THE BLACKSTONE
PROJECT
MTR irradiation
C. Li, NRG
T.O. van Staveren, NRG
M. Joyce, Frazer-Nash Consultancy
B. Davies, EDF Energy
INGSM-20, Brugge
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OVERVIEW
• Background
• Project status
• Design and results
• Conclusion and next steps
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Supporting long life of Advanced Gas Cooled Reactors
EDF Energy operates Advanced Gas Cooled Reactors, supplying
~ 20% of electricity in the United Kingdom
Graphite cores age with time due to neutron damage and
radiolytic oxidation
Accelerated ageing tests to determine graphite properties ahead
of actual AGR core structures
Neutron dose
We
igh
t lo
ss
Project
Blackstone data
Future AGR
operation
BACKGROUND
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PHASE I AND II
• Blackstone Phase I and II were successfully completed on 2015.
Four irradiation facilities have been used to irradiate around 1000
graphite samples from different AGR reactors
• Achievements
• Expansion of the irradiation graphite property database to higher doses and
weight losses ahead of current AGR operation
• Provides data to raise the graphite weight loss limits for Hinkley Point B,
Hunterston B, Hartlepool and Heysham 1 power stations
• AGR safety cases are updated with data from Blackstone Phases I and II to
achieve life-time extension
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PHASE III: MOTIVATION
Provide irradiation data for HYB/TOR reactors:
• Not much HYB/TOR data from Blackstone Phases I and II
• Questions over similarity of HYB/TOR to HPB/HNB graphite
(potential differences in source graphites)
• Need to use HPB/HNB experience to support predictions at
HYB/TOR to avoid increased graphite core inspections rates
• The graphite neutron irradiation at the end of generation for
HYB/TOR is expected to be 10% more than for HPB/HNB
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PROJECT FLOWCHART
Samples drilled from AGR reactor
core and shipped to NRG Petten
Machining of specimens from
extracted discs in hot cell
laboratories (HCL)
Characterisation of radioactive
graphite specimens in hot cell
laboratories
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PROJECT FLOWCHART
Blackstone capsules are
assembled in hot cell laboratories
Blackstone capsules are loaded
into the HFR and connected to a
dedicated gas handling system
that controls graphite oxidation
After irradiation the capsules are
dismantled, and post-irradiation
characterisation on the specimens
is carried out
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PHASE III SCHEDULE
• 2016 Trepanned samples dispatched from NNL
Decontamination of graphite slices
Machining of samples
Pre-characterisation
Review and optimisation Blackstone design
• 2017 Pre-characterisation
Fabrication and assembly of irradiation rig
Load Capsule 5 into HFR
• 2018 / 2019 Irradiation in HFR for 11 cycles
Capsule 5 Post Irradiation Examination (PIE) and reload samples to Capsule 6
• Irradiation of Capsule 6 for ~8 cycles ( Cycle start: 10.10.2019)
• 2020• Capsule 6 PIE (completing in 2021)
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PHASE III: CAPSULE DESIGN
• Irradiation in two stages (11cycles + 8 cycles)
• Reloading specimens from Capsule 05 to 06. In
addition, loading of: virgin material / fuel sleeve
graphite / ACCENT creep specimens
• Target doses: 7.8 and 5.3 dpa
• 7 drums per irradiation capsule, ~250 specimens in
total
• Specimen temperature target: 420°C
• Both capsules contain oxidising environment
(CO2/CO)
• End oxidation (weight loss) target: 14.8 g and 10.8 g
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PHASE III: CAPSULE DESIGN
• Drum based design
• 24 thermocouples per capsule
• Primary gas flow through and
around drums CO2/CO mixture
• Secondary gas around capsule:
stationary He/Ne mixture for
temperature control
• Oxidation is measured by gas
chromatography on inlet and outlet
of experiment
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PHASE III: CAPSULE DESIGN
• Dedicated gas handling system to
control oxidation of the specimens
• Gas chromatographs measure
concentrations at inlet and outlet of
experiments
• Measurements made every 15
minutes every day of the irradiation
• Data is analysed quickly and can be
used to tune the oxidation rate
• Oxidation rate adjusted by changing
gas composition or gas flow
• Redundant design to allow for
multiple experiments
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PHASE III RECENT RESULTS
Phase III first stage irradiation completed on 26.08.2018.
Temperature within the target range (± 15 °C)
Irradiation dose accumulated according to plan
Oxidation target achieved as planned
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• Measured for P>42 MW, at
oxidizing gas mixture
• TC temperature within target
range
• TC target is extrapolated from
sample target temperature
through TM Modelling
IRRADIATION RESULTS:
TEMPERATURE
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IRRADIATION RESULTS:
ACCUMULATED DOSE & OXIDATION
DPA accumulation over 11 cycles Oxidation of graphite specimen over 11 cycles
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PHASE III RECENT RESULTS
Interim sample characterisation (PIE) and assembly completed (status
13.09.2019):
Dimension, Mass, DYM, CTE, ER, TC, XRT measurements were
successfully completed
Measured specimens successfully reloaded
Irradiation capsule for the second stage successfully assembled
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CAPSULE 06 ASSEMBLY
• Due to the high activity of the
specimens, loading and assembly is
carried out inside the hot cells
• Video recordings is used to register
loading of specimens without marks
• Orbital welding setup in hot cell for
welding of the first containment
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CONCLUSIONS
• Blackstone Phase III aims to provide expansion of the graphite
property database for Heysham 2 and Torness reactors, and to
higher doses
• The first irradiation stage and the interim PIE phase has been
sucessfully completed.
• Temperature on target
• Dose and weight loss target achieved
• Next steps:
• Capsule 06 irradiation
• Capsule 06 PIE