Development of a personal neutron dosimetry system. DOPEN project

Neutron dosimetry is an essential aspect of radiation protection in nuclear power plants, medical facilities and research centers, among other facilities. One of the most widely used techniques for personal neutron dosimetry is based on the analysis of radiation induced tracks in materials such as plastic detectors. This technique provides a reliable and accurate measurement of neutron dose and fluence and has become increasingly popular due to its simplicity, low cost and versatility.

This communication presents the project “DOPEN: Personal Neutron Dosimetry”, signed in 2020 by the Ciemat and the Spanish Nuclear Safety Council (CSN), aimed to the development of a personal neutron dosimetry system according to the applicable international standards

The CIEMAT neutron dosimetry laboratory selected the PADC (poly-allyl-diglycol-carbonate) material for the detection of secondary charged particles produced in neutron interactions with the material. 

The energy response of the PADC and the design of the holder were firstly analyzed with MCNP6.2 Monte Carlo code, considering different geometries and materials (polyethylene, nylon, and lithium, among others). Furthermore, the variability in the response depending on the irradiation angle incidence was also studied to analyze the reactions produced inside the material. 

The PADC dosimeters were irradiated with calibrated 252Cf  and AmBe neutron sources on an ISO water phantom at the CIEMAT Neutron Standards Laboratory (LPN) to experimentally characterize the response and compare it with the simulated results. 

Chemical etching method was optimized after testing different procedures for the irradiated dosimeters. These dosimeters were read using the TASTRACK system that is equipped with a high quality microscope, an ultra-fast three axis motorized control and a software analysis based on the size and shape of the tracks to dose assessment.

In order to extend the energy response of PADCs and based on results of MC simulations, a prototype of dosimeter hanger was designed and produced at Ciemat using a 3D printer and nylon material.

Preliminary results on linearity and coefficient of variation tests are in a very good agreement with the criteria established in the standard ISO 21901-1:2021. 

Next steps in the development of the project will be performing angular irradiations and irradiate dosimeters with thermal and monoenergetic neutrons in order to characterize the energy and angular response of the dosimeters.

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