www.inl.gov
Preliminary Results of the
AGC-3 Irradiation in the
Advanced Test Reactor and
Design of AGC-4
Proceedings of the 2014 15th International
Nuclear Graphite Specialists Meeting
INGSM-15
September 15– September 18, 2014, Hangzhou,
China
Michael Davenport, NGNP Irradiations Technical Lead
Idaho National Laboratory
Agenda
• Graphite irradiation overview
• ATR irradiation locations & details
• Graphite specimens
• Capsule & test train design
• Control & monitoring systems
• AGC-3 Experiment
– Irradiation
• AGC-4 Experiment
– Design
• Summary
ATR Core During
Reactor Operation
Graphite Irradiation Experiments
1500 ºC
HTV-1
• Historic nuclear grade graphites
are no longer available due to loss
of feedstock
HTV-2
Graphite material
property database
AGC - 5
1100 ºC
AGC - 6
– 600, 800 & 1100ºC
• Irradiation creep
800 ºC
AGC - 3
AGC - 4
• Thermal changes
• Mechanical changes
600 ºC
AGC - 1
AGC - 2
Database for previous nuclear
graphite grades
1
3
Dose (dpa)
4.5
• Physical changes
High dose tensile irradiation
creep studies needed for
pebble bed design
6
• ATR experiments to be irradiated:
– Up to 4 or 7 dpa (5.5 and 9.6 x
1021 n/cm2 for E > 0.1 MeV)
• AGC-1 was irradiated from
September 2009 to January 2011
• AGC-2 was irradiated from
April 2011 to May 2012
• AGC-3 was irradiated from
November 2012 to April 2014
• AGC-4 will be irradiated from
February 2014 to January 2017
AGC Experiment Locations
North
ON-8
ON-9
ON-10
ON-11
ON-12
ON-3
ON-4
ON-5
ON-6
ON-7
H Positions
ON-2
ON-1
I-19
Fuel Elements
I-20
I-2
I-1
I-3
Small B Position
I21
I24
B9
B1
B8
I-18
I-4
I-17
I-5
B2
B7
I-16
B12
I-6
B10
B3
B6
I-15
East Flux Trap Location
for AGC-3 & 4
I-7
I-14
I-8
B4
B5
B11
I23
I22
I-13
I-12
I-11
I-10
South Flux Trap Location
for AGC-1 & 2
I-9
OS-2
OS-1
OS-3
OS-4
OS-5
OS-6
OS-7
OS-8
OS-9
OS-10
OS-11
OS-12
OS-13
OS-14
OS-15
OS-16
OS-17
OS-18
OS-19
OS-20
OS-21
OS-22
Control Drum
I Positions
ATR Core Cross Section
• AGC-1 & AGC-2 were irradiated in
the South Flux Trap position
• AGC-3 & AGC-4 being irradiated in
the East Flux Trap of the ATR
• Use of ATR Flux Trap
– Maximizes number of graphite
specimens, stacks/channels, loads,
and combinations
– Flux rate minimizes irradiation time to
meet NGNP program schedule
• Test trains rotated to minimize flux
gradient across diameter
• Most of ATR core height (44” of 48”)
used to maximize specimen
numbers and provide spectrum of
fast fluence damage levels
AGC-3 Graphite Specimens
• Same large & small specimens
– Large - Ø ½” (12.3 mm) × 1” (25.4 mm) tall
– Small - Ø ½” (12.3 mm) × ¼” (6.4 mm) tall
• New ‘intermediate’ size specimen container
– Ø ½” (12.3 mm) × ½” (12.7 mm) tall
Small Specimen
Large Specimen
• 6 Perimeter Stacks
– 18 large size specimens above core center
– 18 large and 3 small size specimens below core
center
Spacer
Flux Monitor
• Center Stack
– 152 small and 9 intermediate size specimens
• Flux wires in spacers between graphite
specimens
Compressive Load Push Rod
Loaded Large Specimens
AGC-3 Specimen Stack
Core Centerline
Unloaded Small
Specimens
Full Size Unloaded
Specimens
AGC-3 Irradiation Requirements
• 800ºC design temperature
AGC Experiment
• Fast neutron damage up to 3 to 4 dpa
• Compressive loads on specimens
– 2 stacks with 2 ksi (14 MPa)
compressive load
– 2 stacks with 2.5 ksi (17 MPa)
compressive load
ATR Top Head
– 2 stacks with 3 ksi (21 MPa) compressive
load
• Loaded and unloaded companion
specimens
• Lift specimens during reactor outages
to verify specimen load condition
AGC Being Inserted into the ATR
• Grab samples of temperature control
gas to monitor for oxidation of
specimens
AGC Capsule Design Features
• 6 specimen stacks around capsule
perimeter with compressive load
on upper half of stack
• 7th specimen stack in center
without compressive load
• Graphite holder to contain graphite
specimen stacks and
thermocouples (TCs)
• 12 TC locations with positions
located throughout core height
• Insulating gas jacket to attain
desired temperature
• Radiation heat shield to limit
radiation heat transfer
Specimen Holder
Thermocouples
Lower
Bellows
Gas Line
Temperature
Control Gas
Line
Heat Shield/Gas
Jacket Area
Graphite Specimens
AGC Capsule Cross Section
Temperature Control
• Utilize neutron capture and
gamma heating of specimens
as heat source
• Manipulate temperature by
adjusting ratio of conducting
and insulating gases in
insulating gas gap
• AGC irradiations use He and
Ar to maximize control band
for temperature control
• All AGC experiments utilize
same temperature control
system
• Distributed control system
used for control and data
collection
Compressive Load System
• Pneumatic rams provide compressive load on specimens in six peripheral stacks
located above the ATR core centerline – no load on specimens below core centerline
• Load cells between pneumatic rams and push bars to monitor specimen load
• Push bars translate and transmit compressive load to push rods located in smaller
circle directly over specimen stacks
– Stainless steel push rods transition to graphite in higher temperature areas of experiment
• Gas bellows below core to lift top specimens during outages to verify load conditions
– Position indicators attached to push bars to verify specimen movement during outages
• Compressive loads imposed on diametrically opposite specimen stack pairs to avoid
eccentrically loading the graphite holder
Pneumatic Ram
Load Cell
Push Bar
Push Rod
AGC Test Train
Position
Indicators
Graphite
Specimens
Gas Bellows
AGC-2 Design Changes/Improvements
• TC12 moved to same elevation as TC9 to provide
temperature gradient across the whole
experiment
• Replaced stainless steel with aluminum in some
internal components to reduce weight
–
TC
Locations
Load cell adapter, plates, push bars and sleeves
• Tungsten ‘gamma heaters’ added to top and
bottom of center channel
• Zirconia gamma heaters added to the bottom of
peripheral channels
• Removed spacers in specimen stacks to increase
number of specimens
–
36 large and 14 to 18 small specimens in peripheral
stacks (vs. 29 and 14)
–
170 (vs. 172) small specimens in center stack due to
tungsten heaters
TC Pair Locations in AGC-2
AGC-3 Design Challenges and Changes
Specimen Holder
Thermocouples
• East Flux Trap vs. South Flux Trap
–
15% lower nominal power
–
20% power variation versus 10% for AGC-1 & AGC-2
• Increased specimen creep from higher design
temperature (800ºC)
–
–
–
Lower
Bellows
Gas Line
Temperature
Control Gas
Line
Heat Shield/Gas
Jacket Area
Graphite Specimens
AGC Capsule Cross Section
Slightly smaller diameter specimens
Additional stroke in pneumatic cylinders
Additional room at core center for creep in specimens
& housing
• Elevated mean wall temperature in pressure
boundary from higher temperature
• Five versus single vertical temperature control
zone
–
–
Significantly enhanced temperature control
Significantly improved axial temperature distribution
• Different gamma ‘heaters’
–
Molybdenum vs. tungsten & zirconia
AGC-3 & 4 Schedule & Status
• AGC-3 Status
Gas Bellows before installation in outer shell
Outer shell with gas bellows installed inside
• Start of irradiation - November 2012
–
–
–
–
Moisture level during start-up
Excellent temperature control
Extremely flat axial temperature profile
Compressive load control system
leakage
– Helium shortage
– Loads reduced on stacks 2 & 5 to
replace/supplement stacks 1 & 4
• Completed Irradiation- April 2014
– Accumulated 210 EFPDs
– Peak fast neutron damage – 3.63 dpa
• AGC-4 Status
Lower Gas Bellows installed on test train
• Completed final design July 2014
• Assembly expected to complete November
2014
• Irradiation expected to begin February
2015
AGC-3 Temperatures During Irradiation
AGC-3 Compressive Loads During Irradiation
Summary
AGC-3 Experiment
• Multiple design improvements and lessons
learned from AGC-1 & AGC-2 incorporated
• New design challenges from increased
temperature & new irradiation position
• Irradiation started in November 2012
– Significant improvement in temperature control &
axial temperature profile
AGC Connections to
Control Systems
ATR Flux Trap Top
Head Penetration
AGC Test Train
– Compressive load control system leakage
– Accumulated 210 EFPDs
ATR Vessel
– Peak fast neutron damage level – 3.63 dpa
• Irradiation completed in April 2014
• Sizing and Shipping for PIE expected
November 2014
ATR Core
ATR Fuel
AGC-4 irradiation expected to commence early
2015
AGC Experiment Installed in ATR
Mike Davenport
Idaho National Laboratory
[email protected]
(208) 526-6214