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The paper is devoted to the estimation of the characteristic limits (statistical criteria) for the detection of small amounts of ionizing radiation by a measuring device under conditions of a natural radioactivity background of the environment: the decision threshold, the detection limit, the minimum detectable activity and the confidence interval. The assessment procedures were carried out in accordance with the national harmonized standard DSTU ISO 11929-3:2009. The threshold for making a decision on the presence of 137Cs and 60Co radionuclides in objects of the external environment and the limit of their detection using a measuring device equipped with plastic scintillators manufactured by the Institute of Scintillation Materials of the National Academy of Sciences of Ukraine were estimated. The influence of the energy of the detected radiation, the dimensions of the scintillators and the geometry of the irradiation on the estimation of the characteristic limits were investigated. Keywords: scintillator; decision threshold; detection limit; confidence interval; minimum detectable activity., Работа посвящена оцениванию характерных пределов (статистических критериев) обнаружения измерительной установкой малых количеств ионизирующего излучения в условиях естественного радиоактивного фона окружающей среды: порога принятия решения (decision threshold), предела обнаружения (detection limit), минимальной детектируемой активности и доверительно-вероятностного интервала (confidence interval). Процедуры оценивания проводились в соответствии с национальным гармонизированным стандартом ДСТУ ISO 11929-3:2009. Проведены оценки порога принятия решения о присутствии в объектах внешней среды радионуклидов 137Cs и 60Co и предела их обнаружения с использованием измерительной установки, оснащенной пластмассовыми сцинтилляторами, выпускаемыми Институтом сцинтилляционных материалов Национальной академии наук Украины. Исследовано влияние энергии регистрируемого излучения, размеров сцинтилляторов и геометрии облучения на оценку характерных пределов., Роботу присвячено оцінюванню характерних меж (статистичних критеріїв) виявлення вимірювальною установкою малих кількостей іонізуючого випромінювання в умовах природного радіоактивного фону навколишнього середовища: порога прийняття рішення (decision threshold), межі виявлення (detection limit), мінімальної детектованої активності та довірчо-ймовірнісного інтервалу (confidence interval). Процедури оцінювання проводилися відповідно до національного гармонізованого стандарту ДСТУ ISO 11929-3:2009. Проведено оцінки порога прийняття рішення про присутність в об’єктах зовнішнього середовища радіонуклідів 137Cs і 60Co та межі їх виявлення з використанням вимірювальної установки, оснащеної пластмасовими сцинтиляторами, що випускаються Інститутом сцинтиляційних матеріалів Національної академії наук України. Досліджено вплив енергії реєстрованого випромінювання, розмірів сцинтиляторів та геометрії опромінення на оцінку характерних меж. Оцінювалися характерні межі виявлення при зміні розміру сцинтилятора від 500´300´50 мм (7500 см3) до 500´500´50 мм (12500 см3), зміні енергії реєстрованого випромінювання від 662 кеВ (137Cs) до 1332 кеВ (60Co) та зміні відстані від сцинтилятора до гамма-джерела від 10 до 50 см. Вимірювання чистої швидкості рахунку імпульсів та фонової швидкості сцинтиляторів проводилися в інтервалі енергій 20–2000 кеВ. Показано, що основним чинником, який впливає на величину характерних меж, що визначають чутливість вимірювальної установки, є фон навколишнього середовища. Тому значення характерних меж, в імп/с, не залежать від зміни реєстрованої енергії та відстані до гамма-джерела, але злегка залежать від розміру сцинтилятора. Значення порога прийняття рішення для різних розмірів сцинтиляторів становлять 65–82 імп/с. Значення межі виявлення в два рази вище – 130,5–163,7 імп/с. Ключові слова: сцинтилятор; поріг ухвалення рішення; межа виявлення; довірчий інтервал; мінімальна детектована активність.

Son yılların en yaygın konularından biri olan yapay sinir ağları (YSA), öğrenme kabiliyeti, hızlı çalışması, tanımlama kolaylığı, az bilgi ile çalışabilme, doğrusal olmayan sistemleri modelleyebilme, bilgiyi paralel olarak işleyebilme ve yeni durumlara uyum sağlayabilme gibi özelliklere sahiptir Bu özelliklerinden dolayı, YSA, nükleer spektroskopi alanında örneğin, gama spektroskopisi, alfa spektroskopisi, pik-background oranı, puls tipi dedektörlerin enerji çözünürlük iyileştirmesi, proton kaynaklı X-ışını emisyonları, X-ışını flüoresan ve Rutherford geri saçılma vb. konularında kullanılmaktadır. YSA'nın avantajlarını ve nükleer spektroskopide kullanımını göz önüne alarak, bu tezde, ilk olarak Nükleer Bilimler Enstitüsü sayım laboratuarında bulunan HPGe dedektörü kullanılarak, gama spektral analizi için YSA uygulanmıştır. Geliştirilen YSA modelinin performansı, Çandarlı kıyı sedimenti örneklerinin gama spektral analizi ile test edilmiştir. YSA ile örnekler içerisindeki gama verici radionüklitlerin varlıkları başarıyla tespit edilmiştir. Bu çalışmanın ikinci adımında, YSA, NaI(Tl) Sintilasyon Gama Spektrometre sisteminin değişik sayım sürelerinde ölçebileceği minimum dedekte edilebilir aktivite (MDA)'leri bulmak için kullanılmıştır. Bu amaçla, Enstitüde kullanılan sayım süreleri dikkate alınarak, 5000- 87000s arası, 226Ra, 232Th ve 40K radyonüklitleri için, minimum dedekte edilebilen aktivite (MDA) değerleri, Curie kriterlerine dayalı olarak hesaplanmıştır. YSA'dan elde edilen MDA değerleri ile hesaplanan MDA değerleri karşılaştırıldığında, birbirleriyle örtüştüğü görülmüştür. Bu çalışmada, ilk kez, YSA, NaI(Tl) sintilasyon gama spektroskopisi ile doğal radyonüklit analizleri için uygulanmıştır. Bu amaçla, 126 adet değişik orijinli çevresel materyal; kayaç, toprak, granit, mermer ve gübre örneklerinin içerisindeki radyum, toryum ve potasyum konsantrasyonları hesaplanmıştır. Hesaplanan aktivite değerleri, YSA modelinden tahmin edilen değerlerle karşılaştırıldığında, YSA'nın örneklerdeki 226Ra, 232Th, ve 40K aktivitelerini doğru bir şeklide tahmin edebildiği görülmüştür., Artificial neural networks (ANN), which is one of the most common subjects of recent years, has features such as learning ability, fast work, ease of identification, ability to work with less information, modeling nonlinear systems, processing information in parallel and adapting to new situations. In the field of nuclear spectroscopy, for example, gamma spectroscopy, alpha spectroscopy, peak-background ratio, energy resolution improvement of pulse type detectors, proton-induced X-ray emissions, X-ray fluorescence and Rutherford backscatter, and the like subjects. Considering the advantages of ANN and its use in nuclear spectroscopy, in this thesis, ANN was firstly applied for gamma spectral analysis using the HPGe detector found in the census laboratory of the Institute of Nuclear Sciences. The performance of the ANN model was tested by gamma spectral analysis of Çandarlı coastal sediment samples. With ANN, the presence of gamma emitting radionuclides in the samples has been successfully determined. In the second step of this study, ANN was used to find the minimum detectable activity (MDA) that the NaI (T1) Scintillation Gamma Spectrometer system could measure at different counting times. For this purpose, minimum detectable activity (MDA) values for 226Ra, 232Th and 40K radionuclides between 5000- 87000s were calculated based on Curie criteria, taking into account the counting times used in the Institute. When the MDA values obtained from ANN were compared with the calculated MDA values, it was seen that they overlap with each other. In this study, for the first time, ANN was applied for natural radionuclide analysis by NaI (T1) scintillation gamma spectroscopy. For this purpose, 126 different environmental materials; Radium, thorium and potassium concentrations in rock, soil, granite, marble and fertilizer samples were calculated. When the calculated activity values were compared with the values estimated from the ANN model, it was found that the ANN could accurately predict 226Ra, 232Th, and 40K activities in the samples.

The international monitoring system (IMS) has been developed to verify compliance with the comprehensive nuclear test-ban treaty (CTBT) and radionuclide monitoring stations are the smoking gun for underground nuclear explosions identification. One of the main objectives of the verification regime is to improve the sensitivity of measurements providing background reduction and, as a result, decrease the minimum detectable activity (MDA) values. At this ENEA laboratory an anticoincidence system has been developed: the system is comprised of a high purity germanium (HPGe) detector surrounded by a low–background shield and two plastic scintillators able to detect coincident cosmic-ray interactions. Tests conducted with the anticoincidence system have shown a reduction of the Compton continuum that contributes to the spectrum background and the measured MDA values, compared to those obtained using the standard system, decreased for all the four radioxenon isotopes. © 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group.

This paper presents the results of the tests of High Purity Germanium (HPGe) based gamma spectrometers employed for radioactivity control carried out on a daily basis in steel factories. This new application of this type of detector is part of the Joint Research Project (JRP) MetroMETAL supported by the European Metrology Research Programme (EMRP). The final purpose of the project was the improvement and standardisation of the measurement methods and systems for the control of radioactivity of recycled metal scraps at the beginning of the working process and for the certification of the absence of any radioactive contamination above the clearance levels (IAEA-TECDOC-8S5) in final steel products, Clearance levels for radionuclides in solid materials: application of exemption principles). Two prototypes based on HPGe detectors were designed and assembled to suit the needs of steel mills which had been examined previously. The evaluation of the two prototypes, carried out at three steel factories with standard sources of 60Co, 137Cs, 192Ir, 226Ra and 241Am in three different matrices (slag, fume dust and cast steel) and with samples provided on-site by the factories, was successful. The measurements proved the superiority of the prototypes over the scintillation detectors now commonly used regarding energy resolution and multi-nuclide identification capability. The detection limits were assessed and are presented as well. © 2015 Elsevier B.V.

The article describes aspects of gamma-spectrometric method for monitoring the percentage of natural uranium in technological solutions. A method for determining the minimum detectable activity for radiometric and spectrometric applications is proposed. The measurements and calculations results of the natural uranium minimum detectable activity in technological solutions for various gamma-ray spectrometers are given. Gamma-ray spectrometers with HpGe detectors may be used for the continuous monitoring of uranium in solution at any ratio natural uranium and 234 Th and a wide range of uranium concentrations from 1 mg/l to hundreds g/l. Gamma-ray spectrometers with scintillation detectors are suitable for solving this problem, if radioactive ratio between natural uranium and thorium is known and without other radionuclides. Multizone processing spectra algorithm and is considered and it is shown his preference for the processing of the spectra obtained for gamma spectrometers with scintillation detectors. As a comparison, the estimate of minimum detectable activity of uranium is given for gamma-ray spectrometer with LaBr 3 (Ce) detector in conditions similar to those measured for other gamma-ray spectrometers. It is shown that the spectrometers with LaBr 3 (Ce) crystals more relevant to the measurement of large activities such as technological solutions enriched uranium. Keywords : gamma spectrometry, natural uranium in solutions, minimum detectable activity. (Russian) DOI: http://dx.doi.org/10.15826/analitika.2014.18.1.003 E.I. Denisov, A.A. Pulin Federal State Autonomous Educational Institution of Higher Professional Education «Ural Federal University named after the first President of Russia B.N.Yeltsin» (UrFU) , Ekaterinburg, Russian Federation

My thesis examines the measurement optimalization when the semiconductor HPGe detectors with a low background and a high relative efficiency are used for achieving low values of MDA (minimum detectable activity). I conducted my research in the Department of Spectrometry of SÚRO (National Radiation Protection Institute) in Prague. In this laboratory the standard geometries of detectors with lower efficiency are used. The aim of this thesis is to offer a proposal of new geometry, sizes and shapes of measurement cells which will better correspond with the demand for higher efficiency of updated detectors. The assignment was to find the best mathematical function to descibe the correlation between efficiency and the direction of the radiation point source towards the detector. This function is derived from experimentally obtained data. To conduct measurements, three kinds of detectors with high relative efficiency used for activity measurements at different geometries were selected. As the source of gamma radiation, the point sources with energies of 46 keV, 661 keV, 1332 keV in different distances and positions were used. The function was applied separatelly to each of the three detectors and to the areas above the detector and sidewards of the detector. The objective of the research was to project new measurement geometries or to optimalize the current ones which could be used also in other detectors with high efficiency. After integrating the function in the cylindrical area above the detector and the annular area sidewards of the detector, areas contributing substantially to the overall efficiency were determined. These areas may be considered to be the optimal sizes for new geometries in given positions. After combining all the optimal areas above the detector, sidewards of the detector and for selected energies and the detector, optimal sizes of a new geometry were found. The function can be used both in the front part and the side part of the detector but its validity is limited. The value of MDA for the particular geometry is in indirect proportion to the efficiency square root and thus this new geometry should lead to minimum values of MDA.

The goal of the thesis was to analyse the space arrangement of the gamma - spektrometry laboratory at the RC SÚJB České Budějovice in order to design an optimal regime in a radiological emergency.

A three-layer feed-forward artificial neural network (ANN) with a back-propagation learning algorithm was used to predict the minimum detectable activity ( A D ) of radionuclides ( 226 Ra, 238 U, 235 U, 40 K, 232 Th, 134 Cs, 137 Cs and 7 Be) in environmental soil samples as a function of measurement time. The ANN parameters (learning rate, momentum, number of epochs, and the number of nodes in the hidden layer) were optimized simultaneously employing a variable-size simplex method. The optimized ANN model revealed satisfactory predictions, with correlation coefficients between experimental and predicted values 0.9517 for 232 Th (sample with 238 U/ 232 Th ratio of 1.14) to 0.9995 for 40 K (sample with 238 U/ 232 Th ratio of 0.43). Neither the differences between the measured and the predicted A D values nor the correlation coefficients were influenced by the absolute values of A D for the investigated radionuclides.