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

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%

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

Investigation of the importance of site-specific fauna in environmental risk assessment for routine atmospheric radionuclidesreleases

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A survey on emergency thyroid monitoring strategies and capacities in Europe and comparison with international recommendations

There are ongoing social debates about the risks and benefits of using nuclear reactors to generate electricity. Radiation accidents can occur for different reasons and even be caused deliberately as a result of terrorist actions, and these may affect from a few to thousands of people. After a major release of radioactive iodine as a result of a nuclear accident, large number of potentially affected people may require rapid assessments to determine the degree of thyroid contamination, especially children and young people given that their thyroid is a highly radiosensitive organ and particularly vulnerable to the carcinogenic action of ionising radiation. To date, there is no internationally agreed protocol for measuring 131I in the thyroid of affected persons, especially in children. To address this problem, the Child and Adult Thyroid Monitoring After Reactor Accident (CAThyMARA) project (https://www.eu-neris.net/projects/operra/operra-cathymara.html) focused on post-accidental 131I measurements in the thyroid, giving special attention to children and involved 15 institutions from 12 European countries. One of the Work Packages of the project had the objective to overview existing national plans and means for thyroid monitoring and to review international recommendations about radioiodine monitoring in the thyroid in case of a large scale nuclear accident. To achieve this objective, a questionnaire-based survey was carried out from May to October 2016. The survey results were based on the analysis of the answers of 31 institutions in 18 European countries, which included a wide range of questions related to emergency plan strategies, monitoring strategies for radioiodine in thyroid, dose assessment, etc. In addition, the peer-review literature in this area was reviewed and summarised. The results of the survey together with the current international recommendations about radioiodine monitoring in thyroid could provide important information on existing gaps, which can be used to develop new or update existing guidelines on thyroid monitoring after a nuclear accident. © 201