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Calculation of dose to skin due to beta emitters

1) Discussion and equation

Skin dose is very difcult to measure directly and is usually estimated.

The beta dose rate to the skin expressed in terms o average suraceconcentrations o a radionuclide on the skin gives more reliableestimates or this exposure pathway. However, the data in theliterature vary as much as an order o magnitude. The dose calculated

here is to the basal layer o the skin (! m in depth" due to beta raysand electrons. The gamma contribution to the dose rate is generally aew per cent. The contamination is supposed to be uniormly andthinly spread over the skin. The e#uation is$

%here

HT(skin" & '#uivalent dose to the skin )y*.+skin & verage surace concentration o radionuclide on skin or

clothing -#cm/*.

+0-eta1skin& +onversion actor$ skin beta dose rate ()yh"(-#cm/"*.

S0-eta & Shielding actor or beta radiation due to clothing2representative values o shielding actors are approximately 3 1

4 or light clothing and 5!!! or heavy clothing.t & Time o exposure h*

The e#uation should be calculated or each radionuclide present andthe e#uivalent doses should be summed.

2) Conversion factors

Radionuclid

e

CFBeta-skin(G!")!(Bq!cm2)

H13 !+156 !.3/0157 5.8

9a1// 5.9a1/6 /./l1/: 5.7;13/ 5.8;133 !.7:S134 !.34

+l13: 5.7

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Radionuclide

CFBeta-skin(G!")!(Bq!cm2)

r1849b1

845.:

=o188Tc188m

5.8

Tc188m !./4Tc188 5./?u15!3

?h15!3m!.7

?u15!:?h15!:

/./

g155!m !.:7g1555 5.7

2

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Radionuclide

CFBeta-skin(G!")!(Bq!cm2)

+d15!8 !.46An1555 !.37

An1553m !.3An1554m 5.3Sn15/4 /.3Sb15// /./Sb15/6 /./Sb15/: 5.7

Te15/3m 5.5Te153/ !.7

A15/3 !.37A15/6 !.4/A15/4 !.!/5

A1535 5.:+s1535 !.!5+s1536 5.6+s153 5.:-a1533 !.53

-a156!Ba156!

3.7

Ba156! /.5+e1538 !.68+e1565 5.7+e1563 /.!;r1563 5.

;m156 !.:Sm1543 5.:'u154/ !.8/'u1546 /.5'u154: 5./'r15:8 5.5

@b15:8 5.!?e157: 5.7?e1577 /.3

Ar158/ 5.8u1587 5.Hg158 !.!8/Hg1/!3 !.78Tl1/!5 !./Tl1/!6 5.:;b1/5! !.!!76

;o1/5!:.8!'1

!C1/34 !.57

C1/37

/.3!'1

!3;u1/37 3.!'1

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Radionuclide

CFBeta-skin(G!")!(Bq!cm2)

!3

;u1/385.6!'1

!3m1/65 !.!58

+m1/66/./!'1

!3

+1/4/3./!'1

!3

#) $%am&le

%hat is the e#uivalent tissue dose to the skin or a person who has anaverage skin contamination o 5/4! -#cm/o =o188Tcm188 and /4!

-#cm/o A1535 or / hoursD The S0-etais considered to be e#ual to 5in this case.

=o188Tcm188$ +0-eta1skin& 5.8 (E)yh"(-#cm/"

A 1 535 $ +0-eta1skin& 5.: (E)yh"(-#cm/"

HT(skin) (=o188Tcm188" & 64! )y $ HT(skin)(A1535" & 7!! )y

Total e#uivalent dose to the skin rom this contamination in / hours &4.: m)y.

') References

F'B+?GA, F., )C'??', I.;., B'-B9+, ;., HA+