Applications of microwave radiation environmental remediation technologies Page: 3 of 11
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The DOE laboratories are currently developing a variety of technologies
that use microwave radiation as an integral part of their process to address such
problems. The applications of microwave radiation in these technologies range
from more conventional applications such as sintering and heating to novel
applications such as promoting chemical reactions and sustaining plasmas. This
article will review five technologies: (1) the microwave spaller for concrete
decontamination at Oak Ridge National Laboratory, (2) the microwave
solidification process at the EG&G Rocky Flats Plant, (3) the microwave
vitrification of radioactive waste at Savannah River National Laboratory, (4)
the microwave fluidized bed reactor at Los Alamos National Laboratory, and
(5) the microwave plasma reactor at Argonne National Laboratory.
A. MICROWAVE SPALLER FOR CONCRETE DECONTAMINATION
Concrete contamination is a major problem at many DOE facilities,
including K-25 at Oak Ridge. Research has indicated that the major portion of
the contamination, primarily 235U and 238U, lies within the top few millimeters
of the exposed surface. DOE is currently investigating a number of
decontamination technologies to remove this layer and thus significantly
decrease the cost of decommissioning these facilities.
Present decontamination technologies generally use mechanical
techniques (e.g., impact breaking, mechanical chisels, high-pressure water
sprayers, or steel shot blasters), which utilize high-energy blasting of the
surface. While these technologies can very rapidly remove contaminated
surface layers, they produce large amounts of dust particles that must be
contained and removed. Water, used either for blasting or for suppressing dust
generation and entrainment, produces a secondary waste stream that will
require subsequent treatment. Water can also solubilize some contaminants
driving them deeper into the concrete.
The microwave spaller currently being developed at Oak Ridge(5a-) is a
dry technique that generates little airborn dust. It uses microwaves to heat
absorbed water within the concrete matrix and create pressure-induced
mechanical stresses. These stresses cause the surface to burst, yielding small
particles in the 1- to 10-mm range. A vacuum cleaner collects the dust
The microwave spaller uses microwave radiation, either 2.45 or 10.6
GHz, directed at the concrete surface by a waveguide. The dimensions of the
waveguide depend on the frequency, 7.21 cm x 3.4 cm for 2.45 GHz and 2.29
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Krause, T. R. & Helt, J. E. Applications of microwave radiation environmental remediation technologies, article, May 1, 1993; United States. (https://digital.library.unt.edu/ark:/67531/metadc1317638/m1/3/: accessed April 20, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.