Nuclear Executive Update   
An EPRI Progress Report, May 2011
TECHNICAL HIGHLIGHTS
Sequestration Resins Accelerate Contaminant Removal from Nuclear Power Plant Coolants

Novel resins promise three-fold increase in removal of corrosion products, helping reduce occupational exposures, critical-path downtime, replacement power costs, and waste volumes.

During maintenance and refueling outages, current ion exchange resins used to treat light water reactor coolants may require several days to reduce the concentration of radioactive corrosion products to acceptable levels. This influences outage schedules and replacement power costs, while residual contamination in cooling water contributes to overall site radioactivity levels and occupational exposures. EPRI's Technology Innovation Program is developing novel sequestration resins engineered specifically for faster, higher-capacity uptake of soluble corrosion products.

 
Experimental cobalt sequestration column during laboratory tests.
 
 

Elemental cobalt (Co-59) and nickel (Ni-58) are released into solution by corrosion of welds and base metals in primary water systems. They may be activated by radiation to form Co-60 and Co-58, the isotopes responsible for the majority of dose exposures in boiling water reactor (BWR) and pressurized water reactor (PWR) environments, respectively. Current ion exchange resins used in reactor water cleanup and other applications can remove 90 to 99% of activated and unactivated corrosion products for a short period after entering service, but most of their absorptive capacity is quickly consumed.

EPRI-developed sequestration resins preferentially target activated and unactivated Co and Ni ions and lock these impurities within their chemical structures through geometric and electronic interactions at active binding sites. Laboratory proof-of-concept testing in 2009 on an experimental batch of sequestration resin in powder form demonstrated substantial increases in cobalt uptake as compared to traditional ion exchange materials.

In 2010, sequestration resin powders optimized for reactor water treatment were synthesized and evaluated on simulated coolants in the laboratory and then on primary coolant and spent fuel pool samples at Exelon's LaSalle County Generating Station. Enhanced Co-60 removal was observed, both in terms of rate and sequestration capacity for a given amount of resin. Similar results were observed during high-throughput testing on reactor water cleanup samples from LaSalle and during initial evaluation on radioactive wastewater samples from NextEra Energy's Seabrook Station.

Continuing laboratory research in 2011 focuses on understanding and optimizing resin synthesis, chemical structure, and removal efficacy based on full-scale mockup tests of a filter/demineralizer system. In conjunction with specialty chemical companies and potential resin vendors, large-scale synthesis methods are being developed for production of EPRI-patent-pending powder- and bead-form sequestration resins. Parallel experimental studies address bed regeneration and waste disposal issues and feedwater filtration and radioactive waste treatment applications.

Initial in-plant testing is expected to begin in 2011 at a BWR to determine whether sequestration resins outperform conventional ion exchange resins for reactor water cleanup without adverse impacts. Follow-on demonstrations are planned for PWR coolant and radioactive waste treatment applications. Within three years, reactor-grade sequestration resins are projected to be ready for commercial application at light water reactors. They are expected to provide at least a three-fold increase in removal rates for key transition-metal impurities, supporting dose reduction and accelerating access to the reactor refueling floor during outages. By reducing the wait time before entering containment from up to three days currently to one or two days, nuclear plants could save up to $1-2 million in replacement power costs alone. In addition, higher overall removal efficiencies will reduce occupational exposures and waste management costs.

For more information, contact Susan Garcia at 650.855.2239, sgarcia@epri.com, or Paul Frattini at 650.855.2027, pfrattin@epri.com.