Beta skin dose determination using TLDs, Monte-Carlo calculations, and extrapolation chamber.

Area of Science:

• Radiation Dosimetry
• Applied Nuclear Physics
• Health Physics

Background:

• Accurate measurement of beta radiation doses is crucial for radiation protection and medical applications.
• Thermoluminescent dosimeters (TLDs) are widely used for dose assessment but can exhibit energy-dependent responses.
• Understanding discrepancies between dosimetry methods is essential for reliable dose determination.

Purpose of the Study:

• To compare beta dose measurements from 90Sr-Y and 204Tl sources using Monte-Carlo simulations, TLDs, and an extrapolation chamber.
• To identify and quantify the impact of TLD nonlinear response on beta dose measurements.
• To evaluate the accuracy of low-energy beta dose determination and assess errors related to TLD shielding.

Main Methods:

• Monte-Carlo N-Particle (MCNP) transport code for simulating beta particle interactions.
• Thermoluminescent dosimetry (TLD) using standard elements and varying shield thicknesses.
• Extrapolation chamber measurements for direct skin dose assessment.

Main Results:

• Excellent agreement was observed between Monte-Carlo calculations, TLDs, and extrapolation chamber measurements for beta dose determination.
• TLD nonlinear response led to approximately 20% higher doses for 90Sr-Y and 5% lower doses for 204Tl.
• Minimum TLD shield thickness (13 mg cm-2) prevents direct skin dose measurement for low-energy beta particles, necessitating extrapolation or thinner shields.

Conclusions:

• Monte-Carlo simulations, TLDs, and extrapolation chambers provide consistent beta dose results when TLD nonlinearities are accounted for.
• TLD shielding thickness significantly impacts low-energy beta skin dose accuracy, highlighting the need for thinner shields or data extrapolation.
• Further research into TLD materials and shielding is required for precise low-energy beta dosimetry.