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IDEA Informe resumido

Project ID: FIKR-CT-2001-00164
Financiado con arreglo a: FP5-EAECTP C
País: France

KFKI general application of calibration techniques

The main activities of our institution directed to compile the scientific results achieved by other project partners and summarize the outcomes from the point of view of their possible applications. The main goal of the project was to improve the in vivo and bioassay monitoring techniques to be able to provide improved methods for routine applications. Since the benefits and innovative features of the achieved results are detailed by the corresponding project partners, only the main summary conclusions are given here.

In vivo monitoring:

Though HPGe detectors have quite good characteristics for monitoring low energy photon emitters, in certain circumstances the need of detector cooling may limit their use in in-vivo applications. It seems very promising to apply properly manufactured Si detector arrangements (array, mosaic) for in-vivo measurement of 239Pu deposited in the lung since the lower limit of detection can be improved just because Si detectors are working in room temperature and the cooling system are not hindering the optimum detector positioning on the chest surface. In the higher photon energy range (above 100keV) the conventional large NaI(Tl) scintillation detector can advantageously be applied if the requirements for the spectral energy resolution is not too high. In this case another aspect can also be considered namely the installation and operational costs are much lower for scintillation detectors. However, especially in case of complex gamma spectra large NaI(Tl) detectors cannot compete with HPGe detectors.

As for the calibration of in vivo monitoring systems introducing numerical calibration technique instead of using physical phantoms the main advantages can be summarised as follows.
The method provides the possibility of:
- source-detector geometry optimisation
- simulation different activity distributions
- individual specific calibration
- time-dependent efficiency calibration
- numerical reconstruction of any body part

The difficulty in widespread application of the numerical calibration technique in the routine practice is that the method needs quite powered computer, special software, and properly skilled and experienced personals. Since all the conditions are available in certain, well-equipped and prepared institutions, those laboratories dealing with routine internal contamination monitoring can take the advantage to ask for this service.

Bioassay monitoring:

Mass spectrometry, and especially inductively coupled plasma mass spectrometry (ICP-MS), has evolved as an attractive alternative to alpha spectrometry and beta counting in bioassay monitoring. The work carried out in this project provided acceptable guidelines for optimum performance of ICP-MS measurements of uranium, thorium and certain actinides, including sampling procedure, operational parameters of the instruments, and interpretation of the measured data. This very sensitive technique allows for the detection of atoms present during a given counting time.

More simple, rapid and cost effective method of mass-spectrometry was chosen to standardise bioassay monitoring procedure using high resolution sector field inductively coupled mass spectrometer (HR-SF-ICP-MS), by means of which it is possible to measure very low amount of thorium and uranium with fairly good precision. The detection limit for natural uranium isotopes is generally in the order of 20pg or about 0.5µBq. Summarising the findings on bioassay investigations the application of ICP-MS measurements are relatively simple, rapid and cost saving. The analytical capabilities of ICP-MS studied so far seem to provide sufficient proof that this method has potential to apply for the member of the public and to become as a routine technique to monitor workers for most of the radionuclides incorporated in the body.

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Institut de Radioprotection et de Surete Nucleaire
Rue Auguste Lemaire
92 262 Fontenay aux Roses
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