Strategic Guidance on the Management of LLW and ILW / LLW ...

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LLW Repository LtdNational Waste ProgrammeNWP/REP/011Issue 2.1 – Jan 2013Page 26 of 585.2.4. Mechanical Surface Decontamination (Ultra-High Pressure Water Jetting) [Ref. 5,14, 15]UsageLLWILW/LLWSurface contaminatedVolumetricallycontaminatedActivatedAluminiumCopperMild steelMild steel (coated)Stainless steelStainless steel (coated)Description of techniqueUltra-high pressure (UHP) water jetting is a mechanical decontamination technique which uses ultra-highpressure water to physically remove contamination from the surface of an object. The technique can beapplied manually using hand-held apparatus or remotely; either in-situ or within closed boxes. UHP waterjetting can be used to remove surface coatings (e.g. paint) from surfaces and can be used to remove surfacedeposits without damaging underlying metal surfaces. Decontamination may be improved through the use ofheated water or the addition of abrasives, solvents or detergents to the water.Outcomes Advantages Disadvantages• For LLW:o Waste metal decontaminated to EPRout-of-scope status; oro Waste metal decontaminated to enablefurther processing.• For ILW / LLW cross-boundary waste:o Waste metal decontaminated to EPRout-of-scope status; oro Waste metal decontaminated to LLWto enable further processing ordisposal.• Secondary wastes include large volume ofradiologically contaminated aqueous waste(may contain abrasives, solvents ordetergents if used).A company owned by UK Nuclear Waste Management Ltd• Quick and relativelysimple.• Applicable to a widerange of metals.• Applicable to a widerange of radiologicalactivities.• Useful for theremoval of surfacecoatings.• Less useful for complexgeometries whereuniform coverage of theitem may not beattained.• Not useful forvolumetricallycontaminated oractivated metals (unlessas precursor step foronward transfer).• Large volume ofsecondary wastesgenerated.• Potential for orphansecondary wastegeneration.• Can be dose-intensive ifnot used in automatedconfiguration.NOT PROTECTIVELY MARKED
LLW Repository LtdNational Waste ProgrammeNWP/REP/011Issue 2.1 – Jan 2013Page 27 of 58Technique used at:LLWILW/LLWCase Study A – UHP Water Jetting of Pond Skips at BradwellChallengeTo support accelerated decommissioning of the Bradwell site, a variety of decontamination techniques weretrialled on the ILW / LLW cross-boundary pond skips retrieved from the Bradwell fuel storage pond. One trialtested whether removal of the painted surface coating on a pond skip would reduce the radioactivitysufficiently to enable the waste to be classified and managed as LLW.SolutionUHP water jetting was trialled on a skip as part of this programme. UHP water jetting was used withpressures exceeding 1700 bar using a bespoke built-for-purpose containment system. The trialsuccessfully removed the surface paint from the fuel skip, allowing the skip to be processed as LLW. Theprocess generated approximately 12m 3 of waste water with solids including paint flakes entrained in thewater. The water was allowed to settle and 0.35m 3 of solids were separated and collected for disposal.A company owned by UK Nuclear Waste Management LtdNOT PROTECTIVELY MARKED
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