Sequestration Resins for Accelerating
Removal of Radioactive Contaminants
Technology Innovation
Novel resins enhance contaminant removal, reducing critical-path downtime,
decreasing occupational exposure, and minimizing radioactive waste volume.
During nuclear plant maintenance or refueling outages, current ion
exchange resins may require several days to reduce concentrations of cobalt and other activated corrosion products to safe
levels in reactor coolant streams. This performance limitation often
delays key maintenance activities. EPRI’s Office of Technology
Innovation is developing novel sequestration resins expected to
provide at least a three-fold increase in removal capacity for
transition-metal impurities in light water reactor coolants. They also
offer the potential for higher overall removal efficiencies, which
would reduce occupational exposures and waste management
costs.
What are activated corrosion products?
Elemental cobalt (Co-59) is an impurity in stainless steels, and an
alloying element in certain hardfacing alloys such as Stellite,
while elemental nickel (Ni-58) is a major component in the
Inconel alloys employed for steam generator tubing. When
Co-59 and Ni-58 corrosion products dissolve in light water
reactor coolants, they may be activated by irradiation to form the
isotopes Co-60 and Co-58, which are the main contributors to
occupational exposure in boiling water reactors (BWRs) and
pressurized water reactors (PWRs), respectively.
Co++
“Loosely” bound cobalt on a typical ion exchange resin.
Why is advanced control technology needed?
Current ion exchange resins used in BWR reactor water cleanup
(RWCU) and other applications are capable of removing 90 to
99% of the activated and unactivated corrosion products for a
short period after being put into service, but most of their
absorptive capacity is quickly consumed. As a result, fresh resin
precoats must be applied to filter demineralizers on a regular
basis, and the residual levels of contaminants that cannot be
removed contribute to site activity levels and dose exposures.
Although dramatic innovations in resin technology have occurred
in the biopharmaceutical and other industries, resin vendors have
had little motivation to pursue advanced technologies for nuclear
power industry applications because the market is limited and
profit margins are small.
Co++
Co++ Cobalt
Resin
Ligand Site
“Captured” cobalt on a sequestration resin.
What is the distinction between ion exchange resins and
sequestration resins?
Ion exchange resins used in light water reactors are specialized
polymer-based materials characterized by pores with charged
binding sites that trap transition-metal cations. Co and Ni ions
compete for the same exchange sites with zinc, iron, and other
species that are present in primary systems at significantly higher
concentrations and are less deleterious from a source term
perspective. Sequestration resins being developed by EPRI
preferentially target activated and unactivated Co and Ni ions.
They also lock these impurities within their chemical structures
through geometric and electronic interactions at their active sites,
rather than relying on reversible ion exchange reactions. End
results include improved reaction kinetics and increased overall
effectiveness compared to current technology.
What is EPRI’s role?
EPRI is evaluating a sequestration resin based on initial research
indicating that it provided highly selective Co and Ni removal in
the presence of other cations. In late 2009, small-scale laboratory
tests were completed on an experimental batch of the new resin
produced in a “powdex” form containing multiple components. As
compared to traditional ion exchange materials, the novel resin
demonstrated substantial increases in Co-59 and Co-60 uptake
for solutions containing significant concentrations of other
transition-metal ions.
ter treatments. Full-scale trials are expected by 2012 in collaboration with a resin manufacturer. Within three years, EPRI expects
reactor-grade sequestration resins to be ready for commercial
application in primary coolant systems.
What are benefits from sequestration resins?
Sequestration resin technology is potentially applicable to all
existing and new nuclear power plants. It shows promise for faster
and higher-capacity uptake of Co-60 and Co-58—the activated
corrosion products responsible for the majority of radiation dose
in BWRs and PWRs.
Applying these breakthrough removal capabilities in primary
coolant treatment systems will improve time to reactor head lift
during outages, with reductions in downtime corresponding to
replacement power cost savings of $500,000 to $1 million per
day. Anticipated improvements in abilities to capture activated
corrosion products, control soluble Co-59 source terms, and
eliminate Co-60 and Co-58 production will decrease worker
radiation exposure, extend the lifetime of resin precoats, and help
control radioactive waste production and associated management
and disposal costs.
For more information
For more information, contact the EPRI Customer Assistance
Center at 800.313.3774 ([email protected]).
Contact
Susan Garcia, [email protected], 650-855-2239
Paul Frattini, [email protected], 650-855-2027
Sequestration resins offer higher removal capacity and efficiency than
existing ion exchange resins because they selectively target activated
corrosion products and their source terms and lock these impurities
within stable chemical structures.
In 2010, powdex-form sequestration resins with chemical
structures optimized for reactor water treatment are being
synthesized and evaluated using simulated coolant. The most
promising material(s) will be subjected to in-plant testing using a
pilot-scale, precoated filter demineralizer and primary coolant
samples taken from the reactor water of a BWR. Parallel studies
will address bed regeneration and waste disposal issues,
development of bead-form resins applicable to both BWRs and
PWRs, and possible uses for feedwater and radioactive wastewa-
1021513
August 2010
Electric Power Research Institute
3420 Hillview Avenue, Palo Alto, California 94304-1338 • PO Box 10412, Palo Alto, California 94303-0813 USA
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