Units of Radiation

Almost all naturally occurring elements are made up of isotopes. Isotopes are atoms of the same 

Alpha (a) particle It is a double positive charge carrying helium nucleus He2+) released spontaneously from a high-atomic mass radioactive element. It has low penetration power and can be stopped by a thin sheet of paper or a layer of air. Has no external hazards has internal hazards. 

Beta (0) particle It is a negatively charged particle equivalent to an electron (e or 0 ). It is emitted by a radioactive material. A beta particle carrying a positive charge is called a positron (0+). May cause skin bums. It is both an external and internal hazard. 

X-ray It is a high-energy, highly penetrating radiation. Its origin is the inner orbital electrons in an atom. X-rays are produced by the sudden acceleration of charge particles. It poses high external hazards. 

Example 3.8 Name additional nuclear or extra-nuclear particles. 

---

IAMAP, Terminology and Units of Radiation Quantities and Measurements, Radiation Commission of the International Association of Meteorology and Atmospheric Physics, Boulder, CO, 1978. 

Gray (Gy) SI unit of radiation-absorbed dose, equals 1 J/kg it has replaced the older unit, rad, which is 100 ergs/g (or 0.01 J/kg). 

Roentgen (R) The unit of radiation exposure in the air units for quantities of X-ray or gamma radiation measured by detection and survey meters. Named after Wilhelm Roentgen, German scientist who discovered X-rays in 1895. 

ROENTGEN. A unit of radiation, that quantity of X-rays or gamma rays which will produce, as a consequence of ionization, 1 electrostatic unit of... 

The unit of radiation exposure is the roentgen (R). It is a historical unit of the exposure and characterizes the radiation incident on an absorbing material without regard to the character of the absorber. The unit was formalized in 1928 as The amount of radiation which produces one electrostatic unit of ions (esu), either positive or negative, per cubic centimeter of air at standard temperature and pressure. Translated in modem units ... 

The Roentgen—A Unit of Radiation Exposure 378 Units of Absorbed Dose 379 Units of Dose Equivalent 379... 

Gray unit of radiation dose per second 1 Gray = 1 J/kg... 

Gamma rays are pure electromagnetic radiation with energy = (6.626 x 10 " joules/second-Planck s constant) (frequency of the radiation). Conventional units of radiation to be considered are one electron volt (eV) = 1.6 x 10 joules and one million electron volts (MeV) (Harley, 2001, 2008). 

Rad a unit of radiation dosage corresponding to 10 2 J of energy deposited per kilogram of tissue (from radiation absorbed dose). (21.7)... 

The short history of dose limitations is presented in Table 6.3. It was with the increase in radiation injury that methods for the use of radiation without radiation injury started to be considered. In 1925, an American, Mutscheller, using data on X-ray technicians with no radiation injury, concluded that the quantity of exposure to radiation less than 1/100 of the erythema dose was the safe level. Converted to the present unit of radiation, this equals 2 mSv/day. This quantity was termed the tolerance dose , i.e., the level which can be tolerated by man without radiation injury. 

As shown in Table 3, the biological effect of exposure to nuclear radiation can be expressed in rem. Healthcare professionals are advised to limit their exposure to 5 rem per year. This exposure is 1000 times higher than the recommended exposure level for most people, including you. Other units of radiation measurement can be seen in Table 4. 

Note how the intensity of the radiation varies with the distance from the source. The unit of radiation intensity is millirem per second per square meter. (This is the amount of radiation striking a square meter of area each second.) Use the graph to answer the Thinking Critically questions that follow. 

The absolute intensity of stimulated dipole transition 17 - Y J per unit of radiation density is given by the expression... 

It should be emphasized that oxygen gas dissolves only in the amorphous regions of polymers, and can, therefore, oxidize the material only within the amorphous phase or on the surface. Also the extent of oxidation per unit of radiation dose is very dependent on the dose rate. The lower the dose rate the more time the oxygen has to diffuse into the plastic per unit of dose so that the net amount of oxidation for the same dose is much greater at low rates. 

Gray (Gy). The unit of radiation dose in SI units. One gray is equal to 100 rad. 

Rad. The unit of radiation absorbed dose. One rad is equal to 100 ergs of radiation energy deposited per gram of any matter, or 10 2J/kg of any medium. 

Unless otherwise stated, exposure levels are presented per kg of body weight. In Appendix D, standard and SI units of radiation activity (curies, becquerels) and absorbed dose (rads, grays) are compared in Table D-5 and are discussed in Sections D.2.2 Half-Life and Activity and D.3.1.2 Absorbed Dose and Absorbed Dose-Rate. 

---