Long-term programme of biophysical monitoring of the personnel involved in the construction of the new safe confinement

The international Shelter Implementation Plan (SIP) foresees a step-by-step transformation of the Chornobyl site into the safe condition. The New Safe Confinement (NSC), is an unprecedented 108-meter tall structure over the destroyed Unit 4 of the Chernobyl Nuclear Power Plant, and is a central element of SIP. Many workers involved in SIP may have a direct contact with fragments of the irradiated fuel, fuel-containing aerosols, and other contaminated material at the Chornobyl industrial site. Isotopes of plutonium, americium, strontium, and cesium are dominating in internal exposure of SIP workers. The safety of workers is a high priority of SIP. Starting from 2004 the Ukrainian Radiation Protection Institute (RPI) is performing a large-scale Internal Dosimetry Program as an integral part of SIP. Pu contents in fecal and urine samples and the whole-body counters‟ (WBC) data and are the main source of the quantitative data used for the dose assessment. The RPI radiochemical laboratories in Kyiv and at the Chornobyl site employed the standard radiochemical technique and equipped with ninety six alpha-spectrometers. The range of WBCs includes the scanning low-background WBC, four Canberra FastScan WBCs, and four chair-type WBCs. The car-borne WBC is located in Kiev and reserved for the emergency purposes. As on September 2017 the Internal Dosimetry Program has covered more than 17 000 workers, which undergone 1 230 000 measurements of ¹³⁷Cs on WBCs, 87 000 measurements of ²³⁹⁺²⁴⁰Pu contents in fecal samples and 4 400 measurements of ²³⁹⁺²⁴⁰Pu contents in urine samples. Such a large-scale programme ensured a reliable monitoring of intakes of the insoluble radioactive material.У міжнародному Плані здійснення заходів (ПЗЗ) передбачається поетапне перетворення чорнобильського майданчика у безпечний стан. Новий безпечний конфайнмент є безпрецедентною структурою заввишки 108 м над зруйнованим 4-м блоком ЧАЕС, він є центральним елементом ПЗЗ. Багато працівників, залучених у ПЗЗ, можуть мати прямий контакт із фрагментами опроміненого палива, паливовмісними аерозолями та іншими забрудненими матеріалами на промисловому майданчику в Чорнобилі. Ізотопи плутонію, америцію, стронцію і цезію домінують у внутрішньому опроміненні працівників ПЗЗ. Безпека працівників має високий пріоритет у ПЗЗ. Починаючи з 2004 р., Науково-дослідний інститут радіаційного захисту АТН України (ІРЗ) здійснює великомасштабну програму дозиметрії внутрішнього опромінення як невід‟ємну частину ПЗЗ. Дані вмісту плутонію у пробах калу і сечі та лічильників випромінювань людини (ЛВЛ) і основним джерелом кількісних даних, що використовуються для оцінки дози. Радіохімічні лабораторії ІРЗ у Києві і на майданчику в Чорнобилі використовували стандартну радіохімічну методику, вони оснащені 96 альфа-спектрометрами. Номенклатура ЛВЛ включає в себе скануючий низькофоновий ЛВЛ, чотири ЛВЛ Canberra FastScan і чотири ЛВЛ типу “крісло”. Мобільний ЛВЛ розташований у Києві і зарезервований для надзвичайних цілей. Станом на вересень 2017 р. рамками програми дозиметрії внутрішнього опромінення було охоплено понад 17 000 працівників, які пройшли 1 230 000 вимірювань ¹³⁷Cs на ЛВЛ, 87 000 вимірювань вмісту ²³⁹⁺²⁴⁰Pu у пробах калу і 4 400 вимірювань вмісту ²³⁹⁺²⁴⁰Pu у пробах сечі. Така великомасштабна програма забезпечила надійний контроль надходжень нерозчинного радіоактивного матеріалу.В международном Плане осуществления мероприятий (ПОМ) предусматривается поэтапное преобразование чернобыльской площадки в безопасное состояние. Новый безопасный конфайнмент – это беспрецедентная структура высотой 108 м над разрушенным 4-м блоком ЧАЭС, он является центральным элементом ПОМ. Многие работники, вовлеченные в ПОМ, могут иметь прямой контакт с фрагментами облученного топлива, топливосодержащими аэрозолями и другими загрязненными материалами на промышленной площадке в Чернобыле. Изотопы плутония, америция, стронция и цезия доминируют во внутреннем облучении работников ПОМ. Безопасность работников имеет высокий приоритет в ПОМ. Начиная с 2004 г., Научно-исследовательский институт радиационной защиты АТН Украины (ИРЗ) осуществляет крупномасштабную программу дозиметрии внутреннего облучения как неотъемлемую часть ПОМ. Данные содержания плутония в пробах кала и мочи, а также счетчиков излучений человека (СИЧ) являются основным источником количественных данных, используемых для оценки дозы. Радиохимические лаборатории ИРЗ в Киеве и на площадке в Чернобыле использовали стандартную радиохимическую методику, они оснащены 96 альфа-спектрометрами. Номенклатура СИЧ включает в себя сканирующий низкофоновый СИЧ, четыре СИЧ Canberra FastScan и четыре СИЧ типа “кресло”. Мобильный СИЧ расположен в Киеве и зарезервирован для чрезвычайных целей. По состоянию на сентябрь 2017 г. в рамках программы дозиметрии внутреннего облучения было охвачено более 17 000 работников, которые прошли 1 230 000 измерений ¹³⁷Cs на СИЧ, 87 000 измерений содержания ²³⁹⁺²⁴⁰Pu в пробах кала и 4 400 измерений содержания ²³⁹⁺²⁴⁰Pu в пробах мочи. Такая крупномасштабная программа обеспечила надежный контроль поступлений нерастворимого радиоактивного материала

Assessment from in vivo measurements of thyroid dose due to iodine-131 inhalation when stable iodine has been administered

International audiencePotassium iodide (KI) is a well-known thyroid prophylactic agent that blocks the incorporation of radioactive iodide in the thyroid; it is generally available for oral administration by the population in case of a nuclear release. However, the blockage provided by KI is not 100% effective and therefore activity could still be measured in the thyroid after an intake of radioactive iodine. As a consequence of KI administration the thyroid retention function and the thyroid dose coefficient are modified. To assess the thyroid dose from in vivo measurements these two quantities must be taken into account. In this work we considered the inhalation of 131-iodine by adult, children (1, 5, 10 years-old) and adolescents (15 years). The effect of KI administration was modelled by a time-dependent blood to thyroid transfer rate coefficient. The model was benchmarked against dose coefficient in the absence of KI and against the protective effect curves depending on KI administration time. This KI specific model was used to provide correction factors for dose assessment. These multiplicative correction factors apply to a “classical” dose assessment, i.e. a dose assessment based on the ICRP default model that ignores the KI effect. This solution has been preferred since it provides ready to use values avoiding implementing the KI specific model. The correction factors depend on the measurement time and on the KI administration time. They are relatively independent of age and can be described by simple analytic functions. Working examples are provided in this study. For examples, KI administration 12h before the intake and early in vivo measurements (between 4h and 64h) after the intake give correction factors between 1.2 and 15. For late measurements the correction factors are generally small. If KI has been taken after the intake the correction factors are also generally small, except for very early measurements. © 2019 Elsevier Lt

Current approaches for assessment of the impact of radioactive discharges to the environment: Update of IAEA safety report series 19

The IAEA Fundamental Safety Principles state that “People and the environment, present and future, must be protected against radiation risks. Radiation risks may transcend national borders and may persist for long periods of time. The possible consequences, now and in the future, of current actions have to be taken into account in judging the adequacy of measures to control radiation risks.” This emphasizes the importance of prospective assessment of radiological impacts to proactively prevent significant adverse effects through proper planning of facilities and activities. In the case of planned exposure situations, the authorized discharge of radionuclides to the atmosphere and surface water environments is a legitimate practice in hospitals, research facilities, nuclear power plants, and for other facilities and activities. For such practices, prospective assessment of public exposure and environmental impacts from radioactive discharges is an essential regulatory requirement to support the optimization of authorized discharges. Both the radiological doses received by members of the public (the representative person) and by wildlife (reference animals and plants) are considered in the assessment. An updated screening methodology (superseding Generic Models for Use in Assessing the Impact of Discharges of Radioactive Substances to the Environment (IAEA Safety Report Series No. 19)) for the integrated assessment of doses received by the public and by wildlife has been developed. The methodology provides a structured approach, including pre-calculated screening coefficients, that can be used to assess the impact of radioactive discharges from facilitates and activities. A series of IAEA Safety Reports have been developed that cover: an updated generic screening methodology for the assessment of doses to the public; a new methodology for the assessment of doses to flora and fauna; and a detailed description of the models, assumptions and data that are used to calculate the screening coefficients and additional information on models and data that can be used for more site-specific assessments. Two supporting TECDOCs have also been produced: the first describes the differences in the screening coefficients for doses to the public between the ‘SRS-19’ methodology and the updated methodology; and the second provides a series of scenarios applying the updated methodology that can be used for familiarization and training. The key aspects of this updated methodology and how it can be implemented in the planning, design and operation of nuclear facilities and activities will be presented

Influence of chronic smoking on the dose due to radon exposure

International audienceIntroductionLung cancer is the second most common type of cancer worldwide, with two major causes being smoking and radon exposure. But how chronic smoking affects radon doses to the lungs is not clear. In this study, we identified smoking related parameters that could influence the dose received by the lungs from radon.MethodsChanges in the lungs and respiratory functions caused by smoking found in the literature were used to adjust the Human Respiratory Tract Model and calculations were performed to assess the influence of smoking on the radon doses.Also based in the literature a new dose calculation tool for quantitative assessment of the impact of smoking and other factors, such as age, sex, nasal or mouth breathing habits is under preparation. To ensure the quality of calculations, the developed code is applied for the quality assurance programme of the ICRP Task Group on Internal Dose Coefficients and in the preparation of ICRP publications and electronic datasets. Additionally, PHITS was used for validation of the energy transport calculations. These tools will incorporate functionalities for the analysis of the sensitivity of estimates of lung tissue absorbed doses to changes in the lung deposition pattern, source-target geometry and biokinetics associated with smoking.ResultsSmoking was found to change the thickness of epithelial layers and length of cilia in the respiratory tract and influence respiratory parameters. Clearance of inhaled aerosol also differs in smokers and non-smokers, indicating that smoking could influence absorption into blood and muco-ciliary transport. A pilot version of the tool for calculating the alpha particles energy deposition in the tissues of the human respiratory tract has been developed.ConclusionsData available from the literature suggests that smoking could lead to changes relevant to the calculation of radiation doses in the respiratory tract, potentially impacting the dose received by smokers due to radon

A robust methodology for assessing thyroid absorbed doses based on individual monitoring data after a severe nuclear accident

International audienceThe paper presents a “one-step” procedure for the direct dose assessment based on thyroid monitoring data obtained after a severe nuclear accident at a light water power reactor. The developed methodology is based on the “dose per content” concept that allows the direct conversion of the measured value to the dose estimate. The paper provides methods and data for assessments of the committed absorbed dose to the thyroid based on measurements of the activity of radioactive isotopes of iodine in the thyroid gland. Values of functions “absorbed dose to the thyroid integrated over 30 days per activity of I-131 measured in the thyroid” were calculated for adults and children. For in utero exposure, the absorbed dose to the thyroid of the offspring is provided per activity measured in the maternal thyroid. The contribution of short-lived radionuclides I-132, I-133, I-134, I-135, and Te-132, is considered by applying correction coefficients. Optionally, the methodology permits the use of measurements of the I-132 activity in the thyroid. Primary sources of uncertainty in the assessed thyroid dose are also discussed. © 201

Changes induced in the human respiratory tract by chronic cigarette smoking can reduce the dose to the lungs from exposure to radon progeny

International audienceChronic cigarette smoking leads to changes in the respiratory tract that might affect the dose received from exposure to radon progeny. In this study, changes induced by cigarette smoking in the respiratory tract were collected from the literature and used for calculation of the dose received by the lungs and organs outside the respiratory tract. Morphological and physiological parameters affected by chronic smoking were implemented in the human respiratory tract model (HRTM) used by the International Commission of Radiological Protection (ICRP). Smokers were found to receive lung doses 3% smaller than the ICRP reference worker (non-smoking reference adult male) in mines and 14% smaller in indoor workplaces and tourist caves. A similar dose reduction was found for the extrathoracic region of the HRTM. Conversely, kidneys, brain, and bone marrow of smokers were found to receive from 2.3- up to 3-fold of the dose received by the respective organ in the ICRP reference worker, although they remained at least two orders of magnitude smaller than the lung dose. These results indicate that the differences in the lung dose from radon progeny exposure in cigarette smokers and non-smokers are smaller than 15%

An analysis of the sensitivity of non-urban environments to radioactive contamination under the IAEA EMRAS-II Program

Since the early 1980s the International Atomic Energy Agency (IAEA) has led a succession of international programs to improve environmental transfer models for the assessment of radiological impacts on humans and non-human biota arising from radionuclides in the environment. These programs have included VAMPS (Validation of Model Predictions), BIOMASS (BIOsphere Modelling and ASSessment), and EMRAS (Environmental Modelling for RAdiation Safety). The current EMRAS-II program (2009-2011) includes both routine and accidental emissions of artificial and natural radionuclides .This paper reports on the activities of Working Group 8 dealing with sensitive non-urban environments. In addition to conventional agricultural settings in the temperate zones, the group is considering special environments such as Alpine, Arctic, temperate forests, freshwater aquatic, and coastal marine environments.Initial modelling exercisesare being carried out for depositions of the long-lived radionuclides 137Cs and 90Sr and the short-lived radionuclide 131I. Radionuclides concentrations are calculated in several environmental compartments, especially those leading to human exposures. Short term and long term radiations doses are calculated to the most exposed human populations. The goal of these exercises is not just to compare different models but also to use these models as tools to investigate which environments and which components of each environment would be most sensitive to a major release of radionuclides. The results will aid in the planning and implementation of emergency countermeasures following a nuclear accident