Becquerel - Bq Energy

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

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Capitalization

As with every International System of Units (SI) unit named for a person, the first letter of its symbol is uppercase (Bq). However, when an SI unit is spelled out in English, it should always begin with a lowercase 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 material using title case.

Bq Energy Video

Definition

1 Bq = 1 s^-1

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. Other names considered were hertz (Hz), a special name already in use for the reciprocal second, and fourier (Fr). The hertz is now only used for periodic phenomena. Whereas 1 Hz is 1 cycle per second, 1 Bq is 1 aperiodic radioactivity event per second.

The gray (Gy) and the becquerel (Bq) were introduced in 1975. Between 1953 and 1975, absorbed dose was often measured in rads. Decay activity was measured in curies before 1946 and often in rutherfords between 1946 and 1975.

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Prefixes

Like any SI unit, Bq can be prefixed; commonly used multiples are kBq (kilobecquerel, 10³ Bq), MBq (megabecquerel, 10⁶ Bq, equivalent to 1 rutherford), GBq (gigabecquerel, 10⁹ Bq), TBq (terabecquerel, 10¹² Bq), and PBq (petabecquerel, 10¹⁵ Bq). For practical applications, 1 Bq is a small unit; therefore, the prefixes are common. For example, the roughly 0.0169 g of potassium-40 present in a typical human body produces approximately 4,400 disintegrations per second or 4.4 kBq of activity. The global inventory of carbon-14 is estimated to be 8.5×10¹⁸ Bq (8.5 EBq, 8.5 exabecquerel). The nuclear explosion in Hiroshima (An explosion of 16 kt or 67 TJ) is estimated to have produced 8×10²⁴ Bq (8 YBq, 8 yottabecquerel).

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Relationship to the curie

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.

Conversion factors:

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Calculation of radioactivity

For a given mass ${\displaystyle m}$ (in grams) of an isotope with atomic mass ${\displaystyle m_{a}}$ (in g/mol) and a half-life of ${\displaystyle t_{1/2}}$ (in s), the amount of radioactivity can be calculated using:

${\displaystyle A_{Bq}={\frac {m}{m_{a}}}N_{A}{\frac {\ln(2)}{t_{1/2}}}}$

With ${\displaystyle N_{A}}$=6.022 141 79(30)×10²³ mol^-1, the Avogadro constant.

Since m/ma is the number of moles (n), the amount of radioactivity ${\displaystyle A}$ can be calculated by:

${\displaystyle A_{Bq}=nN_{A}{\frac {\ln(2)}{t_{1/2}}}}$

For instance, on average each gram of potassium contains 0.000117 gram of ⁴⁰K (all other naturally occurring isotopes are stable) that has a ${\displaystyle t_{1/2}}$ of 1.277×10⁹ years = 4.030×10¹⁶ s, and has an atomic mass of 39.964 g/mol, so the amount of radioactivity associated with a gram of potassium is 30 Bq.

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Radiation-related quantities

The following table shows radiation quantities in SI and non-SI units.

Source of the article : Wikipedia