ASTM C1671-20a

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Designation: C1671 − 20 C1671 − 20a
Standard Practice for
Qualification and Acceptance of Boron Based Metallic
Neutron Absorbers for Nuclear Criticality Control for Dry
Cask Storage Systems and Transportation Packaging
This standard is issued under the fixed designation C1671; 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
1.1 This practice provides procedures for qualification and acceptance of neutron absorber materials used to provide criticality
control by absorbing thermal neutrons in systems designed for nuclear fuel storage, transportation, or both.
1.2 This practice is limited to neutron absorber materials consisting of metal alloys, metal matrix composites (MMCs), and
cermets, clad or unclad, containing the neutron absorber boron-10 ( B).
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.
2. Referenced Documents
2.1 ASTM Standards:
B557 Test Methods for Tension Testing Wrought and Cast Aluminum- and Magnesium-Alloy Products
B557M Test Methods for Tension Testing Wrought and Cast Aluminum- and Magnesium-Alloy Products (Metric)
C791 Test Methods for Chemical, Mass Spectrometric, and Spectrochemical Analysis of Nuclear-Grade Boron Carbide
E8/E8M Test Methods for Tension Testing of Metallic Materials
E21 Test Methods for Elevated Temperature Tension Tests of Metallic Materials
E456 Terminology Relating to Quality and Statistics
E1225 Test Method for Thermal Conductivity of Solids Using the Guarded-Comparative-Longitudinal Heat Flow Technique
E1461 Test Method for Thermal Diffusivity by the Flash Method
E2971 Test Method for Determination of Effective Boron-10 Areal Density in Aluminum Neutron Absorbers using Neutron
Attenuation Measurements
3. Terminology
3.1 Definitions:
3.1.1 acceptance test, n—for a neutron absorber material, quality control, tests, and inspections conducted to determine whether
a specific production lot meets selected specified material properties, characteristics, or both, so that the lot can be accepted.
3.1.2 areal density, n—for neutron absorber materials with flat parallel surfaces, the mass of boron-10 per unit area of a sheet,
which is equivalent to the mass of boron-10 per unit volume of boron-10 in the material multiplied by the thickness of the material
in which that isotope is contained.
3.1.3 durability, n—the ability of neutron absorber materials to withstand service conditions without physical changes that
would render them unable to perform their design functions.
This practice is under the jurisdiction of ASTM Committee C26 on Nuclear Fuel Cycle and is the direct responsibility of Subcommittee C26.03 on Neutron Absorber
Materials Specifications.
Current edition approved Jan. 1, 2020July 1, 2020. Published January 2020August 2020. Originally approved in 2007. Last previous edition approved in 20152020 as
C1671 – 15.C1671 – 20. DOI: 10.1520/C1671-20.10.1520/C1671-20A.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C1671 − 20a
3.1.4 lot, n—a quantity of a product or material accumulated under conditions that are considered uniform for sampling
purposes. E456
3.1.5 moderator, n—a material used to reduce neutron energy by scattering without appreciable capture.
3.1.6 neutron absorber, n—a nuclide that has a large thermal neutron absorption cross section (also known as a neutron poison).
3.1.7 neutron-absorber neutron absorber material, n—a compound, alloy, composite, or other material that contains a neutron
absorber.
3.1.8 neutron attenuation test, n—for neutron absorber materials, a process in which a material is placed in a thermal neutron
beam, and the number of neutrons transmitted through the material in a specified period of time is counted. The neutron count can
be converted to areal density by performing the same test on a series of appropriate calibration standards and comparing the results.
3.1.9 neutron cross section, [barn],(barn), n—a measure of the probability that a neutron will interact with a nucleus in the
absorbing medium and is a function of the neutron energy.
3.1.10 open porosity, n—the volume fraction of all pores, voids, and channels within a solid mass that are interconnected with
each other and communicate with the external surface, and thus are measurable by gas or liquid penetration.
C242C21, C21C242
3.1.11 packaging, n—in transport of radioactive material, the assembly of components necessary to enclose the radioactive
contents completely.
3.1.12 probability sampling, n—a sample selection procedure in which the sampling units are selected by a chance process such
that, at each step of the selection, a specified probability of selection can be attached to each sampling unit available for selection.
E456
3.1.13 qualification, n—for neutron absorber materials, the process of evaluating, testing, or both, a material produced by a
specific manufacturing process to demonstrate uniformity and durability for a specific application.
th
3.1.14 systematic sampling, n—a sample selection procedure in which every kth element is selected from the universe or
population, for example, u,u + k, u + 2k,u + 3k, etc., where u is in the interval 1 to k. E456
3.2 Definitions of Terms Specific to This Standard:
3.2.1 Designer,designer, n—the organization responsible for the design or the license holder for the dry cask storage system or
transport packaging. Thepackaging; the designer is usually the purchaser of the neutron absorber material, either directly or
indirectly (through a fabrication subcontractor).
4. Significance and Use
4.1 For criticality control of nuclear fuel in dry storage and transportation, the most commonly used neutron absorber materials
are borated stainless steel alloys, borated aluminum alloys, and boron carbide aluminum alloy composites. The boron used in these
neutron absorber materials may be natural or enriched in the nuclide B. The boron is usually incorporated either as an
intermetallic phase (for example, AlB , TiB , CrB , etc.) in an aluminum alloy or stainless steel, or as a stable chemical compound
2 2 2
particulate such as boron carbide (B C), typically in an aluminum MMC or cermet.
4.2 While other neutron absorbers continue to be investigated, B has been most widely used in these applications, and it is
the only thermal neutron absorber addressed in this standard.
4.3 In service, many neutron absorber materials are inaccessible and not amenable to a surveillance program. These neutron
absorber materials are often expected to perform over an extended period.
4.4 Qualification and acceptance procedures demonstrate that the neutron absorber material has the necessary characteristics to
perform its design functions during the service lifetime.
4.5 The criticality control function of neutron absorber materials in dry cask storage systems and transportation packagings is
only significant in the presence of a moderator, such as during loading of fuel under water, or water ingress resulting from
hypothetical accident conditions.
4.6 The expected users of this standard include designers, neutron absorber material suppliers and purchasers, government
agencies, consultants and utility owners. Typical use of the practice is to summarize practices which provide input for design
specification, material qualification, and production acceptance. Adherence to this standard does not guarantee regulatory approval;
a government regulatory authority may require different tests or additional tests, and may impose limits or restrictions on the use
of a neutron absorber material.
5. Procedure
5.1 Determination of Service Conditions and Design Requirements for the Neutron Absorber Material—The designer shall
specify the service conditions and design requirements, including environmental conditions, mechanical properties, and areal
“Regulations for the Safe Transport of Radioactive Material,” Safety Series Standards, No. TS-R-1, International Atomic Energy Agency, Vienna, Austria.
C1671 − 20a
density or equivalent measure of neutron absorber content. Selection of environmental and service conditions that are important
for neutron absorber material performance and qualification should take into consideration known failure modes and industry
experience.
5.1.1 Environmental conditions to be considered include but are not limited to water chemistry, water temperature, paired
dissimilar materials, hydrostatic pressure, duration of immersion, gamma and fast neutron flux, heat-up rate after draining, and
maximum temperature.
5.1.2 For structural applications, specify the mechanical properties required by the structural analysis. For non-structural uses
of the neutron absorber material, specify mechanical properties sufficient to assure material durability under the service conditions
for which it is designed.
5.1.3 Specify other design properties, for example, thermal conductivity, surface finish, etc., as required for the application.
5.1.4 Product or feed material chemistry shall be specified.
5.2 Neutron Absorber Material Qualification—Qualification shall consist of three components: (1) verify durability for the
intended service as defined in 5.2.5, (2) verify that the physical characteristics of components meet their design requirements
defined in 5.2.6, and (3) verify that the uniformity of the B distribution in the neutron absorber material is within acceptable
bounds as specified by the designer as described in 5.2.6.
5.2.1 Qualification is needed:
5.2.1.1 When the neutron absorber material has not been previously qualified,
5.2.1.2 When a new supplier is producing a qualified neutron absorber material, or
5.2.1.3 When any key process or process control, as defined in 5.2.7, is altered for production of a qualified neutron absorber
material.
5.2.2 The key processes and process controls for producing neutron absorber material for qualification should be the same as
those to be used for commercial production. Differences shall be justified per in accordance with 5.2.7.
5.2.3 If a previou
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