Dating of a quaternary limestone cave by combining the SSNTD technique with paleodose measurements: application to the stalagmite and stalactite growth

Abstract Uranium ( 238 U) and thorium ( 232 Th) contents were evaluated in di erent stalagmite and stalactite samples belonging to a quaternary limestone cave by using a method based on determining mean critical angles of etching of the CR-39 and LR-115 II solid-state nuclear track detectors (SSNTDs). Annual absorbed -, ÿ-and -dose rates were determined in the stalagmite and stalactite materials. The stalagmite and stalactite samples were dated by exploiting data obtained for the total annual absorbed dose rates and measuring the corresponding paleodoses. Results obtained were compared with those obtained by classic thermoluminescence and U=Th disequilibrium methods. The studied speleothem began from about 121 kyr and continued to about 69 kyr, coinciding almost with the last interglaciation corresponding to the fourth and ÿfth isotope stages. The formation rates of the stalagmite and stalactite samples were found equal to 0.88 and 0:94 cm kyr −1 , respectively

<span style="font-size:10.0pt;font-family: "Times New Roman";mso-fareast-font-family:"Times New Roman";mso-bidi-font-family: Mangal;mso-ansi-language:EN-GB;mso-fareast-language:EN-US;mso-bidi-language: HI" lang="EN-GB">Study of ²³⁸U, ²³²Th, ²²²Rn and ²²⁰Rn contents in various samples by using solid state nuclear track detector</span>

685-696Coffee and green tea drinks as well as sugar are widely consumed by Moroccan population. 238U, 232Th, 222Rn and 220Rn contents have been measured inside different soil, sugar beet and table sugar material samples collected in different areas of Morocco by using CR-39 and LR-115 type II solid state nuclear track detectors (SSNTDs). The transfer of contents 238U, 232Th and 222Rn between soil and sugar beet and that between sugar beet and table sugar has been measured. To explore the exposure pathway of 238U, 232Th and 222Rn to the organs and tissues of consumers from the ingestion of coffee and green tea drinks, contents of these radionuclides have been measured in the drinks. The effect of the nature water and pollution on the concentrations of these radionuclides in coffee and green tea has been investigated. Annual committed effective doses due to 238U, 232Th and 222Rn from the ingestion of table sugar and coffee and green tea drinks by the members of the general public and workers have been determined. The maximum total committed effective dose due to 238U, 232Th and 222Rn from the ingestion of tea drinks by the members of the Moroccan rural population was found to be equal to 0.13 mSv y-1

Determination of the gamma-ray effective dose from different cylindrical radioactive solution sources in a biological tissue by using Monte Carlo calculations

A new method was developed based on calculating the absorption coefficients, self-absorption coefficients and transmission coefficients of the gamma-photons emitted by different radioisotopes for evaluating gamma dose equivalent rates, at 1 meter from various cylindrical radioactive solution sources utilized in medicine, in a biological tissue. Results obtained were compared with data given in literature. The influence of the radioisotope half-life and gamma-photon energy and number of photons per disintegration on the gamma dose equivalent rate, effective dose and threshold initial activity of the considered solution sources was studied

U and

Uranium (238U) and thorium (232Th) concentrations were measured in different foods widely consumed in Morocco by using CR-39 and LR-115 type II solid state nuclear track detectors (SSNTDs). Data obtained were compared to those obtained by using isotope dilution mass spectrometry (IDMS). Total daily intakes of 238U and 232Th for a typical food basket were estimated to be 1.3 ± 0.1 mBq d-1 and 0.98 ± 0.08 mBq d-1, 1.4 ± 0.1 mBq d-1 and 1.06 ± 0.08 mBq d–1, 1.7 ± 0.1 mBq d–1 and 1.26 ± 0.08 mBq d–1 and 2.0 ± 0.1 mBq d–1 and 1.5 ± 0.1 Bq d–1 for the 2–7 years, 7–12 years, 12–17 years and adult’s age groups, respectively. Alpha-activities due to annual 238U and 232Th intakes from the ingestion of the studied foodstuffs were determined in different organs and tissues of the human body of members of the public by using the ICRP gastrointestinal tract and systemic part models for these radionuclides. Committed equivalent doses due to annual intakes of 238U and 232Th were evaluated in the human body organs and tissues for different age groups of the Moroccan population by exploiting data obtained for alpha-doses deposited by 1 Bq of 238U and 1 Bq of 232Th in the considered human organs and tissues. The influence of the mass of the target tissue and activities due to 238U and 232Th on the committed equivalent doses due to annual intakes of these radionuclides in the organs and tissues of the human body was studied