Becquerel, defined

Radioactive waste is characterized by volume and activity, defined as the number of disintegrations per second, known as becquerels. Each radionucHde has a unique half-life,, and corresponding decay constant, A = 0.693/tj 2 For a component radionucHde consisting of JS1 atoms, the activity, M, is defined as... 

SI Units—The International System of Units as defined by the General Conference of Weights and Measures in 1960. These units are generally based on the meter/kilogram/second units, with special quantities for radiation including the becquerel, gray, and sievert. 

The radioligand should also have a high specific activity so that very small quantities of bound ligand can be accurately measured. The specific activity, simply defined as the amount of radioactivity, expressed in becquerels (Bq) or curies (Ci) per mole of ligand, is dependent on the half-life of the isotope used and on the number of radioactive atoms incorporated into the ligand molecule. A radioisotope with a short half-life decays rapidly so that many disintegrations occur in unit time,... 

Lind (1961) defines radiation chemistry as the science of the chemical effects brought about by the absorption of ionizing radiation in matter. It can be said that in 1895, along with X-rays, Roentgen also discovered the chemical action of ionizing radiation. He drew attention to the similarity of the chemical effects induced by visible light and X-rays on the silver salt of the photographic plate. This was quickly followed by the discovery of radioactivity of uranium by Becquerel in 1896. In 1898, the Curies discovered two more radioactive elements—polonium and radium. 

The System Internationale (SI) unit for radioactivity is becquerel (Bq), which is defined as one disintegration per second. The SI units and the conversion factors between curie and SI units are listed in Table 15.2. 

The curie unit (Ci) is based on the activity of 1 g of pure radium-226, which undergoes 3.7 X 1010 transformations per second. It is therefore defined as the quantity of a radioactive isotope which gives 3.7 X 1010 disintegrations per second. The SI unit of activity is the becquerel (Bq), which is equal to one nuclear transformation per second. Hence ... 

Decay rate is way to quantify radioactive decay and is equal to the number of radioactive decays or disintegrations occurring per unit time. The official SI unit of decay rate is the becquerel (Bq) defined to be ... 

In order to understand the effects of radiation on any material, let us define how one measures radiation. Radiation is measured in several units. The SI unit for radioactivity is the becquerel (Bq), which is defined as one disintegration (d) per second (s) (Bq = d/s). However, the most common unit is the curie (Ci) and its definition is based on the number of radium-226 isotopes present in 1 gram of the element that disintegrate in one second. One Ci is thus exactly equal to 3.70 x 1010 disintegrations per second... 

Radioactivity is measured in decays per second, the SI unit of which is the Becquerel (Bq) which is defined as one decay per second. The Curie (Ci), which originally corresponded to the number of decays per second in 1 g of radium, is still used and is now related to the Becquerel by the definition ... 

As it was shown above, the static kinetics of tunnelling luminescence is much simpler than the diffusion-controlled kinetics. The static tunnelling luminescence intensity often obeys the empirical Becquerel s law [87] I t) oc t ° , where the distinctive decay parameter a = —d ogI i)/ d ogt) is defined by the spatial distribution of defects only, usually considered to be either the isolated pairs of spatially well-correlated dissimilar defects (low dose irradiation) or the random mixture of dissimilar defects (high doses and/or high temperatures) [88]. Moreover, in the case of pairwise distribution, the partial lightsum method has been presented [88-91] in order to restorate the defect initial spatial distribution /(r) within geminate pairs -see equation (4.2.1) and below. What we have discussed here are the tran-... 

The dimension is s , and the unit is called becquerel (Bq) 1 Bq = 1 s . An older unit is the curie (Ci). It is still used sometimes, related to the activity of Ig of Ra, and defined as 1 Ci = 3.700 lO s = 37GBq. Smaller units are 1 milli-curie (mCi) = 37MBq, 1 microcurie (ixCi) = 37kBq, 1 nanocurie (nCi) = 37 Bq, and 1 picocurie (pCi) = 0.37 Bq. 1 Ci is a rather high activity which cannot be handled directly but needs special installations, such as hot cells. Activities of the order of several mCi are applied in medicine for diagnostic purposes, activities of the order of 1 pCi are usually sufficient for the investigation of the behaviour of radionuclides, and activities of the order of 1 nCi are measurable without special efforts. 

N. The SI unit of activity is the Becquerel (Bq), which represents one disintegration per second. The disintegration per minute or dpm often appears in the literature. An older representation was the Curie (Ci), which is defined as the activity of 1 g of pure Ra or 3.70 X 10 disintegrations per second. The picocurie (pCi), which is... 

The fundamental SI unit of activity is the Becquerel (Bq). One Bq is equal to one disintegration per second (dps). Because this is a very small unit, it is more often expressed in kilobequerels or kBq. However, the older historical unit of activity Q is normally used for radiopharmaceuticals. The Curie was defined in terms of the number of disintegrations per second of 1 g of Ra and is equal to 3.7 x 10 ° dps. Other commonly used imits are millicurie and microcurie (mCi and pCi). The unit of Ci represents absolute activity (A). However, relative activity R is proportional to the efficiency of the counting device. The device reports in counts per minute. 

The defining event of a radioactive nuclide is the transformation of its nucleus into the nucleus of another species, that is, radioactive decay. The number of nuclear transformations occurring per unit of time is called activity . Sometimes radioactivity is used instead of activity . The traditional unit of activity has been the Curie (Ci), which is equal to 3.7 X 10 ° nuclear transformations per second. The conversion of radiation units to the international system (Sysfme International d Unit or SI) has now taken place in the United States. The more fundamental unit of activity, the Becquerel (Bq), equal to 1 nuclear transformation per second, has replaced the Curie. Both units of activity are modified by prefixes such as kilo-, milli-, and micro- to achieve standard multiples of the fundamental unit. A listing of the most commonly used prefixes is given in Table 1. 

The hecquerel (Bq) is the SI unit of radioactivity and is defined as one decay per second (dps). Because 1 Bq is a very small amount of activity, the activity of typical chemistry samples is often expressed in kilobecquerels (kBq). The curie (Ci) is the older, conventional unit it is defined as 3.7 X 10 dps. One curie equals 37 gigabecquerels (GBq). Because the becquerel is inconveniently small and the curie very large, they are typically used as their multiples or submultiples, for example, megabecquerels (MBq) and miUicuries (mCi). One mCi equals 37 MBq. 

The curie (Ci) is a unit frequently used as a measure of the amount of radioactive material. It is defined as the amount of radioactive material that will produce 3.7 X 10 disintegra-tions/s. This is approximately the number of disintegrations per second in 1 g of radium. A more up-to-date unit is the Becquerel, which is the amount of radioactive material that produces cme disintegration per second. 

The SI unit of radioactivity is the becquerel (Bq) it is defined as one disintegration per second (d/s) 1 Bq = 1 d/s. A much larger and more common unit of radioactivity is the curie (Ci) 1 curie equals the number of nuclei disintegrating each second in 1 g of radium-226 ... 

Developing the photographic plates, Becquerel observed an intensely defined silhouette on the first two plates, and a clear but considerably weaker silhouette on the third. Because he had double-boxed his plates inside his dark room and had placed the ensembles inside a drawer that he then closed, he was able to conclude that his mysterious rays were not related to phosphorescence and were not induced by stmfight. 

A number of special units and technical terms are used in work with radioactive isotopes. The old unit for the amount of an isotope was the curie (symbol Ci), which is defined as the amount producing exactly 3.7 x 10 ° disintegrations per second. In the preceding example, we have seen that this is approximately the number of disintegrations produced per second by 1 gram of radium. In 1975 the curie was replaced by the becquerel (Bq) which is defined as the amount of radioactive substance giving one disintegration per second. Thus 1 Bq = 1 s and 1 Ci = 3.7 x 10 ° Bq. 

The specific activity of a preparation can be defined as the number of becquerels or curies of the radioactive isotope divided by the total mass of the element present. For example, if carbon is enriched with the radioactive isotope gC, the specific activity was formerly expressed as... 

There are two separate units of radioactivity in use, the first being the Curie (Ci) which is defined as an activity of 3.7 x 10 ° disintegrations per second. This is a large unit — bear in mind that with a modern day liquid scintillation counter radioactivity levels down to a few hundred coimts per minute can be easily measured — so it is very coimnon to use smaller subunits such as the millicurie (10 Ci) and the microcmie (10 Ci). The second, and more recently introduced miit, is the Becquerel (Bq). At one disintegration per second this is an extremely small amoimt of radioactivity. The conversions are... 

The activity of a quantity of radioactive isotope is defined as the number of disintegrations per second which occur. The usual units are the curie (Ci), which is defined as 3.7 x 10 dps, and the becquerel (Bq), defined as 1 dps. Specific activity for a given isotope is defined as activity per unit mass of the isotope. 

The rate at which a sample decays is called its activity, and it is often expressed as number of disintegrations per unit time. The becquerel (Bq) is the SI unit for expressing activity. A becquerel is defined as one nuclear disintegration per second. An older. 

SECTIONS 21.4 AND 21.5 The SI unit for the activity of a radioactive source is the becquerel (Bq), defined as one nuclear disintegration per second. A related unit, the curie (Ci), corresponds to 3.7 X 10 disintegrations per second. Nuclear decay is a first-order process. The decay rate (activity) is therefore proportional to the number of radioactive nuclei. The half-life of a radionuclide, which is a constant, is the time needed for one-half of the nuclei to decay. Some radioisotopes can be used to date objects C, for example, is used to date organic objects. Geiger counters and scintillation counters count the emissions from radioactive samples. The ease of detection of radioisotopes also permits their use as radiolracers to follow elements through reactions. 

It was Alexandre-Edmond Becquerel, in his 1867 treatise La Lumiere, ses causes et ses ejfets, who first put forward a systematic distinction between fluorescence and phosphorescence. Becquerel designed a phosphoroscope that allowed precise time intervals to elapse between the exposure of a material to light and the observation of the light emitted. He defined fluorescence as emission of light that is immediately extinguished upon removal of the light source, whilst phosphorescence persists for some time after exposure. 

The rate at which a sample decays is called its activity, and it is often expressed as number of disintegrations per unit time. The becquerel (Bq) is the SI unit for expressing activity. A becquerel is defined as one nuclear disintegration per second. An older, but still widely used, unit of activity is the curie (Ci), defined as 3.7 X 10 disintegrations per second, which is the rate of decay of 1 g of radium. Thus, a 4.0-mCi sample of cobalt-60 undergoes... 

---