Management of Problematic Low and Intermediate Level Radioactive Wastes - Introduction - R. Robbins, P. Ormai Waste Technology Section Division of Nuclear Fuel Cycle and Waste Technology International Atomic Energy Agency Technical Meeting of IPN and DISPONET Networks on the Management of Radioactive Waste Streams that Present Specific Challenges, 28 Nov.- Dec. 2. 2016, VIC, Vienna
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Ormai Robbins Intro Management of Challenging Waste
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Management of Problematic Low and
Intermediate Level Radioactive Wastes
- Introduction -
R. Robbins, P. Ormai
Waste Technology Section
Division of Nuclear Fuel Cycle and Waste Technology
International Atomic Energy Agency
Technical Meeting of IPN and DISPONET Networks on the Management of Radioactive Waste Streams that Present
Specific Challenges, 28 Nov.- Dec. 2. 2016, VIC, Vienna
Contents
• Problematic waste – definition
• Problematic waste – examples
• Challenging issues – predisposal
– disposal
• Alternative disposal options
• Meeting objective
Sources of radioactive waste
NPPsResearch
ReactorsDSRS
Front-End Fuel Facilities Hospitals, R&D, Disused
Sealed Sources
Decommissioning &
Environmental Remediation
NPP, Research Reactor & Back-End
Operations Photos courtesy of Dounreay Site Restoration Ltd & NDA, UK;
Cameco Corporation.
Radioactive Waste Management
Of special interest is a category of wastes for which safe, technically correct, efficient, economically attractive and widely
Changing priority in RWM (2) Optimisation, integration
Because of the variety of processes, techniques and
equipment available for different waste streams and waste
management steps, optimized technologies have to be
selected for each stream and step.
To optimize the overall RWM approach, technologies selected
for different waste management steps should be combined
into an integrated system.
Predisposal challenges and
solutions
Relevant IAEA Publications
Major Predisposal Challenges
• Lack of process knowledge
• Variable characteristics
• Unsegregated wastes
• Mixed waste – hazardous items present
• Waste previously disposed in unsatisfactory conditions, e.g. trench disposal
• Degradation of waste package
• Previously conditioned matrix does not meet disposal waste acceptance criteria (WAC)
• One-of-a-kind waste streams
• No suitable processing technology available
• Small volume waste streams – economically unfeasible to build facilities to process these streams
• Lack of access to waste processing facilities
Waste Processing Options
TreatmentSorting &
Segregation
Solid Treatment Technologies
· Low force compaction
· Supercompaction
· Incineration
· Metal melting
· Pyrolysis
Liquid Treatment Technologies
· Ion exchange
· Filtration
· Precipitation
· Evaporation
Storage
Immobilization
· Cement
· Geopolymer
· Polymer
· Ceramic
· Vitrification
Overpack
Packaging
Conditioning
Photos courtesy of Dounreay Site Restoration Ltd and NDA; Sellafield Sites Ltd. and NDA, COVRA N.V.; M. Ojovan, IAEA
Available Conditioning Technologies Process Waste Types
Calcination Aqueous liquids
Crystallization /
Drying
Aqueous liquids,
Wet wastes: IX resins, sludges,
evaporator bottoms
Steam Reforming
Organic wastes, e.g. IX resins
Nitrate wastes
Liquid wastes
Ceramic
processes
IX resins, sludges, evaporator
bottoms, zeolites, PCMs
Sintering
Granular dry solids
Ceramic
processes
IX resins, sludges, evaporator
bottoms, zeolites, PCMs
Sintering Granular dry solids
Molten salt
processing
Wet wastes, such as IX resins, low
activity filter cartridges.
Dry solid wastes, including
combustible, non-combustible
compactable, metal, ash, air filter
Process Waste Tyeps
Graphite annealing /
roasting
Irradiated graphite
Thermo-chemical
treatment
Solids, such as metals, asphalt, concrete, plastics, polymers
Wet solids, such as ion exchange resins, medical waste, biological
objects.
Granular solids, such as ash residues, calcinates, spent inorganic
sorbents, contaminated soils.
Carbon with 14C retention (reactor graphite, lubricants, moulds, etc.).
Fuel rod zirconium
Metal melting Most ferrous and non-ferrous metals
Vitrification Aqueous liquids
Wet wastes, such as sludges, IX resins, filter media, evaporator
concentrates
Solids such as soils, sediments, incinerator ashes, asbestos, medical
wastes, filter media
High-temperature
incineration with
plasma slagging
Combustible solids, wet solids and liquids
Small percentage of non-combustible material is acceptable in waste
Induction melting
Granular dry solids, such as incinerator ash
Metallic wastes
Molten metal
processing
Wet wastes, such as IX resins, low activity filter cartridges.
Dry solid wastes, including combustible, non-combustible
compactable, metal, ash, air filter, asbestos
Plasma processing
Most waste types, solid and liquid, including non-combustibles
Waste Hierarchy
DecommissioningFacility Design Operations
Photos courtesy of Dounreay Site Restoration Ltd & NDA, UK
Waste Minimization
Reuse
Recycle
Disposal Least
Desirable
Most
Desirable
Reducing the amount and
activity of radioactive waste to
a level as low as reasonably
achievable by:
– Reducing waste
generation at source
– Recycle and reuse
Occurs at all radioactive
life cycle stages
Examples of Challenging Waste
Streams
• Spent ion exchange resins
• Sludges
• Evaporator concentrates
• Aqueous waste e.g. oils or decontamination solutions containing organic complexants
• Tritium containing waste
• Carbon-14 containing waste
• Irradiated graphite
• Depleted uranium
• Beryllium
Tritium (H-3) Contaminated Liquids
• t½ = 5,730 years
• Mostly commonly occurs as tritiated water, in aqueous sludges, tritiated oils etc.
• Tritium is highly mobile in disposal environments – readily diffuses from or through porous waste forms (e.g. cement and geopolymers) and highly volatile so not amenable to thermal processing
• Industrial processes exist to remove tritium from heavy water (e.g. in CANDU reactors) – Too expensive to be used on removing low
concentrations of tritium from large volumes of waste water (e.g. Fukushima Daiichi or LWRs)
Modular Tritium Removal System
Photos Courtesy of Kurion Veolia
• Developed by Kurion Veolia – demonstrated at pilot-scale
• Tritiated water is fed into an electrolyser and cracked into
gaseous oxygen and hydrogen streams
• Gaseous streams are decontaminated to leave pure oxygen
and hydrogen/tritium (HT)
• Tritium is extracted (catalytic column) in the form of tritiated
water (HTO) and stored pending recovery and disposal
Problematic Liquid Waste Streams
• Certain wastes are problematic for glass matrices or existing vitrification process technologies
– Waste streams with volatile components, for example I-129 and Tc-99
– Nuclear wastes containing actinides, notably plutonium (surplus weapons Pu and Pu residues)
– Lack access to conventional vitrification facilities
• Development of new waste form matrices for example ANSTO’s Synroc and other glass ceramics
• Development of modular vitrification processes
Intermediate Level Liquids
• Extraction of Mo-99 (precursor of Tc-99m) results
in production of intermediate level aqueous
waste containing dissolved fission products (Cs-
137 & Sr-90)
• Key selection criteria for conditioning method:
• High waste loading
• Mechanically and physically durable
• Amenable to remote handling (hot cell)
• Proliferation resistant
• High Na concentration will limit waste loading
particularly in ceramic hosts
• ANSTO developed a process using hot-isostatic
pressing (HIP) with a glass ceramic
• High waste loading (~26% oxide equivalent)
• Better retention of Tc-99 and Cs-137
In-Can Vitrification
• Relatively low cost alternative to bulk vitrification
• Waste (for example spent ion exchange resin) mixed with glass formers
• Placed in a container that: – Acts as an ICM
– Final disposal container
• Advantages – Good for low volume problematic
waste streams (spent ion exchange resins, salt cake)
– Enhanced incorporation of volatile constituents (e.g. Tc-99)
– Good volume reduction
– Modular system
– Produces waste form in final disposal container
• Currently developed to pilot-scale
Photos Courtesy of Kurion Veolia
Predisposal Path Forward
• Fully understand the waste characteristics
• Develop a national integrated waste management strategy – Understand the legacy, ongoing and future waste
inventory
– Development of cradle-to-grave radioactive waste management solutions for each waste stream – group ‘like’ waste streams together
– Identification of gaps i.e. problematic wastes without predisposal/disposal concepts
– Conduct research and development activities to identify viable processing technologies
• In the future – begin with the end in mind i.e. do not produce waste streams without a clear processing path and end-point
From disposal point of view the most problematic waste streams:
• consists of long-lived, highly mobile like 129I and 14C
• long-lived, highly toxic radionuclides, especially transuranics (TRU)
• The most problematic “TRU” LLW comes mainly from
• MOX fabrication
• reprocessing facilities
(variety of wastes including metal, liquid waste, nitric acid)