LLW Minimization and Treatment Techniques

Chapter 5

Current and EmergingLLW Minimization and

Treatment Techniques

CONTENTSPage

Introduction ● . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99Waste Minimization Techniques . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . 101

Material Substitution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101Good Housekeeping Pracices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .102

Treatment Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .102Post-Generation, Good Housekeeping Practices Including Waste Decontamination . 103Storing Radioactive Material for Decay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .104Compaction and Shredding Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105Incineration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .106Waste Stabilization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109Waste Packaging Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111Long-Term Stability Predictions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

Types of Mixed LLW For Which No Minimization or Treatment TechniquesAre Currently Available . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

The Future for Waste Minimization and Treatment Techniques . . . . . . . . . . . . . . . . . . . . . . 114Future Disposal Volumes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114Interstate LLW Management Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114Mixed LLW Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .114Risks of LLW Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

Chapter 5 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .116

TablesTable Page

5-1. Summary of Mixed Low-Level Generation Practices . . . . . . . . . . . . . . . . . . . . . . . . . . . 1005-2. A Critique of Waste Forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

Chapter 5

Current and Emerging LLW Minimizationand Treatment Techniques

INTRODUCTIONThe management of low-level radioactive waste

(LLW), including mixed LLW, has three mainsteps: waste minimization, treatment, and dis-posal. Waste minimization and treatment techniquesare reviewed here, while disposal technologies arediscussed in chapter 6.

We define waste minimization as in-plant prac-tices that reduce, avoid, or eliminate the generationof harmful waste so as to reduce risks to humanhealth and the environment. Waste minimization,therefore, is applied to the pre-generation of waste.Treatment, in contrast, is applied to the post-generation of waste, but before the waste is disposed.Treatment is defined in the Resource Conservationand Recovery Act (RCRA)1, Section 1004, to mean

. . . any method, technique, or process, includingneutralization, designed to change the physical,chemical, or biological character or composition ofany hazardous waste so as to neutralize such wasteor so as to render such waste nonhazardous, safer totransport, store, or dispose of; or amenable forrecovery, amenable for storage, or reduced involume.

We broaden this definition to include techniquesthat facilitate the overall management of LLW, butmay not be defined as treatment by the Environ-mental Protection Agency (EPA). These techniquesinclude waste decontamination, storing radioactivematerial for decay, compaction, shredding, incinera-tion, and waste stabilization.

Since 1980, escalating LLW disposal costs (seech. 6) have forced the increased use of wasteminimization and treatment techniques. In thefuture, these techniques will likely continue toplay a significant role until disposal costs stabi-lize.

The problem of managing mixed LLW—wastethat contains both radioactive and hazardousconstituents-has also increased the use of waste

minimization and treatment techniques. Since nodisposal option has been available for this wastesince 1985, mixed LLW generators continue to lookfor techniques to avoid generating the waste. Whenthe waste’s initial generation cannot be avoided,these generators use techniques to treat the waste sothat it is either solely radioactive or solely hazard-ous. The generator can then ship the waste to eithera LLW disposal site or a hazardous waste landfill.Furthermore, under EPA regulations, a mixed LLWgenerator is required to treat the hazardous constitu-ent in the waste so that a specified treatment standardis followed. However, the facility necessary to meetthese standards is often inaccessible or nonexistent.2

Once EPA has fully developed and begins to enforcethese standards, waste generators will pressureindustry to build the necessary facilities to meet thestandards, and the use of waste minimization andtreatment techniques will further increase.

From a reducing risk standpoint, waste mini-mization and treatment techniques are oftenmore critical for mixed LLW than for nonmixedLLW. The hazardous constituents (e.g., organicchemicals) in mixed LLW are often more likely tomigrate in a disposal site than are the radionuclides.Furthermore, while radionuclides decay over a settime period, hazardous constituents may not degradesignificantly. As a result, EPA requires that a certaintreatment standard be met for a particular hazardousconstituent before it is disposed.

With respect to waste minimization, substitutiontechniques can eliminate or drastically reduce theamount of radioactive material used, and in-plantprocesses can be modified to reduce the quantity ofwaste generated. Waste treatment techniques areused to make LLW that is generated, includingmixed LLW, safer for storage, shipment, and dis-posal. Generators also frequently use treatmenttechniques to reduce their handling, shipping, stor-age, and disposal costs.

lpub]l~ Law 94-580, &(. 21, 1W6.

i? F~emore, EpA hm ~ct t. &ve]OP ~ea~cnt S[mdwds for some mlxcd LLW, & IS di.~us~ ~]ow in (,he ~[ion on ‘‘~~s of Mixed LLW forWhich No Waste IWnimization or Treatment Techniques Are Cumndy Available. ”

- 9 9 -

Table 5-1--Summary of Mixed LLW Generation Practices

GENERATOR COMMUNITY

NuclearIndustrial facilities Medical/academic institutions power plants

UniversityTYPE OF Pharmaceutical Biotechnology Other Spent fuel Waste Medical/clinical nonmedical

MIXED LLW manufacturing manufacturing manufacturing storage processor & research research

store for decayDeclare BRCRevise proceduresLong-term storage

Organic chemicals Substitute Justify usenonhazardous Store for decaymaterials

Revise proceduresStore for decayLong-term storage

NA store for decay

Use nonlead Decontaminatecontainers

Long-term storage

Lead decontamination NA NAWaste Oil NA NA

Trash with oil NA NA

Chlorofluorocarbon (CFC) NA NA

CFC concentrates NA NA

Aqueous corrosive liquids NA NAChromate waste NA NA

Cadmium waste NA NA

NA

Declare BRC

Substitute NAenvironmentallybenign fluids

Store for decayimprove inventory

practicesLong-term storage

M NA

Long-term storage NA

NA

Solidification

NA

NA

NA

NA

NA

NA

NA

NA

NA

NA

NA

waste

NA

NA

DecontaminateUse coated lead

Filtrationsolidificationincineration

NA

NA

Long-term storage

Long-term storage NA

NA NA

NA NA

environmentally environmentallybenign fluids benign fluids

Declare BRCRevise proceduresLong-term storage

NA EducationNotification prior to

useJustify useLong-term storage

NA M

Use non lead Use nonleadcontainers containers

Minimize use of Minimize use ofcontainers containers

Long-term storage Long-term storageNA NA

NA Long-term storage

NA NA

NA NA

NA NA

NA NA

NA NA

NA NA

Long-term storageRecycleSubstitute other

materialsManage as

radioactive wasteLong-term storage

NA

Decontaminate(onsite or at wasteprocessor)

Long-term storage

NA

FiltrationSolidficationIncineration

Manage asradioactive waste


Recycle solventLong-term storage


DelistLong-term storage

NA

Manage as

Delist bysolidification


NA = Not applicable.

SOURCE: Rogers & Associates Engineering Corp., “Management Practices and Disposal Concepts For Low-Level Radioactive Mixed Waste,” RAE-8830-1, contractor report prepared for the Officeof Technology Assessment, March 1989, p. 2-17

Chapter -%--Current and Emerging LLW Minimization and Treatment Techniques ● 101

Table 5-1 lists all minimization and treatmenttechniques currently in use for all 12 known types ofmixed LLW, which are discussed in chapter 4. Thistable compliments table 4-3 which lists the prac-tice(s) responsible for generating these mixed LLWtypes. Where the phrase ‘‘long-term storage’ ap-pears on table 5-1, either a minimization and/ortreatment technique used at another facility needs tobe transferred or such a technique is currentlyunavailable. Examples of such cases are made in thefollowing sections.

Most of the minimization and treatment tech-niques discussed are applicable to nonmixed radio-active LLW as well as mixed LLW. However, moreexamples of techniques relating to mixed LLW havebeen chosen to illustrate current problems associatedwith managing mixed LLW and to provide somepossible solutions. Furthermore, mixed LLW exam-ples can encourage technical and information trans-fer between generating communities—somethingthat is not fully occurring today.

WASTE MINIMIZATIONTECHNIQUES

Material Substitution

Generators use material substitution to avoid orreduce their use of radioactive material and, in turn,their generation of LLW and mixed LLW. Materialsubstitution is used extensively on scintillationvials, which are used in a wide variety of industrialand medical research procedures. These vials areglass or plastic and often contain an organicchemical solution (e.g., toluene or xylene, bothlisted as hazardous under RCRA) and a radioactivetracer (e.g., carbon-1 4, tritium, and to a lesser degreesulfur-35, phosphorus-32, and iodine-125). Thewaste scintillation liquid is a mixed LLW if:

1. the liquid is RCRA-hazardous, and2. the radionuclides are other than tritium or

carbon-1 4, or3. if the amount of tritium or carbon-14 is greater

than the NRC limit of 0.05 microcuries pergram of scintillation liquid (10 CFR Part20.303-20.306).

Scintillation liquids are the largest contributor tothe overall volume of mixed LLW generated in theUnited States, By substituting a nonradioactive

tracer (e.g., enzymes and fluorescent labels) for theradioactive tracer. a generator not only eliminatesproducing a radioactive waste but also a mixedLLW. In such cases, the liquid waste is defined onlyas a hazardous waste. Procedures using this substitu-tion technique often lead to equivalent or superiorresults (32, 10).

A waste generator can also choose to substitute itsRCRA-listed hazardous scintillation liquid with anon-RCRA listed liquid--often referred to as an‘‘environmentally benign’ or biodegradable scintil-lation liquid (20). As organic-based compounds,these environmentally benign liquids are composedof large organic molecules that are nonhazardous.Once released into the environment, microbial andbacterial activity can destroy these compoundswithout production of hazardous constituents (20).

At some facilities, environmentally benign scin-tillation vials are now required for all new researchat some facilities. If a generator does not want to usethem, the burden is on the generator to justify whya RCRA-hazardous fluid is essential for the proce-dure. There are cases where this justification can bemade. For example, it may not be scientificallyprudent to switch vials in the middle of a long-termexperiment. Some generators also claim that theenvironmentally benign liquids are not completelyinterchangeable with the toluene and xylene liquids(25). In some cases, equipment or procedures needto be changed to use the environmentally benignliquids, In other cases, the environmentally benignliquids may be incompatible with other materials orprocesses used in the experiment or study. A majorreason why some generators want to avoid switchingto environmentally benign liquids is that they aresimply accustomed to using the toluene and xyleneliquids and do not want to learn new procedures (20).Finally, one facility reported that they were notconfident that the environmental] y benign vials werein fact benign (20).

In cases where environmentally benign vials areappropriate. there are great advantages. The liquidwaste would be regulated as only radioactive if itpassed the EPA hazardous characteristic tests. Amixed LLW stream, therefore, would be avoided.

Finally, in some cases it may be possible to useboth substitution techniques-a nonradioactive tracerand an environmentally benign scintillation liquid—

102 ● Partnerships Under Pressure: Managing Commercial Low-Level Radioactive Waste

resulting in neither a mixed LLW nor a radioactivewaste. Generators, in turn, could either send thewaste to an incinerator or, if permitted by theirlicense and local permits, release the material tosanitary sewer systems.

Another example of a material substitution thateliminates a mixed LLW stream is in the corrosioninhibitor used in nuclear power plants’ coolingsystems. A hexavalent chromate, which is RCRA-listed as hazardous, has often been used to stop pipesfrom corroding. Several plants have replaced thistype of chromate with a nonhazardous chemica13 andthus are no longer generating a mixed LLW (20).

Dry cleaning of contaminated clothing can alsogenerate mixed LLW. Waste generators (e.g., nu-clear utilities) will dry clean some of their protectiveclothing (e.g., coveralls) that is slightly radioactiveso that it can be re-used. Chlorofluorocarbon (CFC)solvents, often referred to as freon, are used in drycleaning because of their decreasing capability andare RCRA-listed as a hazardous waste. When thecleaning solution has to be changed, a mixed LLWis produced in the form of sludge and used filters.Several utilities have switched to a water-basedlaundry service so that hazardous chemicals areeliminated and only nonmixed LLW is produced(20).

Good Housekeeping Practices

Especially for biomedical and medical researchinstitutions, it is possible to reduce the quantities ofradioactive material used by improving the schedul-ing of practices that use radioactive material, reduc-ing excess purchases of radioactive material, andcoordinating purchases through a clearinghouse.Education of organic chemical users, for example,has helped sensitize them to avoid generating ofmixed LLW. Organic chemicals are often used toclean radioactively contaminated equipment, butusers are encouraged to consider alternative cleanupmethods.

Good housekeeping practices can also improvetechnical procedures so that liquid wastes and solidwastes are minimized. With respect to liquid wastes,generators use a variety of techniques to minimizetheir production and to concentrate them when they

are produced. Nuclear utilities, for example, havemade small improvements that have resulted in largereductions in the quantity and type of liquid wastesgenerated. These improvements include:

● minimizing the use of chemicals that increasethe quantity of radioactive corrosion productsin the liquid cooling system, and

. identifying and stopping leaks in the coolingsystem so that the amount of contaminatedmaterial generated is further reduced (20).

For solid wastes, LLW generators use techniquesto ensure that material that does not have to beexposed to radioactivity remains uncontaminated.Contaminated lead is a good example of a solidwaste that generators are trying to eliminate, primar-ily because it is a mixed LLW. Pharmaceuticalcompanies, for example, store neutron-activatedstainless steel tubes, which are used to manufacturepharmaceuticals, in underwater storage pools (20).These companies add lead to the aluminum storagecans to ensure that the cans will not be buoyant. Theinside of the cans can become contaminated withvarious radioisotopes. To avoid generating thismixed LLW, companies are replacing the lead withhigh-density, nonhazardous material (e.g., steel).

Lead is also used in manufacturing shieldedisotope shipping containers. These containers typi-cally have a cavity inside for holding a bottle. Attimes the radioisotope in the bottle can spill andcontaminate the lead container. This mixed LLWcan be avoided by either using a container that is notmade of lead or by placing the bottle in a plastic bagbefore it is inserted into the lead container.

Lead is also used as shielding in the form of foil,bricks, or sheets. To ensure that this lead does notbecome contaminated, some generators cover it witha plastic-like substance such as herculon (20).

TREATMENT TECHNIQUESIt is not always possible to use material substitu-

tion or a good housekeeping practice to avoidgenerating a particular waste. Several treatmenttechniques are, however, available to reduce thewaste volume and sometimes the toxicity after thewaste has been generated.

3A ~-v~ent c~mate that is not defined as RCRA hazardous has been USd in some Cues.

Chapter 5-Current and Emerging LLW Minimization and Treatment Techniques ● 103

Post-Generation, Good HousekeepingPractices Including Waste Decontamination

Liquid waste can be concentrated through evapo-ration, ion-exchange, filtration, precipitation andcentrifuging, and distillation. For example, biomedi-cal institutions use these techniques to separate orconcentrate their organic liquids (32). Nuclearutilities use them on several waste streams. Forexample, evaporation systems and ion-exchangeresins are used extensively to treat-concentrate anddecontaminate-the large volume of liquid wastesgenerated during a plant’s normal operation. Evapo-ration is used to concentrate radioactive contami-nants; the water is boiled off of liquid wastes,leaving behind most of the dissolved and suspendedsolids. Ion-exchange resins (demineralizers) areused to remove dissolved radionuclides by adsorp-tion processes. Improvements in the use of thesetechniques in the nuclear power industry can lead toa 75 percent reduction in ‘‘liquid’* waste volumes(5).

Neutralization is another practice that could beused to better manage some liquid wastes. Aqueouscorrosive liquids, which are mixed LLW due to theircorrosiveness, are stored today in tanks. Theseliquids can be neutralized by raising their pH andthen handling them as a purely radioactive waste(20).

One “problem’ liquid waste, which is a mixedLLW, is contaminated organic chemicals. In somecases, it is possible to distill the liquid and condensethe portion that contains the nonradioactively con-taminated chemical. This process would enable thechemical liquid to be reused. Nonetheless, the wastevolume would be reduced, not eliminated. Theresidue would still be a mixed waste. (See sectionbelow on “Types of Mixed LLW for Which NoMinimization or Treatment Techniques Are Cur-rently Available.

A second problem liquid waste is used oil. SomeStates consider this waste a mixed LLW, but theEPA is currently deciding whether or not waste oilshould be a RCRA-listed hazardous waste.4 If wasteoil is determined to be hazardous, mixed LLWvolumes will increase dramatically.

Some generators are filtrating their waste oil, aprocedure that removes particulate radioactive con-tamination. This practice has worked sufficientlywell for some generators to allow the ‘‘clean’” oil tobe released to oil recyclers (20). The used filters aredisposed of as nonhazardous radioactive waste.Some generators, however, have not been able tofilter their waste oil adequately to separate theradioactive constituent from the hazardous constitu-ent. (See section below on “Types of Mixed LLWfor Which No Minimization or Treatment Tech-niques Are Currently Available.”)

A third problem liquid/wet waste, which is amixed LLW, is CFC solvents and their concentrates,As mentioned above, CFCs used to dry cleancontaminated clothing can be substituted with water-based laundry systems. Nonetheless, problem CFCsare those stored from past dry cleaning services andthose generated now or from future cleaning ofcontaminated tools and equipment. The concentratescan be distilled and heated, thereby reducing theCFC concentration in the waste. Then the recoveredCFC solvent can be reused. The residue, however,remains a mixed LLW unless it can be delisted byEPA or found to be a “below regulatory concern”(BRC) waste—waste ‘‘not subject to regulatorycontrol to assure adequate protection of the publichealth and safety because of its radioactive con-t e n t .

For solid waste, sorting can greatly reduce wastevolumes. Sorting nonradioactive from radioactivewastes as well as sorting wastes into differentcategories (e.g., combustible, recyclable, compacti-ble) are important steps in reducing waste volumes.These sorting techniques are well suited for lightly

dEpA eXwtS [. m~c ~ls determination in late 1989.<The Nuclew Regula[ov commlK$lon (NRC) developd a BRC de for specific radionuclides in ~lmid CUCaSSM and Sclntll]atlon fluids In 198 I

(10 CFR Part 20 306). Tlus regulation wales that these wastes conlaifing tritium ~d carbon-14 in concentrations less ~an 0.05 microcunes per gramcan be dmpowxi of without regard to their radioactivity. This regulation enables such wastes that also contain hazardous constituents to be incinerated(see section below on incineration’). NRC is now evaluating BRC limits for more general cases. EPA ha.. a draft LLW standard which includes limitsfor BRC, The proposed hmlts by these agencm are In conflict and this conflict will have to be resolved. Refer to ch. 3 for more detail on the BRC rule.Sec ah 51 Federal Re&ster 168, Aug. 29, 1986; and T Johnson, ‘‘Below Regulatory Concern Wastes-Identification and Impl]cat]ons for Mixed WasteManagement,” Proceedings of US Environmental Protection Agency Mixed Waste Workshop, Denver, CO, July 19-20, 1988.


contaminated dry solid materials such as paper,glass, plastics, metals, rags, and wood. Thesetechniques, in fact, have been argued to achieve thehighest overall reduction in waste volumes (32). Forexample, onsite, semi-automated waste sorting pro-grams can reduce by 40 percent the volume ofradioactive dry waste generated by a nuclear powerplant (22).

A number of relatively inexpensive techniquescan be used to decontaminate radioactive materialsso that they can be reused, reclaimed, or disposed ofas nonradioactive waste. A variety of cleaningtechniques, including sand blasting, high-pressuresteam, acid baths, and electrochemical polishing,can be used to remove surface contamination frommetal equipment and tools (e.g., condensers, turbineblades, and scaffolding) that would otherwise beshipped for disposal (27).

A centralized waste processing facility -QuadrexCorp.-for example, cleaned about 6,000 pounds ofmetal scaffolding over the last several years. In1987, Quadrex processed approximately 200,000cubic feet (2 million pounds) of metallic LLW at itsfacility. Over 90 percent (180,000 cubic feet) of thiswaste material was cleaned to recover its scrap metalvalue or so that it could be reused.6 One estimateplaces the amount of potentially recyclable metallicLLW at about 540,000 cubic feet per year, roughly2.5 times the current national recovery rate (14).

Practices are also available to reduce and poten-tially eliminate lead—the one problem solid wastethat is a mixed LLW. In some cases, contaminatedlead shielding is cleaned by wiping and rinsing. Inother cases, a high-pressure water and chemical hoseis used to decontaminate the surface. Chemicals bythemselves have also been used to remove contami-nation. These techniques allow 95 percent of the leadprocessed to be released as nonradioactive material(20). Lead decontamination solutions can be solidi-fied to pass EPA leachability tests. The solids arethen no longer defined as hazardous waste and canbe disposed of at a currently operating LLW disposalsite (20).

An additional technique for decontaminating leadis separation. If the surface of a particular lead shieldis fairly contaminated and the above techniquescannot remove the contamination, it may be possibleto physically separate (cutting or scrapping) thesurface of the shield so that most of the lead can bereleased as nonradioactive.

Finally, if surface contamination cannot be re-moved by the above practices, lead can be smeltedso that the contamination is distributed homogene-ously throughout the metal matrix. Once EPA andNRC agree on limits for BRC, it may be possible toreduce the radioactivity to such a degree that the leadis found to be BRC. At the Department of Energy(DOE) National Engineering Laboratory’s WasteExperimental Reduction Facility (WERF) in Idaho,this smelting technique is used. In the FederalRepublic of Germany, ingots of these melts are usedas shielding materials at nuclear power plants.

The BRC rule could also have a significant impacton reducing LLW volumes in general. The ElectricPower Research Institute estimates that the nuclearutility industry alone could see a 30 to 40 percentdrop in its volumes from 1988 figures.7

Storing Radioactive Material for Decay

A large fraction of the radioactive materialgenerated by medical and biomedical researchinstitutions is composed of relatively short-livedradionuclides. By storing these LLW materials fortime periods equivalent to 10 to 20 half-lives, theradioactivity can decline to background levels. Thiswaste is essentially nonradioactive in that it can beregulated without regard to its radioactivity.8 Afterstoring such radioactive waste for the necessaryperiod, it can be disposed of with other solid wastesin a landfill, or it can be released into the sewersystem in regulated amounts (see 10 CFR Part20.303).

Most of the radionuclides used in nuclear medi-cine have half-lives that are less than 7 days (26).Storage for decay is typically done by collecting allthe waste generated within specific periods, usually

15Nomm ~dey, @adrex Corp., personal communication, Dec. 15.1988.

Tpa~cla Robinson, LLW program, EltXLI-IC Power Research Ins(i{ute, presentation made al The Fifih AnnIAuL Dwlslonmakers’ For-LW

Management The Available Optwns & Costs, Wild Dunes, SC, June 6-8, 1989.sThe ~~~ Storage time need~ for a radionuc]ide 10 be al or below its concentration in the natural environment (background level) depends on its

concentration in the waste and its half-life.

Chapter 5--Current and Emerging LLW Minimization and Treatment Techniques ● 105

30-day intervals, and then storing the waste as oneunit. Each unit of waste is segregated by radionu-elides. Either shielded or unshielded storage con-tainers are used, depending on the waste. The wasteis stored until it is no longer considered radioactive.

Without storage-for-decay programs, the combus-tible dry waste and animal carcasses generated bymedical institutions could not be incinerated, andapproximately 30 percent of the aqueous wastecould not be emptied into the sewer. A typicalbiomedical research institution can reduce the vol-ume of LLW requiring disposal by 30 to 40 percentthrough an in-house storage-for-decay program (32).

Storage-for-decay programs may also help elimi-nate certain categories of potential mixed LLW. Forused scintillation liquids, it may be possible to useless radioactive material or radionuclides that havevery short (measured in minutes) decay periods.These modifications may be possible by usingdetection equipment with increased sensitivity. Theliquid waste in this example could be considered nolonger radioactive and, thereby, handled as only ahazardous waste (32).

Two problem arise with some of these storage-for-decay programs. First, a RCRA permit for short-lived radionuclides is required for 90-day or longerstorage. 9 Furthermore, even with such a permit,RCRA land disposal restricted waste can only bestored if storage is for the sole purpose of accumulat-ing sufficient quantities to facilitate proper recovery,treatment, or disposal (40 CFR Part 268.50). Sinceno treatment facilities are available that meet theRCRA treatment standard and no disposal facilitiesare available, it is unlikely that storage would beallowed. The storage prohibition does not apply,however, if one of the exemptions to the RCRA landdisposal restrictions are in effect.10 Some proceduresgenerate LLW, as well as mixed LLW, withlonger-lived radionuclides. For example, iodine-

125, which has a half-life of 60 days, should bestored for about 2 years before it can be disposed ofwithout regard to its radioactivity. If this iodine weremixed LLW, storage would not be allowed accord-ing to EPA. This prohibition is a particular problemfor some mixed LLW when no alternative minimiza-tion or treatment technique can alter it so that it iseither solely radioactive or solely hazardous. Formixed LLW containing radionuclides that must bestored longer than 2 years before they decay to suchlow levels that they can be disposed, generators haveno choice but to either stop the practice responsiblefor generating the waste, which can often meangoing out of business, or illegally store the waste.

Most mixed LLW generators have not yet submit-ted their RCRA Part A permits for storage, and EPAhas not begun to enforce its storage regulations.Once enforcement begins, generators will haveproblems handling these mixed waste streams. (Seesection below on “Types of Mixed LLW for WhichNo Minimization or Treatment Techniques AreCurrently Available.”)

Second, some storage-for-decay programs lackquality control over long-term storage. Degradationof waste packages, for example, can result inexcessive radiation exposure to workers.

Compaction and Shredding Techniques

The volume of dry LLW (i.e., trash) can besubstantially reduced before disposal by mechanicalcompaction and shredding techniques. For example,from 50 to 65 percent of the dry waste generated bynuclear power plants can be compacted to reduce thedisposal volume (3).

In general, compactors are simple to operate andrelatively inexpensive: an exception is supercom-pactors which are more complex and cost between$1 million and $5 million to purchase and install.Compactors must be equipped with air filtration

gcen,.=rators hat q~lfy ~ conditionally exempt small quantity generators (they generate less than 100 kIIograms (kg) (220 pounds) of hazardouswaste per month) do not nexd storage permits as long as the total amo~t Of all h~-~dous waste (including mixed LLW) does not cxcced 1,000 kg (2,2oopounds), Generators that produce between 100 and 1,000 kg ~220 to 2,2~ ~~d~) of hm.ardous waste per month may ~orc thi~ waste onsite for up m180 days without a storage permit, provided that the total amOWN of all h~ardous waste f including mixed LLW’) accumulated onsite does not exceed6,000 kg (13,200 pounds). The 180-day limlt Cm be extended to 270 dav If the dist~cc tie w~te must be transported for offslte treatment, storage,or cbsposal is 200 miles or more (40 CFR Part 262).

l~xlg~g Provlslons for exemptions ~dcr the RCRA i and disposal rest.rlctlons include a ~-year national capacity varIancc, an approved no-migrat]onpetition, or an approved case-by-case extension. Caw-by-case extensions arc only allowed if the applicant can demonstrate that he/she has entered intoa binding contract with a treatment facility operator/deveioper that will construct or otherwise provide alternative treatment, recovery, or disposalcapaaty for the entire waste stream after the extertson expires ( 1). See ch, 3 for a more dctwled discussion of storage prohlbmons and thcu relationshipto treatment standards and land ban restrictions.


units to

. “

Photo credit: Scientific Ecology Group

Before and after photos of box compaction using a 5,000-ton supercompactor

control the release of airborne contaminantsand to minimize worker exposure. An added advan-tage of compactors is that the processed waste is ofuniform geometry, which facilitates handling andpackaging and reduces the space needed for interimonsite storage (21).

Super-compactors in use today are either station-ary or mobile units capable of producing a force of1,000 tons or greater. These units can crush contain-ers of waste (55-gallon drums or boxes) into‘‘hockey pucks ‘‘ in a manner of minutes (11). Thesehigh-tonnage systems are capable of handling alarger fraction of the so-called noncompatiblewastes, which represent a large part of a nuclearpower plants’ waste volume (8).

Using a 5,000-ton device, centralized waste proc-essing companies like the Scientific Ecology Group,Inc. (SEG), a waste processing company in Tennes-see, can supercompact the dry wastes from a widevariety of generators. In 1988, SEG processed morethan 800,000 cubic feet of waste, an increase of 40percent from 1987. Only 167,000 cubic feet of thiswaste-a volume reduction of almost 80 percent—was left to be shipped for disposal.11 Before thewaste is compacted, materials like wood and metalthat are nonradioactive or that can be decontami-nated are separated from the waste stream. Liquids

that are released in the compaction process aresolidified in cement and placed with the compactedwaste.

Size reduction devices such as shredders cart alsobe used to reduce waste volumes (27). Shredderstear, rip, shatter, and/or crush waste materials intosmaller sizes. By using supercompactors and/orshredders, it is possible to achieve up to a seven-foldor about an 85 percent volume reduction (27).Shredders can also provide a more uniform feedmaterial for incinerators.

Incineration

Incineration is one of the most efficient ways ofreducing waste volumes. The techniques discussedbelow have mainly been used to treat municipalsolid waste, but they could be used to treat low-radioactivity, combustible liquid and solid dryLLW. The major differences in applying this tech-nology to LLW involve shielding requirements, theuse of high-efficiency filters, and methods of ashdisposal (27). Incineration can reduce waste vol-umes by a ratio of at least 25:1 (or 96 percent).Although this experience indicates that it is ratherdifficult to design a universal incinerator capable oftreating all the various waste types at equal effi-ciency and performance (7). With respect to some

1 IBud Arrow~i~, Scientific Ecology Group, Inc., personal communication, (kt. 19, 1988.

Chapter 5--Current and Emerging LLW Minimization and Treatment Techniques . 107

mixed LLW, incineration can convert the waste intocarbon dioxide and radioactive ash (7). Incinerationis likely to be inappropriate for treating LLW,including mixed LLW, that contains radionuclidesthat cannot be trapped by an off-gas system.

Types of Incinerators

Three major types of incinerators are currentlyused worldwide to reduce LLW volumes: 1) rotarykilns, 2) controlled-air incinerators, and 3) fluidized-bed incinerators.

A typical incinerator facility consists of a wastesorting system, a waste feeding mechanism, a maincombustion chamber, often an afterburner, an elabo-rate off-gas cleaning system, an ash collection andremoval system, a waste conditioning unit, andinstrumentation to monitor critical operating param-eters to ensure that health and safety-related limitsare met. Incinerators differ in their design based onthe amount of air used, the special characteristics ofthe combustion chamber, and the form of theincineration residue.

In a rotary kiln, waste is decomposed (oxidized)by burning in a slowly rotating, refractory-linedcombustion chamber mounted at a slight incline sowaste gradually gravitates toward the ash dischargepoint. This chamber contains more oxygen thannecessary to completely oxidize the waste. Liquidinjection units are often coupled with this design forliquid wastes. To ensure complete combustion, asecondary combustion chamber (afterburner) is oftenused to increase the time that wastes are subjected tohigh temperatures. A relatively large amount of ashand particulate can be produced by this type ofincinerator (24).

In a controlled-air incinerator, waste is fed onto aplatform in the bottom of a combustion chamber.This primary chamber as well as the secondarycombustion chamber can be operated under eitherstarved-air (pyrolytic) or excess-air conditions. Theconditions chosen depend on the waste type. WithLLW incinerators, it is common to operate theprimary chamber under pyrolytic conditions becausethe amount of fly ash produced is greatly reduced.Liquid injectors can also be attached to this chamberto destroy liquid wastes. Particles of incomplete

combustion are then fed into a secondary high-combustion chamber that is oxygen enriched. Theadvantage of this design is that less fly ash isproduced, therefore less radioactive dust is carriedout with escaping combustion gases (24, 7). None-theless, an elaborate off-gas system accompaniesthis design (see following discussion on air pollutioncontrol technologies).

A fluidized-bed incinerator uses a layer of smallparticles (e.g., sand, limestone) suspended in anupward flowing stream of air like a fluid (hence, thename) to help burn highly viscous liquids andsludges not easily burned by other incinerators (24).The flowing particles help the mixing and thecombustion efficiency. This design can also removeacid gases (27). A disadvantage of this design is thatcombustion gases can contain high levels of particu-late (24).

Two other technologies—wet air oxidation andsupercritical water oxidation—are similar to incin-eration but involve water. Wet-air oxidation is usedby hazardous wrote facilities to oxidize organiccontaminants in water (24). LOW temperatures canbe used with this technology because the watermodifies the oxidation reactions. and the reactorvessel is maintained at a pressure high enough toprevent excessive evaporation. Supercritical wateroxidization is similar, but temperature and pressureare higher than with the wet-air oxidation process.By raising primarily pressure and to some degreetemperature, the rate and efficiency of thermaloxidation can be enhanced (24). Neither of thesewater-based thermal oxidation processes is commer-cially available. The DOE Los Alamos Laboratoryhas an on-going research project under its HazardousWaste Remedial Action Program (HAZWRAP)using supercritical water oxidation. These technol-ogies, particularly supercritical water oxidation,may hold promise for destroying organic chemicalscontaining radionuclides like tritium and carbon-14,which are nearly impossible to trap in conventionaloff-gas incinerator systems.12 One European reportnoted a trend toward using special incinerationsystems for less voluminous wastes with specialcharacteristics (e.g., solvents) and/or special con-taminants (7).

]zfil~ ~omcn~u~ ~m ~e~hcd a[ tic Worbhop on SWerC,rltl(a/ Fluld processing of H/gh Ruk W~tes, held at tic LOS Al~o\ Xationtd Laboratory,

I.m Alamos, New Mexico, Aug. 1-2, 1989.


Air Pollution Control Technologies

Air pollution technologies are used to control theemission of gases and radioactive particulate. Theamount of radioactivity released into the atmospherefrom an incinerator depends in part on the volatilityof a particular radionuclide during the combustionprocess. As mentioned above, it is very difficult toprevent the release of volatile radionuclides, likecarbon-14, tritium, and iodine-131, with currenttechnologies.

A small amount of the waste’s total radioactivityis transported in particulate matter by combustiongases leaving the chamber, while most radionuclidesare trapped in the ash or slag (melted ash) that settlesto the bottom of the combustion chamber. Theconcentration of radioactivity in the fly ash can beeven higher if the volume of dust particles producedis limited. A combination of technologies is used toremove these radioactive particles from the combus-tion gases: fabric baghouses, high-temperature ce-ramic filters, electrostatic precipitators, and high-efficiency particulate air (HEPA) filters. For exam-ple, in some systems, gases pass through thebaghouses, and fly ash is collected on the outersurface of the bags. On a periodic basis, the fly ashis driven off of the bags by injecting a burst ofcompressed air through a venturi in the top of eachbag. This burst of air knocks the fly ash off the bagsand into a hopper at the bottom of each baghouse.This fly ash is collected, processed (e.g., solidifiedusing a cement waste form), and disposed of. Aftergases pass through the baghouses, they are sentthrough HEPA filters designed to remove over 99percent of particles larger than 0.3 microns (2).

Operating Experience

Incineration has been used extensively in Europe(e.g., Federal Republic of Germany, Sweden) and inJapan since the early 1970s to treat commercialLLW generated by hospitals, nuclear power plants,and industry. In Sweden, more than 600,000 cubicfeet of dry active waste were incinerated between1976 and 1983 at a central LLW processing facility(16). During this period, less than 2 percent of themaximum permissible amount of beta and gammaradionuclides were released into the atmosphere viathe stack gases. A strict quality control program-toensure that a waste package’s manifest accurately

reflects the waste’s contents-has been found to becritical in minimizing emissions (4).

In the United States, no commercial incinerator islicensed to treat LLW or mixed LLW. About 100individual licensees have incinerators for certaincombustible wastes generated at their sites, butincinerators for commercial use are not available. Incontrast, the DOE has incinerators within its weap-ons complex sites that can treat both LLW andmixed LLW, and these wastes are shipped betweenweapon sites for treatment. The WERF incinerator atthe Idaho National Engineering Laboratory, forexample, routinely burns LLW and on a smallerscale bums liquid mixed LLW. The incinerator iscurrently operating under RCRA interim status (27).The DOE Oak Ridge National Laboratory is plan-ning to open in February 1990 its Toxic Substanceand Control Act (TSCA) incinerator, which will bepermitted to burn mixed LLW. Both of theseincinerators bum or will burn wastes from otherDOE sites.

The only U.S. commercial facility that is sched-uled to be available in November 1989 is acontrolled-air incinerator operated by SEG in OakRidge, TN. The incinerator will be capable ofburning 800 to 1600 pounds of dry solid waste perhour. Included in the design is a system to handleliquid wastes and a glass furnace to stabilize finalash products. This incinerator will be permitted tobum only non-mixed LLW

Incineration of Mixed LLW

In Europe, mixed LLW is defined simply asradioactive waste. Operators of treatment and dis-posal facilities, therefore, do not have to obtainspecial permits or meet special standards for thiswaste.

In the United States, in contrast, there are inciner-ators to treat hazardous waste, but not commercialmixed LLW. Although SEG has the technicalcapability to treat mixed LLW at its soon-to-beoperating incinerator, the company has not filed forthe necessary permits.

The bulk of mixed LLW—scintillation fluids-isincinerated because it is not regulated as a mixedLLW. From a regulatory standpoint, most of thesefluids are below the established limits set by theNuclear Regulatory Commission to be BRC and,

Chapter S---Current and Emerging LLW Minimization and Treatment Techniques ● 109

therefore, are regulated for their nonradioactivecharacteristics. Most of these BRC fluids areshipped to one company in Florida-Quadrex Corp.—that burns them to recover their energy value. Thefluids are an energy supplement to the fuel that runsan incinerator. The heat from the incinerator, in turn,is used to make cement blocks. Because the inciner-ator is an energy recovery system, it does not requirea RCRA permit. This situation will likely changedue to the amendments EPA is currently drafting;13

EPA will likely determine that energy recoveryfacilities, like the incinerator Quadrex uses, willrequire a RCRA permit. Quadrex plans to use anincinerator that has a RCRA permit, if this determi-nation is made.

As with the BRC scintillation fluids, waste oil hastypically been burned as a fuel substitute becauseusually it is only slightly contaminated. This oil isproduced in large quantities by nuclear utilities andsome industrial generators. Many generators incin-erate their waste oil onsite, while others ship it to awaste processor. SEG, for example, treats approxi-mately 30,000 gallons of waste oil annually. ’4

The status of waste oil may soon change. EPA isreevaluating whether waste oil should be listed as ahazardous waste and is expected to make a decisionin late 1989. If waste oil is found to be hazardous,then generators/waste processors will need a RCRApermit to incinerate their waste oil. All States willhave to amend their regulations to include thisdefinition. If waste oil does become defined as aRCRA-listed hazardous waste, the volume of mixedLLW will rise dramatically. Without a RCRA-permitted incinerator available, the waste oil thatcannot be successfully filtered will have to be stored.This volume would only be reduced if this wastefalls below the yet-to-be-finalized BRC limits.

Another type of mixed LLW for which noincinerator is available is organic chemical waste.Several technologies (e.g., supercritical water oxida-tion) have been identified in the laboratory as beingable to possibly treat this waste effectively but theyhave not been developed nor tested commercially

(25). (See section below on “Types of Mixed LLWfor Which No Minimization or Treatment Tech-niques Are Currently Available.”)

Waste Stabilization

Stabilization techniques are used to fix theconstituents of LLW, including mixed LLW, in asolid form that is inert, that has low exchange orrelease rates in water, and that can be safelytransported or stored. The solid form in which awaste is fixed is called the waste form. For example,incinerator ash can be stabilized in a cement-basedwaste form that fixes the ash and retards themigration of radionuclides in the waste. Severaldifferent stabilization media are available. Finally, awaste packaging container designed for a particularwaste form is critical to ensuring long-term stabili-zation of the waste and, in turn, the protection ofpublic health and safety and the environment duringstorage, shipment, and disposal.

Technical Requirements

LLW must be stabilizedrequirements (10 CFR Part

Minimum Requirements.

based on the following61) (28, 30):

for All Classes of LLW

1.

2.

3.

4.

5.

Minimum packaging requirements must be met(e.g., no cardboard boxes are allowed), but thewaste does not have to be solidified or placed ina special container.15

Liquids are to be solidified or packaged in twicethe volume of liquid absorbent. (The use ofabsorbents is, however, prohibited in some Agree-ment States. )

No more than 1 percent of a solid waste’s volumeshall contain liquids.

The waste must not be explosive, pyrophoric,capable of generating harmful gases, toxic, orinfectious.

Waste should not generate gas pressure greaterthan 1.5 atmospheres at 20‘C and must containless than 100 curies per container.

\SEpA ~s~u~ ~ ~upp\ementaI notice on Octokr 26, 1989, that requires energy rc~~vely facilities 10 be permitted. This supplemental notice ISeffectively a reproposal of a proposed rule issued on May 6, 1987. EPA plans to issue a final rule in early 1991.

IQ~owsmi~, op. cil., footnote ! 1.

151n wmhin~on ~d Souti Cwollna, ~e~aln C]ms A wfi~es (those having ra~onuclldes with half-] ives greater than 5 yCWS in concentrations greaterthan 1 microcurie per cubic centimctcr) must also be stabilized (27).


6.

7.

Waste containing hazardous, biological, patho-genic, or infectious material must be treated toreduce to the maximum extent practicable thepotential hazard from the nonradiological ma-terials.

A process control (testing) program must be usedto ensure that the waste product is of consistentquality.

Additional Requirements for Class B and C Waste

1.

2.

3.

4.

5.

6.

The waste form must be structurally stable.

Liquid waste must be converted into a form thatcontains no more than 1 percent of the waste’svolume, when the waste is in a disposal containerdesigned to ensure stability, or 0.5 percent of thewaste’s volume, when the waste is processed to astable form.

Void spaces within the waste and between thewaste and its package must be reduced to theextent practicable.

The gross physical properties of the waste formmust be retained for at least 300 years under alldisposal conditions (e.g., irradiation, high com-pressive loads, exposure to moisture, and bio-logical degradation).

Instead of using solidification agents (e.g., ce-ment) to fix the waste, Class B and Class C wastemay be stabilized in a suitable high-integritycontainer (HIC). When a HIC is used, themaximum amount of free liquid cannot exceed 1percent of the waste volume.

Class C waste must be disposed of so that the topof the waste is at least 15 feet below the surface ordisposed of with intruder barriers designed toprotect against inadvertent intrusion for at least500 years.

Waste Form Types

Typical stabilization techniques include solidify-ing wastes using lime-based cements, bitumen(asphalt), and synthetic polymers (e.g., vinyl ester-styrene and urea-formaldehyde). Wastes are alsostabilized by certain waste packages. HICs com-posed of organic polymers like polyethylene andvarious stainless steel alloys are used to stabilizewaste,

In the United States, cement mixtures have beenpreferred as stabilizing materials, while in Europebitumen has been used for over 20 years to stabilizeradioactive wastes.

In cement-based waste forms, waste solidificationoccurs by a complex chemical hydration reaction(i.e., water and lime are added to produce a calciumoxide). The advantages of this waste form are that:

● it effectively stabilizes most LLW,. it has a high structural strength,. it is inexpensive to produce and easy to use, and. it exhibits a low leachability for most radionu-

elides.

The disadvantages of cement-based waste forms arethat:

●

●

●

it, unlike bitumen, increases a waste’s volumeby 10 to 30 percent,it is difficult, though not impossible, to use insolidifying mixed LLW composed of untreateddetergent, oils, and other organic liquids be-cause these substances interfere with the hydra-tion process (27), andit may also be incompatible with mixed LLWcomposed of metallic-salts.

In a recent NRC Notice (31), other disadvantageswith cement-based waste forms were listed. Theseinclude:

. its failure to solidify completely,

. swelling and bulging of liners, and

. disintegration over relatively short periodsfollowing solidification.

In particular, bead resin, decontamination solutions,berates, sulfates, and oils were listed as wastes thathad problems when solidified using a cement. TheNRC announced at one of its workshops that severalcases of full-scale and lab-scale waste forms havehad these problems (18). Likewise, the IdahoNational Energy Laboratory reported that it hadsimilar problems in using cement-solidified wasteforms and that the waste formed cracks duringleaching (18).

In the United States, cement is often combinedwith numerous natural and synthetic sorbable mate-rials to stabilize waste. This combination makes iteasier to stabilize some organic mixed LLW. How-ever, waste fores that depend on sorption tech-

Chapter 5--Current and Emerging LLW Minimizat ion and Treatment Techniques ● 1 1 1

niques are, by themselves, inadequate stabilizingagents due to the reversible nature of most sorptionprocesses.

Bitumen systems are considered to be both wastestabilization and volume reduction technologiesbecause the heat required to melt the mixture assistsin evaporating any liquid wastes (27). The hotbitumen coats the waste particles, thus encapsulat-ing the waste in a solid matrix that is impermeableto water and structurally stable once it cools.Bitumen can be used to stabilize almost all LLWmaterials with the possible exception of certainmixed LLW, such as those containing liquid organicchemicals (e.g., oil). The major advantages of usingbitumen are:

. its good leach resistance characteristics,

. the low operating costs of producing it,

. the ease of handling it. and● its high waste loading capacity.

The major disadvantages of using bitumen are:

●

●

●

●

its relatively low ignition temperature (i. e., it isflammable),its instability at high temperatures,its relatively low (in comparison to cements)structural strength, andits susceptibility to biological degradation (27).

Polymers, in contrast, solidify wastes by a chemi-cal reaction process called polymerization. Advan-tages of this waste form are that:

●

●

T h e

are:

●

●

●

wastes are very resistant to chemical leaching,andthey exhibit high compressive strengths.

major disadvantages of using this waste form

the high material costs,the complexity of the mixing process, andthe fire and explosive hazard posed by some ofthe chemical ingredients of the polymer.

Table 5-2 summarizes the advantages and disad-vantages of these three waste forms. Cement hasmany advantages, but its quality is inconsistent andit produces higher waste volumes. Bitumen exhibitsthe opposite characteristics, in that its quality isconsistent and it reduces waste volumes; however, itis not as structurally strong as cement, Neither

Table 5-2—A Critique of Waste Forms

Characteristic Cement Bitumen Polymer

Leach resistant . . . . . . . . . . . . Y Y YHigh structural strength . . . . . . . . Y N YNot flammable nor

ignitable . . . . . . . . . . . . . . . . . . Y N NEasy to use . . . . . . . . . . . . . . . . Y Y NConsistent quality . . . . . . . . . . N Y uAppropriate for organic

chemical mixed wastes . . . . . . N N uReduces waste volume . . . . . . . N Y IInexpensive . . . . . . . . . . . . . . . Y Y NKEY :Y =yes

N = noU . unknownI = Indifferent

SOURCE Off Ice of Technology Assessment, 1989

cement nor bitumen can adequately stabilize somemixed LLW, particularly organic chemical waste, In

comparison to either cement or bitumen, polymerwaste forms appear to have no major advantage. Acombination of these waste forms may be mostappropriate for some mixed LLW. NRC has anactive research program in this area to improvewaste form reliability.

Waste Packaging Materials

A variety of different packaging materials areused for LLW containers. Wooden boxes are used atsome disposal sites (in arid regions) for Class Awaste. Steel drums and steel boxes are also used forClass A waste. HICs made from a variety ofmaterials (e.g., polyethylene, steel-reinforced con-crete, and stainless steel) are used for Class B and Cwaste. As noted, these packaging materials aredesigned to retain their physical and chemicalintegrity for at least 300 years (30).

In general, polyethylene is a highly corrosion-resistant material, but its long-term structural integ-rity is of concern. Studies conducted at the BrookhavenNational Laboratory found that polyethylene con-tainers may become brittle, crack. and rupture whenexposed to certain chemical contaminants (e.g.,organic liquids such as oils) and to high doses ofradiation (23). The NRC allows the use of thesecontainers for disposal but only if the requiredstructural stability is provided by other packagingmaterials or engineered structures (17), Containersmade of various steel alloys are also used to stabilizeLLW and some mixed LLW because of their high


structural strength and their ability to resist corro-sion (though not to the same degree as polyethyl-ene).

A number of containers on the market use acombination of several materials to form a containerwith improved stability characteristics (27). Forexample, a polyethylene container within an innersteel or concrete container has been used. Polymer-impregnated cements have also been used to reducethe leaching of some radionuclides (e.g., cesium andstrontium) (19). As with waste forms, more researchis needed on packaging materials that may beappropriate for various mixed LLWs.

Long-Term Stability Predictions

It is important to be able to predict how thematerials used to stabilize LLW and mixed LLWwill behave in a disposal environment over the longterm. The most common prediction methods arebased on the results from short-term laboratory tests.Leachability, due to groundwater, is one of the mostimportant factors in determining the long-termstability of a waste form or container. Leaaching testsmeasure the ability of a particular waste form orcontainer to retard the release of specific radionu-clides or hazardous chemicals. These tests areconducted by placing a sample of the stabilizedmaterial in water and then measuring the releaserates (of individual chemical species) over a periodof about 90 days.

Experimentally determined leaching rate predic-tions must be viewed with caution for severalreasons:

●

●

●

the tests are based on short-term studies (often90 days or less);the experimental conditions are generally notrepresentative of the variety of geochemicalconditions encountered in a disposal environ-ment;16 andvery little to no quantitative information existson the long-term stability of containment mate-rials under disposal conditions.

With respect to the third reason, the only long-term database available is for concrete. Two-thousand-year-old concrete structures (e.g., bridges, aque-ducts, and harbors) from the Roman era are still inexistence. Studies of these structures show that theconcrete has retained most of its structural strength,but often has undergone extensive chemical trans-formation as a result of exposure to ambientenvironmental conditions (12). Many examples canalso be cited where modern concretes have per-formed satisfactorily for at least 100 years. It isdifficult to be certain, however, that concrete willremain structurally stable and resistant to leachingfor much more than a few hundred years (12).

TYPES OF MIXED LLW FORWHICH NO MINIMIZATION

OR TREATMENT TECHNIQUESARE CURRENTLY AVAILABLE

A major problem for mixed LLW generators isthat no commercial facility is available to treattheir wastes. According to EPA regulations. aparticular treatment standard must be met for aparticular hazardous waste before it can be disposed.The standard may be expressed as a specifiedtechnology (e.g., incineration), as a total concentra-tion in the waste, or as a concentration in the wasteextract (i.e., by using a leaching test called theToxicity Characteristic Leaching Procedure or TCLP)(l). In all cases, these treatment standards are basedon the performance of the best demonstrated availa-ble technology (BDAT).

EPA treatment standards for solvents, dioxins,and the hazardous constituents that fall on theCalifornia List17 are in effect and apply to mixedLLW that contains these hazardous constituents.Therefore, mixed LLW generators are required totreat these wastes accordingly. There are threetypes of mixed LLW identified for which treat-ment is necessary, but a treatment facility isunavailable.

16 Baauw of tie “~ety of ~ssible ge~hemlc~] ~ondl[lons at a site, i[ IS difficult 10 devlw a st~dardizeci leaching test that represents the potential

mobility of radioactive (or chemical) contaminants.17~e c~lfofia List ,nc[udes free ~J,~ldcs, ~omoslves, h~.~d~us w~stc mixed wi~ poly~h[onnatcd biphcnyls ( PCB\ ), and ccrtmn melals (1.c..

arsenic, cadmium, chromium, lead, mercury, mckel. thallium, and selenium) (RCRA sectmrrs W04[d][ 1 ], [d][? ], 42 L S.C. 6924 [d ][ 1 ], [d][2] ). Fortreatment standards for these wastes, see EPA’s final rule-52 Federal Rcglster 25760, July 8, 1987.

Chapter S--Current and Emerging LLW Minimization and Treatment Techniques ● 113

First, organic chemicals, in some cases, can bedistilled and the nonradioactively contaminatedchemical can be concentrated for re-use. Nonethe-less, the residue is still a mixed LLW. For the mostpart, organic chemical mixed LLWs fall into thesolvent category, and the BDAT for solvents isincineration. No commercial incinerator, however,is available to treat organic chemical mixed LLW.Furthermore, as mentioned, some organic chemicalscontain high concentrations of radionuclides (e.g.,tritium and carbon-14) that would escape through aconventional off-gas filtering system if incinerated.Newly designed incinerators or completely newtechniques (e.g., some water-based thermal oxida-tion process, like supercritical water oxidation, orsome new stabilization technique) may be needed totreat these wastes.

Second, waste oil may be a problem with respectto treatment. If EPA decides that waste oil is aRCRA-listed hazardous waste, the overall volume ofmixed LLW will dramatically increase, All genera-tors of mixed LLW oil will have to meet theestablished treatment standard, and the BDAT tomeet this standard will likely be incineration, Basedon comments from some generators, it appearsunlikely that filtration will successfully work in allcases for separating radioactive particulate fromoil. Therefore, incineration will be required. As withorganic chemicals, no commercial mixed LLWincinerator is available.

Third, chlorofluorocarbons (CFCS) used in drycleaning of clothing may also be a problem withrespect to treatment. Even though many generatorshave shifted to water-based laundry systems, CFCsolutions from past practices are in storage. More-over, CFC solutions and sludges from decontaminat-ing tools and equipment are in storage and willcontinue to be generated. As with organic chemicals,these solutions can be distilled and the nonradioac-tively contaminated solution can be concentrated forre-use. Nonetheless, the residue is still a mixedLLW. Because the concentration of radioactivity inthese solutions is generally very low, generatorshope to have them delisted or found to be BRC oncethe standard is finalized. The BDAT for CFCS isincineration, and, until a delisting petition is grantedor the BRC standard is finalized, generators shouldbe incinerating them. However, no commercialmixed LLW incinerator is available.

All generators that have land-disposal-restricted mixed LLW for which no treatmenttechnique is available have no options but eitherto stop the practice that generates the waste,which in many cases means going out of business,or to store their waste. Storage is, however, onlyallowed for a period long enough to accumulateenough volume to further manage the waste. Withno treatment or disposal capacity available, it isunlikely that the accumulation argument can be usedby generators. They can apply for a case-by-caseextension to a land disposal restriction for up to 2years, during which time the storage prohibitiondoes not apply. However, to receive the extension,the generator must be able to demonstrate that agood-faith effort has been made to locate andcontract with facilities nationwide to manage itswaste, and that a binding contract has been enteredinto with a treatment operator/developer that willconstruct or otherwise provide alternative treatment,recovery, or disposal capacity for the waste. Thecontract must ensure that this capacity will beavailable at the end of the extension period.

It will unlikely be possible to provide a treatmenttechnique for some mixed LLW types in thistimeframe. In particular, developing techniques andmaking them available for some organic chemicalsolvents with long-lived radionuclides or high con-centrations of radionuclides may be difficult. Ifstorage of such wastes extends significantly, exces-sive radiation exposures to workers could result ifadequate storage conditions are not maintained andwaste packages degrade (20).

Another problem with mixed LLW manage-ment is that EPA has not completed establishingtreatment standards for all hazardous wastes.Nonetheless, it appears that treatment standardshave been established for the majority of commer-cial mixed LLWs (e.g., organic solvents) identifiedthat cannot be treated so that they are no longer amixed LLW. A comprehensive national survey,however, has not been conducted to determine all thepossible mixed LLWs that are being generated. Asurvey may uncover some types of unalterablemixed LLW for which treatment standards are notavailable.

A survey could also serve other needs, Stateswould have a database to draw on to know which


institutions/facilities are generating mixed LLW andto know the waste types and their volumes. Thisinformation would help States in their regulation ofmixed LLW as well as in their development of amixed LLW disposal facility. Furthermore, a mixedLLW survey could provide the treatment industrywith the necessary information to develop treatmentfacilities to meet RCRA standards. This industry hasoften argued that it is leery of developing treatmentfacilities (e.g., incinerators) because it lacks thisinformation. A survey could meet these needs.

A BRC standard could also help resolve someof the mixed LLW management problems. Asmentioned above, by using a BRC standard, genera-tors may be able to dispose of CFC residue and leadas hazardous waste, thereby omitting these twowaste types from the mixed LLW category. Depend-ing on the concentration of radioactivity in waste oil,it too might be removed from the mixed LLW list.18

Theoretically, this would leave one problemmixed LLW-organic chemicals containing highconcentrations of radionuclides that cannot betrapped in an incinerator off-gas system. A newtreatment or stabilization technique may beneeded for these wastes.

THE FUTURE FORWASTE MINIMIZATION

AND TREATMENT TECHNIQUES

Future Disposal Volumes

In reaction to the volume restrictions (i.e., dis-posal allocations established in the Low-LevelRadioactive Policy Amendments Act of 198519) atexisting disposal sites, the slow progress in sitingnew disposal facilities, and increasing disposalcosts, LLW generators have been reducing thevolumes of waste they ship for disposal. Between1980 and 1988, these factors were responsible for a55 percent volume reduction in commercial LLWshipped for disposal (see ch. 4). From 1984 to 1987,the nuclear power industry reduced its waste volumeby about 42 percent, while at the same time theindustry built 20 new reactors (6). Since the late

1970s, institutional generators have used a variety ofthe technologies discussed in this chapter to reducetheir LLW volumes shipped for disposal by 94percent (32).

Waste minimization techniques can be usedmore extensively to avoid generating some LLWsby improving technology transfer between gener-ator communities. Once the waste has beengenerated, incineration and decontamination tech-niques appear to have the greatest potential forreducing future LLW volumes.

Interstate LLW Management Services

The cost of disposing of LLW will almostcertainly continue to rise in the future, due to theincreased costs of constructing the newer engineereddisposal facilities (see ch. 6). Higher disposal costsalone, however, may not drive waste volumes downto the maximum extent practicable, particularly ifcompacts decide to prohibit interstate processing ofLLW. It probably will not be economically viablefor States and compacts with a small waste volumeto develop their own incinerators. The capital costsof constructing an incinerator are high, ranging from$7 million to $9 million for a system capable ofhandling 85,000 pounds of waste per year, whileannual operating and maintenance costs are around$500,000 (27). Incinerators have also been proven tobe very difficult to site and license. With no accessto an incinerator, volumes in these regions will notdecrease significantly. It appears that the overallcosts and some handling and transportation risks(see below) can be reduced by encouraging interstateprocessing of wastes.

Mixed LLW Management

The waste minimization and treatment techniquesdiscussed in this chapter will continue to reduce thevolume of mixed LLW. Generators will be pres-sured even more to maximize their use of thesetechniques, once EPA enforces its RCRA regula-tions and requires all generators to obtain apermit for treating and/or storing their mixedLLW. To avoid dual jurisdiction-to avoid havingto obtain a RCRA permit in addition to the NRC or

I RBY defining ~ ~lxe. LLW ~ BRC with respect t. 1(S radioactivity, however, does not guaramec that a h~~dous wa..lc landfill will a~~cpt the waste.The landfill may have stricter requirements in its pcrmlt and refuse the waste. In such instances, the waste generator IS left with no disposal option atpresent.

19~b11C L~~ 99.’7~, J~, 15, 1986,

Chapter S---Current and Emerging LLW Minimization and Treatment Techniques ● 115

Agreement State license they currently have—mixed LLW generators will try to change theirpractices and not generate mixed LLW or will try totreat all mixed LLW such that it is either solelyradioactive or solely hazardous.

The generation of some mixed LLWs is, how-ever, unavoidable. Of primary concern is thestorage prohibition that applies to mixed LLW.As a remedy, EPA could decide, in establishing itstreatment standards for the final third of hazard-ous wastes (due to be released in May 1990), thatthe storage prohibition does not apply to genera-tors of wastes for which no treatment capacityand/or no disposal capacity is available. In otherwords, storage would be allowed if it is not beingused in place of disposal.

An advantage of this approach is that mixed LLWgenerators would have an intermediate option untiltreatment capacity and disposal capacity are availa-ble. Furthermore, by generators applying for astorage permit, EPA would have a record as to whattypes and volumes of mixed LLW are beinggenerated. EPA could use the data to better ensurethat wastes are not being illegally disposed. Thewaste treatment industry also could use the data asa marketing tool to develop necessary waste treat-ment facilities, as it could with data from a nationalsurvey.

Generators claim that dual jurisdiction is veryburdensome in that they have to meet two separateagencies’ requirements, including filling out sepa-rate forms that often request the same information.EPA has stated, however, that it will try and “accept,to the extent possible, information already submittedto the NRC when processing a RCRA permit.”20

Likewise, NRC has said that the two agencies willwork toward ‘‘resolving the difficulties of simulta-neous licensing and permitting processes, makingthe overall process more uniform, and exploring thepossibility of using the same application docu-merit, ’ but NRC notes that this effort is of lowpriority compared to joint guidance efforts (13).Even given these intentions, generators are discour-aged and anxious about dual jurisdiction because of

the lack of progress they have seen the two agenciesmake toward streamlining the permitting/licensingprocess for the treatment, storage, and disposal(which is discussed inch. 6) of mixed LLW.

Dual jurisdiction is likely to be difficult until EPAand NRC agree to joint rulemaking or joint guidanceconcerning several regulatory issues. In some cases,the two agencies have different approaches and theseapproaches may be in conflict. Joint rulemakingand/or joint guidance will likely be needed on wastepackage manifest requirements, waste package sam-pling and testing, and inspection and enforcement oftreatment, storage, and disposal facilities. For sam-pling, EPA requires a 100-gram specimen. NRC isconcerned that this size sample is too large and inconflict with its principle of keeping worker expo-sure as low as reasonably achievable. EPA head-quarters has told its regional offices that, if thisconflict does arise, the office should accept smallersamples. 21 In addition to other cases of possibleregulatory conflict and overlapping and duplicativeregulations (see ch. 1 and ch. 3), the NRC and EPAmay find other regulatory areas that will require jointrulemaking and/or joint guidance.

Of all the types of mixed LLW discussed, threetypes stand out as the most difficult for generators tomanage-organic chemicals, waste oil, and CFCresidue. Of these three wastes, organic chemicalsseem to offer the greatest challenge from a treatmentperspective. If a comprehensive survey of mixedLLW is conducted and/or EPA develops a recordof stored mixed LLW by permitting such prac-tices, States would have the information theyneed to regulate these wastes and to developdisposal capacity. In addition, industry wouldhave a clearer idea of the technology and capacityneeded to treat these three wastes.

Risks of LLW Management

Neither incineration nor decontamination—the two most efficient waste volume reductiontechniques-will reduce the total curies gener-ated, because curies cannot be destroyed.Through current incineration techniques, some radio-

Z053 F~er~ Register 185, Sept. 23, 1988.

ZITO Ju~ify ~S d~ision, EPA regional offices can cite Section 1006 of RCRA. It StateS ‘ ‘nothing in this chapter shall be construed to apply to (or(o authorize any State, interstate, or local authority to regulate) any activity or substance which is subject to [numerous laws including] the Atomic IkrgyAct of 1954 except to the extent that such application (or regulation) is not inconsisten~ with the requirements of such Acts. ”


nuclides (e.g., tritium and carbon-14) will be re-leased into the atmosphere and some will be fixed inthe ash. The total radioactivity emitted from thesetwo pathways will be equivalent to that in the wasteprior to incineration. Likewise, the radioactivityextracted during decontamination is equivalent tothe radioactivity in the waste prior to decontamina-tion. It is difficult to determine which exposurepathways have the greatest risk to humans and theenvironment. Nonetheless, aside from the limitedradioactivity that escapes via stack gases, all radio-activity disposed of under either scenario (disposalwithout incineration or decontamination versusdisposal following these techniques) will be thesame. Thus, the risks of environmental contamina-tion and human exposure through disposing ofradioactive material remain the same. However,with less waste disposed of and the waste beingmore stabilized before disposal, these techniquesmay reduce the number of handling and trans-portation accidents but not necessarily theirseverity.

Waste stabilization techniques are an importantcomponent of waste management, as is clearlyindicated by the failure of past disposal practices toprevent radionuclide migration. NRC regulations donot require generators to stabilize Class A LLW.Stabilization, however, is a relatively inexpensivemethod of reducing the risk of environmentalcontamination. By stabilizing Class A waste, whichis about 97 percent of LLW, more assurance maybe gained in the stability of disposal sites. How-ever, under certain environmental conditions (e.g.,low precipitation) and given certain engineereddisposal designs, the potential gain in short-term andlong-term site stability may not justify stabilizingClass A waste.

With Class B and C wastes, it is difficult to predictwith high certainty the long-term stability of variouswaste forms and container technologies. This uncer-tainty is primarily due to the relatively smalldatabase on their behavior. Furthermore, the varia-bility in geochemical conditions encountered in adisposal site make it difficult to model site condi-tions. Nonetheless, the stability of most wastes canbe significantly improved by using a combination ofcontainment techniques.

Stabilization of different mixed LLWs re-quires more research to determine which tech-nique or combination of techniques are mostappropriate. EPA recommends monitoring theSuperfund Innovative Technologies Evaluation Pro-gram for information on new techniques (15).

The uncertainty about the long-term stabilityof solidification and containment materials im-plies that long-term in-situ testing of wastestabilization materials will be necessary to man-age LLW disposal sites. Test results can providethe scientific community, policy makers, and thepublic with the necessary information to plan for thenext generation of disposal facilities.

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CHAPTER 5 REFERENCESCraig, Rhonda, “Land Ban: Its Impact on MixedWaste, ’ Proceedings of U.S. Environmental Protec-tion Agency Mixed Waste Workshop, Denver, CO,July 19-20, 1988.Dalton, J. D., EG&G Idaho, Informal Report: SecondProgress Report for the WERF incinerator, contrac-tor report prepared for the U.S. Department ofEnergy, EGG-WM-8154, June 1988.Deltete, C. P., “Dry Active Waste: Volumes, Sourcesand Composition, ” lecture notes from Incinerationof Low-Lu>’el Wastes: 1985, Tucson, AZ, Mar. 21-23,1985, pp. E1-16.Dirks, F., and Hemplemann, W., ‘‘The IncinerationPlant of the Karlshruhe Research Center—A Re-gional Solution, ’ Incineration of Radioactive Waste,C. Eid and A.J. Van bon (eds. ), published for theCommission of the European Communities (Imndon:Graham & Trotrnan Ltd., 1985), pp. 34-47.Ekechukwu, O. E., Propst, R. M., Dameron, H. J.,Ward, G. L., and Atherton, N. G., “Pretreatment andBed Materials for Improved Liquid Radwaste Proc-essing, EPRI Project 2414-2, ” proceedings fromWaste Management ’88, vol. 1, Tucson, AZ, Feb.28-Mar. 3, 1988, pp. 3-19.Farrell, B., “A L’tility Perspective on BRC, ’ paperpresented to the Tenth Annual DOE LLW Confer-ence, 1988.HiId, W., “The Role of Incineration in the Manage-ment of Radwaste, ” Incineration of RadioactiveWas/e, C. Eid and A.J. khn lmon (eds.), published forthe Commission of the European Communities(London: Graham & Trotman Ltd., 1985), pp. 5-21.Hello, T. P., and White, R, G.. “preparing for High-Tonnage Press Processing Options, ” lecture notesfrom Incineration of Low-lzvel Wastes: 1985,Tucson, AZ, Mar. 21-23, 1985, pp. F1-33.

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Denver, CO, July 19-20, 1988,Ohm, G., ‘ ‘Incineration of Low-b’vel DAW Operat-ing Experience at Studsvik, Sweden, ’ lecture notesfrom incineration of IJjh’-[-e\el Wa.rteL7, 1985,Tucson, AZ, Mar. 21-23, 1985, pp. J 1-33.Radioactive Exchange. ‘ ‘NRC Acts Against HDPEHICS. but Says Use at Barnwell Still OK (Washing-ton, DC: Exchange Publications), Jan, 19, 1989.Radioacti\c Exchange, ‘‘LLW Cement Solidifica-tion Problems Detailed at NRC Workshop’ (Wash-ington, DC: Exchange Publications), Apr. 28, 1989.‘ ‘Radioactive Waste Disposal: LAJW and High Level,’”Pollution Technology Revie~, No. 38, William R.Gilmore (cd. ) (Park Ridge, NJ: Nojes Data Corp.,1977), pp. 104-164.Rogers & Associates Engineering Corp., “Manage-ment Practices and Disposal Concepts for Low-l~veiRadioactive Mixed Waste—A Background Report, ’contractor report prepared for the L] .S. Congress,Office of Technology Assessment, May 1989.

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Tucson, AZ, Feb. 28-Mar. 3, 1988, pp. 619-625.U.S. Congress, Office of Technology Assessment,Ocean incineration: lts Role in Managing H(lz(~rd-ous Wastes, OTA-O-313 (Washington, DC: LT. S.Government Printing Office, August 1986).U.S. Congress, Office of Technology Assessment,Workshop on Mixed Waste, Washington, DC, Dec.

15 & 16, 1988.U.S. Department of Energy, ‘ ‘Managing ~mw-LE\elRadioactive Wastes: A Proposed Approach, ’ Na-tional Lmw-hvel Radioactive Waste ManagementProgram, DOE/LLW-9, Apr. 1983.U.S. Department of Energy, ‘‘Low-l~Ye] Radioac-tive Waste Reduction and Stabilization TechnologiesResource Manual, DOE/L LL$’-76T, December 1988.Lr.S. Nuclear Regulatory Commission, ‘ ‘BranchTechnical Position on Waste Form, ’ rev. 0, May1983.L’.S. Nuclear Regulatory Commission, “Manage-ment of Radioactive Mixed Waste in CommercialImw-hvel Wastes, ” Brookhaven National Labora-tory, BhTL-hTUREG-5 1944. January 1986.IJ.S. N’uclear Regulatory Commission, ‘h Low-~velWaste Form Stability,” Draft Regulator>’ Guide,November 1986.U.S. Nuclear Regulatory Commission, ‘ ‘NRC Infor-mation h“otic~ N’o. 89-27. Limitations on the Use ofWaste Forms and High lntegrit~ Containers for theDisposal of I-mw-bvel Radioactive Waste, ’ Mar. 8,1989.University of California. Irvine. bjw-h]el Radio-active Waste Manugernent in Medic ‘al and Bi[)rnc~ii-cal Research institutions, L-ow-hvel RadioactiveWaste Management Handbook Series, DOE/LI.Wr-13T, March 1987.

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LLW Minimization and Treatment Techniques