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French physicist who discovered that rays emitted by uranium salts affect photographic plates (1852-1908) (同)Henri Becquerel, Antoine Henri Becquerel

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/06/21 16:56:38」(JST)

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"Bq" redirects here. For other uses, see BQ and Becquerel (disambiguation).

The becquerel (symbol Bq) (pronounced: 'be-kə-rel) is the SI-derived unit of radioactivity. One Bq is defined as the activity of a quantity of radioactive material in which one nucleus decays per second. The Bq unit is therefore equivalent to an inverse second, s⁻¹. The becquerel is named after Henri Becquerel, who shared a Nobel Prize with Pierre and Marie Curie in 1903 for their work in discovering radioactivity.^[1]

Definition[edit]

1 Bq = 1 s⁻¹^[2]

A special name was introduced for the reciprocal second (s⁻¹) to represent radioactivity to avoid potentially dangerous mistakes with prefixes. For example, 1 µs⁻¹ could be taken to mean 10⁶ disintegrations per second: 1·(10⁻⁶ s)⁻¹ = 10⁶ s⁻¹.^[3] Other names considered were hertz (Hz), a special name already in use for the reciprocal second, and fourier (Fr).^[3] The hertz is now only used for periodic phenomena.^[2]

This SI unit is named after Henri Becquerel. As with every International System of Units (SI) unit whose name is derived from the proper name of a person, the first letter of its symbol is upper case (Bq). However, when an SI unit is spelled out in English, it should always begin with a lower case letter (becquerel), except in a situation where any word in that position would be capitalized, such as at the beginning of a sentence or in capitalized material such as a title. Note that "degree Celsius" conforms to this rule because the "d" is lowercase. —Based on The International System of Units, section 5.2.

Prefixes[edit]

Like any SI unit, Bq can be prefixed; commonly used multiples are kBq (kilobecquerel, 10³ Bq), MBq (megabecquerel, 10⁶ Bq), GBq (gigabecquerel, 10⁹ Bq), TBq (terabecquerel, 10¹² Bq), and PBq (petabecquerel, 10¹⁵ Bq). For practical application, 1 Bq is a small unit; therefore, the prefixes are common. For example, natural potassium (⁴⁰K) in a typical human body produces 4,000 disintegrations per second, 4 kBq of activity.^[4] The global inventory of carbon-14 is estimated to be 8.5×10¹⁸ Bq (8.5 EBq, 8.5 exabecquerel).^[5] The nuclear explosion in Hiroshima (14 kt or 59 TJ) is estimated to have produced 8×10²⁴ Bq (8 YBq, 8 yottabecquerel).^[6]

Relationship to the curie[edit]

The becquerel succeeded the curie (Ci), an older, non-SI unit of radioactivity based on the activity of 1 gram of radium-226. The curie is defined as 3.7·10¹⁰ s⁻¹, or 37 GBq.^[3]

Conversion factors:

1 Ci = 3.7×10¹⁰ Bq = 37 GBq

1 μCi = 37,000 Bq = 37 kBq

1 Bq = 2.7×10⁻¹¹ Ci = 2.7×10⁻⁵ μCi

1 GBq = 0.027 Ci

Calculation of radioactivity[edit]

For a given mass (in grams) of an isotope with atomic mass (in g/mol) and a half-life of (in s), the amount of radioactivity can be calculated using:

radioactivity(in Bq) =

With =6.022 141 79(30)×10²³ mol⁻¹ the Avogadro constant.

For instance, one gram of potassium contains 0.000117 gram of ⁴⁰K (all other isotopes are stable) that has a of 1.248×10⁹years=39.38×10¹⁵ seconds, and has an atomic mass of 39.963 g/mol, so the radioactivity is 31 Bq.

References[edit]

^ "BIPM - Becquerel". BIPM. Retrieved 2012-10-24.
^ ^a ^b "BIPM - Table 3". BIPM. Retrieved 2012-10-24.
^ ^a ^b ^c Allisy, A. (1995), "From the curie to the becquerel", Metrologia 32 (6): 467–479, doi:10.1088/0026-1394/31/6/006
^ Radioactive human body — Harvard University Natural Science Lecture Demonstrations
^ G.R. Choppin, J.O.Liljenzin, J. Rydberg, "Radiochemistry and Nuclear Chemistry", 3rd edition, Butterworth-Heinemann, 2002. ISBN 978-0-7506-7463-8.
^ Michael J. Kennish, Pollution Impacts on Marine Biotic Communities , CRC Press, 1998, p. 74. ISBN 978-0-8493-8428-8.

External links[edit]

Look up becquerel in Wiktionary, the free dictionary.

Derived units on the International Bureau of Weights and Measures (BIPM) web site

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