Ionising radiation units

United Nations Scientific Committee on the Effects of Atomic Radiations, Sources, effects and risks of ionising radiation. United Nations, New York, 1988. 

The gray is also used for the ionising radiation quantities, specific energy imparted, kerma, and absorbed dose index, which have the SI unit joule per kilogram. 

The use of ionising radiation for the preservation of food is not a new technology. In fact, about 90 years ago, a patent was issued in the United Kingdom (UK) which detailed the use of the process for the preservation of foods, especially cereals. Despite this initial interest in the technology, progress was hindered because of the limited availability of suitable sources of ionising radiation. 

United Nations Scientific Committee on Effects of Atomic Radiations (1977) Ionising Radiation Sources and Biological Effects. New York United Nations. 

CoUinson E, Dainton FS, Smith DR, Taziike S. (1962) Evidence for the unit negative charge on the Hydrogen Atom formed hy the action of ionising radiation on aqueous systems. Proc Chem Soc, p. 140. 

United Nations Scientific Committee, 1977. Natural sources of radiation. In Sources and Effects of Ionising Radiation. Report to the General Assembly, United Nations, New York, pp. 35-114. 

Values differ befween counfries due to differences in climate, rocks, construction methods and materials and living habits. A worldwide figure of 25 Bq for fhe geomefric mean level of radon has been estimated by the United Nahons Scienhfic Committee on the Effects of Ionising Radiations (UNSCEAR). Surveys in the UK suggest a national average of abouf 20 Bq m. In some areas — e.g. Einland, Sweden — concenfrahons of many thousands of Bq m have been measured in large numbers of houses. 

Since the middle 1950s, both national and international procedures have imposed strict control upon the nuclear industry in the United Kingdom, to ensure that the dangers from ionising radiation to both the general public and workers in nuclear power plants are at the lowest reasonably achievable levels (ALARA— As Low As Reasonably Achievable ). 

The United Kingdom always recognised that misadventures from ionising radiations would result in adverse reaction, from the public and press, much disproportionate to the reaction from conventional industrial accidents. 

The absorbed dose is the quantity of energy deposited by ionising radiation in a unit mass of material. It is expressed in a unit called the gray, Gy. A Gy corresponds to a joule per kilogram. 

There are two principal units of radiation - the becquerel (1 Bq) which measures the amount of radiation in a given environment and the millisievert (1 mSv) which measures the ionising radiation dose received by a person. 

G values have been predominantly used during the last two decades. Recently, however, authors have returned to M/N since it is the more fundamental unit . Also, G depends upon the measurement of the total energy absorbed which is difficult or impossible (with y-radiation) to determine in a gaseous system. When the ionisation energy of the compound investigated is lower than the energy of the photon absorbed, the product yields can be expressed unambiguously in terms of the number of molecules formed per ion pair (M/N). 

These measure the radiation in units of dose rate and normally contain an ionisation chamber or Geiger-Muller tube. They are usually used to monitor P and Y radiation fields. Special instruments are used for measuring neutron radiation dose rates. 

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