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Petrographic examination of iron-ore and colemanite aggregates used in radiation shielding concrete
Radiation shielding concrete (RSC) is used in applications such as nuclear power plants, health care facilities, collegiate test reactors, national laboratories, and research facilities. The type and quantity of aggregates in RSC are important component for radiation protection properties of the concrete. Either natural heavyweight aggregates or synthetic aggregates are used in RSC. ASTM C638 Standard provides two classes of aggregates/materials used in RSC; (1) Class 1 - gamma ray shielding, and (2) Class 2 - neutron shielding. Iron ores are one of the most common Class 1 natural aggregates for gamma ray shielding. Colemanite is the most common Class 2 natural aggregate. Minerals with substantial boron content, such as colemanite, have been proven to be particularly effective in absorbing thermal neutrons without producing highly penetrating gamma rays. Iron ore and colemanite aggregate samples were petrographically examined in accordance with ASTM C295 to detect potentially harmful (deleterious and undesirable) materials in RSC. Each sieve fraction of an aggregate sample was examined, and its constituents identified, classified, and tabulated into the following three categories: (1) particles consisting almost entirely of ironbearing metallic minerals (or boron minerals for the "colemanite" aggregate), (2) particles of mixed iron-bearing metallic minerals and impure materials, and (3) particles of impure materials. Particles in each category were examined using different test methods and techniques (combinations of transmitted and reflected light microscopy, X-ray diffraction, and X-ray fluorescence) to determine potentially harmful materials in RSC. Although ASTM C295 applies to aggregates for general use as well as for RSC, petrographic examination of these specialized aggregates for RSC involves in more stringent QA requirements, different levels and extent of examination, and proper experience and training of the petrographer performing the examination.
Petrographic examination of iron-ore and colemanite aggregates used in radiation shielding concrete
Radiation shielding concrete (RSC) is used in applications such as nuclear power plants, health care facilities, collegiate test reactors, national laboratories, and research facilities. The type and quantity of aggregates in RSC are important component for radiation protection properties of the concrete. Either natural heavyweight aggregates or synthetic aggregates are used in RSC. ASTM C638 Standard provides two classes of aggregates/materials used in RSC; (1) Class 1 - gamma ray shielding, and (2) Class 2 - neutron shielding. Iron ores are one of the most common Class 1 natural aggregates for gamma ray shielding. Colemanite is the most common Class 2 natural aggregate. Minerals with substantial boron content, such as colemanite, have been proven to be particularly effective in absorbing thermal neutrons without producing highly penetrating gamma rays. Iron ore and colemanite aggregate samples were petrographically examined in accordance with ASTM C295 to detect potentially harmful (deleterious and undesirable) materials in RSC. Each sieve fraction of an aggregate sample was examined, and its constituents identified, classified, and tabulated into the following three categories: (1) particles consisting almost entirely of ironbearing metallic minerals (or boron minerals for the "colemanite" aggregate), (2) particles of mixed iron-bearing metallic minerals and impure materials, and (3) particles of impure materials. Particles in each category were examined using different test methods and techniques (combinations of transmitted and reflected light microscopy, X-ray diffraction, and X-ray fluorescence) to determine potentially harmful materials in RSC. Although ASTM C295 applies to aggregates for general use as well as for RSC, petrographic examination of these specialized aggregates for RSC involves in more stringent QA requirements, different levels and extent of examination, and proper experience and training of the petrographer performing the examination.
Petrographic examination of iron-ore and colemanite aggregates used in radiation shielding concrete
Petrographische Untersuchung von Eisenerz und Colemanit-Zuschlägen, verwendet in Strahlenschutz-Beton
Lee, Sang Y. (author) / Daugherty, Ann (author) / Broton, Donald (author)
2013
16 Seiten, 4 Bilder, 4 Tabellen, 14 Quellen
Conference paper
English
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