A practical method for assessment of dose conversion coefficients for aquatic biota

Abstract

Radiological impact assessment for flora and fauna requires adequate dosimetric data. Due to the variability of habitats, shapes, and masses of the non-human biota, assessment of doses is a challenging task. External and internal dose conversion coefficients for photons and electrons have been systematically calculated by Monte Carlo methods for spherical and ellipsoidal shapes in water medium. An interpolation method has been developed to approximate absorbed fractions for elliptical shape organisms from absorbed fractions for spherical shapes with reasonable accuracy. The method allows an evaluation of dose conversion coefficients for arbitrary ellipsoids for photon and electron sources with energies from 10 keV to 5 MeV, and for organism masses in the range from 10(-6) to 10(3) kg. As an example of the application of the method, a set of dose coefficients for aquatic organisms discussed as reference animals and plants in a draft of an up-coming publication of the International Commission on Radiological Protection has been determined.

Uncertainties of internal dose assessment for animals and plants due to non-homogeneously distributed radionuclides

“…Uncertainties of whole body DCC for internal exposure due to non-homogeneously distributed sources Previously reported DCCs for the internal exposure of reference organisms (Taranenko et al, 2004;Ulanovsky and Pröhl, 2006;Ulanovsky et al, 2008) were calculated assuming a homogeneous distribution of photon and electron sources within the whole body of the considered organisms. Because the defined reference organisms are approximated by elliptical phantoms without any internal structure, it seems rather meaningless to calculate new sets of DCCs for any arbitrary distribution of the internal contaminant within the organism.…”

“…In particular, Eq. (5) could be used to obtain a more accurate estimation of the organ dose using the corresponding values of the absorbed fraction for a spherical shape organ of a given mass in a water medium (Ulanovsky and Pröhl, 2006) to approximate fðE; S)SÞ, and the average activity concentration per unit mass in the organ, A/m.…”

“…These reference organisms were defined as ''entities that provide a basis for the estimation of radiation dose rate to a range of organisms which are typical, or representative, of a contaminated environment'' and, consequently, they do not correspond to actual individuals or species but consist of three dimensional ellipsoidal phantoms used to calculate internal and external dose rates per unit activity concentration in animals and plants of a given size (Amiro, 1997;Vives i Batlle et al, 2004;Taranenko et al, 2004;Ulanovsky and Pröhl, 2006;Ulanovsky et al, 2008).…”

Utilização De Peixes Como Biomonitor Para Fins De Radioproteção Ambiental Em Ecossistemas Aquáticos Continentais. Um Modelo Conceitual

“…Utiliza modelos ecológicos para avaliar as alterações de biomassa do ecossistema, um modelo de distribuição de radionclídeos para avaliar o comportamento dos radionuclídeos nos meios bióticos e abióticos, e por fi m um modelo de avaliação de dose, promovendo uma visão integrada desde o termo fonte até a avaliação de dose. Ulanovsky & Prohl (2006) desenvolvem uma formulação matemática das possíveis geometrias dos organismos, entre eles dos peixes e, utilizando metodologia baseado em simulação de Monte Carlo aponta as frações de energia absorvida pelos peixes.…”

External Dose Conversion Coefficients to Assess the Radiological Impact of an Environmental Radiation on Aquatic and Terrestrial Animals

“…6) The absorbed energy fraction was determined by the empirical equation associated with the Monte Carlo simulation, which was developed by Ulanovsky and Pröhl. 4) …”