Exploitable results General guideline The consortium collated and analysed experience on the assessment of internal dose from incorporation monitoring data. A wide range of radionuclides was covered, with emphasis on the actinides (e.g. uranium, plutonium), fission products (e.g. caesium, strontium) and activation products (e.g. cobalt). From this experience a general philosophy for the evaluation of incorporation monitoring data has been derived based on the following principles: (i) Harmonisation: A well-defined procedure is needed and for this reason the process is defined here primarily by means of a series of flow-charts. For routine monitoring situations, where typically there is only one measurement relating to each intake, it is reasonably straightforward to define a procedure. However, in special monitoring situations, where typically there is more than one measurement and quite possibly more than one type of measurement different options for data handling can easily lead to different evaluated doses, even when the same model, parameter values and software are used. Proposals are made here for a systematic approach to dose assessment in all these situations. (ii) Accuracy: It is recognised that the uncertainties associated with assessed internal dose can be considerable, especially for the actinides, which are difficult to detect in the body and have relatively high dose coefficients. If the initial estimate of dose exceeds 1mSv, it could well be that the possibility of a substantially higher dose (e.g. 6mSv) cannot easily be excluded. It is then important to make best use of the available information. (iii) Proportionality: The effort applied to the evaluation of incorporation monitoring data should broadly correspond to the expected level of exposure, and the complexity of the case. On the one hand, if the exposure is likely to be very low with respect to the dose limits, simple evaluation procedures with a relatively high uncertainty may be applied. On the other hand, if the monitoring values indicate the exposure to be close to or even above the dose limits, more sophisticated evaluation procedures will need to be applied. Based on this general philosophy the following "Levels of task" has been defined: Level 0: Annual dose <0.1mSv. No evaluation of dose needed. Level 1: Simple, "reference" evaluation, with ICRP defaults used for all parameter values, except where there is better a priori information available (annual dose typically 0.1 - 1mSv). Level 2: Sophisticated evaluation using additional information to give more realistic assessment of dose; comparisons are made of the model predictions with the data, to choose between alternative parameter values, or to find optimum parameter values (dose from the intake typically 1 - 6mSv). Level 3: More sophisticated evaluation, which applies to cases where there are comprehensive data available, as would be the situation after an accident. The evaluation is an extension of Level 2, typically to parameters relating to the subject. The fundamental approach at this Level is to adjust the model parameter values systematically, until the goodness of fit is acceptable (dose from the intake typically > 6mSv). Based on the "Level-of-task-structure" the General Guidelines have been defined. These guidelines provide: (i) background information about the biokinetic models and the corresponding bioassay functions which should be used for the interpretation of incorporation monitoring data, (ii) detailed information about the handling of the monitoring data, including general aspects considering the handling of single data and multiple data sets, the handling of extended exposures and the number and type of data required for the dose assessment and special aspects considering the processing of data before use, the assessment of the uncertainty on data, the handling of data below the limits of detection, the handling of data influenced by chelation therapy and the identification of rogue data. The general guidelines are illustrated by well-defined flowcharts, giving detailed guidance to the assessors on how to evaluate the incorporation monitoring data in any situation. Potential end-users and applications. It is considered that there are three groups of potential users of the guidelines: (1) Health physicists who perform routine and special incorporation monitoring in order to assess the internal dose due to the occupational handling of radioactive materials or due to incidental or accidental intakes. (2) Groups of experts involved in developing guidance or standards relating to exposure to radioactive materials, in particular members of the ICRP Task Group on Internal Dosimetry, who are developing revisions of ICRP Publications 30/68 and 54/78. (3) National and international authorities who define and control radiation protection standards and procedures. Pilot program units of contractors' computer codes with new algorithms Individual Monitoring of the Internal Exposure (IMIE) computer code is developed for the purposes of the retrospective dosimetry. It gives to the assessor the power engine for the analysis and interpretation of bioassay measurements. The main aim of the IMIE program is the reconstruction of multiple intakes on the base of the body counter or bioassay data and known exposure conditions, such as date of exposure, route of intake, AMAD and Type of Materials (in the inhalation case). The program allows comparing wide range scenarios of exposure in the case of unknown or non-standard exposure conditions: date of intake, route of intake (inhalation, ingestion, etc.), AMAD, Type of Materials of inhaled aerosols. Parameters listed above could be combined into user-defined "mixtures". The program analyses all combinations of parameters from the selected ranges and finds the best fit to the analysed measurement series. Simultaneous analysis of several data sets (e.g. faeces and urine) and 'direct dose assessment' for selected radionuclides (e.g. 3H, 137Cs) are also available. The trial version of the IMIE is available from http://rpi.kiev.ua/products/IMIE/. Data input: Time trends of measurements can be entered into spreadsheet forms or loaded from a text file with delimiters (import from other application) Radionuclides: 28 elements, 46 radionuclides: 3H, 32P, 33P, 35S, 51Cr, 54Mn, 59Fe, 58Co, 60Co, 65Zn, 89Sr, 90Sr, 95Zr, 95Nb, 99Tc, 99mTc, 103Ru, 106Ru, 110mAg, 132Te, 123I, 125I, 131I, 132I, 134Cs, 137Cs, 140Ba, 141Ce, 144Ce, 201Tl, 202Tl, 210Pb, 210Po, 226Ra, 228Th, 232Th, 234U, 235U, 238U, 237Np, 238Pu, 239Pu, 240Pu, 241Pu, 241Am, 243Am Measurements: Urine, Faeces, Lung, Thyroid and Whole Body Route of intake: Inhalation (aerosols, gases and vapours), Ingestion, Injection, Wound, Arbitrary mixture of intake routs Type of Material: F, M, S, arbitrary mixture of Types AMAD: 0.001 to 20µm, polymodal distribution represented by superposition of lognormal distributions ("mixture of AMADs") Intake pattern: One or several intakes (acute or chronic) Mode of interaction with user: Interactive Windows-style Extended graphical tools for the data presentation and analysis: - graphical selection of time intervals for analysis by means of the mouse-oriented 'drag-and-drop' technology; - both linear and logarithmic scales; - auto-scaling; - mouse (like 'drag-and-drop' technology) zooming of XY plot fragments; - 'right mouse button' quick menu; - customised pattern of the graph, axes, grid, titles etc. Mode of analysis: -Full automatic modes: ICRP-78, Smart (these modes give the quickest results) -Interactive modes: Semi-automated, Manual (for expert) -Special Accident mode (modification of the Manual mode useful for analysis of accidental cases) -Simultaneous analysis of several data sets from different data sources Dose (intake) calculation Best estimate: - weighted least-squares fit; - unweighted least-squares fit. Data output: - In the table and on the XY plot (program window): original (fitted) data points; fitting curve; - In the table (program window): pattern of the reconstructed intake(s) (date and amplitude) assessed Type of Materials and AMAD (for each reconstructed intake) committed effective dose associated with each reconstructed intake annual doses total committed effective dose Report about analysis results to: - text file (with tab or comma delimiters); - rich text format file (rtf); - web page (html) Additional Tools: - Reference system on radionuclide information (more than 800 radionuclides) - Clipboard tools for the export of data to Microsoft Windows applications (such as Microsoft Excel or Microsoft Word) - Data export to other applications (curves: flat text file; graphics: metafile '.WMF', '.EMF' and bitmap '.BMP') IDEAS database As part of the IDEAS project to develop General Guidelines for the Assessment of Internal Dose from Monitoring data, three databases were compiled. The IDEAS Bibliography database contains references dealing with problems related to cases of internal contamination. The IDEAS Internal Contamination Database now contains more than 200 cases of internal contamination. In the near future, the IDEAS Internal Contamination database will be made available to the internal dosimetry community. The database has several potential applications, including: training, testing biokinetic models, testing software for calculating intakes and doses from bioassay data, comparison of data from a new accidental intake with that from previous exposures to similar materials. The database is by no means complete, and this is also an appeal for internal contamination cases to extend and update it. In WP3 many case studies were evaluated (assessed) by the contractors using standard software. The evaluations were collated, and the IDEAS Evaluation of Cases Database (ElavDB) was set up. The EvalDB contains a summary of information for 95 evaluations on 52 cases (17 radioisotopes) and can link to the IDEAS Internal Contamination Database, where the original monitoring data can be found. With the EvalDB it is possible to: -View a summary of information on each evaluation including hypotheses and results. -Select case evaluations on the basis of the radioisotope, the case number used in the IDEAS Internal Contamination Database, or the assessor. -Compare different evaluations on the same case scenario. -Select evaluations on the basis of evaluated committed effective dose (4 categories). From the database it is also possible to open the text file describing the evaluation where detailed information on each assessor's approach, assumed hypotheses and parameters can be found. In the near future the IDEAS EvalDB will be made available to the internal dosimetry community. The database has potential application in training on internal dose assessment and on methodologies to be applied in complex internal contamination cases. Searching for OpenAIRE data... There was an error trying to search data from OpenAIRE No results available
