Table 5-14. DCFo (Sv/observed Bq), CEDE, for various ITPs and particle sizes

DOE-HDBK-1184-2004

be provided by pre-job or in-job contamination surveys. To determine the "actual"

activity on a filter, it would be necessary to dissolve the ITPs. Otherwise, self-

absorption of the beta radiation from tritium leads to underestimates of the airborne

activity. However, many ITPs (especially Type S) are extremely difficult to dissolve,

requiring strong acids for extended periods of time. CEDE DCFs for ITPs of Type

S, when determined based on "actual" activity, are found to be highly dependent

upon particle size. Table 5-13 data indicate that variations can be as much as a

factor of 30 for particle sizes from 0.5 to 10 m AMAD (for a given material).

Fortunately, it is not necessary to rely on "actual" activity or to dissolve ITPs prior to

counting samples. Not only is dissolution cumbersome, but "observed" activity on

filters counted by LSC without dissolution is a much better indicator of dose or dose

potential than is "actual" activity. The reason for this is that (due to self-absorption)

only the beta radiation that escapes ITPs is capable of causing lung dose and, if the

ITPs are not dissolved prior to counting, only the beta radiation that escapes is

counted.

Table 5-14 shows CEDE DCFs in terms of Sv per "observed" Bq when undissolved

ITPs are counted via LSC. The values in the table were calculated by dividing the

CEDE DCFs in Table 5-13 by the corresponding SAFs from Table 5-10. The term

"DCFo" is used to represent DCFs that are based on "observed" activity, as

determined by LSC counting without dissolution.

Table 5-14. DCFo (Sv/observed Bq), CEDE, for various ITPs and particle sizes

(AMAD, s g = 2.5), Type S assumed

CEDE DCFo vs. Particle Size [AMAD (m), s g = 2.5]

Base Material*

0.5

1.14x10- 10 1.92x10- 10 2.75x10- 10 2.67x10- 10 2.35x10- 10

Organic [∼(CH2)n]

1.39x10- 10 2.19x10- 10 3.04x10- 10 3.12x10- 10 3.29x10- 10

Rust [∼FeO(OH)]

1.42x10- 10 2.24x10- 10 3.11x10- 10 3.27x10- 10 3.62x10- 10

Ti H2

1.64x10- 10 2.42x10- 10 3.30x10- 10 3.66x10- 10 4.44x10- 10

Zr H2

1.97x10- 10 2.61x10- 10 3.55x10- 10 4.29x10- 10 5.61x10- 10

Hf H2

* Variable amount s of elemental hydrogen are isotopically tritium.

Table 5-14 data indicate that the CEDE DCFos, based on "observed" activity of

ITPs of Type S, are less dependent on particle size than are the CEDE DCFs,

based on "actual" activity, from Table 5-13. The assumption of a single particle size

distribution would result in much smaller errors than noted above; for example,

when using "observed" activity, CEDE DCFs vary only by a factor of about 5 for

particles ranging in sizes from 0.5 to 10 m AMAD. Compare this with a factor of

25 when using "actual" activity.

The 10 CFR Part 835 recommended default particle size for occupational exposure

is 1 m AMAD (s g = 2.5). From Table 5-14, the most conservative CEDE DCFo for

1 m AMAD is about 4.3 10- 10 Sv per observed Bq (1.6 103 rem/Cio). This is the

value that should be used to compute CEDE assessments for inhalation intakes of

tritiated particulates, based on air monitoring and observed results from that

monitoring.