Evaluation of Th series disequilibrium in Western Australian monazite

Journal Article · Thu Feb 01 04:00:00 EST 1990 · Health Physics; (USA)

DOI:https://doi.org/10.1097/00004032-199002000-00002· OSTI ID:6996364

Kerrigan, G C; O'Connor, B H ^[1]

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1. Curtin Univ. of Technology, Perth (Western Australia)

Estimation of inhaled radiation doses associated with mineral sands processing is commonly performed by gross alpha-counting dust collected on air filters. The technique requires knowledge of the extent of disequilibrium in Th-bearing minerals. The daughters which can be expected to give rise to disequilibrium, viz. {sup 228}Ra and {sup 220}Rn (designated thoron), were investigated in a typical Western Australia monazite. The thoron flux from a dry, infinitely thick layer of monazite was found to be 41 Bq m-2 s-1. The depth of monazite from which thoron is exhaled is limited to 40-50 mm, and within the first 10 mm is a linear function of bed thickness. The relative loss within the linear region is approximately 0.02% of the equilibrium concentration and progressively less for layers beyond 10 mm. The sample investigated gave no indication of disequilibrium involving {sup 228}Ra. The results indicate that secular equilibrium may be assumed when calculating {sup 232}Th daughter concentrations in monazite from the gross alpha activity. More extensive work on monazite samples from a number of sites will be necessary before this can be stated as a general conclusion applicable to all Western Australian monazite deposits.

• OSTI ID: 6996364
• Journal Information: Health Physics; (USA), Journal Name: Health Physics; (USA) Vol. 58:2; ISSN 0017-9078; ISSN HLTPA
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540130* -- Environment
Atmospheric-- Radioactive Materials Monitoring & Transport-- (1990-)
ACTINIDE COMPOUNDS
ACTINIDES
AIR POLLUTION
ALKALINE EARTH ISOTOPES
ALPHA DECAY RADIOISOTOPES
AUSTRALASIA
AUSTRALIA
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
DAUGHTER PRODUCTS
ECOLOGICAL CONCENTRATION
ELEMENTS
EVEN-EVEN NUCLEI
HALF-LIFE
HEAVY NUCLEI
ISOTOPES
MATERIALS
METALS
MINERALS
MONAZITES
MONITORING
NUCLEI
OXYGEN COMPOUNDS
PHOSPHATES
PHOSPHORUS COMPOUNDS
POLLUTION
RADIATION MONITORING
RADIOACTIVE MATERIALS
RADIOACTIVE MINERALS
RADIOECOLOGICAL CONCENTRATION
RADIOISOTOPES
RADIUM 228
RADIUM ISOTOPES
RADON 220
RADON ISOTOPES
RARE EARTH COMPOUNDS
SECONDS LIVING RADIOISOTOPES
THORIUM
THORIUM COMPOUNDS
THORIUM MINERALS
THORIUM PHOSPHATES
YEARS LIVING RADIOISOTOPES