Total effective dose equivalent assessment after exposure to high-level natural radiation using the RESRAD code

Area of Science:

• Environmental Science
• Radiological Science
• Geochemistry

Background:

• The Khak-Sefid area in Ramsar, Iran, is known for elevated natural radiation levels.
• Understanding radionuclide activity concentrations and their associated health risks is crucial for public safety.

Purpose of the Study:

• To quantify the activity concentrations of radium-226 (Ra-226), thorium-232 (Th-232), and potassium-40 (K-40) in the Khak-Sefid area.
• To evaluate the total effective dose equivalent (TEDE) for different population groups.
• To assess potential remediation strategies for high radiation exposure.

Main Methods:

• Soil samples were analyzed using a high-purity germanium detector.
• Total effective dose equivalent (TEDE) was calculated using the Residual Radioactive Material Guidelines (RESRAD) modeling program.
• Exposure scenarios were developed for farmers, construction workers, and residents.

Main Results:

• Mean activity concentrations were 23,118 ± 468 Bq/kg for Ra-226, 25.8 ± 2.3 Bq/kg for Th-232, and 402.6 ± 16.5 Bq/kg for K-40.
• Maximum calculated TEDE exceeded the safe dose limit of 1 mSv/year for all scenarios, particularly for farmers.
• RESRAD modeling indicated that a soil cover of 50 cm or more could reduce the farmer scenario TEDE below the safe limit.

Conclusions:

• The high activity concentrations of Ra-226 in the Khak-Sefid area pose a significant radiological risk.
• Effective dose equivalents for all critical groups exceed international safety standards.
• Soil cover is a viable remediation strategy to mitigate radiation exposure and ensure public health.