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History of HFIR
Why Was HFIR Built?
The status of the transuranium production
program was critically reviewed by
the U.S. Atomic Energy Commission (AEC)
Division of Research at a meeting on
January 17, 1958. At that time the
AEC decided to embark on a program
designed to meet the anticipated needs
for transuranium isotopes by undertaking
certain irradiations in existing reactors.
By late 1958 it became apparent that
acceleration of this program was desirable.
Following a meeting in Washington,
D.C., on November 24, 1958, the AEC
recommended that a high-flux reactor
be designed, built, and operated at
ORNL, with construction to start in
FY 1961.
As a result of this decision ORNL
submitted a proposal to the AEC in
March 1959. Authorization to proceed
with the design of a high-flux reactor
was received in July 1959. The preliminary
conceptual design of the reactor
was based on the "flux trap" principle,
in which the reactor core consists of an annular region
of fuel surrounding an unfueled moderating region or "island." Such
a configuration permits fast neutrons leaking from
the fuel to be moderated in the island and thus produces
a region of very high thermal-neutron flux at the center
of the island. This reservoir of thermalized neutrons
is "trapped" within the reactor, making it available
for isotope production. The large flux of neutrons
in the reflector outside the fuel of such a reactor
may be tapped by extending empty "beam" tubes
into the reflector, thus allowing
neutrons to be beamed into experiments
outside the reactor shielding. Finally,
a variety of holes in the reflector
may be provided in which to irradiate
materials for later retrieval.
In June 1961, preliminary construction activity was
started at the site. In early 1965, with construction
complete, final hydraulic and mechanical testing began.
Criticality was achieved on August 25, 1965. The low-power
testing program was completed in January 1966, and
operation cycles at 20, 50, 75, 90, and 100 MW began.
From the time it attained its design power of 100 MW
in September 1966, a little over 5 years from the beginning
of its construction, until it was temporarily shut
down in late 1986, the HFIR achieved a record of operation
time unsurpassed by any other reactor in the United
States. By December 1973, it had completed its 100th
fuel cycle, approximately 23 days each.
Notable accomplishments resulting from HFIR operation
include the production of californium-252, which is
used for reactor startup sources, scanners for measuring
the fissile content of fuel rods, neutron activation
analysis, and fissile isotope safeguards measuring
systems. In addition, californium-252 is used as a
medical isotope to treat several types of cancer. Also,
neutron activation analysis at HFIR has been used by
the semiconductor industry, environmental remediation
operations, and the Food and Drug Administration.
The Fusion Energy Program has been supported by the
HFIR in three major areas, including neutron interactive
materials (structural materials and ceramics), high
heat flux materials, and plasma interactive materials.
The neutron-scattering
facility at HFIR has provided support to basic
research programs involving neutron scattering from
polymers, colloids, magnetic materials, alloys, superconductors,
and biological materials.
In November 1986 tests on irradiation surveillance
specimens indicated that the reactor vessel was being
embrittled by neutron irradiation at a rate faster
than predicted. The HFIR was shut down to allow for
extensive reviews and evaluation of the operation of
this facility. Two years and five months later, after
thorough reevaluation, modifications to extend the
life of the plant while protecting the integrity of
the pressure vessel, and upgrades to management practices,
the reactor was restarted. Coincident with physical
and procedural improvements were renewed training,
safety analysis, and quality assurance activities.
Documents were updated, and new ones were generated
where necessary. Technical specifications were amended
and reformatted to keep abreast of the design changes
as they were accepted by DOE. Not only were the primary
coolant pressure and core power reduced to preserve
vessel integrity while maintaining thermal margins,
but long-term commitments were made for technological
and procedural upgrades.
After a thorough review of many aspects of HFIR operation,
the reactor was restarted for fuel cycle 288 on April
18, 1989, to operate initially at very low power levels
(8.5 MW) until all operating crews were fully trained
and it was possible to operate continuously at higher
power. Following the April 1989 restart, a further
shutdown of nine months occurred as a consequence of
a question as to procedural adequacy. During this period,
oversight of the HFIR was transferred to the DOE Office
of Nuclear Energy (NE); previously, oversight was through
the Office of Energy Research (ER). Following permission
by Secretary of Energy James Watkins to resume startup
operation in January 1990, full power was reached on
May 18, 1990. Ongoing programs have been established
for procedural and technological upgrade of the HFIR
during its operating life.
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