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The CONRAD Project is a Coordinated Network for Radiation Dosimetry funded by the European Commission 6th Framework Programme. The activities developed within CONRAD Work Package 5 ('Coordination of Research on Internal Dosimetry') have contributed to improve the harmonisation and reliability in the assessment of internal doses. The tasks carried out included a study of uncertainties and the refinement of the IDEAS Guidelines associated with the evaluation of doses after intakes of radionuclides. The implementation and quality assurance of new biokinetic models for dose assessment and the first attempt to develop a generic dosimetric model for DTPA therapy are important WP5 achievements. Applications of voxel phantoms and Monte Carlo simulations for the assessment of intakes from in vivo measurements were also considered. A Nuclear Emergency Monitoring Network (EUREMON) has been established for the interpretation of monitoring data after accidental or deliberate releases of radionuclides. Finally, WP5 group has worked on the update of the existing IDEAS bibliographic, internal contamination and case evaluation databases. A summary of CONRAD WP5 objectives and results is presented here.

The EUropean RAdiation DOSimetry Group (EURADOS) initiated in 2005 the CONRAD Project, a Coordinated Network for Radiation Dosimetry funded by the European Commission (EC), within the 6th Framework Programme (FP). The main purpose of CONRAD is to generate a European Network in the field of Radiation Dosimetry and to promote both research activities and dissemination of knowledge. The objective of CONRAD Work Package 5 (WP5) is the coordination of research on assessment and evaluation of internal exposures. Nineteen institutes from 14 countries participate in this action. Some of the activities to be developed are continuations of former European projects supported by the EC in the 5th FP (OMINEX and IDEAS). Other tasks are linked with ICRP activities, and there are new actions never considered before. A collaboration is established with CONRAD Work Package 4, dealing with Computational Dosimetry, to organise an intercomparison on Monte Carlo modelling for in vivo measurements of 241Am deposited in a knee phantom. Preliminary results associated with CONRAD WP5 tasks are presented here. © The Author 2007. Published by Oxford University Press. All rights reserved.

Emergency response plans have long been focused on accidents at nuclear power plants. Recently, the malevolent use of radiation aimed at creating disruption in the society has been considered as a possible threat. In this kind of emergency situations casualties will most likely be members of the public and the number of affected people can vary from a few to mass casualties. There is an evident need for rapid measurements of large groups of internally contaminated people. Radiation and Nuclear Safety Authority (STUK) in Finland has obtained new monitors for thyroid and simple whole-body measurements in field conditions as a part of the continuous improving of emergency preparedness. The new monitors consist of a NaI(Tl) detector and a control unit. The monitors work as spectrometers allowing real-time spectrum analysis in the field.

Urine monitoring is the preferred method to determine exposure to soluble compounds of uranium in workplaces. The interpretation of uranium contents in workers bioassay samples requires knowledge on uranium excretion and its dependence on intake by diet. Exceptionally high concentrations of natural uranium in private drinking water sources have been measured in the granite areas of Southern Finland. Consequently, high concentrations of natural uranium have been observed in the urine and hair samples of people using water from their own drilled wells. Natural uranium content in urine and hair samples of family members, who use uranium-rich household water, have been analyzed by using ICP-MS. The uranium concentrations both in urine and hair samples of the study subjects were significantly higher than the world-wide average values. In addition, gammaspectrometric methods have been tested for determining uranium in hair samples. This method can be used only for samples with highly elevated uranium concentrations.

In a preliminary study, in vivo skull measurements and in vitro urine measurements of 210 Pb and nat U have been performed to find out the individual, chronic exposure to waterborne natural radionuclides of a small group of Finnish people. For their domestic water, the studied individuals use water from drilled wells containing elevated concentrations of natural uranium and its daughter nuclides ( 234,235,238 U, 222 Rn, 226,228 Ra, 210 Po, 210 Pb). Enhanced 210 Pb and 235 U activities were observed in several people. A positive correlation is observed between the U concentration in urine (μg d -1 ) and the number of counts (cpm) in the gamma ray energy peaks originating from the decay of 235 U and 234 Th respectively. Calibration of the detector setup and the determination of background sources are in progress.

The aim of this study was to estimate the current concentrations of 90 Sr and 137 Cs in the urine of Finnish people and to estimate the doses. Two to three daily urine samples were collected from 18 adult Finnish volunteers in connection with studies of 137 Cs body burdens in 1999-2001. The 90 Sr activities in urine varied between 1.4 and I 1 mBq I 1 The 137 C, activity in urine varied between 0.36 and 56 Bq 1 1 . The daily urinary excretion was found to he 4.8-17 mBq for 90 Sr and 0.81-68 Bq for 137 Cs. Assuming that the daily 90 Sr intake was constant and that 18% of the infested activity was excreted in urine, the mean intake in the investigated group would vary between 27 and 96 mBq d 1 . Based on these estimated intake values the respective annual effective internal doses iron 90 Sr and 90 Y varied from 0.3 to 1.0 μSv and from 137 Cs from 4 to 350 μSv during the sampling period.

In a large village, Veprin of the Bryansk region of Russia contaminated with radionuclides as a result of the Chemobyl accident, 137 Cs concentration in food products of agricultural produce and natural origin was regularly measured, local inhabitants were polled on the composition of their diet, and the 137 Cs content in their bodies was measured at the same time. These results were used as the basis for calculation of annual effective doses of internal exposure to inhabitants and for reconstruction of the dose during the entire period after the accident (1986-1996). The efficiency of countermeasures performed for reduction of the internal dose was assessed. The internal dose in inhabitants during the 10 years after the accident was shown to be reduced by countermeasures by a factor of 2, namely down to 35 mSv instead of the expected 70 mSv. The dose of external gamma radiation during the same time period is close to the obtained dose of internal exposure. The presence of peat and water-meadow soils in the vicinity of this village that are characterised by high transfer factors for radionuclides from soil to vegetation causes a high contribution of internal exposure to the total dose of population exposure. The contribution of natural products to the internal dose increased from 6% in 1987 increased to 25% in 1996. The individual content of 137 Cs in the body of inhabitants reliably correlates with consumption of milk in the initial period after the accident and with consumption of forest mushrooms in the subsequent period.

Three types of modular phantom were tested. All can be assembled to fit different geometries and to simulate different body masses. The radionuclide distribution is homogeneous in each module, but uneven distributions in the body can be simulated. The basic modular phantom consisted of flat plastic bottles filled with calibrated radionuclide solutions. An improved version was filled with a solution of plastic monomers, that was polymerised with gamma radiation to form a semi-rigid hydrogel. The third type of phantom is the 'St. Petersburg' modular block phantom, consisting of inactive tissue-equivalent plastic blocks into which rods containing known activities of the desired radionuclides are inserted. The precision of assembling the phantoms was very good for all three types. The standard deviation of the mean pulse rate was less than 2% when each phantom was measured repeatedly; the modules were removed and re-assembled between measurements. The accuracy in measuring unknown activities of 134 Cs, 137 Cs and 60 Co was 5% or better.

Some of the quality assurance tasks of whole-body counting are specific to that method of measurement, whereas others are similar to those of gamma spectrometric sample measurements. Quality assurance in whole-body measurement and the associated calculation of internal doses is a complex matter. The uncertainty in the measurement geometry between the radiation source and the detector is unavoidable when measuring humans. Quality assurance includes quality control with procedure and protocol descriptions, detector calibrations, instrument control, documentation of measurement results and evaluation internally or by outside persons. This evaluation also involves regularly repeated comparative measurements. An intercomparison study in the Nordic countries was carried out using a phantom that corresponded to a person weighing 62 kg. The radionuclides used were 60 Co, 137 Cs and 40 K. The phantom was circulated to seventeen laboratories. The results agreed well with the reference values. The results from this project showed that the preparedness for performing body and organ measurements in emergency situations has improved greatly since the Chernobyl reactor accident.

The deposition of 137 Cs from Chernobyl was very unevenly distributed. This resulted in big variations in foodstuffs especially those of wild origin. For estimation of internal doses groups of people were studied with whole-body counting techniques. A Helsinki group. deposition 3kBq.m -2 , was studied from 1965 onwards and groups from Viitasaari, deposition 29 kBq.m -2 , and Ammansaari, deposition 1.5 kBq.m -2 were studied from 1987 to 1994. Special items in the diet of people from Viitasaari were local freshwater fish and from Ammansaari reindeer meat. In spring 1987 the mean body burdens of the Viitasaari (10 kBq) and the Ammansaari (7.4 kBq) were 4 to 5 times that of the Helsinki group (1.9 kBq). In 1994 only 15% of the maximum mean body burden in the Viitasaari group was found. In the Helsinki and Ammansaari groups the corresponding percentage was about thirty. The great influence of the consumption of foodstuffs of wild origin was seen.

Monitoring of the workforce in the nuclear industries is carried out primarily in order to demonstrate compliance with European Union (EU) legislation and the Basic Safety Standards for the protection of the health of workers against the dangers arising from ionizing radiation recommended by the International Atomic Energy Agency (IAEA). There is, however, no common strategy for internal dose monitoring programmes currently in use in the EU countries. Surveys have been carried out in which organisations were asked to provide information on the design of their internal dose monitoring programmes and on the costs of these programmes. Information was requested from both EU countries and Associated States. Databases for storage and reporting of all gained information were constructed, and results from the surveys have been compiled. This work was carried out within the EC 5th Framework Programme project, OMINEX, which aims to provide advice and guidance on designing and implementing internal dose monitoring programmes in the workplace in such a way that best use is made of available resources, while minimising costs.

The costs of monitoring for internal exposure in the workplace are usually significantly greater than the equivalent costs for external exposure. Therefore, there is a need to ensure that resources are employed with maximum effectiveness. The EC-funded OMINEX (optimisation of monitoring for internal exposure) project is developing methods for optimising the design and implementation of internal exposure monitoring programmes. Current monitoring programmes are being critically reviewed, the major sources of uncertainty in assessed internal dose investigated, and guidance formulated on factors such as programme design, choice of method/techniques, monitoring intervals, and monitoring frequency. OMINEX will promote a common, harmonised approach to the design and implementation of internal dose monitoring programmes throughout the EU.

Previous ICRU reports have dealt with the formulation and properties of tissue substitutes and phantoms that are used to calibrate in vivo measurement systems. This report provides guidance on the overall process of the direct measurement of radionuclides in the human body for radiation protection and medical applications. It addresses the detectors and electronics used for the measurement; methods of background reduction and control; measurement geometries for whole body, partial body or organ counting; physical and mathematical calibration methods; data analysis; and quality assurance. It is directed to readers who need practical advice on the establishment and operation of direct measurement facilities.