Biokinetics of radionuclides and treatment of accidental intakes

This paper describes the objectives and reviews the progress of EULEP Working Party 5, convened under the auspices of the European Union's Fifth Framework Programme, to 'cluster' two EU-supported contracts, Biokinetics and Dosimetry of Internal Contamination (BIODOS (EU Contract FIS5-1999-00214)) and Radionuclide Biokinetics Database (EULEP) (RBDATA-EULEP (Concerted Action Contract FIS5-1999-00218), and two non-EU funded projects, Biokinetics of Radionuclides in Human Volunteers (RNHV (non-EU funded project)) and Treatment of Accidental Intakes of Radionuclides (TAIR (part funded by EULEP)).     

Assessment of doses to the offspring of the Techa River cohort due to intakes of radionuclides by the mother

The Techa River was contaminated as a result of radioactive releases by the Mayak plutonium production facility in 1949-1956. The residents of riverside communities were exposed to internal irradiation from radionuclides ingested mainly with river water, and also to external gamma irradiation resulting from shoreline and flood-plain contamination. The most important role in population exposure was played by (89,90)Sr and 137Cs. The persons born after the onset of the contamination have been identified as the 'Techa River Offspring Cohort' (TROC). The TROC has the potential to provide direct data on health effects in progeny that resulted from exposure of a general population to chronic radiation. This report describes the results of the calculation of fetal doses due to intakes of radionuclides by their mothers. Particular attention has been given to fetal dose from 90Sr because this nuclide is the most significant in terms of population dose for the Techa River. The comparison of the fetal bone marrow doses evaluated using different approaches proposed in the literature has shown a large dispersal in dose values. The main cause of this is the difference in model assumptions simplifying some developmental aspects of fetal haematopoiesis and bone formation. This paper presents an analysis of these basic assumptions that could be useful for further improvements in fetal dosimetry.     

Uncertainties in doses from intakes of radionuclides assessed from monitoring measurements

The evaluation of uncertainties in doses from intakes of radionuclides is one of the most difficult problems in internal dosimetry. In this paper, the process of assessing internal doses from monitoring measurements is reviewed and the major sources of uncertainty are discussed. Methods developed independently at HPA and at IRSN for the determination of uncertainties in internal doses assessed from monitoring measurements are described. Both use a Monte Carlo simulation approach. Results are described for three illustrative examples. An alternative method developed at the Los Alamos National Laboratory that uses Bayesian statistical methods is also described briefly.     

The development of protection standards for intakes of radionuclides (1955-2005)

The last 50 y has seen a dramatic increase in understanding of the behaviour of radionuclides in the body as well as of their effects. This has resulted in substantial improvements to the way that protection standards are set. This paper aims to chart the development of radiological protection as it applies to intakes of radionuclides by those who are occupationally exposed and by members of the public. It is not concerned with medical uses of radionuclides.     

Dose coefficients for the embryo and fetus following intakes of radionuclides by the mother

The International Commission on Radiological Protection has recently issued Publication 88, giving dose coefficients for the embryo, fetus and newborn child from intakes of selected radionuclides of 31 elements by the mother, either before or during pregnancy. The biokinetic models used for calculating these doses were based upon the available human data and the results of animal experiments. This paper summarises the approach used for the development of biokinetic and dosimetric models. It also compares the estimates of dose received by the offspring with those received by the reference adult. The main findings are that, in general, doses to the offspring are similar to or lower than those to the reference adult. For a few radionuclides, however, the dose to the offspring can exceed that to the adult. The reasons for these variations in comparative doses are examined.     

The computation of ICRP dose coefficients for intakes of radionuclides with PLEIADES: biokinetic aspects

The ICRP has published dose coefficients for the ingestion or inhalation of radionuclides in a series of reports covering intakes by workers and members of the public including children and pregnant or lactating women. The calculation of these coefficients conveniently divides into two distinct parts--the biokinetic and dosimetric. This paper gives a brief summary of the methods used to solve the biokinetic problem in the generation of dose coefficients on behalf of the ICRP, as implemented in the Health Protection Agency's internal dosimetry code PLEIADES.     

Content of uranium in urine of uranium miners as a tool for estimation of intakes of long-lived alpha radionuclides

Uranium in the urine of 10 uranium miners (hewers), 27 members of general population and 11 family members of miners was determined by the High-Resolution ICP-MS method. Concentration of uranium in urine of the miners was converted to daily excretion of (238)U under the assumption that the daily excretion of urine is 2 l and compared with the modelled excretion of (238)U. Daily excretion of (238)U was modelled using input data from personal dosemeters from a component for measurement of intake of long-lived alpha radionuclides. A reasonable agreement between evaluated and measured values was found. The uncertainty of inhalation intakes, derived from measurements of filters from personal dosemeters, and uncertainty of concentration of uranium in urine are discussed.     

Assessment of contributors to radiation dose following intakes of rapidly excreted [14C]-compounds

The International Commission on Radiological Protection default biokinetic model for the assessment of radiation dose received following intakes of unspecified [14C]-compounds (DCM) appears to overestimate the radiation doses delivered by many [14C]-compounds. The DCM does not specify the route of elimination and this review of the biokinetic data for four [14C]-compounds, [14C]sevelamer, [14C]colestipol, [14C]levetiracetam and [14C]ifetroban, that are rapidly lost from the human body via different excretory pathways, indicates that the excretory pathway is the critical determinant for both the individual tissue doses and the effective dose. If there is significant faecal excretion the DCM does not overestimate the effective dose.     

Assessment of doses and risk due to natural radionuclides in edible biota of Domiasiat, Meghalaya

A radiation dose assessment exercise was carried out for the edible biota Solanum nigrum, Carica papaya, Raphnus sativum and Phaseolus domesticus due to naturally available radionuclides (40)K, (238)U and (232)Th in the Domiasiat area in Meghalaya, India. The concentration of radionuclides in biota and corresponding soil was measured by the NaI(Tl) detector having a minimum detection limit (efficiency, 32.4%) and machine counting time of 3000 s. The obtained transfer factor for (40)K was 0.3061, 0.7163, 0.1988 and 0.1279, for (232)Th 0.0003, 2.22E-05, 2.71E-05 and 3.45E-05 and for (238)U 1.46E-05, 9.73E-05, 1.46E-05 and 3.11E-05 (ratio) in each biota, respectively. The detailed physiological and morphological study of the biota was carried out. The point source dose distribution (source?target) hypothesis was applied for the radiation absorbed fraction. The generated data were modelled using FASSET and obtained un-weighted total dose was 1.78E-04, 6.84E-03, 8.46E-03 and 1.73E-04 μGy h(-1), respectively, finally compared with the IAEA and UNSCEAR data set for screening level dose risk assessment.     

Assessment of radiological significance of naturally occurring radionuclides in soil and rock matrices around Kakrapar environment

The activity and gamma-absorbed dose rate due to the naturally occurring radionuclides in the terrestrial environment such as (238)U, (232)Th and (40)K were determined in soil and rock samples collected around Kakrapar Atomic Power Plant site, using gamma-ray spectrometry. The mean concentration levels measured in Kakrapar soil from naturally occurring radioisotopes such as (238)U, (232)Th and (40)K are lower than the corresponding global average values obtained in worldwide soil. The external hazard index (H(ex)) and absorbed gamma dose rate in air outdoors is observed to be 0.04-0.18 and 3.1-14.1 nGy h(-1), respectively.     

Assessment of solid reactive mixtures for the development of biological permeable reactive barriers

Solid reactive mixtures were tested as filling material for the development of biological permeable reactive barriers for the treatment of heavy metals contaminated waters. Mixture selection was performed by taking into account the different mechanisms operating in sulphate and cadmium removal with particular attention to bioprecipitation and sorption onto the organic matrices in the mixtures. Suspensions of eight reactive mixtures were tested for sulphate removal (initial concentration 3 g L⁻¹). Each mixture was made up of four main functional components: a mix of organic sources for bacterial growth, a neutralizing agent, a porous medium and zero-valent iron. The best mixture among the tested ones (M8: 6% leaves, 9% compost, 3% zero-valent iron, 30% silica sand, 30% perlite, 22% limestone) presented optimal conditions for SRB growth (pH 7.8 ± 0.1; E_h = −410 ± 5 mV) and 83% sulphate removal in 22 days (25% due to bioreduction, 32% due to sorption onto compost and 20% onto leaves). M8 mixture allowed the complete abatement of cadmium with a significant contribution of sorption over bioprecipitation (6% Cd removal due to SRB activity). Sorption properties, characterised by potentiometric titrations and related modelling, were mainly due to carboxylic sites of organic components used in reactive mixtures.     

Investigation of radionuclides in phosphogypsum

A determination was made of the content of uranium and²²⁶Ra in samples of phosphogypsum using gamma spectrometry. Translated from Izmeritel'naya Tekhnika, No. 3, pp. 64–68, March, 1999.     

Assessment and improvement of viscosity models for miscible binary and ternary liquid mixtures

Abstract

Experimental viscosities of 74 binary and 11 ternary systems, ranging from ideal to non‐ideal solutions, are compared with values calculated with several different equations, including five polynomial functions, to gain an insight of each method and the way of improvement.

The 2‐constant and 3‐body equations of McAllister and Heric seem adequate for most of the binary systems except those with the complex viscosity‐composition characters. The error distribution discloses for these two equations about 80% of the predicted values show an error below 1%. The proposed two polynomials η_m=A+Bx ₁ +Cx ² ₁ and η_m=A+Bx ₁ +Cx ² ₁ +Dx ³ ₁ are superior to any binary viscosity model when evaluated on the bases of simplicity, generality and over‐all accuracy. Mean errors for all two approaches rarely exceed 2–3% even for the system exhibits a strong non‐ideal behavior.

Of all the ternary viscosity models tested, the proposed two polynomial expressions η_m=A+Bx ₁ +Cx ² ₁ +Dx ₂ +Ex ² ₂ +Fx ₁ x ₂ and η_m= A+Bx ₁ +Cx ² ₁ +Dx ₂ +Ex ² ₂ +Fx ₁ x ₂ +Gx ₁ x ² ₂ +Hx ² ₁ x ₂ are the most reliable with mean deviations generally being smaller than 2%. A 5‐parameter polynomial η_m=A+Bx ₁ +Cx ² ₁ +Dx ₂ +Ex ² ₂ proposed by us and the Ausländer formula are also recommended as two relatively simple methods of evaluating the ternary viscosities with reasonable accuracy for many practical purposes.     

The medical management of unintentional radionuclide intakes

As a general medical problem, radionuclide intakes that may cause significant health effects are uncommon events. In preparing to manage a radionuclide accident, planning is the key. The medical aspects of such an accident are only one part of the management, and a professional team approach is required. Specific priorities and sequencing are necessary in medically managing a radionuclide intake. As soon as is reasonably practical, promptly remove the victim(s) from further radionuclide, radiation field, or chemical exposure. Life and limb-saving medical aid takes precedence over ionising radiation concerns in nearly all cases. Next are the prevention and/or minimisation of internal intake of radionuclides and evaluation and control of external radionuclide contamination, followed by institution of treatment to minimise the retained radionuclide. Communication with the accident victim, and his or her family, and public affairs/media issues are important. Finally, follow-up treatment for internal intakes that may cause delayed health effects is given.     

Assessment of the radiological hazards due to naturally occurring radionuclides in soil samples collected from the north western areas of Pakistan

(226)Ra, (232)Th and (40)K were measured in soil samples, these were collected from different localities of the North West Frontier Province and Federally Administered Tribal Areas, Pakistan. In order to measure the specific activities in these samples P-type coaxial high purity germanium based gamma-ray spectrometer was used. Average values of the measured activities of (226)Ra, (232)Th and (40)K were 26 +/- 11, 39 +/- 17 and 485 +/- 177 Bq kg(-1), respectively. Average radium equivalent activity was found to be 122 +/- 42 Bq kg(-1). External and internal hazard indices were also calculated and found to be 0.33 +/- 0.12 and 0.40 +/- 0.14, respectively. Average effective dose received due to gamma rays was 0.34 +/- 0.12 mSv y(-1). Measured natural radioactivity, hazard indices and effective doses received by the population were found within the recommended limits. The aim of this work was to make a baseline data of natural radioactive elements for the soil of the area and to assess it radiological significance if used as a building material for the construction of houses.     

Determining activities of radionuclides from coincidence signatures

The spectral analysis of simultaneously observed photons in separate detectors may provide an invaluable tool for radioisotope identification applications. A general recursive method to determine the activity of an isotope from the observed coincidence signature rate is discussed. The method coherently accounts for effects of true coincidence summing within a single detector and detection efficiencies. A verification of the approach with computer simulations is also discussed.