Source terms, shielding calculations and soil activation for a medical cyclotron

Area of Science:

• Nuclear Physics and Engineering
• Radiation Shielding and Dosimetry
• Environmental Safety

Background:

• Medical cyclotrons are essential for producing radioisotopes.
• Accurate assessment of radiation shielding and soil activation is crucial for operational safety and regulatory compliance.
• Neutron and gamma radiation from medical cyclotrons require careful characterization.

Purpose of the Study:

• To calculate shielding requirements for a medical cyclotron.
• To estimate soil activation levels resulting from cyclotron operations.
• To assess neutron and gamma dose rates in public areas outside the facility.

Main Methods:

• Neutron source term calculations using MCNP6 and FLUKA codes, and manufacturer-supplied data.
• Estimation of neutron and gamma dose rates using the MCNP6 Monte Carlo code.
• Soil activation analysis performed with the FLUKA code.

Main Results:

• MCNP6 and FLUKA calculations for neutron source terms showed comparable results.
• Manufacturer-supplied neutron yield was approximately five times lower than code calculations due to unconsidered reaction channels.
• Estimated dose rate in public areas was 0.035 µSv h⁻¹, significantly below the 0.5 µSv h⁻¹ reference value.
• Soil activity concentration reached approximately 0.34 Bq g⁻¹ after 5 years of operation and 30 days decay time.

Conclusions:

• The shielding and operational procedures for the medical cyclotron are adequate.
• Radiation levels are well within regulatory limits, ensuring public safety.
• FLUKA and MCNP6 are reliable tools for predicting radiation effects from medical cyclotrons.