Introduction to Health Physics: Fourth Edition - Ruang Baca FMIPA UB

406 CHAPTER 8
For dosimetric purposes, six nonexclusive categories of bone seekers are used in
the ICRP 30 bone model:
1. photon emitters,
2. alpha-emitting volume seekers,
3. alpha-emitting surface seekers,
4. beta-emitting surface seekers whose mean beta energy is at least 0.2 MeV,
5. beta-emitting surface seekers whose mean beta energy is less than 0.2 MeV, and
6. beta-emitting volume seekers.
These categories are not mutually exclusive because a radionuclide, such as a beta–
gamma emitter, belongs in two categories. In this case, each different type of radiation
is considered separately. The AF for the various particle emitters are given in
Table 8-23. The AFs for photons are given in Appendix D.
Using the physiologically based biokinetic model for a bone-seeking radionuclide,
we can calculate the dose to the bone or bone surface and the doses to the
other organs and tissues due to the intake, by ingestion or inhalation, of 1 Bq or 1
μCi of activity. Then, using either the ICRP and IAEA criterion of 0.02-Sv effective
dose limit, or U.S. NRC criterion of 5-rems (0.05-Sv) effective dose limit or 50-rems
(0.5-Sv) organ dose limit, or we can calculate the secondary ALI and the tertiary
DAC or maximum concentration in water. If we were to use the ICRP criterion of
a mean annual effective dose of 0.02 Sv and the DC of 2.4 × 10−9 Sv/Bq for 5-μm
moderately soluble 45Ca particles, then the inhalation ALI would be
0.02 Sv
ALI(effective) =
= 8.33 × 10
−9 Sv
2.4 × 10
Bq
6 Bq = 225 μCi.
For example, the U S NRC’s inhalation ALI for soluble (class D) 90 Sr, using the DCs
for the bone surface and for whole-body effective dose listed in Table 8-20, we have
0.5Sv
ALI(bone surface) =
= 6.86 × 10
Sv
7.29 × 10−7 Bq
5 Bq = 1.86 × 10 1 μCi
0.05 Sv
ALI(effective) =
= 7.73 × 10
Sv
6.47 × 10−8 Bq
5 Bq = 2.09 × 10 1 μCi.
TABLE 8-23. Recommended Absorbed Fractions for Dosimetry of Radionuclides in Bone
A, α, β, β, Ē ≥ 0.2 β, Ē < 0.2
SOURCE TARGET Vol. BS Vol. MeV, BS MeV, BS
Trabecular Surface (BS) 0.025 0.25 0.025 0.025 0.25
Cortical Surface 0.01 0.25 0.015 0.015 0.25
Trabecular Red Marrow 0.05 0.5 0.35 0.5 0.5
Cortical Red Marrow 0.0 0.0 0.0 0.0 0.0
Abbreviation: BS, bone surface.
Reproduced with permission from ICRP Publication 30, Part 1: Limits for Intakes of Radionuclides by Workers. Ann ICRP.
1979; 2(3/4):42. Copyright c○ 1979 International Commission on Radiological Protection.