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ENVIRONMENTAL REMEDIATIONSTRATEGIES & TECHNIQUES FOR CLEANING RADIOACTIVELY CONTAMINATED SITES

BY W. EBERHARD FALCK

Actions for a cleaner andsafer environment haverisen on social and

political agendas in recentyears. They include efforts toremediate contaminated sitesposing a radiological risk tohumans and the surroundingenvironment.

Radiological risks can resultfrom a variety of nuclear andnon-nuclear activities. Theyinclude:■ nuclear or radiologicalaccidents;■ nuclear weaponsproduction and testing;■ poor radioactive wastemanagement and disposalpractices;■ industrial manufacturinginvolving radioactive materials;■ conventional mining andmilling of ores and otherproduction processes, e.g. oiland gas production, resultingin enhanced concentrations ofnaturally occurring radioactivematerials (NORMs).

The IAEA has developed acomprehensive programmedirected at the remediation ofradioactively contaminated sites.The programme collates anddistributes knowledge aboutcontaminated sites; appropriatemethods for theircharacterization; assessment oftheir potential environmentaland radiological impact; andapplicable methods for theirclean-up, followinginternationally recommendedsafety criteria. The overall

objective is to enable regions inthe world with restrictedresources, and which aretechnologically less advanced, tofocus their efforts and choseappropriate strategies for theabatement or removal ofexposure to radiation. Animportant aspect is the intentionto “close the loop” in the nuclearfuel cycle in the interests ofsustainable energy developmentincluding nuclear power.

Such activities involve manyinterrelated factors, includingthe legal and institutionalframework, prevailing socio-economic conditions, and theneed to balance technologyperformance and risk reductionwithin fixed and limitedbudgetary resources. A centralaspect is that the overallefficiency of a remediationproject is of particularimportance and not just theeffect of the physicalremediation effort itself.

Public perceptions of theremediation process and itsresults can be of overrulingimportance in projectdevelopment, as they invariablyinfluence strategic and technicaldecisions. Cost-benefitassessments vis-a-vis theavailability of resources over timehave a decisive influence.Underlying rationales andincentives for remediation,which may be of an economicnature -- such as future land use-- or ethical considerations, alsoneed to be included.

Factors InfluencingDecisions on RemediationPractices. The remediation ofsites with radiologicallyrelevant contamination isjustified on the basis ofguidance and criteria set out bythe IAEA and the InternationalCommission on RadiologicalProtection (ICRP). Within thisframework, a wide variety oftechnical options may beavailable, ranging from a “donothing” option to a full-scaleremoval of the contaminant,depending on the extent ofcontamination.

Proper accounting for allfactors affecting the outcome ofan environmental remediationproject enables finding anoptimum solution for a givenknowledge base that will satisfythe societal goals and add valueto the project itself. A formalapproach to evaluating availabletechnologies and theirapplicability -- and accountingfor variables and factorsinfluencing the decision-makingprocess in technology selection --will increase transparency and,hence, the likelihood of allstakeholders accepting itsoutcome. The process is alsoindispensable for ensuring up-to-date quality control andassurance procedures. As a

Mr. Falck is a staff member inthe IAEA Waste TechnologySection, Division of NuclearFuel Cycle and WasteManagement.

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consequence, the technologyand strategy selected may notnecessarily be the best in apurely technical sense, but alsotakes social and economicconsiderations into account.

There is a considerabledivergence of thoughts,however, on the methods for theformal incorporation of allthese factors. The methods usedrange from a straightforwardreliance on experts’ opinion,through qualitative ranking, tocomplex quantitative multi-variate option assessments.Quantitative assessments oftenrequire a common denominatorand the conversion of non-numerical properties intonumerical categories for thepurpose of comparison. Thereexists a considerable controversyover acceptable conversionmethods, mainly due to theoften inevitable“monetarization” of ethicalvalues.

The factors influencing thedecision-making processes intechnology selection for

environmental remediation arethe focus of an IAEA projectand a planned technicaldocument will outline possibleapproaches and concepts.

Scoping the Problem ofContaminated Sites. Althougha Herculean task, the IAEA isseeking to create a worldwideDirectory of RadioactivelyContaminated Sites (DRCS).The DRCS is intended tobecome a major vehicle for thecollection and dissemination ofsuch information via the WorldWide Web. Relying on MemberStates’ contributions, the DRCSwill provide information onremediation measuresundertaken, in addition to basicdata on a wide variety ofradioactively contaminated sites.

The definition of whatconstitutes “contamination”continues to be a major obstaclein developing such a directory.Due to the wide variation innational legislation, aunanimous definition of what is“contaminated” is difficult toachieve.

Apart from scientificdefinitions based onconcentration/activity data ordose rates, definitions orclassifications may beundertaken for administrativepurposes, where widerconsiderations, including socio-economic and political ones, aretaken into account. Having asite listed in an internationaldirectory can have significantimplications and that is whyMember States are sometimesreluctant. For the furtherdevelopment of the DRCS,therefore, a mechanism wasadopted, whereby sites are onlylisted for which Member Statesofficially provide information.

The directory’s purpose isnot just to be a mere listing ofcontaminated sites, but to serveas an information source onsuitable remediation measures.It also could serve as a rolemodel for similar undertakingson a national level.

Promoting Cost-EffectiveTechniques. IAEA MemberStates have quite different levels

IAEA DOCUMENTS & ACTIVITIES ON ENVIRONMENTAL REMEDIATIONSAFETY

Cleanup of AreasContaminated by PastActivities & Accidents -Safety Requirementsdocumentin preparation

Management ofRadioactive Waste fromMining & Milling of Ores- Safety Guidein preparation

Monitoring &Surveillance forEnsuring theRadiological Safety ofResidues from Miningand Milling ofUranium/Thorium -Safety Report inpreparation

MANAGEMENTFactors for Formulatinga Strategy forEnvironmentalRestorationTECDOC-1032

Characterization ofRadioactivelyContaminated Sites forRemediation PurposesTECDOC-1017

Compliance Monitoringfor Remediated SitesTECDOC-1118

Factors Impacting onEnvironmentalRestoration PracticesTECDOC in preparation

DATABASESA Directory ofInformation Resources onEnvironmentalRestorationTECDOC-841

Directory ofRadioactivelyContaminated SitesTECDOC in preparation

Restoration CostsTECDOC in preparation

TECHNOLOGYTechnologies for theRemediation ofRadioactivelyContaminated SitesTECDOC-1086

Technical Options for theRemediation ofGroundwatersTECDOC-1088

Site CharacterizationTechniques Used inEnvironmentalRestorationTECDOC-1148

Remediation of Siteswith Low Levels ofRadioactiveContaminationTECDOC in planning

SPECIAL TOPICSTechnologies for LongTerm Stabilization &Isolation of Uranium MillTailingsTECDOC in preparation

EnvironmentalContamination byNORMs and RelevantAbatement MeasuresTECDOC in preparation

Remediation of SitesContaminated byHazardous andRadioactive SubstancesTECDOC in planning

IAEA publications are available from the IAEA Division of Conference and Document Services. Email: sales.publications@iaea.org.Also see the WorldAtom web site at http://www.iaea.org/programmes/ne/nefw/nefwpubl.htm

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of experience and knowledgewith respect to remediation ofradiologically contaminatedsites. The field of environmentalremediation has seen rapidadvancements over the pastdecade, adding to theimportance of disseminatingknowledge about appropriate,efficient and cost-effectivemethods for clean-up.

Owing to the diversity of thecauses and forms ofenvironmental contaminationwith radionuclides, the technicalsolutions are varied. Eachcontaminated environmentalmedium requires its ownapproach. Appropriately theIAEA has addressed the problemof contaminated soils andgroundwaters, and themonitoring of compliance withpre-set standards and acceptedresidual contamination levels indedicated technical documents.(See box, page 21.)

Remediation techniques forsites with well-definedcontamination of relatively highconcentrations levels are welldeveloped by now. Clean-up andremediation of disperse andrelatively low levels ofcontamination, however, stillconstitute a challenge whenconsidering factors such as costand minimal additionaldisturbance of the environment.

Similar deliberations applyto further lowering the residualcontamination following otherremedial measures, since theefficiency of most techniquesdecreases exponentially withthe remaining contamination.The probable answers are low-intensity, low-tech and, hence,low-cost solutions. Aforthcoming technicaldocument on this subject willcollate and review informationand performance data on

SUPPORTING STEPS IN BULGARIA

Many Central and Eastern European Countries had uranium miningactivities of varying size and importance. While in many countriesactivities did not develop beyond exploratory digs, in Bulgaria orequality and reserves enabled establishment of several mines and twomills. However, in the wake of political changes and owing to thefalling market price for uranium, mining and milling was abandonedin the mid-1990s. An IAEA technical cooperation project has helpedthe authorities to establish a radiation monitoring infrastructure andto provide advice for the decommissioning and environmentalremediation of the mining and milling sites. Much of the work hasfocused on the Buhovo mill tailings ponds, which were unstable andreleased contaminants to the floodplain beneath. The training andadvice included expert missions on specific subjects, such as effluenttreatment, and a two-week workshop on risk-assessmentmethodologies for aspects of uranium mining and milling.Participants included not only staff from the responsible ministrydepartments, but also staff from the former mining company incharge of the actual remediation operation. The IAEA’s support andtraining helped national authorities to better understand and focus theaid provided under umbrellas such as the CEC PHARE programme,which supports much of the actual remediation work now beingundertaken.

Photos: Top, mining waste heaps at Buhovo in 1995. Below: thesorption facility at Buhovo in 1995.

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appropriate techniques andstrategies, such as phyto- andbio-remediation, or monitorednatural attenuation. Theapplicability andappropriateness of thesetechnologies and theirprerequisites will be discussedin it.

Many sites suffer from both,conventional hazardous andradioactive contamination at thesame time. Typically, such

incidences include certainformer industrial sites (e.g.NORMs as by-products and inresiduals), civilian and defenserelated nuclear researchinstitutions (e.g. processingsolvents), mining and millingsites (e.g. heavy metals andarsenic), and former low-levelwaste disposal practices (e.g. co-disposal of hazardous and low-level radioactive waste). Thespecific environmental problems

mainly stem from theinteraction between, and thediverse chemical nature andbehaviour of the variouscontaminants, such as heavymetals and radionuclides, bothunder the existing conditionsand in response to theremediation.

A given remediationtechnique might effect in situfixation or the removal of onecontaminant, but at the same

APPLYING LESSONS LEARNED FROM GERMANY

The former East Germany was a major supplier of uranium and the second biggest producer in the worlduntil 1990. After the dissolution of the Soviet Union and the unification of Germany, a political decisionwas taken to stop all mining activities by the Wismut company. Since the IAEA provides technicalassistance to developing countries, Germany’s experience benefitted the Agency’s technical cooperation projectson aspects related to the closure, decommissioning and remediation of the many Wismut mining and millingsites. For instance, Wismut has made staff available for service on IAEA expert missions and receivestrainees from IAEA Member States with similar problems. Thus, the IAEA programmes help to disseminatethe knowledge and experience gained with the remediation of the numerous open cast and deep mines, andthe disposal facilities for mining and milling residues.

Photos: Remediation of the waste rock dump at Hammerberghalde. Top: View in 1960. Middle: View in 1993.Bottom: View in 1997. (Credit: Wismut GmbH).

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time result in the mobilizationof another. The mixed wastesarising from remedial actionsmight pose an additionaltechnical and administrativeproblem. Either a disposalroute has to be found thataccommodates the variouscontaminants and the legalrequirements applicable tothem, or the contaminantshave to be separated.

These issues are to beaddressed in a forthcomingIAEA project that will provideexamples for relevantcontamination cases anddescribe the remediationactions taken. These cases willbe analyzed with a view toidentify the controlling factorsand processes. A procedure willbe developed, which will helpto identify potentialproblematic combinations ofcontaminants, and which aimsto give guidance on how tohandle such problems.

Assisting National Efforts.The IAEA assists MemberStates in various ways in theireffort to assess radiologicalcontamination problems andto clean such sites. In the early1990s, the IAEA initiated aregional technical cooperationproject involving mostcountries of Central andEastern Europe with theobjective to assess the size andscale of radiation-relatedenvironmental problems. Thishelped to identify problemareas and to better understandindividual State needs.

There are two majorproblem areas which havebeen, and continue to be, inthe focus of interest, namelythe lands affected by theChernobyl accident, and landsaffected by uranium miningand milling.

Direct assistance to MemberStates is provided throughtechnical cooperation projects.In such way, for instance, theCzech Republic, Slovenia andBulgaria were given assistanceto deal with the uraniummining legacy through expertmissions, training courses andthe provision of monitoringand analytical equipment. (Seebox, page 22.) Under a newproject, similar assistance isbeing given to Portugal.

Member States alsoparticipate in CoordinatedResearch Projects (CRPs) thatbring together researchersworking on similar problems.Recently, a CRP on sitecharacterization techniqueswas completed, and a newCRP on techniques for thestabilization of uranium milltailings was initiated in theyear 2000.

A common mode of disposalof uranium mill tailings is innear-surface impoundments inthe vicinity of the respectivemine or mill. Suchimpoundments were oftenarranged in a haphazardfashion, utilizinggeomorphological depressions.As a result, there was little orno care taken to isolate thetailing materials from theirenvironment. The hazard ofthese tailings originates intheir residual contents of long-lived radionuclides and otherhazardous components, forinstance heavy metals andarsenic.

Geomechanical aspects, suchas the stability of pile slopes,dikes and retaining dams, arestandard engineeringproblems, and most MemberStates make provisions forthem in the relevant buildingor mining regulations.

However, environmental andradiological impacts are oftenneglected. Typicalenvironmental problems areradon emanation and theleaching of contaminants intosurface and groundwaters.Based on the objective to keepenvironmental impacts to aminimum over long timeperiods, the task of the CRP isto contribute to conceptualand technical solutions thatrender tailings more inert overprolonged time-spans; thatrender impounded materialsand engineered structuresstable over prolonged timespans; that minimize the needfor active maintenance; andthat are both technically andeconomically feasible.

Networks of Cooperation.The results of IAEA activitiesin environmental remediationhave been published in avariety of technicaldocuments, and presented atinternational conferences andmeetings. These activitiesparticularly address the needsof less developed MemberStates, which typically havefewer resources and often littleexperience in handling a legacythat has arisen under pastpolitical and administrativecircumstances.

Efforts to bring togetherexperts from all parts of theworld through research andtechnical cooperation projectsfoster the exchange ofknowledge, thus ensuring thatadequate strategies andtechniques are implemented.As importantly, the transfer ofknowledge can helpdeveloping countries to betterunderstand and criticallyevaluate the assistanceprovided by donor institutionsand governments. ❐