ASTM C1671-07

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 ¹⁰B. The boron is usually incorporated either as an intermetallic phase (for example, AlB₂, TiB₂, CrB₂, etc.) in an aluminum alloy or stainless steel, or as a stable chemical compound particulate such as boron carbide (B₄C), typically in an aluminum MMC or cermet.

While other neutron absorbers continue to be investigated, ¹⁰B has been most widely used in these applications, and it is the only thermal neutron absorber addressed in this standard.

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.

Qualification and acceptance procedures demonstrate that the neutron absorber material has the necessary characteristics to perform its design functions during the service lifetime.

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.

The expected users of this standard include designers, neutron absorber material suppliers and purchasers, government agencies, consultants and utility owners. 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.

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 (¹⁰B).

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.