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ASTM Selected Technical Papers
Graphite Testing for Nuclear Applications: The Validity and Extension of Test Methods for Material Exposed to Operating Reactor Environments
Editor
Athanasia Tzelepi
Athanasia Tzelepi
Symposium Co-Chair and STP Editor
1
National Nuclear Laboratory
,
Sellafield,
GB
Search for other works by this author on:
Martin Metcalfe
Martin Metcalfe
Symposium Co-Chair and STP Editor
2
Nuclear Graphite Research Group, Nuclear Engineering Department of MACE, University of Manchester
,
Manchester,
GB
Search for other works by this author on:
ISBN:
978-0-8031-7725-3
No. of Pages:
312
Publisher:
ASTM International
Publication date:
2022

Postirradiation examination (PIE) of graphite samples trepanned from the UK reactor cores has been carried out for more than 50 years. Due to the nature of the material, there are sample size and geometry restrictions and no standard test methods to cover measurements on this material. Nevertheless, these measurements are used to support the continued operation of the UK reactor cores, and hence a large program of trials is carried out to provide confidence that each method is accurate and reproducible. These trials typically involve a study of size effects using virgin graphite and simulant materials for the irradiated and oxidized graphite, but a corresponding study with irradiated samples is usually not possible. This paper combines the work of two UK studies to investigate the size effect of the PIE test methods on irradiated graphite on the basis of the characterization of graphite used in the advanced gas-cooled reactors (AGRs) and Magnox reactors. The AGR study focused on the static Young's modulus, three-point bend strength of unnotched and notched beams, and the work of fracture. The Magnox study focused on the coefficient of thermal expansion, diametral compression, and flexural strength. The two studies used large irradiated graphite samples from “installed sets” (i.e., precharacterized graphite samples installed in the reactor cores before the start of operation for monitoring purposes). Large Magnox samples that were trepanned from the reactor core after shutdown were also tested. The purpose of these investigations was to relate the graphite measurements normally undertaken on small trepanned samples to property values obtained using standard test methods on irradiated material. The sample selection was such that it covered as wide a range of dose and radiolytic weight loss as possible. This paper outlines the methodology, results, and conclusions for each of the studies and provides some guidelines for similar studies on new graphites.

1.
Standard Specification for Isotropic and Near-Isotropic Nuclear Graphites
, ASTM D7219-19 (
West Conshohocken, PA
:
ASTM International
, approved November 1,
2019
),
2.
Standard Specification for Nuclear Graphite Suitable for Components Subjected to Low Neutron Irradiation Dose
, ASTM D7301-11 (
West Conshohocken, PA
:
ASTM International
, approved October 1,
2011
),
3.
Carroll
M. C.
and
Rohrbaugh
D. T.
, “
Statistical Comparison of the Baseline Mechanical Properties of NBG-18 and PCEA Graphite
,” INL/EXT-13-30011, August
2013
, http://web.archive.org/web/20221130185920/https://inldigitallibrary.inl.gov/sites/sti/sti/5851911.pdf
4.
Standard Guide for Measurements on Small Graphite Specimens
, ASTM D7775-16 (
West Conshohocken, PA
:
ASTM International
, approved December 15,
2016
),
5.
Standard Guide for Categorization of Microstructural and Microtextural Features Observed in Optical Micrographs of Graphite
, ASTM D8075-16(2021) (
West Conshohocken, PA
:
ASTM International
, approved April 1,
2021
),
6.
Davies
M. W.
, “
Graphite Core Design in UK Reactors
,” in
Graphite Moderator Lifecycle Behaviour
(
Vienna, Austria
:
IAEA
,
1996
), 47–56.
7.
Tzelepi
A.
, “
Sample Size Effects on Ultrasonic Measurements of Elastic Moduli—Experimental and Theoretical Investigations
,” in
Graphite Testing for Nuclear Applications: The Significance of Test Specimen Volume and Geometry and the Statistical Significance of Test Specimen Population
, ed.
Tzelepi
N.
and
Carroll
M.
(
West Conshohocken, PA
:
ASTM International
,
2014
), 144–171.
8.
Tzelepi
A.
,
Ramsay
P.
,
Steer
A. G.
, and
Dinsdale-Potter
J.
, “
Measuring the Fracture Properties of Irradiated Reactor Core Graphite
,”
Journal of Nuclear Materials
509
(
2018
): 667–678,
9.
McNally
K.
,
Fahad
M.
,
Tan
E.
,
Warren
N.
,
Hall
G. N.
, and
Marsden
B. J.
, “
A Numerical Study of Internal Brick Stresses in AGR Moderator Bricks
,”
Nuclear Engineering Design
309
(
2016
): 277–293,
10.
Maul
P. R.
and
Robinson
P. C.
, “
Cracking Down
,”
Nuclear Engineering International
51
(
2006
): 44–48.
11.
Testing of Engineering Ceramics—Part 4: Thermo-Physical Properties—Section 4.1 Method for Determination of Thermal Expansion
, BS 7134-4.1 (
London, UK
:
British Standards Institute
,
1990
).
12.
Standard Test Method for Flexural Strength of Manufactured Carbon and Graphite Articles Using Four-Point Loading at Room Temperature
, ASTM C651-11 (
West Conshohocken, PA
:
ASTM International
, approved June 1,
2011
),
13.
Awaji
H.
and
Sato
S.
, “
Diametral Compressive Testing Method
,”
Journal of Engineering Materials and Technology
101
(
1979
): 139–147.
14.
Rudnick
A.
,
Hunter
A. R.
, and
Holden
F. C.
, “
An Analysis of the Diametral-Compression Test
,”
Materials Research Standards
3
(
1963
): 283–289.
15.
Standard Test Method for Tensile Strength Estimate by Disc Compression of Manufactured Graphite
, ASTM D8289-20 (
West Conshohocken, PA
:
ASTM International
, approved May 1,
2020
),
16.
Metcalfe
M.
,
Tzelepi
A.
, and
Wilde
D.
, “
Effect of Test Specimen Size on Graphite Strength
,” in
Graphite Testing for Nuclear Applications: The Significance of Test Specimen Volume and Geometry and the Statistical Significance of Test Specimen Population
, ed.
Tzelepi
N.
and
Carroll
M.
(
West Conshohocken, PA
:
ASTM International
,
2014
), 1–29.
17.
Standard Test Method for Flexural Strength of Manufactured Carbon and Graphite Articles Using Three-Point Loading at Room Temperature
, ASTM D7972-14 (
West Conshohocken, PA
:
ASTM International
, approved December 1,
2014
),
18.
Jordan
M. S.
L.
, “
Studies of the Crack Initiation and Notch Sensitivity Behaviour of Gilsocarbon
” (PhD thesis,
University of Oxford
,
2019
).
19.
Brocklehurst
J. E.
, “
Fracture in Polycrystalline Graphite
,” in
Chemistry and Physics of Carbon
, vol.
13
, ed.
Walker
P. L.
 Jr.
and
Thrower
P. A.
(
New York
:
Marcel Dekker
,
1977
): 146–272.
20.
Standard Guide for Work of Fracture Measurements on Small Nuclear Graphite Specimens
, ASTM D8255-19 (
West Conshohocken, PA
:
ASTM International
, approved May 1,
2019
),
21.
Tzelepi
N.
and
Ramsay
P.
, “
Development of New Techniques for AGR Graphite Post-Irradiation Examination
,” in
The 4th EDF Energy Nuclear Graphite Symposium: Engineering Challenges Associated with the Life of Graphite Reactor Cores
, ed.
Flewitt
P. E.
J.
and
Wickham
A. J.
(
Brussels, Belgium
:
EMAS Publishing
,
2015
), 397–412.
22.
von Karman
T.
, “
Über die Grundlagen der Balkentheorie
,” in
Über die Grundlagen der Balkentheorie/Die Spannungen und Formänderungen von Balken mit rechteckigem Querschnitt/Stegbeanspruchung hoher Biegungsträger/Zur Theorie des Druckversuchs
(
Berlin, Germany
:
Springer
,
1927
), 3–10.
23.
Yoda
S.
,
Ioka
I.
, and
Oku
T.
, “
Effects of Specimen Volume on Tensile Strength for Nuclear-Grade Isotropic Graphite
,”
Japan Atomic Energy Research Institute
120
(
1985
): 45–47,
24.
Losty
H. H.
W.
and
Orchard
J. S.
, “
The Strength of Graphite
,” in
Proceedings of the Fifth Biennial Carbon Conference
, vol.
1
, ed.
Mrozowski
S.
,
Studebaker
M. L.
and
Walker
P. L.
 Jr.
(
New York
:
Pergammon Press
,
1961
), 519–532.
25.
Tucker
M. O.
, “
The Fracture of Polygranular Graphites
,”
Carbon
24
, no.
5
(
1986
): 581–602.
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