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Plutonium Chlorides - doe-std-1128-98_ch10030
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DOE Standard Guide of Good Practices for Occupational Radiological Protection In Plutonium Facilities
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Transfer to the Fetus


DOE-STD-1128-98
the ICRP 48 model yielding the lesser value. Factors affecting radiobiological effects
include the mode of entry of plutonium into the body, its distribution in the body, and
its transfer to a fetus.
2.4.1
Modes of Entry into the Body
Radioactive material can enter the body by four different pathways: by
inhalation, through a wound, by ingestion, or by absorption through intact
skin. These pathways may occur singly or in any combination.
-- Inhalation is probably the most prevalent mode for occupational intake
of plutonium. It also provides a generally conservative assumption of
intake for designing bioassay programs.
-- Wounds are potentially the most serious mode of intake because of the
high dose-per-unit uptake of plutonium. Wounds can result from direct
penetration by an object (i.e., a puncture or cut), from abrasion, or from
burning by an acid, caustic, or thermal source.
-- Occupational ingestion of plutonium poses a relatively small risk
because the uptake factor from the GI tract to the blood is quite small
and because most of the alpha energy from transformations within the
GI tract is absorbed by the contents of the GI tract, rather than by the
target tissues of the tract itself.
-- Absorption of plutonium through intact skin is, for practical purposes,
almost nonexistent. However, when removing skin contamination, care
must be taken to ensure that the skin integrity is not damaged by rough
or extensive decontamination procedures. If the skin integrity is
damaged, the result can be considered a wound, regardless of how it
occurred.
2.4.2
Distribution Within the Body
Three commonly encountered biokinetic models have been promulgated by
the ICRP for the internal distribution and retention of plutonium. These
models are identified by the ICRP publications in which they were first
reported: ICRP 30, Part 1 (1979), ICRP 48 (1986), and ICRP 30, Part 4
(1988b). The models are similar with regard to the organs of significance,
but differ with regard to the fraction of uptake deposited in the organ and
its respective retention (or clearance) half-time in the organ. The three
models represent the ones most widely used in dosimetry and in
commercially available computer codes. In all three ICRP models, once
plutonium has reached the bloodstream, it is translocated primarily to the
liver and skeleton. In the skeleton, it is deposited primarily on the endosteal
surfaces of mineral bone, from which it is gradually redistributed
throughout the bone volume by resorption and burial. Because of the
extremely slow nature of this redistribution, plutonium is considered to be
uniformly distributed over bone surfaces at all times following skeleton
deposition. A small fraction of the translocated plutonium reaches the
gonads. Although the gonadal fraction is different for males and females,
2-17


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