l1 overview of predisposal management of radioactive · pdf filegeneral scheme for treatment...

International Atomic Energy Agency

RAS/9/071 Regional Training Course on Modular Desig n of Processing and Storage Facilities for Small Volumes of Low and Intermediat e Level Radioactive Wastes

including Disused Sealed Sources, Indonesia, 30 Sep – 4 Oct, 2013

Overview of Predisposal Management of Radioactive

Waste

S.K.SamantaWaste Technology Section (WTS)

Division of Nuclear Fuel Cycle and Waste Technology


What is radioactive waste?

• Waste is material for which no further use is foreseen

• The waste can be in gaseous, liquid or solid form.• Radioactive waste is a waste that contains, or is

contaminated, with radionuclides at concentrations equal to or greater than clearance levels established by the regulatory body (definition for legal and regulatory purposes)


Nuclear Fuel Cycle and Waste

Natural Uranium & Thorium


Non-Nuclear Fuel Cycle Waste

• Application of radioactive material in medicine, industry, agriculture and research

• Research reactors• Non-nuclear industry (mining of ores, oil industry, phosphate

industry, etc.)

Lightning conductorRadioisotope thermoelectric

generator - RTG Teletherapy machine


Categorization of operational waste

• Point of origin− Nuclear fuel cycle, Nuclear

power plants, Research reactors, Nuclear applications, etc

• Physical state− Solid, liquid, gas

• Types of waste, e.g.− Wet solids – spent resins, filter

media, sludge− Combustible solids and liquids− Compactable solids− Metal


Classification of radioactive waste - IAEA

• Exempt waste (EW)• Very short lived waste (VSLW)• Very low level waste (VLLW)• Low level waste (LLW)• Intermediate level waste (ILW)• High level waste (HLW)

This classification defines the most appropriate disposal routes (end-points) for solid or solidified waste.


Example of application of IAEA classification schem e


Terminology

IAEA Safety GlossaryTerminology Used in Nuclear Safety and Radiation Protection — 2007 Edition


What is Predisposal?

• Any waste management steps carried out prior to disposal, such as pre-treatment, treatment, conditioning, storage and transport activities.• Predisposal is used

as a contraction of ‘pre-disposal radioactive waste management’, not a form of disposal


Pre-Treatment of radioactive waste

• Pre-treatment includes any operations prior to waste treatment, to allow selection of technologies that will be further used in processing of waste (treatment and conditioning), such as:• Collection;• Segregation;• Chemical adjustment; and• Decontamination

Sorting waste at Bohunice Treatment and Conditioning Centre for radwaste, Slovakia


Treatment of radioactive waste

• Operations intended to benefit safety and/or economy by changing the characteristics of the waste

• Three basic objectives:−Volume reduction−Removal of radio-nuclides−Change of composition


General scheme for treatment of liquid waste

Treatment

Waste concentrate

Conditioning

Storage/Disposal

Discharge to environment

Liquid waste

Treated effluent

DF = A1/A2

VRF = V1/V2

V1, A1

V2

A2


Selection of treatment process for liquid waste

• Waste characteristics (volume, generation rate, activity, chemical composition, etc)

• Discharge requirements for decontaminated effluents

• Technology options (availability, performance, cost, etc)

• Conditioning of concentrates resulting from the treatment

• Storage and disposal of conditioned concentrates

Important considerations:


Treatment processes for liquid waste

• Filtration• Chemical precipitation• Ion exchange• Evaporation• Membrane methods


Filtration

• Filtration is used to separate fine particulates from liquid waste, either to pre-treat before treatment or polish after treatment

• Various filtration methods:−Gravity filtration through sand bed−Pressure filtration−Vacuum filtration


Typical filters used for liquid waste treatment

Tubular support pressure pre-coat filter Disposable cartridge filter


Chemical precipitation

• Addition of reagents to form the precipitate

• Flocculation• Sedimentation• Solid-liquid separation• Discharge of treated

effluent, either immediately or after polishing

• Collection of sludge for conditioning


Chemical treatment plants

Large facility

•100 m3/batch

Small facility

•5 m3/batch


Typical precipitants for different radionuclides

Jar test


Ion exchange

• Reversible exchange of ions having charges of the same sign between an electrolyte solution and the ion exchanger.

• Exchangers can be − Organic or Inorganic− Natural or synthetic− Conventional or selective

• Mode of application− Batch or column− Once-through or cyclic (loading-elution-regeneration)

RM(solid) + 137Cs+(solution) R137Cs(solid) + M+ (solution)

RX(solid) + 131I-(solution) R131I(solid) + X- (solution)


Fe Co K

1.0

06

nm

CH

SO3H CH

CH CH2

CH2

CH2

Examples of conventional and selective ion exchange rs

Cation exchange resin Zeolite

Phenolic resin

Ammonium molybdophosphate

K-Co-Hexacyanoferrate


Evaporation

• Features− High DF (104-106)− High VRF

• Limitations− Scaling− Foaming


Typical evaporators used for liquid radwaste

Pot evaporator Natural circulation evaporator with external heater


Membrane methods

• Microfiltration• Ultrafiltration• Nanofiltration• Reverse Osmosis


Pressure driven membrane processes


Feed stream

Retentate stream

Permeate

Feed stream

Filtrate

Conventional (dead end) filtration

Cross-flow filtration

Mode of application of membranes


Reverse osmosis plants for LLW

Small facility

•100 l/hour

Large facility

•100 m3/day


Treatment of gaseous waste (1)

• Particulates and aerosols in gases may be removed using HEPA filters;

• Iodine and noble gases can be removed by filters or sorption beds with activated charcoal;


Treatment of gaseous waste (2)

• Redundant filters may be required for safety reasons;

• Pre-filters or roughing filters, temperature and humidity controls, and monitoring equipment;

• Used filters and sorption beds are managed as solid waste ;

• Concentrations of radionuclides should not be allowed to exceed levels accepted for future conditioning, storage or disposal.


Treatment methods for solid radioactive waste

• Mechanical treatment − Low force compaction− High force compaction (supercompaction)

• Thermal treatment− Incineration− Pyrolysis− Molten salt oxidation

• Melting− Metal melting

• Chemical methods− Acid digestion− Chemical/photochemical oxidation

• Biochemical decomposition

30


In-drum Compaction

• Compressive force− 10-50 tonne

• Volume reduction factor− 2-5


Super-Compaction

• Compressive force− 1200-1500 tonne

• Volume reduction factor− 10-15


Incineration

• High volume reduction factor− 50-100

• Temperature− 900-950 °C

• Off-gas purification− Scrubber− Filter


Conditioning of radioactive waste

• Those operations that produce a waste package suitable for handling, transport, storage and/or disposal

• May include:− Immobilization, i.e., conversion of waste

into waste form by solidification, embedding or encapsulation

−Enclosure of the waste in containers−Providing an over-pack (if necessary)


Waste streams for conditioning

Examples:

− Precipitated sludge from chemical treatment − Spent ion exchange resins from ion exchange

treatment − Retentate from Reverse Osmosis − Retentate from Cross-flow Filtration− Evaporator concentrates− Organic liquids


Matrix materials for waste conditioning

• Cement• Bitumen• Polymer• Glass• Ceramics


Cementation of aqueous waste

In-drum mixing In-line mixing


Organic liquid waste solidification using cement


Waste packaging

200 l drums

5 to 10 m3 metal boxes

metal ingots

Concrete shells and concrete boxes


Storage of radioactive waste

• Storage is the holding of radioactive sources, spent fuel or radioactive waste in a facility that provides for their/its containment, with the intention of retrieval. • Storage is by definition

an interim measure.


Waste Acceptance Criteria (WAC)

• The most common definition of WAC is “those requirements that are to be met by conditioned radioactive wastes, forming packages, to be accepted at an Interim Storage or a Disposal Facility”

• WAC is also important for the different stages of Predisposal activities in a Waste Management System.


WAC – Technical issues

• Technical issues can be safety and design/operation related.

• Examples of safety related issues are − durability of waste packages− activity limitation− external dose rate− surface contamination.

• Examples of design/operation related issues are − dimensions− mass− mechanical properties− handling requirements− restricted components


Waste characterization

• Waste characterization has an important role at every stage of radioactive waste management, e.g.• For raw waste,

characterization is needed to decide what processing is required

• For conditioned waste package, characterization is needed to ascertain if the package meets acceptance criteria for storage or disposal.


IAEA

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Thank you for your attention

l1 overview of predisposal management of radioactive · pdf filegeneral scheme for treatment...

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