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The use of microdosimetric methods for the determination of dose equivalent quantities and of basic data for dosimetry

Objective


This project was mainly devoted to the improvement and also the design of various detector systems for radiation protection dosimetry in neutron-photon fields. The techniques investigated are based on the measurement of absorbed dose and LET in order to determine the dose equivalent. Depending on the type of application, TEPCs working at very low pressures and personal dosemeters have been investigated. The dose equivalent response of these TEPCs was determined in calibration fields with realistic spectra. Furthermore, to improve the calibration of individual dosemeters according to the new recommendations of ICRP, a transfer device for the determination of dose equivalent quantity was studied.

Finally, since the understanding and the usefulness of microdosimetric devices strongly depends on the basic knowledge of many microscopic physical quantities, special emphasis was devoted to the determination of basic data such as W values for neutrons and heavy charged particles, electron-molecule cross-sections in organic vapours, Kerma factors, etc.
The measurement of dose equivalent in practical radiation environments with photon neutron dose components pose problems due to the generally poor knowledge of the fluence- and LET-spectra. A solution consists in using devices capable of measuring simultaneously the absorbed dose and the LET dose distribution, or a reasonable approximation. The product of the dose and the average quality factor, derived from the measured LET spectra, determines the dose equivalent to be compared with the recommended operational quantities. Low pressure tissue-equivalent proportional counters (TEPC) are reference instruments in this approach and a well established method for area monitoring. Other techniques using microdosimetric principles may contribute to extend the applicability of dose-LET detectors. Multi-Cellular proportional counters (MCPC) and semi-conductor detectors (SCD), as microdosimetric devices, in particular, offer powerful solutions to the problem of implementing electronic personal dosemeters into radiation protection practice.
The project is aimed at improving the TEPC as reference method and providing operational instruments with a response nearly independent of neutron energy on the largest range possible. The SCD and MCPC detectors will be developed as personal dosemeters and their applicability will be assessed by comparing prototypes with the TEPC in well characterised radiation fields. The project is based on the collaboration activated between the partners during the previous period and within Eurados activities to combine their experience in detector development, intercomparison work and numerical calculations. Modelling studies will be performed to understand the basic characteristics of the detectors, and to simulate their dose equivalent response. To calibrate the dosemeters, the partners will provide reference neutron beams as well as realistic fields simulating those encountered at work places. The work will be extended to high energy neutron fields of interest for radiation protection dosimetry at environments with high energy radiations. The new recommendations by the ICRP will be taken into account and relevant information will be provided to allow judgement with regard to the new operational quantities and the application of dose-LET detectors. The project will improve the knowledge of basic physical data for dosimetry.

Topic(s)

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Call for proposal

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Coordinator

ASSOCIATION POUR LE DEVELOPPEMENT DE LA PHYSIQUE ATOMIQUE
Address
118,Route De Narbonne 118
31062 Toulouse
France
 

Participants (5)

Commissariat à l'Energie Atomique (CEA)
France
Address
Centre D'études De Fontenay-aux-roses
92265 Fontenay-aux-roses
 
Forschungszentrum Jülich GmbH
Germany
Address
Wilhelm-johnen-straße
52405 Jülich
 
Nederlandse Organisatie voor Toegepast Natuurwetenschappelijk Onderzoek
Netherlands
Address
310,Utrechtseweg
6800 ES Arnhem
 
PHYSIKALISCH-TECHNISCHE BUNDESANSTALT
Germany
Address
Bundesallee 100
Braunschweig
Universität des Saarlandes
Germany
Address
Am Markt
66125 Saarbrücken