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