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Immobilisation and Storage of Nuclear Waste
 

Immobilisation and Storage of Nuclear Waste

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This lecture was facilitated by Dr. John Roberts from the Dalton Nuclear Institute of Manchester University.

This lecture was facilitated by Dr. John Roberts from the Dalton Nuclear Institute of Manchester University.

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    Immobilisation and Storage of Nuclear Waste Immobilisation and Storage of Nuclear Waste Presentation Transcript

    • Immobilisation and Storage of Nuclear Waste Dr John Roberts Dalton Nuclear Institute The University of Manchester NI Rough Guide to the Nuclear Industry 2010
    • Radioactive Waste Generation
      • Military programmes
      • Hospitals and research laboratories
      • Nuclear Energy Industry
        • Mining and milling of uranium ores
        • reprocessing of fuel discharged from reactors
        • decommissioning
    • Massive Source of Energy
      • In an AGR reactor 1 tonne of U is equivalent to 20,000 tonnes of coal
      • In a fast reactor - equivalent to 2,000,000 tonnes of coal
      • A typical nuclear power station requires 40 tonnes of fuel per year - one lorry load per fortnight
      • An equivalent coal power station requires 3,000,000 tonnes per year - two train loads per day
    • Worldwide Nuclear Industry
    • UK Radwaste Sources
    • UK Radwaste Volumes
    • Nuclear Fuel Cycle Return to customers for final disposal Enrichment Conversion Uranium Ore Natural Uranium All plant requires final decommissioning Recycle Fuel (MOX) Electric Power Reactor Transport Reprocessing Spent Fuel Storage Waste Management Fuel Fabrication Recycled Uranium
    • Nuclear Reactor
      • Fuel - Originally uranium metal but now many variations
        • typically 75 tonnes for 1000 MWe
      • Moderators - carbon, H 2 O, D 2 O
      • Cladding - contains fuel and prevents release of radioactive fission products
      • Coolant - gas or liquid circulated through core of reactor for heat extraction
      • Control rods - usually B or Cd with large σ c
      • Shield - usually steel and concrete used for radiation protection and pressure vessel
    • Magnox Fuel Assembly 1 fuel rod per assembly, Magnox cladding, U metal fuel
    • PWR Fuel Assembly 264 fuel rods per assembly, Zircaloy cladding, UO 2 fuel
    • AGR Fuel
    • Pebble Fuel
    • Storage of Spent Fuel
      • Spent fuel is highly radioactive and very (thermally) hot
      • Initially stored in ponds at the reactor site
      • Water cools the rods and acts as shielding
      • Can also be stored in dry stores with air cooling
    • Storage Pond Dungeness storage pond, Kent
    • Storage Pond THORP storage pond at Sellafield
    • Water Shielding
    • Reprocessing
      • Only about 4% of U is burnt up
      • 235 U content reduced to less than 1%
      • Some Pu remains from fission reactions
      • Reprocessing separates the U and Pu from waste products by chopping up the fuel rods and dissolving them in acid
      • U can re-enriched
      • Pu can blended with U to produce MOX fuel
      • LLW - Wastes not exceeding 4 GBq/t alpha or 12 GBq/t beta/gamma discarded equipment, tools, protective clothing
      • ILW - Above levels of LLW but not significantly heat generating stripped/leached remains of cladding or PCM
      • HLW - Significantly heat generating fission products
      UK Waste Classification
    • Challenges of Radioactive Waste
    • Total Waste Volume 2007
    • Waste by Activity Total conditioned waste volumes from each business activity Total volume 1,750,000 m 3 57% Commercial Reprocessing 30% Commercial Reactors 9% Research & Development 2% Ministry of Defence 1% Medical & Industrial <1% Fuel Fabrication & Uranium Enrichment
    • LLW
    • Low Level Waste
    • LLW Container
    • LLW Repository near Drigg
    • LLW Repository near Drigg
    • ILW
    • Magnox Fuel Assembly 1 fuel rod per assembly, Magnox cladding, U metal fuel
    • Magnox De-canning
    • Magnox Swarf
    • Magnox Swarf
    • Solid Waste
    • Transport of Drums
    • Testing of Drums
    • Container Testing
      • • Tests are impact from 25 m and 1000 ˚C
      • • Bounding hazards encompassed by these two criteria are:
      • • building collapse
      • • roof collapse
      • • aircraft crash
      • • train crash
      • • explosives / explosive gases
      • • crane failure / aggressive feature
      • • seismic fault
      • train fire • flammable gases • explosion • electrical fire • package fire • overheating
    • Results
    • HLW
    • Vitrification of HLW
    • Storage of Canisters
    • Nuclear Power Generation 80 year lifetime use of electricity for 1 person generates this much high level waste
    • Dounreay
    • Dounreay Shaft
    • Dounreay Shaft - past
      • Excavated in the 1950s during construction of under sea tunnel for the discharge of low level liquid effluent 4.6m diameter, 65m deep
      • On completion a concrete plug was used to separate the shaft from the tunnel and it was allowed to fill up with groundwater
      • In 1958 the Scottish Office authorised the UKAEA to use the shaft as a disposal facility for radioactive waste
      • More than 11,000 disposals took place until 1977
      • Environmental legislation has been tightened and the UKAEA are now required to remove all waste from the Shaft
    • Dounreay Shaft 1984
    • Borehole Plan
    • Shaft Platform - Schematic
    • Shaft Platform - Actual
    • Shaft - Waste Retrieval
      • The shaft was isolated in 2008 ahead of programme and budget
      • Waste retrieval can now commence
      • Radioactive conditions mean that everything must be done by remote control
      • Complications include -
        • quantity and diversity of the waste
        • working depth
        • amount of corrosion after 50 years
        • Base of shaft is immersed in 60 m of contaminated water
      • In March 2010 it was announced that waste retrieval will be deferred until the completion of the site license competition
    • Waste Retrieval Plant
    • What next ??
      • HLW and ILW can be successfully immobilised in either cement, glass or bespoke ceramics
      • Where should the waste be moved to for storage (retrievable) or disposal (non-retrievable) ?
    • Possible Options
      • Disposal in Space
      • Disposal in Ice Sheets
      • Disposal in Subduction Zones
      • Direct Injection
      • Disposal at Sea
      • Sub-seabed Disposal
      • Dilute and Disperse
    • Probable Options
      • Indefinite Storage
      • Near Surface Disposal
      • (Phased) Deep Disposal
      • Very-deep Borehole Disposal
    • Underground Storage
      • USA have (de)selected Yucca Mountain
      • South Korea have selected Gyeongju
      • Finland have selected Olkiluoto
      • Sweden has selected Forsmark
      • France, Belgium and Switzerland all have experimental sites
    • What is the UK doing ?
      • Set up a committee - CoRWM
        • Committee for Radioactive Waste Management
      • Presented recommendations to government in July 2006
      • Government accepted all the recommendations in November 2006
    • CoRWM Summary
      • Geological disposal is the best form of long-term management
      • Coupled with safe and secure interim storage
      • Development of volunteerism/partnership approach to secure facility siting
      • Government’s response
        • Accepted CoRWM’s proposal on geological disposal
        • Accepted need for safe and secure interim storage
        • Supportive of exploring the concept of volunteerism/partnership arrangements (recognising that geological/scientific requirements must be met)
    • Nuclear Decommissioning Authority
      • Established April 1st 2005
      • All civil nuclear liabilities
      • Two aims
        • reduce the predicted cost of nuclear clean-up
        • maintain the required skillsbase
      • £70 billion budget
    • NDA Sites
    • Hunterston A
    • Hunterston A
      • Located near West Kilbride, 2 units 160 MWe each, first grid connection 1964, shutdown 1990
      • Area of 15 hectares
      • Current site end state plans are removal of all waste and buildings to be cleared with the site delicensed, landscaped and available for alternate use
      • Key dates
        • 2006 - Construction of ILW store complete
        • 2014 - All operational ILW retrieval/processing complete
        • 2017 - Entry into care and maintenance stage
        • 2090 - Final site clearance and closure
    • Hunterston ILW Store
    • Hunterston ILW Store
    • Sellafield
    • Sellafield
      • Located on the West Cumbrian coast, supported the nuclear power programme since the 1940s. Operations include processing of fuels removed from nuclear power stations, mixed oxide (MOX) fuel fabrication and storage of nuclear materials and radioactive wastes
      • Area of 262 hectares
      • Site end state will be decommissioned to passively safe state with plutonium and uranium stored on site
    • Äspö Hard Rock Laboratory
    • Multibarrier Concept
    • Spent Fuel Canister
    • Phased Disposal Concept
    • Underground Access
    • Vault Concept
    • Very-Deep Borehole Disposal
    • Drill the first stage of the borehole Insert the casing. Pour in the cement basement. Drill the next stage of the borehole. Insert the casing. Pour in the cement basement Drill the next stage of the borehole Constructing the Borehole And so on, down to > 4 kms 0.6 - 0.8 m diameter Constructing the Borehole Drill the first stage of the borehole Insert the casing Pour in the cement basement Drill the next stage of the borehole Insert the casing Pour in the cement basement Drill the next stage of the borehole And so on, down to > 4 km
    • Placement of Canisters Insert the casing Insert the canisters Pour in the grout and allow it to set Placement of Canisters Insert the casing Insert the canisters Pour in the grout and allow it to set
    • Separation of Canisters Insert Bentonite clay Insert another stack of canisters Repeat until the bottom km of the borehole is filled 4 kms Separation of Canisters Insert Bentonite clay Insert another stack of canisters Repeat until the bottom km of the borehole is filled
    • Sealing the Borehole Pour in some backfill (crushed granite) Insert heater and seal the borehole Pour in more backfill and seal the borehole again 3 km deep (topmost canister) Fill the rest of the borehole with backfill Sealing the Borehole 3 km deep (topmost canister) Pour in some backfill (crushed granite) Insert heater and seal the borehole Pour in more backfill and seal the borehole again Fill the rest of the borehole with backfill
    • Natural Analogues I
      • Isolating Clay
        • 50 ancient tree stumps found preserved in Dunarobba, Italy
        • Trees had grown 1.5 million years ago
        • They had not yet begun to rot
        • Clay isolated them from oxygen and water
    • Natural Analogues II
      • Canadian deposit/repository
        • Cigar Lake uranium deposit lies 430m below ground
        • Thickness 1- 20 m Width 50 -100 m Length 2 km
        • Surrounded by clay there is there no radiological trace at the surface
    • Natural Analogues III
      • Fossil Reactors
        • Most famous is in Oklo, Gabon
        • A layer of uranium ore is sandwiched between sandstone and granite.
        • Water trickling through moderated the neutrons allowing fission of the uranium
        • A chain reaction occurred until the water was boiled away
        • Reactor worked on and off for more than a million years
        • HLW created held in place by the rocks, Pu had only travelled 3m in almost two billion years
    • Useful Websites
      • http://www.nltv.co.uk
      • http://www.nuclearliaison.com
      • http://www.rwin.org.uk
      • http://www.corwm.org.uk
      • http://www.nda.gov.uk
      • http://www.sellafield.com
      • http://www.nuclearinst-ygn.com