Effective dose scaling factors for use with uranium series cascade impactor data: a reassessment using the IMBA code

Area of Science:

• Radiological protection
• Environmental health
• Nuclear science

Background:

• Air sampling with cascade impactors assesses airborne radioactivity by particle size for accurate dose assessment.
• Previous methods using mono-sized distributions required computational effort for realistic distributions.
• Effective dose scaling factors (SF(E)) were introduced to simplify dose calculations with varied radioactivity distributions.

Purpose of the Study:

• To reexamine inhalation dose coefficients and effective dose scaling factors for (238)U series radionuclides.
• To update SF(E) values using the IMBA program with current ICRP biokinetic models.
• To assess the impact of updated models on dose calculations compared to previous methods.

Main Methods:

• Utilized the IMBA program with ICRP 69 biokinetic models for uranium.
• Calculated inhalation dose coefficients and effective dose scaling factors for (238)U series radionuclides.
• Compared results with previous calculations using the LUDEP code and ICRP 30 models.

Main Results:

• Inhalation dose coefficients differed up to a factor of 5 for Type F uranium but were similar for Type S.
• ICRP 69 model showed higher retention in bone/kidneys and significantly higher in liver/soft tissues than ICRP 30.
• Effective dose scaling factors from IMBA were nearly identical to LUDEP, indicating particle deposition and lung clearance are key factors, not biodistribution.

Conclusions:

• Updated effective dose scaling factors are nearly identical to previous values, validating their use.
• Significant dose re-scaling (>10%) is needed for certain particle sizes and distribution assumptions.
• The study confirms the utility of SF(E) for realistic airborne radioactivity dose assessments.