Simplified organ retention functions for physiologically based recycling biokinetic models

Area of Science:

• Radiological protection
• Biokinetics
• Computational modeling

Background:

• International Commission on Radiological Protection (ICRP) is shifting towards complex, physiologically-based biokinetic models.
• These advanced models demand significant computational resources, limiting accessibility for many users.
• Previous models, like those in ICRP Publication 30, utilized simpler catenary models.

Purpose of the Study:

• To simplify complex physiologically-based biokinetic models for wider accessibility.
• To develop accurate approximations for plutonium biokinetics using fewer computational resources.
• To provide simplified expressions for organ retention and daily excretion rates of plutonium.

Main Methods:

• An eigenvalue method was employed to solve the plutonium biokinetic model from ICRP Publication 67.
• Organ retention expressions were derived for intakes via inhalation, ingestion, and injection.
• Least squares minimization was used to reduce complex expressions into sums of a few exponential terms.

Main Results:

• Simplified exponential functions accurately approximate plutonium retention in body compartments.
• These simplified functions yield committed doses with accuracy within 5%.
• Plutonium activity levels are predicted within 10% accuracy using the simplified models.
• Simplified expressions for daily plutonium excretion rates were also obtained.

Conclusions:

• Complex biokinetic models can be effectively simplified using sums of exponential functions.
• This simplification enhances accessibility without significant loss of accuracy in dose and activity assessments.
• The developed methods provide practical tools for radiological dose assessment involving plutonium.