Official internal dose factors are like SS which name shower a chamber gas. (The cesium 137 case.)

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.