A group of spectators gathers at the ACRR for its 10,000th operation. The shot was videostreamed live to a nearby auditorium to accommodate more than 150 onlookers. The ACRR has been in operation for more than 32 years at Sandia. Photo: Randy Montoya |
With a muffled “pop,”
a flash of blue light, and a few ripples through 14,000 gallons of deionized
water, Sandia National Laboratories’ Annular Core Research Reactor (ACRR)
recently conducted its 10,000th operation.
“The ACRR has been a
real workhorse for Sandia, and laboratories leadership and the nation rely on
these experiments and other weapons component testing done at Sandia to support
certification of the nuclear weapon stockpile,” says Lonnie Martin, an ACRR
operator.
In its 32-year
history, the ACRR time and again has proved itself a valuable resource for a
wide variety of experiments in nearly every branch of nuclear science,
especially the testing of radiation-hardened electronic components.
With a dry, 9-in
diameter cavity in the core’s center, and a 20-in diameter external cavity, the
ACRR subjects electronics to high-intensity neutron irradiation and conducts
reactor safety research. The ACRR also has done testing for semiconductor
manufacturers, NASA, the Large Hadron Collider in Switzerland, and dozens of other
users.
Sandia’s ACRR is a
water-moderated, pool-type research reactor capable of steady-state, pulsed,
and tailored transient operations and, in the past, has been configured for
medical isotope production. Other duties for ACRR include: reactor-driven laser
experiments; space reactor fuels development; pulse reactor kinetics; reactor
heat transfer and fluid flow; electronic component hardening; and explosive
component testing. It is also routinely used for education and training
programs.
At peak power in its
steady state mode, the ACRR produces up to four megawatts of power. But during
a maximum pulse, it generates a whopping 35,000 MW of power for 7 msec. Nuclear
engineer and former University of New Mexico professor Ron Knief compares its power
output to that of the Palo Verde Nuclear Generating Station, outside of Phoenix. “For that very
short time, we produce three times more power than the nation’s largest nuclear
power station. They have three big reactors, and yet, for a fraction of a
second, we produce three times more power than they do,” Knief says.
The ACRR is a
descendent of the Sandia Annular Core Pulse Reactor (ACPR), which was replaced
in 1978 and is part of a large family of Training, Research Isotope Production,
General Atomics (TRIGA) reactors. The TRIGA concept is credited to Manhattan
Project physicist Edward Teller and a group of distinguished scientists who
assembled the first model in a “Little Red Schoolhouse” in San Diego in 1956. Teller’s mandate to the
team was to “design a reactor so safe … that if it was started from its
shut-down condition and all its control rods instantaneously removed, it would
settle down to a steady level of operation without melting any of its fuel,”
according to Freeman Dyson’s, “Disturbing the Universe.” Essentially, even if
all the engineered safety mechanisms failed, the reactor would operate safely,
based on the laws of physics.
In 1978, the original
ACPR TRIGA fuel was replaced with a new ACRR ceramic-metal, uranium dioxide/beryllium
oxide fuel, which is designed to allow steady state and pulsed operation at
fuel temperatures up to 2,552 degrees (1,400 C). The reactor underwent
extensive upgrades in 2002, including upgrades to reactivity control circuitry.
