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Radiation Dose and Exposure Indicators
Published in Ken Holmes, Marcus Elkington, Phil Harris, Clark's Essential Physics in Imaging for Radiographers, 2021
There are three SI units to remember:Absorbed dose Gray. Defined as: one Gray deposits 1 joule of energy per kilogram of matter. It is used as a measure of absorbed dose, specific energy (imparted), and kerma (an acronym for kinetic energy released per unit mass). The Gray is defined independently of any target material. However, when measuring kerma the reference target material must be defined explicitly, usually as dry air at standard temperature and pressure.Equivalent dose is determined by multiplying the absorbed dose by a quality factor depending on the type of radiation and related to human tissue.Effective dose is determined by equivalent dose multiplied by the sensitivity of the tissue irradiated.
Tables and Guidelines for Laboratory Safety
Published in Thomas J. Bruno, Paris D.N. Svoronos, CRC Handbook of Basic Tables for Chemical Analysis, 2020
Thomas J. Bruno, Paris D.N. Svoronos
The committed dose (or more properly, the committed dose equivalent, HT, 50) is the total dose accumulated over a 50-year period after the ingestion or inhalation. The equivalent dose (also called the dose equivalent or biological dose) describes the effect of radiation on human tissue, rather than the physical effects of the radiation alone. This quantity is expressed in Sieverts (Sv) and is found by multiplying the absorbed dose, in grays, by a dimensionless quality factor Q (which depends on the radiation type) and by another dimensionless factor N (the tissue weighting factor). Q is also called the relative biological effectiveness (RBE). The factor N depends upon the part of the body irradiated, the time and volume over which the dose was spread, and the species of the subject.
Artificial Events: Clouds Explosions, Dangerous Clouds, and Physical Protection
Published in Maurizio Cumo, Antonio Naviglio, Safety Design Criteria for Industrial Plants, 2019
Radioactive substances have identical fire and explosion hazards than the same material when not radioactive. More, they represent a supplementary danger because of the radiation emitted. The hazard can come from external irradiation and/or from contamination. The integrated equivalent dose is measured in Sievert (1 Sv = 1 Jkg−1). The effects of exposition even to small doses of ionizing radiation are long-term effects (cancer) and genetic effects. Significant doses, of the order of many Sieverts, can produce in humans immediate serious consequences; massive doses (tens of Sieverts) within a short period of time can be fatal to humans. The maximum yearly reference dose for professionally exposed workers is 0.05 Sv. Some corresponding yearly intakes by inhalation are 2 104 Bq for Po210, 2 102 Bq for Pu239, and 2 106 Bq for I131. A radioactive substance has an activity of 1 Bq (1 Bq = 2.7 10−11 Curie) when it has a disintegration per second. (See Chapter 2 for further details).
MLEM Neutron Spectra Unfolding in a Radiotherapy Bunker Using Bonner Sphere Spectrometer
Published in Nuclear Science and Engineering, 2023
S. Oliver, S. Morató, B. Juste, R. Miró, G. Verdú, N. Tejedor, J. Pérez-Calatayud
The biological effects of ionizing radiation on the human body are measured with the equivalent dose. The weighting factor wr for neutrons and alpha particles presents a high value. In the case of neutrons, depending on the energy, wr includes values in the range from 5 to 20 producing an equivalent dose on the patient or clinical staff up to 20 times larger than the absorbed dose. Considering these facts, exposure to these nonnegligible doses produced by secondary neutrons could be significant for people’s health, causing a radiological protection issue.9