When a radioactive nucleus emits beta particles these

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When a radioactive nucleus emits beta particles, these particles ionize the gas in the instrument, which registers the ionization by indicating that an electric current has passed between two electrodes. Another measuring device, called a scintillation scintillation counter counter , has a phosphor that emits a unit of light when a beta particle or gamma ray strikes it. Intensity is recorded in counts/min or counts/s. 17
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Detecting Nuclear Radiation Ionizing radiation 18
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Characteristics of Nuclear Radiation Figure 9-6 Penetration of radioactive emissions . 19
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Radiation Dosimetry Although alpha particles cause more damage than X-rays or gamma radiation, they have very low penetrating power and cannot pass through skin. Consequently alpha particles are not harmful to humans or animals as long as they do not get into the body; if they do get into the body, they can be quite harmful. Beta particles are less damaging to tissue than alpha particles but penetrate farther and so are generally more harmful. Gamma rays, which can easily penetrate skin, are by far the most dangerous and harmful form of radiation. 20
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Radiation Dosimetry Terms and units 1 Becquerel (Bq): 1 Becquerel (Bq): 1 Bq is 1 dps. 1 Bq is 1 dps. 1 Curie (Ci): 1 Curie (Ci): Ci = 3.7 x 10 10 dps. Roentgen (R): Roentgen (R): The amount of radiation that produces ions having 2.58 x 10 -4 coulomb/kg; a measure of the energy delivered by a radiation source. Radiation absorbed dose (Rad): Radiation absorbed dose (Rad): A measure of the ionizing radiation absorbed; the SI unit is the gray (Gy). gray (Gy). 1 Gray (Gy): 1 Gray (Gy): Gy = 1 joule/kilogram (1 J/kg). Roentgen-equivalent-man (Rem): Roentgen-equivalent-man (Rem): A measure of the effect of the radiation when one roentgen is absorbed by a person; the SI unit is the sievert (Sv) sievert (Sv) where one Sv = 1 J/kg. 21
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Radiation Dosimetry The relationship between delivered dose in roentgens (R) and the absorbed dose in rads; exposure to 1 R of high energy photons yields 0.97 rad in water, 0.96 rad in muscle, and 0.93 rad in bone. For lower-energy photons such as soft x-rays, 1 R yields 3 rads of absorbed radiation in bone; soft tissue lets radiation pass, but bone absorbs it, giving an x-ray. 22
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Radiation Dosimetry Table 9-4 Average exposure to radiation from common sources 23
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Radiation Dosimetry A single whole-body irradiation of 25 rem is noticeable in decreased white blood cell count.
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