POWER August 2018 - 39

RADIOACTIVE WASTE MANAGEMENT
Fluidized Bed Steam Reforming
Technology Reduces Volume of
Radioactive Waste
A patented Fluidized Bed Steam Reforming (FBSR) technology uses superheated
steam-instead of an open flame-and mineralizing additives to treat
and immobilize radionuclides in a water-insoluble matrix. Results show a
6:1 average volume reduction for ion-exchange resins, which allows disposal
without entering into higher, more-restrictive and expensive waste
classifications. Since initial pilot studies beginning in 1997, FBSR technology
has been deployed in the U.S., Japan, and France.
James M. Hylko
T
he nuclear industry annually produces
voluminous amounts of radioactively
contaminated
ion-exchange
resins
(IERs) comprised of organic material, usually
a styrene polymer containing sulfonic
acid and amine groups. The resins, for example,
are used to concentrate and remove
activation, corrosion, and fission-product
radionuclides from nuclear plant liquid
waste streams. Traditional high-temperature,
flame-induced combustion treatment processes
(such as incineration) form and release
sulfur and nitrogen oxides, including
vaporization of cesium-137, requiring highperformance
filtering systems. The retained
radioactively contaminated fly ash is solidified
and containerized according to transportation
and low-level radioactive waste
(LLRW) disposal regulations.
Following a number of pilot studies beginning
in 1997, Studsvik developed and patented
a non-incineration Fluidized Bed Steam
Reforming (FBSR) technology-that uses
steam-to treat a variety of LLRWs containing
high organic, nitrate, nitrite, solids, and heavymetal
content, while producing a dry, stable,
granular, final waste form. Because there is no
flame present in the primary waste treatment
vessel, the treatment process is not considered
incineration. Additional advantages include
no liquid effluents other than water vapor and
Clean Air Act-compliant off-gas emissions.
Treating Low-Level Radioactive
Wastes
POWER interviewed Adam Foster, PE, head
of engineering services with Studsvik Inc.,
who is based in Atlanta, Georgia, for details
about the FBSR technology. One location that
utilizes FBSR technology is the Erwin Resin
August 2018 | POWER
Solutions (ERS) Facility located in Erwin,
Tennessee (Figure 1). It is a production-scale,
shielded facility that houses equipment for
handling and converting LLRW into an inert,
stable, and volume-reduced final waste form.
Studsvik's FBSR waste
decomposition
process uses steam pyrolysis as an alternative
to incineration and other traditional thermal
treatment methods. This yields a solid,
inert, stable, and substantially smaller volume
waste matrix, while meeting all federal
and state radioactive waste processing laws,
codes, and standards.
Foster described how spent IERs from
commercial nuclear plants are shipped to the
ERS and transferred as a water/IER slurry
to waste holding tanks located in shielded
vaults. After the IERs settle in the holding
tanks, excess water is decanted from the top.
Mixing the settled IERs creates a homogenous
mixture, which is transferred to a
metering tank to start the FBSR process. A
mineralizing additive is mixed with the IER
as it is metered/fed into the FBSR vessel to
prevent agglomerations from forming in the
fluidized bed. Other process additives, such
as mineralizing clay, may be added depending
on the type/composition of the waste
and the desired final waste matrix durability
characteristics, which include water solubility
and leach resistance.
Low-pressure superheated steam is introduced
through gas nozzles, creating a fluidized
bed at the FBSR vessel bottom with a
gas-phase freeboard in the vessel top. In the
fluidized bed, the waste feed is instantly dried,
and the large active surface of dried organics
readily pyrolyze in the reducing environment,
resulting in the destruction/volatization of
organics into carbon dioxide and water vawww.powermag.com
1.
Volume reduction in a small
footprint. The Erwin Resin Solutions (ERS)
Facility in Erwin, Tennessee, has been in operation
since 1999. It has received more than
3,000 shipments and treated greater than
11,300 cubic meters of low-level waste. Various
types of wastes have been treated at the
ERS facility, but they have primarily consisted
of ion-exchange resins. EnergySolutions purchased
Studsvik's processing facility in 2014.
Courtesy: Studsvik Inc.
por with small amounts of elemental carbon,
methane, carbon monoxide, and hydrogen.
Granular carbon is added directly to the
FBSR where a portion is oxidized to produce
necessary process energy. The carbon
also serves as the " reductant, " facilitating the
chemically reducing environment in which
the desired reactions occur inside the fluidized
bed, including alkali and radionuclide
mineralization, and formation of metal oxides,
carbonate salts, carbon dioxide, inorganic
particulates, and process gas.
The remaining inorganic waste residues,
also known as reformed residue (RR), are
carried (elutriate) out of the FBSR vessel
with the process gases. The amounts are
directly related to waste composition, additives,
and operating conditions. The RR
solids contain greater than 99.99% of the
incoming radionuclides and essentially all
other inorganics present in the original waste
feed. High-temperature ceramic filters inhibit
RR solids from entering the gas oxidation
system, preventing fouling or an altered final
39
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POWER August 2018

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