Monitoring Nuclear Waste KNOO: WP2

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Monitoring Nuclear WasteKNOO WP2

• P. Constantinou, S. Simandjuntak? ,
• N. McNeill, P.H. Mellor D.J. Smith
• Dept of Electrical and Electronic Engineering
• Dept of Mechanical Engineering
• ? European Technology Development

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OVERVIEW

• Objectives of research
• Wireless Sensor Node EGG development
• Mechanical energy source
• Protective Shell Material
• Initial system level appraisal
• Future work

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Nuclear Waste
Sources nuclear power stations, from the
production and processing of the nuclear fuel
the use of materials in industry in research in
healthcare and in military programmes.

The 2004 UK Radioactive Waste Inventory, Main
Report, Nirex Defra
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Storing and Storage of radioactive waste
One of the Australia low-level waste storage
facility
Storage of LLW and Close Handled-ILW packaging at
COVRAs LOG store, Netherland
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Waste Routes
Above Ground Storage
Underground Repository
LLW / ILW/HLW
Placed in containers
Current Practice
HLW
Placed in containers
Cooling
Future Practice
50 ?100 years
Unprocessed spent fuel
Vitrification for HLLW
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Waste storage typical parameters

• Temperature varies from -20 to 80?C
• Cooling by circulating air (for ILW and HLW)
• Operation times from 10 years for HLW storage to
  1000 years for repository geological sites

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Underground waste tank, Savannah river
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Objectives of sub workpackage

• Monitoring is required in both current and future
  waste storage practices without breaching the
  integrity of the storage environment
• Monitoring Container
• Monitoring Container Vaults
• Objective
• To develop a Wireless Sensor Node (WSN) that is
  capable of monitoring autonomously in a harsh
  remote environment,

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Challenges

• Nuclear Environment
• Harsh
• Minimal Human Interference
• Unique requirements
• Protective Shell
• to protect the WSN from the hostile irradiated
  environment.
• Alternative Energy Source
• to supply energy to the WSN, from a
  non-degradable source, allowing it to operate in
  an autonomous fashion

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Wireless Sensor Node EGG Concept
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Main elements

• Low power sensing, data acquisition and wireless
  transmission
• Energy source and power management electronics
• Protective shell

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Signal conditioning, energy storage , power
supply and wireless transmission

• Continuous operation of 4 channels at 1000
  samples per second requires 20J per minute

WSN
Power Electronics
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Energy Source - Mechanical Storage

• Suitable for a WSN that is required to wake-up
  after a long time (e.g. 50years) acquire and
  transmit data before running out of energy.
• Current system under investigation utilises a
  mechanical spring
• Constant torque clockwork Negator spring
• Comprises of a strip of flat spring material that
  has been given a curvature by continuous heavy
  forming
• In its relaxed/un-stressed state the material is
  in the form of a tightly wound spiral, on a
  storage bushing

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Configuration under investigation
Pre operation The material is wound round the
output bushing in its charged state.
Initiation Stage 1 After a certain time the
bushings are allowed to rotate, using the release
mechanism allowing the stored energy to be
converted. Stage 2 3 Mechanical step up.
Torque reduced and angular velocity is
increased Stage 4 Motor armature is rotated
converting mechanical energy to electrical
energy. Stage 5 Electrical energy conditioned to
WSN ratings
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Characterisation
Total Energy Stored 1kJ Mechanism weight 0.9kg
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Prototype unit
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Experimental results

• Optimal transfer through appropriate load
  matching
• Relatively low transfer efficiency 11
• Output energy 110J over a lt1 minute discharge

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Shell material considerations

• Distortion due to swelling
• Stress Corrosion Cracking (SCC)
• Corrosion fatigue
• H-embrittlement
• Creep-fatigue interaction
• Flow assisted corrosion
• Radiation induced segregation

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Currently used container materials

• Copper, copper-beryllium alloy
• Concrete
• Carbon steel for LLW
• Low alloy steel (Ni-Cr alloy) for ILW
• Stainless steel (300 series e.g. 304, 309, 316)
  for ILW and HLW
• Incoloy 800 or 800H
• Borosilicate glass in the vitrification process

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Review of shell materials
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Review of shell materials
Borosilicate glass

• From the material selection review, borosilicate
  was one of the suitable candidate for shell
  material, because of its low thermal conductivity
  and low absorption rate per cross section area,
  in addition to those, it is relatively less
  costly than other candidate materials such as 316
  steels.
• Compositions (wt) are 2-7 Al2O3, 7-13 B2O3,
  4-8 Na2O and K2O, 70-81 SiO2.
• Density 2.40 g/cc
• Youngs Modulus, E 60-64 Gpa
• Fracture toughness 0.77 MPa-m1/2
• CTE (0-300C) linear 4 µm/m.C
• Thermal conductivity 1.1 W/m.K
• Melting point (softening point) 800C

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System level integration

• WSN installed in Borosilicate jar and temperature
  measurement undertaken in a thermal chamber to
  give indication of performance

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Temperature measurement
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Summary and future work

• Principal elements of prototype system identified
  and components demonstrated
• Focus is now on full system level integration and
  optimisation. This investigation will include
• The release mechanism
• A reduction in size of the mechanical storage
  system and improved mechanical to electrical
  energy conversion efficiency
• The use of power management protocols / sleep
  modes to prolong the sensor operating lifetime

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Acknowledgments

• This work was carried out as part of the TSEC
  programme KNOO and as such we are grateful to the
  EPSRC for funding under grant EP/C549465/1
• www.knoo.org