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Update on Dose Coefficients for Internal Exposures to Workers and the Public

Dose coefficients are essential to the practical implementation of the system of radiological protection. Significant progress is being made on preparing a comprehensive set of dose coefficients for occupational and public internal exposure based on ICRP Publication 103.

Dose coefficients rely on physical data and anatomical and biokinetic models. Publication 107 provides nuclear decay data. Publication 110 presents adult reference computational phantoms using voxels (three-dimensional pixels) to define organs and tissues within the body. Using these phantoms, Publication 133 provides Specific Absorbed Fractions, an important intermediate step in the calculation of organ and tissue doses from radionuclides retained in body tissues.

The Occupational Intakes of Radionuclide (OIR) series of publications presents biokinetic models, using these along with decay data and the adult voxel phantoms with their SAFs to calculate dose coefficients for occupational exposure.Publication 130 (OIR part 1) describes the methodology. Publication 134 (OIR part 2) and Publication 137 (OIR part 3) provide dose coefficients and bioassay data for:  H, C, P, S, Ca, Fe, Co, Zn, Sr, Y, Zr, Nb, Mo, and Tc in OIR part 2, and: Ru, Sb, Te, I, Cs, Ba, Ir, Pb, Bi, Po, Rn, Ra, Th, and U in OIR part 3.

OIR part 4 is nearing completion, covering: La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Ac, Pa, Np, Pu, Am, Cm, Bk, Cf, Es, and Fm. OIR part 5 will cover the remaining, less commonly encountered elements and radioisotopes. This last report in the OIR series will take additional time to complete as biokinetic data are difficult to obtain.

Dose coefficients for public exposure are also underway. These require anatomical models for adults, infants, and children, as well as the pregnant woman and embryo/fetus. These computational phantoms are complete and will be published soon, followed by a publication providing SAF values. They, and the already published adult phantoms, are already being used to compute dose coefficients for public exposure to adults, infants, and children of various ages. These will be published in two parts, one covering the elements in OIR parts 2-4, and one covering the elements in OIR part 5. The former should be published shortly after OIR part 4, while the latter, like OIR part 5, will take additional time. Dose coefficients will also be published for the embryo/fetus, and the breast-fed infant.

For more information on dose coefficients, see the ICRPædia Guide to Dose Coefficients.