Purolite has the ability to ensure that the chemistry of Graphite-Gas Reactors (AGR) operate at the highest efficiency with our CriticalResin™ products. 

From helping to extend your unit's life to ensuring that your plant maintains a safe environment from radioactive isotopes, our on-site technical experts can find solutions to help you to meet the nuclear promise. 

The graphite-gas reactor was one of the first types to be introduced. Initial designs were the Magnox and later the advanced gas-cooled reactor (AGR) system. All of these operate with two reactors in a single structure and use uranium as the fuel. In the reactor core, fuel rods located inside a block of graphite acts as a moderator.

The coolant is pressurized CO2, which passes through the reactor core, removing heat. This heated CO2 stream drives turbine generators that generate electricity. One of the primary advantages seen with the graphite-gas design is its ability to allow for the online replacement of fuel elements. Operating difficulties make graphite-gas reactors commercially less attractive to build and have restricted widespread use of this design. Ion exchange technology treats four circuits in a graphite-gas nuclear plant.  They are the makeup water, the returned condensate, the turbo blower and the spent fuel pool. 

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Almost all AGR units operate their makeup treatment systems. These systems commonly employ pre-filtration followed by reverse osmosis (RO) technology with a final, high-purity mixed bed polisher. Nuclear power plants that continue to own and operate their makeup water-treatment systems will generally use standard resins that produce high-quality water and have good regeneration efficiency.

The following resins configured in the order shown can be used to demineralize the makeup water for AGR reactors:

• NRW100 strong acid cation exchanger
• PFA100 weak base anion exchanger
• NRW400 strong base anion exchanger
• NRW3240 for polishing mixed beds

The recommended condensate-polishing system consists of a strong acid cation gel, NRW1100, to remove ammonia from condensate and a mixed bed, NRW3460, to complete the condensate-purification step. These resins can be regenerated onsite, but non-regenerable resins are also available.  These include the strong acid cation macroporous NRW160 and the mixed bed NRW3560. Morpholine, along with ammonia, is used to adjust condensate pH to a target range of 9.2 to 9.5 to minimize corrosion. Since the system contains a small quantity of makeup water and the opportunity for blowdown is limited, low levels of impurities in feed water are critical.

Waste fuel is stored underwater in spent fuel ponds. This pond water contains radioactive elements which must be removed using mixed bed ion exchange resins. NRW3560 is a mixture of macroporous cation resin (NRW160) and a gel anion (NRW600). NRW3550 (a mix of macroporous cation and anion resins NRW160 and NRW5050) can also be used.