry,
materials science, engineering, and
biology.
The 85-megawatt High Flux Isotope
Reactor (HFIR) provides one of the
highest steady-state neutron fluxes
of any of the world's research reactors.
The intense neutron flux, constant
power density, and constant-length
fuel cycles are used by more than
200 researchers each year for neutron
scattering for probing the fundamental
properties of condensed matter. The
Neutron Scattering Research Facilities possess
a powerful collection of spectrometers
and unique thermal-neutron scattering
capabilities used for fundamental
and applied research on the structure
and dynamics of matter. The reactor
is also used for medical, industrial,
and research isotope production;
research on severe neutron damage
to materials; and neutron activation
to examine trace elements in the
environment.
The HFIR is the western world's sole
supplier of californium-252, an isotope
with uses including cancer therapy
and detecting pollutants in the environment
and explosives in luggage. The Activation
Analysis Facility is a powerful tool
for analyzing environmental pollutants.
Since it began full-power
operations in 1966, the High
Flux Isotope Reactor (HFIR)
at the Oak Ridge National Laboratory
(ORNL) has been one of the
world's most powerful research
reactors. The major use of
the HFIR is for neutron-scattering
experiments to reveal the
structure and dynamics of a
very wide range of materials.
The neutron-scattering instruments
installed on the horizontal
beam tubes are used in fundamental
studies of materials of interest
to solid-state physicists,
chemists, biologists, polymer
scientists, metallurgists,
and colloid scientists. These
instruments are open to use
by university and industrial
researchers on the basis of
scientific merit.
One of the original primary
purposes of the HFIR is the
production of californium-252
and other transuranium isotopes
for research, industrial, and
medical applications. These
materials are produced in the
flux trap in the center of
the HFIR fuel element where
a working thermal-neutron flux
of 2.0 x 1015 neutrons/(cm²·s)
is available to irradiate the
target material. Additional
irradiation facilities are
also provided in the beryllium
reflector.
Beyond its contributions to isotope
production, the HFIR also provides
for a variety of irradiation tests
and experiments that benefit from
the exceptionally high neutron
flux available. In the fuel element
flux trap, a hydraulic rabbit tube
provides access to the high thermal-neutron
flux in the reactor for short-term
irradiations, and other positions
are ideal for fast-neutron irradiation-damage
studies. A modification of the
flux trap experiment facilities
in 1986 has provided two locations
in the maximum flux region that
can accommodate instrumented capsules
and engineering loops. The beryllium
reflector contains numerous experimental
facilities with thermal-neutron
fluxes up to 1.0 x 1015 neutrons/(cm²·s).
These facilities can accommodate
static experimental capsules, complex
fuel-testing engineering loops,
and special experimental isotope
irradiations.
Benefits from Research at HFIR
Picking the Right Material for the Job
Any airline passenger who has struggled to open
those bags of peanuts and pretzels knows that thin
polymer films can be strong. The frustratingly durable
packages are often blends of high- and low-density
polymers. High-density polyethylene is a strong,
hard, bricklike material made of long linear polymer
chains; low-density polyethylene materials are made
of polymer chains with many branches. Not surprisingly,
blends of high-density and low-density polymers are
popular and important materials. About 100 million
tons are now produced each year for other ubiquitous
consumer products such as sandwich bags and high-strength
garbage bags.
To develop new types of polymer blends for even higher-performance
materials, a critical question is: Will the separate
components of the polymer really blend to make a
new material, or will they simply congregate in small
intermingled globs of the original materials? More
precisely, will the materials blend or will they
segregate?
This critical question would likely be impossible
to answer without small-angle neutron scattering.
Neutrons--neutrally charged particles that help make
up part of an atom's nucleus--have a handy ability
to penetrate materials. To make use of that ability,
researchers first replace the hydrogen atoms in one
of the polymer components with deuterium, another
form of hydrogen. The deuterium scatters neutrons
passing through the material differently but does
not affect the property of the polymer. Measuring
how the neutrons "scatter" can reveal the difference
between a real polymer blend and a segregated material.
It's important to know which is which. Segregated
material deteriorates over time, whereas true blends
do not. Exxon, Phillips Petroleum, and Dow Chemical
are among manufacturers who use the neutrons produced
in Oak Ridge National Laboratory's High Flux Isotope
Reactor to sort polymer blends from segregates. They
can then determine how long the material will last
and thus tailor the material for its intended application.
It's worth much more to these industries than peanuts.
Putting Your Car in a Quiet Gear
We all want our cars to run well and run quietly.
Whether they do depends in part on the precision
and uniformity of the gears that transfer power from
the engine to the wheels.
Manufacturing processes, however, can introduce distortions
and residual stresses deep inside the gear material.
These flaws--difficult to measure with conventional
techniques-- often cause poor performance or premature
breakdowns, not to mention an annoying growl. Researchers
can now use capabilities provided by Oak Ridge National
Laboratory's High Flux Isotope Reactor and the Residual
Stress User Center, which is part of the High Temperature
Materials Laboratory user facility at ORNL, to determine
residual stresses in an automobile transmission gear.
Neutrons from the reactor can penetrate far into
most engineering materials without damaging the material,
allowing engineers using sophisticated materials
analysis equipment to identify residual stresses
without destroying the gear. Measurements on a General
Motors Saturn gear proved that residual stresses
can be mapped at points separated by only one millimeter
(less than 1/25th of an inch).
These promising initial results led General Motors
Corporation, Ford Motor Company, and other industrial
members of the National Center for Manufacturing
Sciences to ask that ORNL's Residual Stress User
Center and Los Alamos National Laboratory join them
in collaborative research. For automobile owners,
the result of this collaboration could be a quiet
ride that lasts for miles and miles.
Saving Lives and Money with Isotopes
Both lives and money are being saved with isotopes
produced by the High Flux Isotope Reactor at Oak
Ridge National Laboratory. The HFIR, with its intense
neutron flux, is the West's sole source of californium-252,
an intense neutron-emitting radioisotope used extensively
in medical and industrial applications: cancer therapy,
neutron radiography, elemental analysis, and as a
startup source for nuclear reactors.
Californium-252 is effective in treating certain
cervical and brain cancers that are otherwise incurable.
Using it, Dr. Yosh Maruyama at the University of
Kentucky has treated more than 450 patients with
advanced cervical cancers, improving the 5-year survival
rate for this type of cancer from 12% to 54%. With
this kind of progress in mind, researchers are investigating
its applications to other cancers.
Other medical isotopes produced at the HFIR include
potassium-43 (for evaluation of coronary heart disease),
palladium-103 (for treatment of prostate cancer),
gadolinium-153 (for measuring bone loss in women),
and tungsten-188 (associated with the treatment of
cancer and arthritis). Thousands of patients undergo
clinical evaluation or treatment using these and
other isotopes each year. In fact, more than 100
million Americans receive diagnosis or therapy annually
using some aspect of nuclear medicine. Of those,
10 million radioimmunoassays are performed annually.
In addition to its role in combating disease, californium-252
is used for radiography of aircraft to detect metal
fatigue. At McClellan Air Force Base, engineers use
californium- 252 to examine fighter aircraft, a technique
that saves $5 million a year in repair costs alone.
As a lifesaver in a different sense, the isotope
is also used to detect explosive devices.
Alvin Weinberg, a former ORNL director, once observed: "If
at some time a heavenly angel should ask what the
laboratory in the hills of East Tennessee did to
enlarge man's life and make it better, I daresay
the production of radioisotopes for scientific research
and medical treatment will surely rate as a candidate
for very first place."
New Cask, Racks will Help HFIR Fulfill Its New "Extended
Mission"
The High Flux Isotope Reactor will remain an important
asset for neutron research for ORNL and the nation
for the foreseeable future. Two recent developments
at HFIR reduce the concerns regarding spent-fuel
storage and should help ensure the reactor's increasingly
important continued operation.
The problem with spent fuel has been twofold: DOE
has long been without an acceptable container for
shipping spent fuel over the roadways, most likely
to the Savannah River Plant. Unable to be shipped
for lack of a certified container, spent fuel has
been stored in the reactor's pool, which is an acceptable
method of storage as long as there is room for it.
Space, however, was running out. In a nutshell, the
HFIR can't operate if there is nowhere to store its
spent fuel. The General Electric-made spent-fuel
container, examined by DOE's Dave Rosine, features
a leak-tight cask contained witha fire- and impact-resistant
outer shell. A spent-fuel cask made specifically
for the Research Reactors Division by General Electric
was exhibited in January cinched to the back of a "low-boy" semi
trailer. The container's dumbbell- shaped exterior,
fastened to the trailer with thick steel cables,
conceals a cylindrical, leak-tight cask. The cask
and curiously shaped overpack are designed to withstand
impacts and fires that could occur during transport.
The $2.6 million container meets stringent Nuclear
Regulatory Commission requirements.
Loading the spent fuel into the container is an interesting
process: The cask will be removed from the outer
shell and lowered into the reactor pool. There, under
about 6 meters of water, a spent-fuel assembly will
be loaded into the cask. After some drying out, the
cask will be checked for leaks, placed back in the
overpack, and sent on its way. It is hoped that shipments
of spent fuel will commence about midyear when DOE
lifts a moratorium on such shipments.
In the meantime, spent fuel has accumulated in the
HFIR's storage pool almost to capacity. A redesign
and installation of new fuel- storage arrays will
conserve space in the pools and allow safe storage
of more fuel elements. The new design uses jacketed
assemblies to store fuel in silo clusters, connected
in groups of four or five. RRD engineers designed
the clusters and performed most of the analyses,
taking into consideration criticality, thermal, seismic,
structural, and shielding safety factors. Plant and
Equipment Division craftsmen made them. The first
new racks were installed on December 1; further installations
will continue.
HFIR's spent-fuel storage arrays sit behind the reactor
pool. With no acceptable container to ship spent
fuel, pool space for the spent fuel was running out.
The new racks, along with the new shipping cask,
should clear a barrier to HFIR's continued operation.
HFIR operations are a showpiece of strict adherence
to procedures and conduct of operations, and the
new cask and arrays are no exception. Their fruition
took many months of work--with strict attention to
detail--by the organizations involved. The benefits
will probably go beyond the HFIR operation. Efforts
are under way to expand the certification of the
cask to ship fuel from other DOE research reactors.
Also, the availability of a properly certified shipping
cask should help speed the decommissioning of the
Bulk Shielding Reactor and the Tower Shielding Reactor
at ORNL.
HFIR's last shipping cask was retired in 1986, and
spent fuel has been stored in the pool ever since.
The new cask and the more space-efficient racks should
help the HFIR continue to crank out neutrons on its
now extended tour of duty.
Neutrons and JFK
Most Laboratory personnel learned of the assassination
of President John Kennedy over the Laboratory's public
address system on the afternoon of November 22, 1963.
A week later, the Federal Bureau of Investigation
(FBI) asked the Laboratory to study fragments of
the bullets that struck the president and the paraffin
casts taken of the hands and face of Lee Harvey Oswald,
the accused assassin.
This request was made because the Laboratory had
facilities and scientists available for performing
neutron activation analysis. When neutrons from a
reactor activate the atomic elements in a material,
each element emits characteristic gamma rays, revealing
its presence and concentration in the material.
About five years after John Kennedy had admired the
Oak Ridge Research Reactor as a U.S. senator, evidence
relating to his assassination came to the Laboratory,
where William Lyon Jr., Frank Dyer, and Juel Emery,
all of the Analytical Chemistry Division, tested
it in the High Flux Isotope Reactor's neutron flux.
The FBI hoped Laboratory researchers could match
gunpowder particles on the paraffin casts with gunpowder
from a rifle found at the crime scene. The fact that
Oswald had fired a pistol, killing a Dallas policeman,
the day of the assassination, and earlier tests made
on the paraffin casts complicated the research and
made the Laboratory's results inconclusive.
The FBI hoped that ORNL's neutron activation analysis
of the bullet fragments taken from the president's
limousine could determine whether the bullets were
fired from a single weapon. Lead bullets have traces
of silver and antimony, and the Laboratory's analysis
of these traces indicated that the bullets did indeed
come from the same rifle. Later independent study
by a University of California neutron activation
specialist confirmed the Laboratory's conclusion.
ORNL's Nuclear and Radiochemistry Analysis group
complied with many requests for neutron activation
analysis in connection with crimes until the 1970s
when commercial laboratories entered the field.
Presidential Visit from the Grave
Shortly after breaking ground for the Washington
Monument on July 4, 1850, President Zachary Taylor,
a hero of the Mexican War, fell ill. When he died
suddenly a few days later, the cause was listed as
gastroenteritis (inflammation of the stomach and
intestines).
Some historians suspected that Taylor's death may
have had other causes, and in 1991 one convinced
Taylor's descendants that the president might have
suffered arsenic poisoning. As a result, Taylor's
remains were exhumed from a cemetery in Louisville
and Kentucky's medical examiner brought samples of
hair and fingernail tissue to Oak Ridge National
Laboratory for study.
In the Chemical and Analytical Sciences Division,
Larry Robinson and Frank Dyer headed the Taylor investigation,
using neutron activation analysis to measure the
amount of arsenic in the hair and nail samples. After
placing the samples in a beam of neutrons from the
High Flux Isotope Reactor, Dyer and Robinson looked
at the gamma rays coming from the samples for the
distinctive energy levels associated with the presence
of arsenic. Arsenic is among the easier elements
to identify through neutron activation and can be
detected in a few parts per million. Most human bodies
contain traces of arsenic, so the essential issue
in the Taylor case was whether the samples from Taylor
contained more arsenic than would be normal after
141 years in the crypt.
Working late in the evenings, Dyer and Robinson in
a few days calculated the arsenic levels in the samples
and sent them to the Kentucky medical examiner for
his decision. After reviewing the test results, the
examiner announced that the arsenic levels in the
samples were several hundred times less than they
would have been if the president had been poisoned
with arsenic. This finding acquitted several of Taylor's
prominent contemporaries of the suspicion of murder
and proved that history and science share a common
quest for truth.
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