TY - JOUR

T1 - Nuclear Chemical Effects in the Paragenetic Mineral Association Based on Polycrase

AU - Hosseinpour Khanmiri, M.

AU - Bogdanov, R. V.

PY - 2018/1/1

Y1 - 2018/1/1

N2 - A natural polymineral compound in which the major uranium-containing mineral is polycrase (Ti- Ta-niobate) described by the formula АВ2О6 was chosen as a model for studying the behavior of recoil atoms produced by α-decay of actinides. Polycrase, despite its metamict structure, is characterized by the following features distinguishing it from Ti-Ta-niobates of the formula А2В2О7 (pyrochlore and betafite): (1) 1/3 of uranium atoms preserve the initial valence state, U(IV); (2) the U(IV) fraction is characterized by the isotope activity ratio AR(234U/238U) close to that at secular equilibrium; (3) the uranium atoms that underwent oxidation “memorize” their radiogenic origin; as a result, the AR(234U/238U) ratio in the U(VI) fraction is 0.90, and in the most altered part of the mineral it decreases to 0.77; (4) the parent uranium is relatively stable in the metamict structure of polycrase: The half-leaching time for 238U atoms is 2 times longer than that in betafite, zircon, or sphene.

AB - A natural polymineral compound in which the major uranium-containing mineral is polycrase (Ti- Ta-niobate) described by the formula АВ2О6 was chosen as a model for studying the behavior of recoil atoms produced by α-decay of actinides. Polycrase, despite its metamict structure, is characterized by the following features distinguishing it from Ti-Ta-niobates of the formula А2В2О7 (pyrochlore and betafite): (1) 1/3 of uranium atoms preserve the initial valence state, U(IV); (2) the U(IV) fraction is characterized by the isotope activity ratio AR(234U/238U) close to that at secular equilibrium; (3) the uranium atoms that underwent oxidation “memorize” their radiogenic origin; as a result, the AR(234U/238U) ratio in the U(VI) fraction is 0.90, and in the most altered part of the mineral it decreases to 0.77; (4) the parent uranium is relatively stable in the metamict structure of polycrase: The half-leaching time for 238U atoms is 2 times longer than that in betafite, zircon, or sphene.

KW - actinide immobilization

KW - chemical effects of α-decay

KW - incongruent dissolution

KW - metamict minerals

KW - mineral-like HLW matrices

KW - titano-tantalo-niobates

KW - uranium and thorium isotopes

KW - ACID-RESIDUES

KW - HIGH-LEVEL

KW - URANIUM

KW - ALPHA-RECOIL

KW - THORIUM

KW - DECAY

KW - COLORADO CARNOTITE

KW - MONAZITE

KW - chemical effects of alpha-decay

KW - PYROCHLORE

KW - RADIATION-DAMAGE

UR - http://www.scopus.com/inward/record.url?scp=85043326111&partnerID=8YFLogxK

U2 - 10.1134/S1066362218010137

DO - 10.1134/S1066362218010137

M3 - Article

AN - SCOPUS:85043326111

VL - 60

SP - 79

EP - 91

JO - Radiochemistry

JF - Radiochemistry

SN - 1066-3622

IS - 1

ER -