Generation of Radioactive Waste Radioactive Waste Management and Disposal NUCP 2311 1.

Generation of Radioactive Waste

Radioactive Waste Management and Disposal

NUCP 2311

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Sources of LLW

• Defense and other national programs• Commercial nuclear power• Medical research activities• Academic research activities• Industrial activities

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Licensees (non-DOE)

• NRC regulates about 6,700 licensees• 37 agreement states have responsibility• Agreement states regulate about 15,000

radioactive materials licenses

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Sources of Disposed LLW (1994-95)*

• Nuclear reactors - 44.0% 55%• Industrial users - 39.9% 24%• Government sites - 13.4%

19%• Academic users - 2.1%

1%• Medical facilities - 0.6% 1%

• * total volume 858,677 ft3 690,000 ft34

Nuclear Reactors

Commercial Nuclear Power

Reactors in the United States

Commercial Nuclear Power

Reactors in the United States

Nuclear Fuel Cycle

Nuclear Power Reactors

• Ion exchange resins• Filters• Concentrated liquids• Dry active waste (DAW)• Decommissioning wastes

• BWRs usually generate more LLW than PWRs

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Ion Exchange Resins

• Organic beads or granules designed to remove radionuclides from liquids

• May be either anion or cation resins• When exhausted must be regenerated or

replaced• Regeneration produces chemical waste which

must be disposed

9Modified from J. Poston, Sr. Lectures

Ion Exchange Resins

• Chemical waste usually concentrated by evaporation and solidified prior to shipment for disposal

• Spent resins transferred by slurry to shipping containers

• Must be “dewatered” prior to shipment• Some resins are solidified in cement or a

polymer prior to shipment


Ion Exchange Resins

• Radionuclide concentrations may be high enough to require shielding

• Must be concerned about radiolytic gas generation

• Chemical or biological degradation may occur in some resins

• Need to be careful so that the resin does not become greater than class C waste

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Filters

• Cartridge filters – contain disposable elements made of woven or wound fabric, or pleated or matted paper supported on a SS mesh

• Precoat filters – use filter aids, such as diatomaceous earth, powdered mixtures of cation- and anion-exchange resins, and high purity cellulose fibers


Filters

• Cartridges are disposed as radioactive waste directly when replaced

• Precoat filters are removed by “back-flushing” and disposed of as “dewatered” but unsolidified waste

• PWR’s typically use cartridge filters whereas BWR’s typically use precoat filters


Concentrated Liquids

• Evaporators are used to reduce volume• Concentrated liquids are known as

“evaporator bottoms”• Have a high solids content and an average

density in the range 1.0 to 1.2 g/cm3• Usually are solidified prior to disposal


Dry Active Waste (DAW)

• Applied to a wide variety of waste products• May be compactable or non-compactable• May be combustible or non-combustible• Volume varies based on activities at the site• Characterization of waste is important to

disposal decisions


Dry Active Waste Treatment

• Compaction• Baling• Shredding• Sectioning• Combustion• Decontamination


Example

• Minimization of Low-Level Waste (LLW) at Nuclear Reactor Sites.– Consider a typical example in the United States.

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Example for Discussion

• Two-unit pressurized water reactor (1125 MWe).

• Sorting/segregating dry active waste (DAW).• Free release of clean trash.• Laundry operations.

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Motivation

• Reduce waste generation.• Reduce disposal costs.• Take advantage of other disposal options.• Recycle materials where possible.• Make employees aware of important of waste

minimization.

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DAW Collection and Segregation

• Collected in washable nylon bags.• Brought to waste collection areas.• Screened according to dose rate.• Placed in collection boxes.


Dose Rate Screening

• If dose rate >2 mR/h, placed in a container for shipping to an off-site facility.

• If dose rate <2 mR/h, sent to sorting and segregation facility.

• Contents of these bags are sorted for free release.

• Contaminated items combined in plastic bags and placed in container with >2 mR/h waste.


Monitoring the <2 mR/h DAW

• Each bag is opened and the contents monitored at a sorting table.

• Table contains 4 400-cm2 gas-flow hand-held proportional counters.

• Each item monitored individually and clean and contaminated items are separated.

• Trash is rebagged and routed based on the results.


Monitoring the <2 mR/h DAW

• Clean trash is monitored again with a large, rotating NaI(TI) detector.

• Bags passing monitoring are considered “clean” and disposed.

• Bags failing this monitoring may be resorted and/or considered contaminated.


Results of Program

• Monitored a total of 162,235 lbs of waste.• Monitored 117,378 lbs of clean trash.• Clean trash release rate ~ 89%.• Monitored 44,857 lbs of <2 mR/h DAW.• DAW free release rate ~ 65%.


Results of Program

• Cost of program estimated to be about $0.70 per pound of waste monitored.

• Clean trash savings estimated at $56,300.• <2 mR/h DAW savings estimated at $210,800.• Total savings over 18-month period $267,100.


On-Site Laundry Operations

• Waste minimization often produces an increase in launderable goods.

• Replaced disposal goods with launderable products.

• Made decision to wash other items that, in the past, might have been disposed.


On-Site Laundry Operations

• Concluded cost was about the same as using a commercial operation.

• Avoids shipping and receiving problems associated with commercial operations.

• Actual cost less because less anti-C clothing required in inventory.

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Medical and Academic Institutions

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Institutions

• Liquid scintillation counting fluids• Organic and inorganic liquids• Biological wastes• Trash• Sealed sources and accelerator targets

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Institutions (primary isotopes)• Typical Radionuclides

– 3H, 14C, 32P, 35S, 51Cr, 57Co, 60Co, 90Sr, 99mTc, 125I and 192Ir• Used in research , diagnostics and treatment• Other, short-lived radionuclides are stored for decay before

disposal• Some radionuclides can be sent down the sanitary sewer

( C-14, H-3)– 0.o5 uCi/ml– Water soluble– 5Ci/yr limit

• Material that are waste products of patients are excluded from regulation 30

Liquid Scintillation Fluids

• Often contain flammable organic fluids – a mixed waste (i.e., radioactive and hazardous chemical).

• May be disposed by incineration.• Switch to aqueous-based scintillation fluids –

dispose in the sanitary sewer.

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Biological Wastes

• Generated by research programs – generally have low specific activity.

• Consists of animal carcasses, tissues, animal bedding and excreta, vegetation, & culture media.

• May contain pathogenic or carcinogenic substances.

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Biological Wastes

• Care required in packaging because of biodegradation.

• Material often shipped with absorbent paper and lime.

• Some facilities use incineration of much of this waste.

• Off-gas control and economics “drive” the solution

• Exceptions for biological waste33

Trash

• Differs from that at nuclear power plants.• Most is compactable and combustible.• Incineration is often the disposal method of

choice.• Some use of sorting, storage and compaction

are also used.

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Industrial Waste

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Industrial

• Industrial applications of radioactive material can be found in almost every industry;– Chemical– Petrochem– Steel mill– Mining– Food production– Paper mills– Hospitals– Coal burning power plants

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Sources

Sources that are used in industry can be anywhere from H-3 to Am-241

mostly Cs-137 and Co-60Activities range from

mCi to 1000s CiUsually in sealed sourcesSources that are too old to make readings are disposed

of----- wasteCan not reuse because of unknown integrity of capsule

Point Level or Density Gauge

rti

Beam angle is approximately 130.

Source Head Detector

Continuous Level Gauge

rti

Source Head Detector

Beam angle can vary from around 30o to better than 45o.

Scatter Field

Government

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Low-Level Waste Management (DOE)

• Many activities within the DOE complex similar to those we have already discussed.

• Largest volume of LLW is managed by the Office of Environmental Restoration (ER).

• Other waste generated by DOE activities is transferred to the Office of Waste Management.


Low-Level Waste Management (DOE)

• LLW is segregated into contact-handled and remote-handled waste just as with TRU waste.

• Some wastes may contain transuranic radionuclides.

• LLW containing hazardous waste or PCBs is handled separately.

• DOE manages some NORM and NARM.


Sources of LLW at DOE Sites

• Process, create, or handle radioactive materials.

• Chemical conversions or separations.• Fabrication of nuclear components.• Support activities.• Pretreatment of HLW.


Sources of LLW at DOE Sites

• Environmental restoration activities• Facility deactivation• Facility decommissioning• Facility demolition• Treatment and handling of TRU waste• Treatment and handling of mixed LLW


DOE LLW Disposal

• Current approach is to use shallow-land burial facilities.

• Disposes LLW at six sites and buried waste is present at eight additional sites.

• Active sites include Hanford, Idaho Falls, Los Alamos, Nevada, Oak Ridge, and Savannah River.


Low-Level Waste from Nuclear Weapons Production


DOE LLW Disposal

• LLW typically stored in metal drums• Some LLW stored in metal or plywood boxes• Large items wrapped in plastic sheets• LLW must be certified prior to disposal• LLW with >10 nCi/g may be managed

separately


DOE LLW Disposal

• LLW is treated prior to disposal to stabilize it• Usually conducted on-site• Solidification to control liquids or particulates• Reduction of volume (incineration or

compaction)


DOE LLW Volume and Radioactivity• Process Volume (m3) Activity (Ci)• Mining, etc. 460,000 (14%)• Chemical Sep. 570,000 (17%) 10 x 106

• RD & T 800,000 (25%) 14 x 106

• Fuel & Target• Fab. 680,000 (21%) 9.2 x 106

• Nonweapons 470,000 (14%) 14 x 106

• Enrichment 110,000 (9%) 2.8 x 106

• NNPP 18,000 (1%) 1.5 x 105

• TOTAL 3.3 x 106 m3 50 x 106 Ci


Radioactive Content of Disposed DOE-LLW

• Fission products 11 x 106 Ci (24%)• Internal activation 6.2 x 106 Ci(15%)• Tritium 15 x 106 Ci (33%)• Uncategorized 13 x 106 Ci (29%)


DOE LLW

• Divided into two categories• Waste from environmental restoration (ER)• Waste from non-environmental restoration

activities (non-ER)• Latter category represents stored waste only

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DOE LLW


Physical Matrices of LLW – ER Activities


Physical Matrices of LLW – Non-ER Activities

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Questions

Generation of Radioactive Waste Radioactive Waste Management and Disposal NUCP 2311 1.

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