Tracking radioactive
scrap metal
Durable, versatile polycarbonate enclosures
for detection systems
Radioactive material contaminates scrap metal, rubble, and other industrial
waste much more often than most people would expect. Cetto develops
measurement systems for steel plants, recycling operations, and landfills to
keep these dangerous substances out of reclaiming and recycling processes.
The analyzing systems are encased in extremely durable plastic cabinets made
by Finnish enclosure manufacturer Fibox. By choosing polycarbonate over sheet
steel cabinets, Cetto has reaped many benefits ranging from far more flexible
configurability to a longer product lifespan.
< Mobile radioactivity measuring systems can be mounted directly under a scrap metal grabber
Even outside the nuclear industry, there
are numerous civilian uses for radioactive
materials. Radium, thorium, americium,
and cobalt are used in medicine, research,
and technology, for instance in radiation
therapy, in contrast agents, sterilizing
equipment, and in measurement and test
equipment. If radioactive waste gets into
the recycling system by accident or due to
criminal intent, there is a threat of serious
damage to people and the environment.
The costs for decontaminating and
restoring industrial plants are incalculable.
Additional hazards arise from imports of
radioactively contaminated steel or of
goods and technology from contaminated
regions. Decommissioned military
machines and devices can also cause
problems. The military used radioactive
luminous paints based on strontium or
radium on a large scale until the second
half of the 20th century. They were applied to make switches, dials, and
control elements visible in the dark. “To
this date, old aircraft instrument panels
painted with such glow-in-the-dark
paints keep appearing on junkyards,”
says Torsten Knoll, who is in charge of
Reliable identification of radiation
sources that can be installed under any type of
scrap metal grabber. Here, the distance
between the checked material and the
detector is shorter, and the average
measurement time is longer than with
portal measuring systems. Sources of
radioactivity are reliably detected because
there is less surrounding material. The
detectors consist of a crystal scintillator,
a photomultiplier, and measurement
electronics. A single crystal of sodium
iodide or cesium iodide is used as crystal
scintillator. “Single crystal” means that
the atoms or molecules of the crystal
form a continuous, homogeneous crystal
lattice. When exposed to gamma radiation
(or high-energy photons and ions), the
molecules of such a single crystal are
energetically stimulated and emit light. A
photomultiplier converts the light pulses
“Unfortunately, installing suitable
measuring systems at scrapyards and
recycling plants is currently left entirely
at discretion of the operators,” Knoll
points out. Many of those who run metal
collection centers are unaware of the
risk. On the other hand, scrap metal
deliveries to many steel and rolling mills
are scrupulously tested for radioactivity at
several stops along the way. Cetto supplies
stationary and mobile measuring systems
for various measuring points. Measuring
systems for portals can check truck or car
loads as the vehicles enter the premises.
This screening procedure only takes a
few seconds. To check smaller amounts
of material, there are conveyor belt
measuring systems and mobile systems
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PECM Issue 28
metrological technology development at
Cetto. His company is based in Ratingen,
Germany. Cetto has been a specialist for
the installation of highly sensitive crystal
detectors for radioactive emitters for some
25 years.
Torsten Knoll is in charge of the development of metrological systems at Cetto
into electrical signals. The signal spectrum
is measured with 1024 channels. Measured
values are then transmitted to a PC. Cetto’s
analysis software identifies the radiation
source’s composition by matching the
measured spectrum with a nuclide
database that can be edited by the user.
Portal measuring systems check trucks or
railway cars for radioactive emitters – they do
not have to be unloaded