Dana Landrum, Quality Assurance technician, is reflected in the four-sided pyramidal mirror of CoLOSSIS, a computed tomography imaging system unique to Pantex and used to nondestructively determine the integrity of pits.
What does it take to look inside the core of a
nuclear weapon? Start with four cryogenically cooled astronomy cameras
capable of 8,000 by 8,000-pixel images, one four-sided pyramidal mirror
and a burst of photons generated by an X-ray source
nearly 100 times more powerful than a medical computed tomography (CAT)
scan, and you have the world’s only computed tomography imaging system
used to determine integrity of pits – CoLOSSIS.
As many as 1,800 images of each pit are taken over
multiple days at Pantex using the Confined Large Optical Scintillator
Screen and Imaging System, or CoLOSSIS, to nondestructively determine if
they will function as expected. A pit is a
component made of plutonium metal and is the heart of a nuclear weapon.
The imaging is conducted on surveillance units as designated by the
Prior to the introduction of CoLOSSIS three years
ago, film was used for analysis of pits, which offers only a
two-dimensional perspective. But confidence in the nation’s nuclear
stockpile required more efficient technology.
The 32,000-pound, lead-shielded CoLOSSIS is
operated by highly trained quality assurance technicians whose
background stems from the medical or industrial non-destructive
It takes an average of 15 to 18 hours for CoLOSSIS
to work its magic, during which time a component rotates approximately
0.2 degrees for each image until it has rotated 360 degrees to capture
an entire data set. During each rotation, the
X-ray source known as a linear accelerator, or LINAC, produces photons
collected by a scintillator that converts the photons into green light
used to create a digital image. Collimators direct the energy, focusing
the X-ray beam onto a pyramid-shaped mirror
that reflects the light into the cameras, which in turn collect the
Data is then transmitted to Lawrence Livermore
National Laboratory, designer of the system, and Los Alamos National
Laboratory. The labs use computer code to reconstruct the analyses by
stitching images taken by the four cameras into one.
This offers scientists a three-dimensional view inside the nuclear
weapon’s core that they can literally “walk through” to detect
manufacturing flaws and the effects of aging.
“This system represents a successful collaboration
between Pantex and the Design Laboratories, despite the technical
challenges that are to be expected of a one-of-a kind system like
CoLOSSIS,” said Gerken.
Designs for a second CoLOSSIS system are in the
works and equipment is being procured, Gerken said. “Once operational,
this system will give us a second line to aid in workflow throughput and
could possibly provide capabilities for analysis
of different components,” he said.