ASTM D8091-16
(Guide)Standard Guide for Impregnation of Graphite with Molten Salt
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 samples 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 is described. Some indication of the sensitivity of the procedure to graphite type and impregnation conditions is given in He, et al.3
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.
5.5.2 Some molten salts (for example, FLiBe) are poisonous and it is therefore necessary to provide containment by performing procedure...
SCOPE
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 have been exposed to a molten salt environment that may not necessarily represent material exposed to an operating 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 and health practices and determine the applicability of regulatory limitations prior to use.
General Information
Standards Content (Sample)
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Designation: D8091 − 16
Standard Guide for
1
Impregnation of Graphite with Molten Salt
This standard is issued under the fixed designation D8091; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope was no damage to the microstructure of the graphite during
impregnation, then parameter D based upon open pore volume
1.1 This guide covers procedures for the impregnation of
would be unity at saturation. At high impregnation pressures,
graphite with molten salt under a consistent pressure and
closed porosity may be broken into by the molten salt and
temperature. Such procedures are necessary if the user wishes
parameter D based upon open pore volume could have values
to prepare graphite specimens for testing that have been
greater than unity. It is therefore useful to express parameter D
exposed to a molten salt environment that may not necessarily
in terms of both open pore volume and total (open and closed)
represent material exposed to an operating reactor environ-
pore volume.
ment.
3.2.1.1 Discussion—Parameter D is based upon open pore
1.2 The values stated in SI units are to be regarded as
volume (typically applicable at low impregnation pressures)
standard. No other units of measurement are included in this
and is calculated as follows:
guide.
W 2 W
1.3 This standard does not purport to address all of the
2 1
D 5 (1)
o
ρV
safety concerns, if any, associated with its use. It is the
o
responsibility of the user of this standard to establish appro-
where:
priate safety and health practices and determine the applica-
W = theweightofthegraphitesamplebeforeimpregnation,
1
bility of regulatory limitations prior to use.
W = the weight of the graphite sample after impregnation,
2
ρ = the density of molten salt, and
2. Referenced Documents
V = the open pore volume in the sample.
o
2
2.1 ASTM Standards:
3.2.1.2 Discussion—Parameter D based upon total pore
C559 Test Method for Bulk Density by Physical Measure-
volume (typically at high impregnation pressures) is calculated
ments of Manufactured Carbon and Graphite Articles
as follows:
D7775 Guide for Measurements on Small Graphite Speci-
mens
W 2 W
2 1
D 5 (2)
t
ρV
t
3. Terminology
where:
3.1 Definitions:
V = the total pore volume in the sample.
t
3.1.1 impregnation pressure (P ), n—the pressure of cover
I
gas used in the impregnation.
4. Summary of Guide
3.1.2 impregnation temperature (T ), n—the system tem-
I
4.1 This guide provides guidance on the impregnation of
perature before the graphite sample has been immersed in the
graphite with molten salt. The guide gives the various factors
molten salt.
which need to be considered to perform the impregnation
3.2 Definitions of Terms Specific to This Standard:
procedure. These include pretreatment of graphite samples,
3.2.1 Parameter D—provides a measure of the extent of
immersion of graphite in the molten salt, safe handling of the
penetration of the graphite porosity by the molten salt. If there
molten salt, and selection and control of the impregnation
pressures and temperatures.
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This guide is under the jurisdiction of ASTM Committee D02 on Petroleum
Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcom-
5. Significance and Use
mittee D02.F0 on Manufactured Carbon and Graphite Products.
5.1 The molten salt reactor is a nuclear reactor which uses
Current edition approved Dec. 1, 2016. Published January 2017. DOI: 10.1520/
D8091-16.
graphite as reflector and structural material and fluoride molten
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
salt as coolant. The graphite components will be submerged in
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
the molten salt during the lifetime of the reactor. The porous
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. structureofgraphitemayleadtomoltensaltpermeation,which
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D8091 − 16
can affect the thermal and mechanical properties of graphite. 6.1.1 Since fluoride molten salts are toxic and a small
Consequently, it is important to assess the effect of impregna- amountofwatercansignificantlyaffectthewettingbehaviorof
tion of molten salt on the properties of the as-manufactured graphite, the conditions for the procedure should be strictly
graphite material. controlled during molten salt impregnation. The schematic
diagram of an impregnation setup is shown in Fig. 1.
5.2
...
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