Doses to be Assessed

DOE-STD-1121-98

Bioassay and other supporting data can often require considerable expense and effort to obtain. It is

neither necessary nor cost-effective to assess all intakes using the same level of effort; rather, it is more

reasonable to employ a graded approach to bioassay collection and dose assessment whereby the level of

effort expended on the assessment increases with the magnitude of the anticipated dose. Minor exposures

may be assessed using generalized biokinetic models for a reference individual and conservative (or

default) assumptions regarding the nature of the exposure and characteristics of the contaminant. The

generalized model and assumptions should be based on previous experience or supporting studies at the

facility or models recognized by ICRP or NCRP. The facility should document the default models and

assumptions and when these are appropriate for use. For projected doses of increased magnitude,

sufficient bioassay and source characterization data should be obtained to enable adjustments to be made

to the generalized models, as appropriate, to account for the specific behavior of the radionuclide(s) in the

body. The facility should establish and document specific dose levels which require enhancement of data

collection and individual specific dose assessment efforts.

7.1 DOSES TO BE ASSESSED

10 CFR 835 requires that the following doses be calculated:

committed effective dose equivalent from intakes occurring during the year

committed dose equivalent to tissues of concern from intakes occurring during the year

total effective dose equivalent

cumulative total effective dose equivalent.

The RadCon Standard also recommends the calculation of "lifetime occupational dose," which is

taken to be the same as cumulative total effective dose equivalent.

7.1.1 Committed Effective Dose Equivalent

All confirmed occupational intakes, above the decision level, should be assessed. Based on each

assessment, the committed effective dose equivalent HE,50 should be calculated for each intake during the

calendar year.

Where there are multiple intakes or where several radionuclides are involved, each facility may

establish a per-radionuclide or a per-intake minimum assessment value so that the intent of the above

recommendation is met. In practice, it is not necessary to record the contribution from a radionuclide or a

specific group of radionuclides (when their respective source terms are independent and the measurement

system provides discrimination) that contributes less than 1-mrem committed effective dose equivalent.

7.1.2 Committed Dose Equivalent to Tissue of Concern

Each facility should identify the tissues of concern relative to radionuclides at the facility and should

justify and document the selection in the technical basis document. Specific requirements for identifying

the organs of concern are given in the definition of weighting factor in 10 CFR 835 . Wound site tissue

and associated lymph nodes should be excluded from committed dose equivalent calculations (Nnot and

Stather 1979; National Research Council 1988).

The committed dose equivalent HT,50 to the tissue(s) of concern should be calculated for those years

where a committed effective dose equivalent is calculated.