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ASTM D8093-16

(Guide)

Standard Guide for Nondestructive Evaluation of Nuclear Grade Graphite

Standard Guide for Nondestructive Evaluation of Nuclear Grade Graphite

SIGNIFICANCE AND USE
4.1 Nuclear grade graphite is a composite material made from petroleum or a coal-tar-based coke and a pitch binder. Manufacturing graphite is an iterative process of baking and pitch impregnation of a formed billet prior to final graphitization, which occurs at temperatures greater than 2500 °C. The impregnation and rebake step is repeated several times until the desired product density is obtained. Integral to this process is the use of isotropic cokes and a forming process (that is, isostatically molded, vibrationally molded, or extruded) that is intended to obtain an isotropic or near isotropic material. However, the source, size, and blend of the starting materials as well as the forming process of the green billet will impart unique material properties as well as variations within the final product. There will be density variations from the billet surface inward and different physical properties with and transverse the grain direction. Material variations are expected within individual billets as well as billet-to-billet and lot-to-lot. Other manufacturing defects of interest include large pores, inclusions, and cracks. In addition to the material variation inherent to the manufacturing process, graphite will experience changes in volume, mechanical strength, and thermal properties while in service in a nuclear reactor along with the possibility of cracking due to stress and oxidation resulting from constituents in the gas coolant or oxygen ingress. Therefore, there is the recognized need to be able to nondestructively characterize a variety of material attributes such as uniformity, isotropy, and porosity distributions as a means to assure consistent stock material. This need also includes the ability to detect isolated defects such as cracks, large pores and inclusions, or distributed material damage such as material loss due to oxidation. The use of this guide is to acquire a basic understanding of the unique attributes of nuclear grade graphite and its appl...
SCOPE
1.1 This guide provides general tutorial information regarding the application of conventional nondestructive evaluation technologies (NDE) to nuclear grade graphite. An introduction will be provided to the characteristics of graphite that defines the inspection technologies that can be applied and the limitations imposed by the microstructure. This guide does not provide specific techniques or acceptance criteria for end-user examinations but is intended to provide information that will assist in identifying and developing suitable approaches.  
1.2 The values stated in SI units are to be regarded as the standard.  
1.2.1 Exception—Alternative units provided in parentheses are for information only.  
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

General Information

Status
Historical
Publication Date
30-Nov-2016
ICS
71.060.10 - Chemical elements
Technical Committee
D02 - Petroleum Products, Liquid Fuels, and Lubricants
Drafting Committee
D02.F0 - Manufactured Carbon and Graphite Products
Current Stage
Ref Project

Relations

Replaced By
ASTM D8093-19 - Standard Guide for Nondestructive Evaluation of Nuclear Grade Graphite
Effective Date
01-Nov-2019

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ASTM D8093-16 - Standard Guide for Nondestructive Evaluation of Nuclear Grade GraphiteASTM D8093-16 - Standard Guide for Nondestructive Evaluation of Nuclear Grade Graphite
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ASTM D8093-16 - Standard Guide for Nondestructive Evaluation of Nuclear Grade Graphite
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D8093 − 16 An American National Standard
Standard Guide for
1
Nondestructive Evaluation of Nuclear Grade Graphite
This standard is issued under the fixed designation D8093; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Summary of Guide
1.1 This guide provides general tutorial information regard- 3.1 This guide describes the impact specific material prop-
ing the application of conventional nondestructive evaluation erties have on the application of three nondestructive evalua-
technologies (NDE) to nuclear grade graphite.An introduction tion technologies: Eddy current/electromagentic testing (ET)
will be provided to the characteristics of graphite that defines (surface/near surface interrogation), ultrasonic testing (UT)
the inspection technologies that can be applied and the limita- (volumetric interrogation), radiographic (X-ray) testing (RT)
tions imposed by the microstructure. This guide does not (volumetric interrogation), to nuclear grade graphite.
provide specific techniques or acceptance criteria for end-user
4. Significance and Use
examinations but is intended to provide information that will
4.1 Nuclear grade graphite is a composite material made
assist in identifying and developing suitable approaches.
from petroleum or a coal-tar-based coke and a pitch binder.
1.2 The values stated in SI units are to be regarded as the
Manufacturing graphite is an iterative process of baking and
standard.
pitch impregnation of a formed billet prior to final
1.2.1 Exception—Alternative units provided in parentheses
graphitization, which occurs at temperatures greater than
are for information only.
2500°C.The impregnation and rebake step is repeated several
1.3 This standard does not purport to address all of the
times until the desired product density is obtained. Integral to
safety concerns, if any, associated with its use. It is the
thisprocessistheuseofisotropiccokesandaformingprocess
responsibility of the user of this standard to establish appro-
(that is, isostatically molded, vibrationally molded, or ex-
priate safety and health practices and determine the applica-
truded) that is intended to obtain an isotropic or near isotropic
bility of regulatory limitations prior to use.
material. However, the source, size, and blend of the starting
materialsaswellastheformingprocessofthegreenbilletwill
2. Referenced Documents
impart unique material properties as well as variations within
2
2.1 ASTM Standards:
the final product. There will be density variations from the
C709Terminology Relating to Manufactured Carbon and
billet surface inward and different physical properties with and
Graphite
transverse the grain direction. Material variations are expected
D7219 Specification for Isotropic and Near-isotropic
withinindividualbilletsaswellasbillet-to-billetandlot-to-lot.
Nuclear Graphites
Other manufacturing defects of interest include large pores,
E94Guide for Radiographic Examination
inclusions, and cracks. In addition to the material variation
E1025 Practice for Design, Manufacture, and Material
inherenttothemanufacturingprocess,graphitewillexperience
Grouping Classification of Hole-Type Image Quality In-
changes in volume, mechanical strength, and thermal proper-
dicators (IQI) Used for Radiology
ties while in service in a nuclear reactor along with the
E1441Guide for Computed Tomography (CT) Imaging
possibility of cracking due to stress and oxidation resulting
from constituents in the gas coolant or oxygen ingress.
Therefore, there is the recognized need to be able to nonde-
1
This guide is under the jurisdiction of ASTM Committee D02 on Petroleum
structively characterize a variety of material attributes such as
Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcom-
uniformity, isotropy, and porosity distributions as a means to
mittee D02.F0 on Manufactured Carbon and Graphite Products.
assure consistent stock material. This need also includes the
Current edition approved Dec. 1, 2016. Published March 2017. DOI: 10.1520/
D8093-16.
abilitytodetectisolateddefectssuchascracks,largeporesand
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
inclusions,ordistributedmaterialdamagesuchasmaterialloss
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
due to oxidation. The use of this guide is to acquire a basic
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. understandingoftheuniqueattributesofnucleargradegraphite
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C
...

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ASTM C714-23(Guide)
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FIG. 1 Block Diagram of Typical Test Apparatus  
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5.1 Two- and three-parameter formulations exist for the Weibull distribution. This practice is restricted to the two-parameter formulation. An objective of this practice is to obtain point estimates of the unknown Weibull distribution parameters by using well-defined functions that incorporate the failure data. These functions are referred to as estimators. It is desirable that an estimator be consistent and efficient. In addition, the estimator should produce unique, unbiased estimates of the distribution parameters (6). Different types of estimators exist, such as moment estimators, least-squares estimators, and maximum likelihood estimators. This practice details the use of maximum likelihood estimators.  
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1.1 This test method provides a comparative oxidation mass loss of manufactured carbon and graphite materials in air.  
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5.1 This test method can be used to measure the rate of oxidation for various grades of manufactured carbon and graphite in standard conditions, and can be used for quality control purposes.  
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1.3 This test method also provides a standard oxidation temperature (as defined in 3.1.7), and the kinetic parameters of the oxidation reaction, namely the apparent activation energy and the logarithm of pre-exponential factor in Arrhenius equation. The kinetic parameters of Arrhenius equation are calculated from the temperature dependence of oxidation rates measured over the temperature range where Arrhenius plots (as defined in 3.1.8) are linear, which is defined as the “kinetic” or “chemical control” oxidation regime. For typical nuclear grade graphite materials it was found that the practical range of testing temperatures is from about 500 °C to 550 °C up to about 700 °C to 750 °C.  
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Standard Guide for Impregnation of Graphite with Molten Salt

SIGNIFICANCE AND USE
5.1 The molten salt reactor is a nuclear reactor which uses graphite as reflector and structural material and fluoride molten salt as coolant. The graphite components will be submerged in the molten salt during the lifetime of the reactor. The porous structure of graphite may lead to molten salt permeation, which can affect the thermal and mechanical properties of graphite. Consequently, it is important to assess the effect of impregnation of molten salt on the properties of the as-manufactured graphite material.  
5.2 The purpose of this guide is to report considerations that should be included in the preparation of graphite specimens representative of that after exposure to a molten salt environment. The degree to which the molten salt will infiltrate the graphite will depend upon a number of factors, including the type of graphite and the type and extent of porosity, the properties of the molten salt, the impregnation pressure and temperature, and the duration of the exposure of the graphite to the molten salt.  
5.3 The user of this guide will need to select impregnation parameters sufficiently representative of those in a molten salt reactor based on parameters provided by the designer. Alternatively, the user may select a standard set of impregnation conditions to allow comparisons across a range of graphites.  
5.4 This guide is not intended to be prescriptive. A typical apparatus and associated procedure are described. Some indication of the sensitivity of the procedure to graphite type and impregnation conditions is given in He, et al.5  
5.5 There are four major practical issues that must be addressed during the impregnation process:  
5.5.1 The density of molten salt is greater than that of graphite. A specially designed tool is required to submerge graphite samples in the molten salt during the impregnation process.  
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1.1 This guide covers procedures for the impregnation of graphite with molten salt under a consistent pressure and temperature. Such procedures are necessary if the user wishes to prepare graphite specimens for testing that represent material that has been exposed to a molten salt environment in a molten salt nuclear reactor. The user will need to ensure that impregnation temperature and pressure conditions reflect those pertaining to the molten salt environment, noting that the properties of the material will change once it becomes irradiated.
Note 1: The term impregnation is used throughout this guide as this is the correct term for the described process. Other terms such as infiltration and intrusion may be encountered by the user in other texts and the term intrusion is commonly used to describe penetration of open porosity in graphite in a molten salt reactor environment.  
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this guide.  
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

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ASTM D8377-21a(Guide)
Standard Guide for High Temperature Strength Measurements of Graphite Impregnated with Molten Salt

SIGNIFICANCE AND USE
5.1 The Molten Salt Reactor is a nuclear reactor which uses graphite as reflector and structural material, and molten salt as coolant. The graphite components will be submerged in the molten salt during the lifetime of the reactor. The porous structure of graphite may lead to molten salt permeation, which can affect the thermal and mechanical properties of graphite. Consequently, it may be necessary to measure the various strengths of the manufactured graphite materials after impregnation with molten salt and before exposure to the reactor environment in a range of test configurations in order for designers or operators to assess their performance.
Note 1: Depending upon the salt selected for the reactor, there may be some chemical reaction between the salt and the graphite that could affect properties. The user should establish, prior to following this guide, that any interactions between the molten salt and graphite are understood and any implications for the validity of the strength tests have been assessed.  
5.2 For gas-cooled reactors, the strength of a graphite specimen is usually measured at room temperature. However, for molten salt reactors, the operating temperature of the reactor must be higher than the melting temperature of the salt, and so the salt will be in solid state at room temperature. Consequently, room temperature measurements may not be representative of the performance of the material at its true operating conditions. It is therefore necessary to measure the strength at an elevated temperature where the salt is in liquid form.
Note 2: Users should be aware that a small increase in graphite strength is expected with increasing temperature. Testing at the plant operating temperature will eliminate this small uncertainty.  
5.3 The purpose of this guide is to provide considerations, which should be included in testing graphite specimens impregnated with molten salt at elevated temperature.  
5.4 For the test results to be meaningful, the...
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1.1 This guide covers the best practice for strength measurements at elevated temperature of graphite impregnated with molten salt.  
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
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Standard Test Method for Compressive Strength of Carbon and Graphite

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4.1 Carbon and graphite can usually support higher loads in compression than in any other mode of stress. This test, therefore, provides a measure of the maximum load-bearing capability of carbon and graphite objects.
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1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.  
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
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