A HIGH-RESOLUTION MAP OF GAMMA DOSE RATES IN CLUJ COUNTY, ROMANIA USING LIF:MG,CU,P DETECTORS Monica Dolha 1,2, *, Alida Timar-Gabor 1,2 , Tiberius Dicu 1,2 , Robert Begy 1,2 , Mircea Anton 1 and Constantin Cosma 2 1 Faculty of Environmental Sciences and Engineering, Babes ¸-Bolyai University, Fa ˆnta ˆnele 30, Cluj-Napoca 400294, Romania 2 Interdisciplinary Research Institute on Bio-Nano-Sciences, Babes ¸-Bolyai University, Treboniu Laurian 42, Cluj-Napoca 400271, Romania *Corresponding author: monica.zeciu@ubbcluj.ro Outdoor gamma radiation measurements in Cluj County, Romania have been performed using solid-state thermoluminescent detectors in order to develop a high-resolution database for natural gamma dose rates. Integrated measurements have been carried out for an exposure time of minimum 3 weeks. According to European Union requirements, the territory has been divided into 69 grids of 10 ` 3 10 km. The cells were monitored using LiF:Mg,Cu,P detectors. For two locations the results were 136 + 7 and 150 + 7 nGy h 21 , respectively. These results can be explained by the existent geological substrate. The values rangedfrom 56 + 4 to 150 + 7 nGy h 21 , with an average value of 91 + 2 nGy h 21 , being in agreement with the 2008 United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) Report. A high-resolutionmap of gamma dose rates in Cluj County is presented for the first time. INTRODUCTION Natural radiation contributes to ≏85 % of the annual total radiation dose received by humans (1) . In the case of a terrorist attack or a nuclear accident it is neces- sary to assess the right value for the natural radiation dose rate, taking into account that natural radioactive background presents important variations from one location to another around the world. For this purpose, mapping terrestrial gamma dose rates has been per- formed in many countries. There are two different approaches to obtain data for mapping the gamma dose: active and passive measurements. In the case of active measurements, the most extended survey is represented by the EURDEP network (European radiological data exchange platform) that is currently used by 33 European countries. On this plat- form, each country sends their local data at least once at 24 h (2) . Data from over 4700 stations in Europe are collected. Passive measurements have the advantage of obtaining integrated data and the use of relatively cheap equipment. This paper aimed to develop the first high-resolution map of gamma dose rate in Romania using passive thermoluminescence dosemeters. Romanian National Commission for Nuclear Activities Control has limited public dose at 1 mSv y 21 above the natural background (3) . Thus, more sensitive materials are required and LiF:Mg,Cu,P is one of the most suitable dosemeter for measuring such low doses. Besides its high capability to be sensitive at very low levels (1 mSv), this material also presents very promising features such as long-term information, simple readout, good reproducibility and linearity (1 mSv–10 Sv), tissue equivalence, easy handling and storage (4) . MATERIALS AND METHODS To obtain a map of gamma dose rates for Cluj county, .240 detectors based on LiF:Mg,Cu,P [coded MCP-7 produced by thermoluminescent dose- meter (TLD) Poland] in the form of pellets of 4.5 mm diameter and 0.9 mm thickness have been used. The dosemeters have been placed in 69 different locations from Cluj County between April and August 2013 (by dividing the territory in cells of 10 ` Â 10 km as European Union requires), thus covering ≏7000 km 2 (around 3 % of Romania’s territory). Cluj county relief is characterised by the presence of plateau and mountain areas. About a quarter of the territory surface is mountainous (Apuseni Mountains). Before placing the dosemeters in the environment, a standard annealing procedure by heating the dose- meters at 2408C for 10 min was performed. A number of 3 up to 5 MCP-7 pellets for each location were used. Detectors were placed at a distance of 1 m above ground, according to standard procedures (5) . The time exposure ranged from 24 to 51 d. A Harshaw 3500 TLD Reader was used for reading the detectors. For the calibration procedure reference is made to a previ- ous study of the authors (6) . A high-resolution gamma-ray spectrometry analysis was carried out on a ORTEC hyper-pure germanium detector. Relative calibration has been performed using IAEA 312 soil standard. RESULTS AND DISCUSSION A typical glow curve for a detector exposed at Ma ˘guri-Ra ˘ca ˘ta ˘u is presented in Figure 1. The # The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com Radiation Protection Dosimetry (2014), pp. 1–6 doi:10.1093/rpd/ncu209 Radiation Protection Dosimetry Advance Access published July 9, 2014 at Universitatea Babes Bolyai, Cluj-Napoca on July 17, 2014 http://rpd.oxfordjournals.org/ Downloaded from