[ RadSafe ] Article: "Researchers pursue the goal of a portable detector . . ."

[John Jacobus]

It is nice to see some new developments in detector
technology.

>From the Oak Ridge National Laboratory Review, Volume
39, Number 1, 2006, at 
http://www.ornl.gov/info/ornlreview/v39_1_06/article19.shtml

Quickly and Accurately

Researchers pursue the goal of a portable detector
that instantly identifies a package's radioactive
contents.

Hand-held radiation detectors and radiation monitors
can sense radioactivity in abandoned packages. Today's
security challenges, however, require a portable
detector that instantly reveals the precise nature of
an unidentified package's radioactive contents.

Such a detector can be built if a material can be
identified that captures radiation efficiently and
provides highly detailed information about an isotopic
source. ORNL researchers are working on this goal.

"The federal government wants radiation detectors that
are smaller, simpler, faster, more sensitive, higher
resolution, and less expensive than today's
instruments," says Lynn Boatner, 

[Picture: ORNL researchers developed silicone rubber
bonded with boron compounds that emits blue light in
the presence of neutrons.]
   
a materials physicist in ORNL's Condensed Matter
Sciences Division who directs the new Center for
Radiation Detection Materials and Systems at ORNL. "We
are investigating various new materials and systems
for detecting radiation and for tracking sensitive
items for the Department of Energy's Nuclear
Nonproliferation Office, the Department of Homeland
Security, and other government agencies."

ORNL researchers are fabricating and characterizing
the radiation response of detectors made of innovative
"scintillators," including crystalline materials and
glasses with high density that give off photons of
light when exposed to radiation. "These materials show
the potential for detecting radiation with great
efficiency and yielding an ultrafast response on the
order of tens of nanoseconds or less," says Boatner,
who is an ORNL corporate fellow. "Some of these
materials have a relatively high energy resolution,
suggesting they could enable a detector to distinguish
among radiation emissions from different
radioisotopes."

The best of these materials may be strong candidates
for portable radiation detectors at airports, train
stations, and ports. Other materials might be
practical for large-area portal monitors that screen
truck containers at weigh-and-inspection stations for
radioactive cargo. The goal is to distinguish between
benign radioactive products found in normal
commerce—such as medical radioisotopes, smoke
detectors, ceramic pots, and kitty litter—and
potentially dangerous nuclear materials (cesium,
strontium, uranium, and plutonium) that could be
intended for a terrorist bomb.

Boatner and colleagues John Neal, Joanne Ramey, and
Jim Kolopus are striving to develop a powerful,
versatile, alternative method for producing large,
transparent inorganic scintillators without the need
to grow large single crystals, a task that is often
time consuming and difficult to accomplish. They have
recently synthesized zinc oxide nanoparticles doped
with gallium using urea precipitation methods and were
able to produce translucent ZnO ceramics by techniques
based on hot pressing.

Sheng Dai of ORNL's Chemical Sciences Division is
investigating nanocrystalline and glass scintillators
formed by sol-gel processes. Dai and Zane Bell of
ORNL's Nuclear Science and Technology Division have
been fabricating and characterizing neutron
scintillators that are high in lithium or boron. Bell
has been investigating new types of mercury-containing
scintillators.

Bell has led the development of a new radiation
detector material and detector prototype, both of
which have been licensed to NucSafe, an Oak Ridge
manufacturer of radiation detectors. Bell's research
team developed a silicone rubber laced with boron that
emits a blue-green light in the presence of alpha,
beta, gamma, and neutron radiation. Having an 18%
boron content makes the silicone rubber material an
excellent detector of neutrons that indicate the
presence of uranium and plutonium. Researchers believe
the silicone rubber could be incorporated into another
invention, the HotSpotter, an inexpensive, handheld
gamma-ray spectrometer.

The heart of the HotSpotter is a scintillator made of
cadmium tungstate, whose extremely high density
increases the probability that gamma rays will
interact with the crystal's light-emitting molecules.
The HotSpotter software analyzes the gamma-ray
spectrum to identify the radioisotope present.

Other ORNL work in the new center includes research on
cerium-doped, rare-earth double phosphates for
radiation detectors, as well as related research on
new phosphor materials for possible use in tagging,
tracking, and locating sensitive items.

The collective goal for all of these projects is the
ability to prevent an increasing array of dangerous
materials from reaching the hands of America's adversaries.

+++++++++++++++++++
"Those who corrupt the public mind are just as evil as those who steal from the public purse."
Adlai Stevenson

-- John
John Jacobus, MS
Certified Health Physicist
e-mail:  crispy_bird at yahoo.com

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