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Evaluation of Individual Dosimetry in Mixed Neutron and Photon Radiation Fields

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Radiation protection in mixed neutron-photon fields

The EVIDOS project focused on radiation protection dosimetry in mixed neutron/photon fields through spectrometry and dosimetry investigations in representative work-places in the nuclear industry.

Climate Change and Environment

Seventeen different work-places were investigated including nuclear energy production, transport of nuclear fuel, fresh MOX fuel rod manufacturing and a site handling nuclear material. Based on reference spectrometry measurements from various work-places in the nuclear industry, a new catalogue with neutron spectra was derived and published in the open literature. These measurements showed that neutron energy distributions have a similar pattern with a thermal peak, a rather flat intermediate energy region and a peak from fast neutrons within 100keV-1MeV. Despite that, there was a significant variation in neutrons' contributions to fluence, a measure of the quantity of radiation in a beam. On the basis of the spectrometry information gathered, reference values were collected for a number of radiation protection quantities. Such quantities included ambient dose equivalent, personal dose equivalent and effective dose. The well established spectrometry method Bonner sphere (BS) was used for ambient dose equivalent measurements. The BS method offers increased reliability and accuracy on the condition that the response matrix of the spectrometer is precisely known and data analysis is carefully performed. Using suitable direction spectrometers that are still under development, personal dose equivalent reference values were derived and improved with the aid of BS angle integrated spectra as pre-information. The improved values were in good agreement with data coming from transport calculations performed for workplace fields under simulation conditions and at the VENUS research reactor. The reference values for personal dose equivalent and other radiation protection quantities have been published.

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