Dose to lung from inhaled tritiated particles

Area of Science:

• Radiological physics
• Occupational health
• Nuclear safety

Background:

• Tritiated particulate materials present hazards in tritium handling facilities.
• Current safety guidelines (ICRP Publication 71) assume complete energy absorption for tritium in the alveolar-interstitial (AI) region.
• Accurate dose assessment requires precise calculation of absorbed fractions.

Purpose of the Study:

• To calculate absorbed fractions for tritiated particles deposited in the alveolar-interstitial (AI) region of the respiratory tract.
• To evaluate the energy deposition in alveolar tissue from various tritiated materials.
• To determine the committed equivalent dose to alveolar tissue for adult male workers inhaling these particles.

Main Methods:

• Employed Monte Carlo methods to model energy deposition in alveolar sac walls.
• Utilized the ICRP 66 lung model and Mercer's (1967) particle dissolution model.
• Calculated absorbed fractions for tritiated beryllium, graphite, titanium tritide, iron hydroxide, and zirconium tritide particles of 1 and 5 micrometers.

Main Results:

• Absorbed fractions in alveolar tissue varied significantly with particle size, ranging from 0.31-0.61 (1 microm) and 0.07-0.21 (5 microm).
• For 5 microm particles, the committed equivalent dose to alveolar tissue was 32-42% lower than estimates assuming absorbed fractions of unity.
• Energy absorbed in lung regions outside the AI region was negligible.

Conclusions:

• The assumption of absorbed fraction unity for tritium in the AI region is an overestimation.
• Calculated absorbed fractions provide a more realistic basis for dose assessment in occupational settings.
• These findings are crucial for refining radiation protection strategies in tritium handling facilities.