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Investigation of Alteration of Li-6 Enriched Neutron Shielding Glass

Published

Author(s)

Jamie Weaver, Danyal J. Turkoglu

Abstract

Silicate glass doped with 6Li is a common slow neutron shielding material, and has been utilized as such in several neutron research facilities. 6Li is a unique isotope for thermal neutron capture as it has a large thermal neutron capture cross section (≈ 941 b), and the compound nucleus primarily decays via 6Li(n, α)3H. This nuclear reaction produces a minor prompt-gamma ray branch (0.004 %, ≈ 37 mb), but otherwise meets the requirement that neutron shielding materials should produce minimal gamma-ray emissions [1]. Although 6Li has a low natural isotopic abundance (7.5 %), it is commercially available at enrichments greater than 95 % in the United States. Of the variety of 6Li materials proposed for neutron shielding, a review of which can be found in Ref. [1], 6Li enriched silicate glass is preferred as it provides a large specific neutron attenuation due to high 6Li content, and can be fabricated into a variety of shapes and sizes with polished surfaces. Additionally, as the silicate glass structure can readily accept other elements (e.g., B and Al) the glass can be formulated to include elements that will improve its formability and durability. The radiation durability of 6Li silicate glass has been studied in detail, but the chemical durability has received less attention. The durability of the glass is important considering silicate glasses can form a hydrated, gel-like surface layer when exposed to a humid atmosphere [2]. This alteration layer can incorporate H and release alkali. The result of these chemical reactions can be the slow depletion of 6Li in the bulk glass with time, and/or a change in the distribution of 6Li across the glass surface. Both outcomes could lead to a change in the glass's neutron shielding properties.
Conference Dates
October 29-November 2, 2017
Conference Location
Washington DC, DC, US
Conference Title
American Nuclear Society 2017 Winter Meeting

Keywords

neutron shielding, glass alteration, neutron depth profiling, prompt gamma activation analysis

Citation

Weaver, J. and Turkoglu, D. (2018), Investigation of Alteration of Li-6 Enriched Neutron Shielding Glass, American Nuclear Society 2017 Winter Meeting, Washington DC, DC, US, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=924112 (Accessed February 25, 2024)
Created January 31, 2018, Updated April 12, 2022