Electronic equilibrium as a function of depth in tissue from cobalt-60 point source exposures

Thesis/Dissertation · Mon Aug 01 04:00:00 EDT 1994

DOI:https://doi.org/10.2172/471437· OSTI ID:471437

Myrick, Jo Ann ^[1]

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1. Texas A & M Univ., College Station, TX (United States)

The Nuclear Regulatory Commission has set the basic criteria for assessing skin dose stemming from hot particle contaminations. Compliance with 10 CFR 20.101 requires that exposure to the skin be evaluated over a 1 cm² area at a depth of 0.007 cm. Skin exposure can arise from both the beta and gamma components of radioactive particles and gamma radiation can contribute significantly to skin doses. The gamma component of dose increases dramatically when layers of protective clothing are interposed between the hot particle source and the skin, and in cases where the hot particle is large in comparison to the range of beta particles. Once the protective clothing layer is thicker than the maximum range of the beta particles, skin dose is due solely to gamma radiation. Charged particle equilibrium is not established at shallow depths. The degree of electronic equilibrium establishment must be assessed for shallow doses to prevent the over-assessment of skin dose because conventional fluence-to-dose conversion factors are not applicable. To assess the effect of electronic equilibrium, selected thicknesses of tissue equivalent material were interposed between radiochromic dye film and a ⁶⁰Co hot particle source and dose was measured as a function of depth. These measured values were then compared to models which are used to calculate charged particle equilibrium. The Miller-Reece model was found to agree closely with the experimental data while the Lantz-Lambert model overestimated dose at shallow depths.

• Research Organization: Oak Ridge Associated Universities, Inc., TN (United States)
• Sponsoring Organization: USDOE Assistant Secretary for Environment, Safety, and Health
• DOE Contract Number: AC05-76OR00033
• OSTI ID: 471437
• Report Number(s): ORISE--97052305; ON: DE97052305
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
BETA PARTICLES
COBALT 60
CONTAMINATION
GAMMA RADIATION
LAYERS
OCCUPATIONAL EXPOSURE
PROTECTIVE CLOTHING
RADIATION DOSES
SKIN