Cesium
137 (L. caesius, blue sky); Cs; at. mass 136,9070895; at. n° 55; m.p. 28,44°C;
b.p. 671°C; sp. gr. 1,873; half-life 30,07 years; 8,684E1 Ci/gr; β-;
0,514 MeV; range β- in body ~1560 μ.
Cesium
137 have a physical half-life of 30,07 years, a biological half-life of 70 days
an a effective half-life of 69,56 days. His official inhalation dose factor value is 4,8E-9 Sv/Bq.
(λ
physic 7,309E-10, λ biologic 1,146E-7, λ
effective 1,153E-7.)
Assessing
the rationality of official internal dose factor.
The
absorbed dose is calculate taking account all the disintegrations that occurs
in 50 years produce by the incorporation of a matter mass which initially emitted
1 Bq. Taking account of the effective "biological half-life" the incorporation of 1 Bq of cesium 137 conduce after 50 years to suffer
(1 Bq/1,153E-7 λe) * 1-(EXP(50*31536000*-1,153E-7)) =
8,670E6 disintegrations β- and absorb 8,67E6 disintegrations *
0,514 MeV * 1,602E-13 Joule per MeV = 7,140E-7 Joule and 7,14001 Erg which
dissipate, for IRCP, in a body mass of 148,75
kg... ((8,67E6 Emissions * 0,5140 MeV * 1,602E-6 Erg par
MeV * 1 EBR)/(4,800E-9 Sv/Bq * 1 Bq * 100 Erg/gr * 100 Rad/Sv) = 148,75 kg)
with a radius of (148750,2595 cm3/(4/3*3,14159))(1/3) =
32,8693 cm. The particle β-
which penetrate no more than 1560 μ in tissues travel in "rational" calculation 210,7 times far away it can physically go... (328692,43 μ/1560
μ
= 210,7.) In other words the real absorbed dose is reduce 9,35
millions times. (210,703 = 9,35E6 or 1,49E5
gr/1,59E-2 gr = 9,35E6.)
Calculating
the dose produce by one β- particle with 0,514 MeV energy and
1560 μ
penetration capacity in tissues: (1 Bq * 0,5140 MeV * 1,602E-6 Erg par MeV * 1
EBR)/((4/3 * 3,14159 * (1560 * 0,0001^3)) gr * 100 Erg/gr * 100 Rad/Sv) =
5,18E-9 Sv/Bq or 5,18 nanoSievert per Becquerel. The real committed dose for 1 Bq in
50 years is then (1 Bq/1,15E-7 λe s-1 * (1-Exp(50*365*24*60*60 *
-1,15E-7 λe)))
* 5,18E-9 Sv/Bq) = 0,0449 Sv/Bq or 44,90 milliSievert per Becquerel.
Official internal dose factors are like SS
which name shower a chamber gas.
