atw - International Journal for Nuclear Power | 11/12.2019

atw Vol. 64 (2019) | Issue 11/12 ı November/December
steel. Tested paint layers can be
ablated at fluence above 1.8 J/cm²,
while oxide layers can be removed at
even lower fluence.
The achieved ablation depth for
the above mentioned materials is
plotted in Figure 2.
It can be seen that the removal
speed is about 100 times higher for
paint than for metals, what supports
the selective removal of the paint on
the metal ground. A variation of laser
fluences between 1.8 – 3.5 J/cm² has
been tested for its decontamination
effect on blank austenitic steel. Single
scans resulted in a contamination
reduction of 50 – 90 % for all surrogates.
Similar tests have been conducted
on painted surface applying a
laser fluence of 4.4 J/cm², to prove
complete removal of the covering
layer (Figure 3).
Both tested cases result in a
decreased contaminant concentration
and decontamination factors up to
98.9 have been achieved.
4 Laser-based PCB
degradation
The TU Dresden has developed a PCB
decontamination process by utilising
a continuous wave diode laser.
Laboratory experiments on concrete
surfaces coated with epoxy paint
demonstrated a reduction of 96.83 %
of the PCB value. The PCB decomposition
rate on the surface and in
the exhaust gas before filtering is
88.75 % [16].
PCB decomposes at temperatures
above 800 °C. At optimized process
parameters the temperature in the
laser spot is much higher [17], enable
the full decomposition of the PCB.
Rapid cooling of the exhaust gas is
required to prevent the formation of
toxic polychlorinated dioxins and
furans (PCDD/PCDF) which can be
ensured by the laser processing. The
application of a fabric filter in the
extraction and filtration unit limits
the temperature of filtered exhaust
gas to