Strategic Guidance on the Management of LLW and ILW / LLW ...
Strategic Guidance on the Management of LLW and ILW / LLW ...
Strategic Guidance on the Management of LLW and ILW / LLW ...
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<strong>LLW</strong> Repository LtdNati<strong>on</strong>al Waste ProgrammeNWP/REP/011Issue 2.1 – Jan 2013Page 45 <strong>of</strong> 58Technique Descripti<strong>on</strong> Limitati<strong>on</strong>s <strong>and</strong> c<strong>on</strong>straints Trials <strong>of</strong> process Outcome <strong>of</strong> trialsDFDX [Ref.22]DFDX is a variant <strong>of</strong> <strong>the</strong> DFD process, <strong>and</strong> is achemical dec<strong>on</strong>taminati<strong>on</strong> process which involves <strong>the</strong>treatment <strong>of</strong> surface c<strong>on</strong>taminated metal objects (sizereduced when required) with dilute fluoroboric acid witha c<strong>on</strong>trolled oxidati<strong>on</strong> potential. This process removes<strong>the</strong> outer scale <strong>and</strong> a thin surface layer <strong>of</strong> metal, thusremoving surface c<strong>on</strong>taminati<strong>on</strong> from <strong>the</strong> metal. Thefluoroboric acid is recirculated through <strong>the</strong> system <strong>and</strong>is regenerated through an electrochemical cell. The use<strong>of</strong> <strong>the</strong> electrochemical cell enables <strong>the</strong> metal i<strong>on</strong>s in <strong>the</strong>spent fluoroboric acid to be c<strong>on</strong>verted to a solid metalparticulate, which can be collected <strong>and</strong> removed fordisposal. This reduces <strong>the</strong> volume <strong>of</strong> sec<strong>on</strong>dary wasterequiring management by <strong>the</strong> waste owner, relative to<strong>the</strong> DFD process. Use <strong>of</strong> this process enables <strong>the</strong> reclassificati<strong>on</strong><strong>of</strong> metal ei<strong>the</strong>r to EPR out-<strong>of</strong>-scope (thusallowing for unrestricted recycling <strong>and</strong> reuse) or else toa state where <strong>the</strong> metal is suitable for alternate metaltreatment (e.g. metal melting).• Less useful <strong>on</strong> simplegeometries.• Only applicable to surfacec<strong>on</strong>taminated wastes (unlessas a precursor step to o<strong>the</strong>rwaste treatment technologies).• Only applicable to paintedsurfaces where paint is in poorc<strong>on</strong>diti<strong>on</strong>.• Trialled at HinkleyPoint A (MagnoxLtd.) to testwhe<strong>the</strong>r DFDXcould be used forpaint removal <strong>and</strong>metaldec<strong>on</strong>taminati<strong>on</strong> <strong>of</strong>a fuel skip.DFDX observed tobe successful inmetaldec<strong>on</strong>taminati<strong>on</strong>.Fur<strong>the</strong>r trials orusage <strong>of</strong> <strong>the</strong> systemfor p<strong>on</strong>d furnitureitems in UK nuclearindustry has beenlimited.The system can be deployed at ei<strong>the</strong>r high or lowtemperature, depending <strong>on</strong> <strong>the</strong> nature <strong>of</strong> <strong>the</strong>c<strong>on</strong>taminati<strong>on</strong> <strong>on</strong> <strong>the</strong> metallic waste <strong>and</strong> <strong>the</strong> c<strong>on</strong>straints<strong>on</strong> <strong>the</strong> waste owner. The process can be deployedei<strong>the</strong>r from a mobile plant at <strong>the</strong> waste owners site orA company owned by UK Nuclear Waste <strong>Management</strong> Ltdelse at an <strong>of</strong>f-site locati<strong>on</strong>.NOT PROTECTIVELY MARKED
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