[he relationship of these factors is given in the following equation.
D-Ef WQ{t)F
1
M
Where E = the effective energy of 137cs beta_=_0.59 Mev.
f; = the gut transfer coefficient for 'W3ics = 1.0.
M = the body mass = 70,000 g.
W = the constant to convert pCi to g-rem/Mev=d = 51.2x1078,
Q (t) = the term for the time integration over the exponential
functions-representing the retention time of 13/cs in the
body with the parameters listed in the above text.
The
uu
mT
value for Q(t) for 30 years is = 1.04 x 10® pCi-d/(pCi/d)
“
©
Thus
intake.
the quality factor for beta radiation = 1.0 rem/rad
.
51.2x1079 x 0.59 x 1.0 x 1.04 x 10© x 1.0 = 0.000 45 rem
7 x 10%
Not only is the physiological half-time for children for !3/cs shanter
than that of adults but the dietary intake of 3/5 is usually less
.
The net result of the more rapid turnover of 137¢5 in the hady and the lower
intake of
Cs via the diet makes the dose from ingested
C s less for
children than adults.
External Gamma
The primary external gamma exposure is from \3/cs, with a very smal}
contribution from
°YCo.
To convert external gamma measurements in ur/h to
an absorbed dose in tissue, we chose the conversion factor from exposure dose
in air to absorbed dose in tissue given in the UNSCEAR report 22) that. is
(0.87) (0.82) = 0.71.
The value of 0.87 is the conversion from exposure to
absorbed dose in air and 0.82 is the conversion from absorbed dose in air to
the mean absorbed dose in the body.
In ICRP Publication 21, the conversion factor for 137¢5 gamma rays
(0.66 MeV) is 0.65 and it is 0.7 for [Co (1.17 Mev) (23). The value for
the conversion factor for total body given by ney n and Sanna for 0.5-MeV
gamma rays is 0.52; for 1] MeV the value is 0.56
For the skeleton, the
conversion factors are 0.49 and 0.54 for 0.5 and 1.0 MeV, respectively.
The range of possible living patterns and lifestyle scenarios can lead to
a reduction by as much as a factor of 2 in the open field external gamma dose
calculated as described above.
Thus, a refinement for beta exposure for
“shallow dose" and eyes of some 10 to 50% is not included because reductions
in open field gamma doses to wholebody and bone marrow listed in this report
and reference 5, 10 and 11 would generally be reduced by 50% or more depending
on the scenario developed for lifestyle and living pattern.
7.2
The 9%r Methodology
The conversion factors to convert the concentration of 2%Sr in bone to
dose to bone cells are quoted by the United Nations Scientific Committee on
S000112
D-7