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Radioisotope Production and Application
Published in Paul R. Bolton, Katia Parodi, Jörg Schreiber, Applications of Laser-Driven Particle Acceleration, 2018
As in all diagnostic applications, we must also consider the dose. The equivalent dose, i.e. the dose that accounts for the biological effects of the radiation is measured in sievert (Sv) units. The corresponding physical quantity is the gray (Gy). One gray (i.e. 1 Gy) corresponds to one joule of radiation energy deposited in one kilogram of tissue, without differentiation of the origin of the radiation. For photons, whatever its energy, the biological weighting factor is equal to one; so, 1 Gy of photons corresponds to 1 Sv. For protons, the biological weighting factor is 2, indicating that the biological effect is higher such that 1 Gy of protons represents 2 Sv. For neutrons, the factor is bigger than one and also depends on the energy of the neutrons. Natural radiation dose, i.e. the equivalent dose we typically receive on Earth, is about 2 mSv/year. The dose for a whole-body PET scanning depends on the tracer and also depends on whether or not it is combined with a CT. Typically it can be of the order of 10 mSv or more. This is a high value, comparable to a few years of natural radioactivity. Therefore, molecular imaging with radiotracers must be medically justified, particularly for whole-body images. Among other things, the activity of the radiotracer needed for a PET data acquisition depends on the photon sensitivity of the gamma detectors that form the image. Technology is evolving to increase this sensitivity, because it can result in a radiation-dose reduction. This aspect is relevant when considering laser-based approaches to radioisotope production.
Ionizing Radiation
Published in Ivan G. Draganić, Zorica D. Draganić, Jean-Pierre Adloff, Radiation and Radioactivity on Earth and Beyond, 2020
Ivan G. Draganić, Zorica D. Draganić, Jean-Pierre Adloff
A whole body irradiation during several hours at doses above 1 sievert gives rise to nausea and vomiting. This disease is known as “radiation sickness” and occurs a few hours after exposure as a result of damage to cells of the intestinal wall. The mortality risk is low at doses below about 1.5 sieverts, but at 8 sieverts, the prognosis is poor. When doses up to 10 sieverts are fatal, death is usually due to secondary infections because of depletion of the white blood cells, which normally provide protection against infection. The chances of survival in such cases can be increased by special medical treatment, which includes isolation in a sterile environment and the stimulation of leukocyte production.
Human physiology, hazards and health risks
Published in Stephen Battersby, Clay's Handbook of Environmental Health, 2023
Revati Phalkey, Naima Bradley, Alec Dobney, Virginia Murray, John O’Hagan, Mutahir Ahmad, Darren Addison, Tracy Gooding, Timothy W Gant, Emma L Marczylo, Caryn L Cox
Stochastic effects – These are effects where the probability of occurrence depends on the radiation dose. They include carcinogenesis and induction of heritable defects. Radiation-induced cancer is clinically and pathologically indistinguishable from other cancers. A linear no-threshold model is assumed at all levels of dose, though there are scant data for very low exposures. Therefore, there is no ‘safe’ radiation dose, but very small exposures convey very small stochastic risks. The absolute cancer risk per unit of radiation dose (risk coefficient) is estimated to be 5.5% per sievert.
Operational Considerations for Space Fission Power and Propulsion Platforms
Published in Nuclear Technology, 2021
Andrew C. Klein, Allen Camp, Patrick McClure, Susan Voss, Elan Borenstein, Paul VanDamme
Humans and equipment associated with space exploration and travel will be affected by the natural radiation fields in space and by radiation sources carried aboard a spacecraft or included in a surface outpost operation. NASA has performed research and developed a set of radiation exposure standards for astronauts,3 and these may be applied to future space missions including fission power and propulsion sources. The basis for the standard is related to the planned career exposure for any astronaut that “shall not exceed 3% Risk of Exposure-Induced Death (REID) for cancer mortality at a 95% confidence level to limit the cumulative effective dose (in units of Sievert) received by an astronaut throughout his or her career.” The resulting dose limits depend upon the mission’s length, and the astronaut’s age, sex, and other considerations. For example, the effective dose limit for a 1-year mission for a never-smoking, 40- to 60-year-old male astronaut would range from 0.88 to 1.17 Sv. The effective dose limit for a similar-age female astronaut is about 20% lower.
Radiological hazard assessment of natural radioactivity in Avcilar region, Turkey: a case of Istanbul University-Cerrahpasa Avcilar Campus
Published in International Journal of Environmental Health Research, 2022
Naim Sezgin, Bilge Ozdogan Cumali, Namik Aysal, George William Kajjumba, Semih Nemlioglu
Long-term exposure to radiation from natural radioactivity in the soil, especially in residential settlement areas, can result in terminal illnesses like cancer. Regulatory authorities use a quantitative risk indices assessment process to define an Excess Lifetime Cancer Risk (ELCR). This value is determined using expected intakes and exposures combined with chemical-specific dose-response data to assess cancer risk during a lifetime. ELCR was calculated using Equation 7; here, AEDE is the annual effective dose equivalent, DL is life expectancy (estimated to be 70 years), and RF is the risk factor given as 0.05 Sv−1 (fatal cancer risk per Sievert) (Ramasamy et al. 2013).
Validation of the MS-CADIS Method for Full-Scale Shutdown Dose Rate Analysis
Published in Fusion Science and Technology, 2018
Stephen C. Wilson, Scott W. Mosher, Katherine E. Royston, Charles R. Daily, Ahmad M. Ibrahim
The value of 0.91 is an approximate conversion from energy deposition in dry air (in Gray per hour) to biological dose (in Sievert) and represents an energy-averaged conversion between energy deposition in air versus soft tissue. This unit conversion and the appropriate source normalization are applied to the raw MCNP f6 tally output after generating the activation gamma source for the first experimental campaign with the ORNL SDDR code suite. The results at different cooling times are compared with the experimental values in Table X.