curie

同

Ci

　

WordNet

1. a unit of radioactivity equal to the amount of a radioactive isotope that decays at the rate of 37,000,000,000 disintegrations per second (同)Ci
2. a unit of radioactivity equal to one thousandth of a curie
3. French chemist (born in Poland) who won two Nobel prizes; one (with her husband and Henri Becquerel) for research on radioactivity and another for her discovery of radium and polonium (1867-1934) (同)Marie Curie, Madame Curie, Marya Sklodowska
4. French physicist; husband of Marie Curie (1859-1906) (同)Pierre Curie
5. an inferior dog or one of mixed breed (同)mongrel, mutt
6. a cowardly and despicable person

PrepTutorEJDIC

1. Channel Islands
2. キュリー夫人(『Marie』 ~;1867‐1934;夫のPierreと協力してラジウムを発見したフランスの化学者) / 〈C〉《C-》キュリー(放射能の単位)
3. のら犬 / くだらない人間

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/03/05 20:22:46」(JST)

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[Wiki en表示]

For other uses, see Curie (disambiguation).

The curie (symbol Ci) is a non-SI unit of radioactivity, named after Marie and Pierre Curie. It is defined as

1 Ci = 3.7 × 10¹⁰ decays per second.

While its continued use is discouraged by NIST and other bodies, the curie is widely used throughout the US government and industry.

One curie is roughly the activity of 1 gram of the radium isotope ²²⁶Ra, a substance studied by the Curies.

The SI derived unit of radioactivity is the becquerel (Bq), which equates to one decay per second. Therefore:

1 Ci = 3.7 × 10¹⁰ Bq = 37 GBq = 37,000,000,000 atoms decaying per second

and

1 Bq ≅ 2.703 × 10⁻¹¹ Ci ≅ 27 pCi

Another commonly used measure of radioactivity is the microcurie:

1 μCi = 3.7 × 10⁴ disintegrations per second = 2.22 × 10⁶ disintegrations per minute

Correspondingly, and more commonly encountered with natural levels of radiation, a picocurie is:

1 pCi = 0.037 disintegrations per second = 2.22 disintegrations per minute

The power in milliwatts emitted by one curie of radiation can be calculated by taking the number of MeV for the radiation times approximately 5.93.

A radiotherapy machine may have roughly 1000 Ci of a radioisotope such as caesium-137 or cobalt-60. This quantity of radioactivity can produce serious health effects with only a few minutes of close-range, unshielded exposure.

Ingesting even a millicurie is usually fatal (unless it is a very short-lived isotope). For example, the LD-50 for ingested polonium-210 is 240 μCi, about 5.5 nanograms.

The typical human body contains roughly 0.1 μCi (14 mg) of naturally occurring potassium-40. A human body containing 16 kg of carbon (see Composition of the human body) would also have about 24 nanograms or 0.1 μCi of carbon-14. Together, these would have an activity of approximately 2×0.1 μCi or 7400 decays (mostly from beta decay and rarely from gamma decay) per second inside the person's body.

Curies as a measure of quantity

Curies are occasionally used to express a quantity of radioactive material rather than a decay rate, such as when one refers to 1 Ci of caesium-137. This may be interpreted as the number of atoms that would produce 1 Ci of radiation. The rules of radioactive decay may be used to convert this to an actual number of atoms. They state that 1 Ci of radioactive atoms would follow the expression:

N (atoms) × λ (s⁻¹) = 1 Ci = 3.7 × 10¹⁰ (Bq)

and so,

N = 3.7 × 10¹⁰ / λ,

where λ is the decay constant in (s⁻¹).

We can also express a Curie in moles:

$\begin{align}\text{1 Ci}&=\frac{3.7\times 10^{10}}{(\ln 2)N_{\rm A}}\text{ moles}\times t_{1/2}\text{ in seconds}\\ &\approx 8.8639\times 10^{-14}\text{ moles}\times t_{1/2}\text{ in seconds}\\ &\approx 5.3183\times 10^{-12}\text{ moles}\times t_{1/2}\text{ in minutes}\\ &\approx 3.1910\times 10^{-10}\text{ moles}\times t_{1/2}\text{ in hours}\\ &\approx 7.6584\times 10^{-9}\text{ moles}\times t_{1/2}\text{ in days}\\ &\approx 2.7972\times 10^{-6}\text{ moles}\times t_{1/2}\text{ in years} \end{align}$

where N_A is Avogadro's number and t_1/2 is the half life. The number of moles may be converted to grams by multiplying by the atomic mass.

Here are some examples:

Isotope	Half life	Mass of 1 Curie	Specific activity (Ci/g)
232Th	1.405×1010 years	9.1 tonnes	1.1×10−7 (110,000 pCi/g, 0.11 µCi/g)
238U	4.471×109 years	2.977 tonnes	3.4×10−7 (340,000 pCi/g, 0.34 µCi/g)
40K	1.25×109 years	140 kg	7.1×10−6 (7,100,000 pCi/g, 7.1 µCi/g)
235U	7.038×108 years	463 kg	2.2×10−6 (2,160,000 pCi/g, 2.2 µCi/g)
129I	15.7×106 years	5.66 kg	0.00018
99Tc	211×103 years	58 g	0.017
239Pu	24.11×103 years	16 g	0.063
240Pu	6563 years	4.4 g	0.23
226Ra	1601 years	1.01 g	0.99
241Am	432.6 years	0.29 g	3.43
14C	5730 years	0.22 g	4.5
238Pu	88 years	59 mg	17
137Cs	30.17 years	12 mg	83
90Sr	28.8 years	7.2 mg	139
241Pu	14 years	9.4 mg	106
60Co	1925 days	883 μg	1132
210Po	138 days	223 μg	4484
3H	12.32 years	104 μg	9621
131I	8.02 days	8 μg	125000
123I	13 hours	0.5 μg	2000000

The number of Curies present in a sample decreases with time because of decay.

Radiation Related Quantities

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

Quantity	Name	Symbol	Unit	Year
Exposure (X)	roentgen	R	esu / 0.001293 g of air	1928
Absorbed dose (D)			erg•g−1	1950
	rad	rad	100 erg•g−1	1953
	gray	Gy	J•kg−1	1974
Activity (A)	curie	Ci	3.7 × 1010 s−1	1953
	becquerel	Bq	s−1	1974
Dose equivalent (H)	roentgen equivalent man	rem	100 erg•g−1	1971
	sievert	Sv	J•kg−1	1977
Fluence (Φ)	(reciprocal area)		cm−2 or m−2	1962

See also

• Geiger counter
• Ionizing radiation
• Radiation exposure
• Radiation poisoning
• Radiation burn
• United Nations Scientific Committee on the Effects of Atomic Radiation

References

UpToDate Contents

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リンク元	「キュリー単位」「CI」
拡張検索	「millicurie」
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「キュリー単位」

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英

curie Ci

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ベクレル Bq

• 放射能の単位。
• 1 Ci = 3.7×10¹⁰ Bq = 37 x G Bq
• 1mCi = 37 MBq

「CI」

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• 心係数 cardiac index
• 信頼区間 confidence interval
• キュリー単位 curie　→　Ci

　

「millicurie」

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ミリキュリー

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mCi

　

「Curie」

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キュリー

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Ci