Radiation Attenuation Assessment of Serpentinite Rocks from a Geological Perspective

Our plain-English summary of Radiation Attenuation Assessment of Serpentinite Rocks from a Geological Perspective, by M.A. Masoud, A.M. El-Khayatt, M.G. Shahien, et al (Toxics, 2022).

The study

• Authors: M.A. Masoud, A.M. El-Khayatt, M.G. Shahien, B.R. Bakhit, I.I. Suliman, A.M. Zayed
• Journal: Toxics
• Published: 2022;10(11)
• Cited by: 7 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Serpentinites are metamorphic rocks that are widely applied as aggregates in the production of radiation-shielding concrete. Different varieties of massive serpentinite mountains located in Egypt exist without real investment. Hence, this study aims to evaluate the radiation shielding efficacy of three varieties of serpentinite rocks from different geological perspectives: mineralogical, geochemical, and morphological characteristics. X-ray diffraction, transmitted-light microscopy, and thermal analysis were required to characterize their mineralogical composition, while X-ray fluorescence was necessary to investigate their geochemical features. Moreover, scanning electron microscopy was used to detect their morphological characteristics. On the other hand, the PuBe source and stilbene detector were employed for the experimental determination of fast neutrons and γ-ray attenuations, which were conducted at energy ranges of 0.8−11 and 0.4−8.3 MeV, respectively. Based on the mineralogical, geochemical, and morphological characteristics of these rocks, the radiation attenuation capacity of lizardite > antigorite > chrysotile. However, these serpentinites can be applied as a natural alternative to some radiation-shielding concrete in radiotherapy centers and other counterpart facilities.

In plain English

This laboratory study tested rocks, not people, and did not examine health effects. The authors measured how well three serpentinite rocks from Egypt's Eastern Desert reduced radiation. One rock was made mainly of antigorite (AS), one mainly of lizardite (LS), and one mainly of chrysotile fibres (CS). Slabs 2 to 12 cm thick were placed between a plutonium-beryllium source and a detector, which measured fast neutrons (0.8 to 11 MeV) and gamma rays (0.4 to 8.3 MeV). For both radiation types, the lizardite rock reduced radiation most and the chrysotile rock least. Fast neutron removal cross-sections were 0.168 plus or minus 0.013 per cm (LS), 0.139 plus or minus 0.011 (AS) and 0.130 plus or minus 0.010 (CS). Gamma-ray attenuation coefficients were 0.136 plus or minus 0.01 (LS), 0.106 plus or minus 0.007 (AS) and 0.096 plus or minus 0.007 (CS) per cm. The chrysotile rock had the lowest density (2.24 g/cm3) and highest water absorption (8.30%). The authors attributed its weaker performance to its lower density and its dolomite and chrysotile veinlets. They concluded that serpentinite rocks are promising radiation shields.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory experiment on rock samples: mineral, chemical, physical and thermal characterisation, plus measurement of fast neutron and gamma-ray attenuation through rock slabs using a collimated plutonium-beryllium (PuBe) source and a stilbene detector
• Who was studied: Three serpentinite rock samples from two locations in the Egyptian Eastern Desert. The antigorite serpentinite (AS) came from Gabal Umm Khasila. The lizardite (LS) and chrysotile (CS) serpentinites came from Wadi Atalla. Slabs 2, 4, 6, 8, 10 and 12 cm thick were tested. No people were studied.
• Exposure: Not a human exposure study. The rocks were exposed to fast neutrons in the 0.8 to 11 MeV range and gamma rays in the 0.4 to 8.3 MeV range from a PuBe source. The CS sample consisted mainly of chrysotile serpentine fibres; chrysotile also appeared as veinlets in the AS and LS samples.
• Main results:
  • Fast neutron attenuation of the three rocks ranked lizardite (LS) highest, then antigorite (AS), then chrysotile (CS).
  • Fast neutron removal cross-section, with statistical uncertainty from counting data at 1 sigma: AS 0.139 ± 0.011 per cm (half value layer 4.99 ± 0.40 cm); LS 0.168 ± 0.013 per cm (half value layer 4.13 ± 0.45 cm); CS 0.130 ± 0.010 per cm.
  • Gamma-ray attenuation followed the same order, LS > AS > CS.
  • Gamma-ray linear attenuation coefficient, with statistical uncertainty from counting data at 1 sigma: AS 0.106 ± 0.007 per cm (half value layer 6.54 ± 0.46 cm); LS 0.136 ± 0.01 per cm (half value layer 5.10 ± 0.36 cm); CS 0.096 ± 0.007 per cm.
  • Measured density (Table 2): AS 2.60, LS 2.46, CS 2.24 g/cm3.
  • Measured water absorption: AS 1.58%, LS 4.21%, CS 8.30%.
  • Thermal analysis showed the chrysotile sample had the lowest crystalline water content, even though it had the highest loss on ignition (17.16%). The authors attributed this to its dolomite content.
  • The authors attributed the chrysotile sample's lower gamma-ray performance to its lower density and to more dolomite and chrysotile veinlets.
  • The authors compared the three rocks with concrete mixes from their earlier studies, using values taken from those references. The rocks showed higher attenuation than some of those concrete mixes.
• The authors' conclusion: The authors concluded that serpentinite rocks are promising shields against fast neutrons and gamma rays in nuclear facilities. They judged the antigorite and lizardite rocks more suitable than the chrysotile rock.
• Limitations the authors state:
  • Neutron energies below 0.8 MeV and gamma-ray energies below 0.4 MeV were not considered. The authors did this to avoid background radiation and because detector efficiency was unreliable at low energies.

Topics

Medical terms in this study, explained in our Lexicon: Serpentinite, X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Lizardite, Antigorite, Chrysotile.

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