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DOE-STD-1136-2004
Guide of Good Practices for Occupational Radiation Protection in Uranium Facilities
exposed to radiation in the workplace. Limits were also established for nonstochastic effects that prevented
these effects from occurring even if the exposure occurred at the annual limit over the lifetime of the
worker.
For stochastic effects, the ICRP specified in Publication 26 that radiation exposure be limited by
the effective dose equivalent, HE, which can be expressed by the relation:
(6.1)
Table 6-2 lists the weighing factors, taken from 10 CFR 835. Effective dose equivalent has the
benefit that it is additive, and internal and external radiations can be added numerically to derive an
overall estimate of risk.
Table 6 -2. Tissue Weighing Factors
Tissue or Organ
Tissue Weighing Factor, wT
Gonads
0.25
Breast
0.15
Bone marrow (red)
0.12
Lungs
0.12
Thyroid
0.03
Bone surfaces
0.03
Remainder(a)
0.30
Whole body(b)
1.00
(a)
Remainder means the five other organs or tissues with the
highest dose (e.g., liver, kidney, spleen, thymus, adrenal,
pancreas, stomach, small intestine, and upper large intestine).
The weighing factor for each remaining organ is 0.06.
(b)
For the case of uniform external irradiation of the whole
body, a weighing factor equal to 1 may be used in
determining the effective dose equivalent.
The methodology of ICRP-26 has been incorporated into 10 CFR 835. Table 6-3 lists the annual
radiation dose limits for DOE activities. However, DOE contractors usually establish lower annual
administrative control levels, typically 500 mrem/year or less.
In practice, it is difficult to measure the effective dose equivalents specified in Table 6-3 because it
is necessary to know not only the type of radiation but also its energy and direction. If the flux, energy, and
direction of incidence are known, it is possible to calculate effective dose equivalent using fluence to
effective dose equivalent conversion coefficients presented in ICRP Publication 51 (ICRP 1987), which
presents the effective dose equivalent as a function of energy for various irradiation
6-2


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