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Air, Noise, and Radiation
Published in Gary S. Moore, Kathleen A. Bell, Living with the Earth, 2018
Gary S. Moore, Kathleen A. Bell
Since ionizing radiation can neither be seen nor felt, human exposure is measured in terms of the amount of tissue damage it causes. Under the International System of Units, the term gray (Gy) is the unit of absorbed dose, used to quantify the amount of energy form ionizing radiation absorbed per unit mass of material. There is little evidence that present average levels of exposure to ionizing radiation are having a serious adverse effect on the health of the general public. However, higher doses can be injurious to living tissues. The International Congress of Radiation Research has been involved in a long-running argument over what is considered a safe dose of radiation. United States radiation experts from the University of California (UC) at Davis have stated that there are safe values of exposure to radiation (i.e., threshold) that the body can tolerate without the development of cancer. Conversely the International Commission on Radiological Protection stands behind the linear no-threshold theory, stating that the indicated safe dose proposed by the UC Davis researchers does not exist. These arguments about the validity of the linear no-threshold theories are important because regulators use the theory when setting radiation exposure standards.94,95
Application of ICRP Biokinetic Models to Depleted Uranium
Published in Alexandra C. Miller, Depleted Uranium, 2006
Internal dosimetry is based on the widely held premise that the risks of harm from irradiation of tissue by ionising radiation (such as alpha particles, beta particles, and gamma rays) are related to the mean absorbed dose to that tissue, i.e., the amount of energy deposited per unit mass of tissue. It is expressed in grays, symbol Gy. One Gy is equal to one joule per kilogram. The organ dose is taken to be the average absorbed dose in the organ or tissue of interest. For some organs, e.g., liver, kidneys, the organ dose calculated is the average dose to the whole organ, i.e., it is considered that the radiation sensitive cells are distributed throughout the whole organ. In other cases, notably in the parts of the gastrointestinal (GI) tract and respiratory tract, sensitive cells are identified, and the average dose to these is calculated, i.e., the average dose to the tissue at a specified range of depths from a specified organ surface.
Radioactivity and Radiation Hazards
Published in Roland Pusch, Raymond N. Yong, Masashi Nakano, Geologic Disposal of Low- and Intermediate-Level Radioactive Waste, 2017
Roland Pusch, Raymond N. Yong, Masashi Nakano
Absorbed dose is an amount of radiation energy given to a material, which induces the excitation of various molecules (atoms) in materials. The SI unit is gray (Gy), which is defined as the dosage giving energy of 1 J to a material of 1 kg.
Prompt Radiation Dose Analysis Within the European Spallation Source Connection Cell
Published in Nuclear Science and Engineering, 2023
Second, if the absorbed dose rate of a material not listed in Table IV is needed, one can use the effective dose rate to humans as an upper limit. In this case, assume that 1-Sv effective dose is equivalent to 1-Gy absorbed dose. The assumption that effective dose and absorbed dose are equivalent is good for photons but is conservative for neutrons. Assume once again that ESS will operate 5400 h/yr and the presence of borated concrete in the monolith vessel head, the maximum absorbed dose rate to a material not listed in Table IV, is 788.4 Gy/yr (±10.4%) based on the assumption that effective dose and absorbed dose are equivalent. If this dose rate exceeds the maximum allowable dose rate for a material, the three options mentioned in the previous example are still available, i.e., change the material, relocate the material, or shield the material. In this case there is a fourth option available as well, which is to perform new calculations that evaluate absorbed dose for this new material. With these new material dose results, see the example in the previous paragraph.
Gamma-radiation exposure-induced modifications in the thermal, dielectric, and electro-optical properties of two-room temperature antiferroelectric liquid crystal mixtures
Published in Liquid Crystals, 2022
Asim Debnath, Biplab Kumar Singha, Debarghya Goswami, Sripada Haldar, Pradip Kumar Mandal
Irradiation of the AFLC mixtures by γ-rays was done using a 60Co γ-source (1.17 and 1.33 MeV) having an average energy of 1.25 MeV and an absorbed dose rate of 1.5 kGy/hr (absorption of one joule of radiation energy per kilogram of matter, or 100 rads, is measured in Gy, gray) at the UGC-DAE Consortium for Scientific Research (CSR), Kolkata Centre, India. The diameter and length of the gamma irradiation chamber are 10.6 cm and 14 cm, respectively. This irradiation chamber has a facility to move the sample from the loading position to the irradiation position. Gamma irradiation chamber, similar to the one described schematically by Kumar et al. [25], was used in the present investigation. To irradiate, a sample can be placed in the irradiation chamber while it is in the loading position, and a timer is set by a control panel unit to deliver a pre-selected dose. The irradiation chamber along with the sample is automatically transferred to the irradiation position at the push of a button located on the control panel and is returned to the unloading position at the end of the pre-set irradiation period.
Effect of γ-irradiation on the display parameters of a room temperature ferroelectric liquid crystal mixture
Published in Liquid Crystals, 2021
Asim Debnath, Debarghya Goswami, Biplab Kumar Singha, Sripada Haldar, Pradip Kumar Mandal
Irradiation of the FLC mixture M2 by γ-rays was carried out using a 60Co γ-source having absorbed dose rate of 1.5 kGy/hr (1 Gray (Gy) is defined as the absorption of one joule of radiation energy per kilogram of matter which equals to 100 rad) at the UGC-DAE Consortium for Scientific Research (CSR), Kolkata Centre, India. Dielectric cells, made of low resistive (about 20 Ω/sq) transparent indium tin oxide (ITO) coated glass plates as electrodes with an effective area of 1cm2 and of thickness 5 µm, were filled by the mixture in isotropic phase and then placed in the γ-radiation chamber at room temperature. Cells were continuously exposed for different time durations to obtain the total doses of radiation in the range of 7.5–53.25 kGy. Polarising optical microscopy, dielectric, and electro-optic studies of the irradiated samples were done using these dielectric cells. Inside surfaces of the cells were pre-rubbed with polyimide to get a homogeneous alignment of the LC molecules when cooled at a very slow controlled rate resulting in bookshelf geometry [24] required for the dielectric spectroscopic study.