Intrinsic background of the beta channel of the aerosol volumetric activity monitor

The work is devoted to the study of the features of generation of the intrinsic background of the measuring beta channel of the aerosol monitor in real conditions of measuring the volumetric activity of aerosols, caused by radionuclides of technogenic origin. The influence of external factors on the generation of the level of the intrinsic background of the measuring channel of the monitor and its metrological characteristics is investigated. The reliability of the results of measurements of the volumetric activity of air aerosols substantially depends on the correct accounting of external factors, parameters of the monitored environment and the specified operating mode of the monitor. Aerosol volumetric activity monitors, as a rule, operate in a continuous mode, in which the aspiration method of aerosol accumulation is implemented, followed by measuring the volumetric activity of aerosols by alpha radiation and (or) beta radiation generated by technogenic radionuclides. This article describes the results of experiments on measuring the iCAM aerosol monitor’s intrinsic beta channel background under real operating conditions, and its dependence on external factors. The studies were carried out on iCAM aerosol monitors (iCAM/D and iCAM/MF modifications) manufactured by Canberra Industries Inc. in a laboratory room in normal climatic conditions with a radon volumetric activity of 35±10 Bq·m-3 and an equivalent dose rate of gamma radiation of 0.13±0.02 μSv·h-1. In modern aerosol monitors, software and hardware solutions are implemented that allow to significantly reduce the background level and, as a result, to expand the measurement range of the volumetric activity of aerosols towards low values.

Adapted Method of Radiation Response Function Calculation for Development of High-Sensitivity Reference Meters Based on Scintillation Detection Units with NaI(Tl) Crystals for Dosimetry of Low-Intensity and Near-Background Levels

Metrological support of photon radiation fields of low-intensity and near-background levels (0.04–100 μSv/h (μGy/h)) by ambient equivalent dose rate or kerma rate in air using scintillation detectors with NaI(Tl) crystals looks promising and in demand in dosimetry, but nontrivial due to the complex dependence of efficiency registration of gamma quanta from energy. The solution of such problems with the use of these detectors can be based on the use of the radiation response functions, which are functionals of the energy distribution of the radiation field fluence. The paper proposes a method for calculating the radiation response function adapted for solving metrological support problems for creating high-precision dosimetric measuring instruments based on scintillation detection units with NaI(Tl) crystals.

177Lu-DOTA-0-Tyr3-Octreotate Infusion Modeling for Real-Time Detection and Characterization of Extravasation During PRRT

Purpose. Given the recent and rapid development of peptide receptor radionuclide therapy (PRRT), increasing emphasis should be placed on the early identification and quantification of therapeutic radiopharmaceutical (thRPM) extravasation during intravenous administration. Herein, we provide an analytical model of 177Lu-DOTA0-Tyr3-octreotate (Lutathera®) infusion for real-time detection and characterization of thRPM extravasation. Methods. For 33 Lutathera®-based PRRT procedures using the gravity infusion method, equivalent dose rates (EDRs) were monitored at the patient’s arm. Models of flow dynamics for nonextravasated and extravasated infusions were elaborated and compared to experimental data through an equivalent dose rate (EDR) calibration. Nonextravasated infusion was modeled by assuming constant volume dilution of 177Lu activity concentration in the vial and Poiseuille-like laminar flow through the tubing and patient vein. Extravasated infusions were modeled according to their onset times by considering elliptically shaped extravasation with different aspect ratios. Results. Over the 33 procedures, the peak of the median EDR was reached 14 min after the start of the infusion with a value of 450 uSv/h. On the basis of experimental measurements, 1 mSv/h was considered the empirical threshold for Lutathera® extravasation requiring cessation of the infusion and start again with a new route of injection. According to our model, the concentration of extravascular activity was directly related to the time of extravasation onset and its duration, a finding inherent in the gravity infusion method. This result should be considered when planning therapeutic strategy in the case of RPM extravasation because the local absorbed dose for β-emitters is closely linked to activity concentration. For selected EDR values, charts of extravasated activity, volume, and activity concentration were computed for extravasation characterization. Conclusion. We proposed an analytical model of Lutathera® infusion and extravasation (gravity method) based on EDR monitoring. This approach could be useful for the early detection of thRPM extravasation and for the real-time assessment of activity concentration and volume accumulation in the extravascular medium.

Assessment of the Radiation and Health Physics Situation in the Area of Ship Repair Enterprises in Kamchatka Krai

The objectives of the study are to examine the radiation and health physics situation in the area of ship repair enterprises servicing ships with nuclear power installation; to assess its possible impact on the environment and the population. Materials and research methods. The study of radiation and health physics situation on the territory was conducted by walking gamma survey using portable gamma spectrometric complexes MKS-01A "Multirad-gamma" and MKS-AT6101C. Gamma-spectrometric and radiochemical methods of analysis were used to determine the specific activity of man-made and natural radionuclides in environmental samples. Results of the study and their analysis. Practical medical and hygienic measures to study the radiation and health physics situation were carried out in 2019. It was found that the ambient equivalent dose rate in the areas of ship repair enterprises is at the level of regional values and does not exceed 0.12 μSv/h. Radionuclide specific activity in the soil of the surveyed areas does not exceed 4.5 Bq/kg — for 90Sr and 12 Bq/kg — for 137Cs, which does not exceed the established norms for unrestricted use of solid materials. Radionuclide content in the sea water samples taken in the area of closed administrative territorial unit Krasheninnikov Bay does not exceed on average: for 137Cs — 7 mBq/L, for 90Sr — 2.1 mBq/L. When comparing the results obtained with the official data on the radionuclide content in the water of Avacha Bay (90Sr up to 2.08 mBq/L at the annual average of 1.14 mBq/L), we may state that they are at the same level as the regional ones. Radionuclide content in bottom sediment samples varies within the following limits: for 137Cs — from 0.14 to 3 Bq/kg, for 90Sr — from 0.11 to 1.5 Bq/kg and is similar to the general values for soil samples. Thus, the radiation and health physics characteristics of the study area vary little and remain practically at the level of the results of studies conducted in 2014-2015. The content of man-made radionuclides in the samples of environmental objects is at the level of average values typical for the region. Potentially radiation-hazardous works carried out in 2019 at enterprises of closed administrative territorial unit Vilyuchinsk had no reliable radiation impact on the environment and population.

Analysis of Indoor Radon Level and its Health Risks Parameters in Three Selected Towns in Port Harcourt, Rivers State, Nigeria

Analysis of indoor radon level and its health risk parameters has been carried out in Borikiri (BT), Diobu (DR), and Rebisi (RB) towns in Port Harcourt, Rivers State, Nigeria. A pocket sized Corentium Arthings digital radon detector meter was used to record the indoor radon concentration levels. The geographical coordinates were recorded using a hand-held geographical positioning system (GPS) for the various sample points. A total of ten houses were measured for each town making a total of 30 sample points for the three communities. The results obtained show that for Borikiri town, the concentration level varied from 30.7100 - 19.9800 Bqm-3 with an average of 11.32 ± 2.59 Bqm-3 . The annual absorbed dose varied from 7.7478 - 1.1202 mSv/yr with a mean value of 2.59 ± 0.65 mSv/yr while the annual equivalent dose rate varied from 0.829 - 0.336 mSv/yr with an average of 0.69 ± 0.16 mSv/yr The excess life time cancer risk calculated for seventy years (70yrs) varied from 6.510 - 0.941 with an average of 2.45 ± 1.71. The results of the indoor concentration level for Diobu town ranged from 37.74 - 5.9200 Bqm ?3 with a mean value of 12.95 ± 2.91 Bqm-3 . The annual absorbed dose for the area ranged from 9.5214 - 1.1494 with an average of 3.26 ± 0.73 mSv/yr, the annual equivalent dose rate varied from 0.694-0.359 with a mean of 0.78±0.8, the excess life time cancer risk calculated for seventy years ranged from 8.000-1.725 with a mean of 2.91±0.61. The indoor concentration level for Rebisi town ranged from 12.9500?4.0700 Bqm-3 with an average of 8.55 ± 1.00, the annual absorbed dose ranged from 3.2671 - 1.0268 mSv/yr, the annual equivalent dose rate varied from 0.784 - 0.269 with an average of 0.52 ± 0.06, the excess life time cancer risk of 2.745 - 0.863 with an average of 1.82 ± 0.21. The results of the indoor concentration levels, the annual absorbed dose and the annual effective dose rate are all below the ICRP safe limit. However, the results of the excess life time cancer risk are all higher than the ICRP safe standard limit of 0.029 × 10-3 .

Natural Radioactivity and Radon Exhalation from Building Materials in Underground Parking Lots

The change of natural ionizing radiation and the radon exhalation rates from typical building materials in underground parking lots are presented in the article. The activity concentration of natural radionuclides 232Th, 226Ra, and 40K in six important types of construction materials, which are mostly used in Lithuania, were analyzed using high-resolution gamma spectroscopy. The highest values were found in concrete and ferroconcrete samples: 226Ra 44 and 90 Bq kg−1; 232Th 29 and 34 Bq kg−1; 40K 581 and 603 Bq kg−1. A strong positive correlation (0.88) was observed between radium activity concentration and radon concentration. The activity indexes (Iα and Iγ) and radium equivalent activity (Req) evaluating the suitability of materials for such constructions from the view of radiation safety were determined. The average values of the calculated absorbed dose rate in samples ranged from 18.24 nGy h−1 in the sand to 87.26 nGy h−1 in ferroconcrete. The calculated annual effective dose was below the limit of 1.0 mSv y−1. The values of the external and internal hazards index (Hex and Hin) were all below unity, and the values of Iγ and Iα were below the recommended levels of 0.5 and 1. Dosimetric analysis of underground parking lots was carried out. It was determined that the external equivalent dose rate caused by the 222Rn progeny radiation in the underground car parking lots varies from 17 to 30% of the total equivalent dose rate.

Model for Reconstruction of γ-Background during Liquid Atmospheric Precipitation

With regard to reconstructing the gamma background dose rate, existing models are either empirical with limited applicability or have many unknown input parameters, which complicates their application in practice. Due to this, there is a need to search for a new approach and build a convenient, easily applicable and universal model. The paper proposes a mathematical model for reconstructing the temporal evolution of the ambient equivalent γ-radiation dose rate during rain episodes, depending on the density of radon flux from the soil surface, as well as the duration and intensity of rain. The efficiency of the model is confirmed by the high coefficient of determination (R2 = 0.81–0.99) between the measured and reconstructed ambient equivalent dose rate during periods of rain, the simulation of which was performed using Wolfram Mathematica. An algorithm was developed for restoring the dynamics of the ambient equivalent γ-radiation dose rate during rainfall. Based on the results obtained, assumptions were made where the washout of radionuclides originates. The influence of the radionuclides ratio on the increase in the total γ-radiation dose rate was investigated.

Влияние зданий на суммарный гамма-фон

The influence of buildings on the total gamma background radiation was investigated. The total gamma radiation between a building made from bricks and a field, which are 100 m apart (away from the influence of other buildings), was measured using a scintillation detector. Measurements of ambient equivalent dose rate at different heights above the soil and a horizontal distance from 0.1 m – 100 m in variable steps were taken. A new approach was developed to assess the contribution of gamma background radiation from the soil and the building to the total gamma background radiation. It was obtained that the gamma background radiation contributed by buildings, greatly affects the total gamma background radiation up to a distance of 2 m, at which there was a significant decrease in the total gamma background radiation. The percentage of the building that contributes to the total gamma background radiation is noted to be between 4 – 29% of the total gamma background. This shows that most of the background radiation in the environment is contributed by the gamma background radiation in the soil. Also, the annual equivalent dose received by a person who sits near the building was 0.09 mSv, which was higher than an adult who works far away from the building (0.08 mSv). Both were however less than the global level. It also was found that the best place to install a detector for measuring gamma radiation was found to be a distance of 1.5 m away from the building. Исследовано влияние зданий на общий гамма-фон. Гамма-фон между кирпичным зданием и полем, находящимся на расстоянии 100 м друг от друга (вдали от влияния других зданий), измерялось с помощью сцинтилляционного детектора. Были проведены измерения мощности амбиентного эквивалента дозы на разной высоте над почвой и на горизонтальном расстоянии от 0,1 м до 100 м с переменным шагом от здания. Был разработан новый подход для оценки вклада от почвы и здания в общий гамма-фон. Было получено, что гамма-излучение, вносимое зданиями, сильно влияет на суммарный гамма-фон на расстоянии до 2 м, на котором наблюдалось значительное уменьшение излучения в общем. Отмечено, что процент вносимого зданием вклада в общий гамма-фон, составляет от 4 до 29%. Это показывает, что большая часть фонового излучения в окружающей среде обеспечивается гамма-излучением почвы. Кроме того, годовая эквивалентная доза, полученная человеком, сидящим рядом со зданием, составила 0,09 мЗв, что выше, чем у взрослого, работающего далеко от здания (0,08 мЗв). Однако оба значения ниже среднемирового. Также было обнаружено, что лучшим местом для установки детектора гамма-излучения будет удаленное на 1,5 м от здания.

Environmental Estimation of Radiation Equivalent Dose Rates in Soils and Waters of Northern Calabria (Italy)

In this study, the equivalent dose rate of natural radionuclides ( H T ) in 99 spring water and surface soil samples was determined using an alpha, beta, and gamma high sensitivity detector up within a Geiger-Muller tube and with an external probe NaI (Tl). The samples were collected in the Crati basin (southern Italy), and during sample collection, water quality parameters were detected in situ and at the University of Calabria laboratories. A Pearson correlation coefficient analysis was applied to identify and clarify the relationships between water physical-chemical properties and soil and water radioactivity. Results show that the mean H T for spring waters is 97.07 μSv/h. Furthermore, the mean H T for surface soils is 97.92 μSv/h, thus evidencing higher mean H T values than worldwide ones reported in a previous literature. Low correlation coefficients were detected between water H T and conductivity and pH. On the contrary, a reasonable correlation was found between H T in spring water and in soil. This relationship is associated with some rocks of the Sila Massif and of Coastal Chain, i.e., plutonic and metamorphic crystalline rocks. Finally, the estimation of the health risk was calculated: results did not evidence serious dangers for people living in the studied environment. The results from this survey for the H T evaluation provide an extensive assessment of the background exposure levels in the investigated area.

Operative assessment of radioactive contamination of agricultural land for their return to use

Significant regression dependencies between ambient equivalent dose rate and 137Cs contamination density, as well as between 137Cs and 90Sr contamination densities were obtained. An economically inexpensive approach to estimating the density of soil contamination by 137Cs, 90Sr, and plutonium isotopes with controlled uncertainties has been proposed and tested. The approach allows also the immediate evaluation of the density of radionuclide soil contamination even if there is a contamination gradient within the agricultural land.