RECORD ID D00-04-013

STANDARD NUMBER

INFORMATION DATE 04-19-2000

SUBJECT Rad Dose Limits

QUESTION

10 CFR 835.206, and 835.207 lists dose limits for embryo/fetus and minors as a dose equivalent (or CDE). This is different that 835.208, which lists dose limits for members of the public as an effective dose equivalent (or CEDE). These are two very different measurements. A dose equivalent is a organ limit and a effective dose equivalent is the sum of the dose equivalents multiplied by a weighting factor (i.e. simulating an effective whole body dose). These values can be almost a factor of 10 different (e.g. dose limit for a rad worker is 50 rem CDE and 5 rem CEDE; 835.202). If the limits in 835.206 and 835.207 are CDEs (500 mrem CDE and 100 mrem CDE respectively), then the corresponding CEDE limits would a factor of 10 less than that (about 50 mrem CEDE and 10 mrem CEDE). The limit at which you are required to bioassay a declared pregnant worker or a minor is 10% of the limits in 835.206 (835.402(c)(2)) and 50% of the limit in 835.207 (835.402(c)(3)), which would be about 5 m Therefore, are the limits described in 835.206 and 835.207 CDE or a CEDE?

REGULATORY REVIEW

In response to your response line question (D00-040013) on the proper dose term to associate with the limits for occupationally exposed minors and the embryo/fetus we have the following reply. The annual occupational (whole body) dose limit for minors specified in 10 CFR 835.207 is 100 mrem Total Effective Dose Equivalent (TEDE). Per 10 CFR 835.2(b) TEDE is defined as the sum of the effective dose equivalents (for external exposures) and the committed effective dose equivalent (for internal exposures). The term, total effective dose equivalent is used immediately after the numerical value of the dose limit (0.1rem). For purposes of initiating internal dose monitoring, 10 CFR 835.402(c)(3) requires that internal dosimetry programs be conducted for occupationally exposed minors likely to receive a CEDE of more than 50 mrem in a year from all radionuclide intakes. The proper dose term to associate with limits for the embryo/fetus specified in 10 CFR 835.206(a) is dose equivalent. The dose equivalent is to be determined over the time from conception to birth and includes dose equivalents received from both internal and external exposures. Note that the internal component of the dose equivalent is not the committed effective dose equivalent (CEDE) for 50 years following intake. Guidance on how to calculate the external and internal components of the dose equivalent to the embryo/fetus is provided in implementation guide DOE G 441.1-6 “Evaluation and Control of Radiation Dose to the Embryo/Fetus Guide.” With regard to external sources of exposure, Section 4.4.1 states that “The dose to the embryo/fetus from radiation external to the mother should be taken as the deep dose equivalent to the mother's abdomen or torso.” With regard to internal exposure, section 4.4.1 states that the internal dose should be calculated as “the dose equivalent to the embryo/fetus from intakes of radionuclides in the embryo/fetus and the dose equivalent to the embryo/fetus resulting from intakes of radionuclides in the declared pregnant worker.” For purposes of initiating internal dose monitoring 10 CFR 835.402(c)(2) requires that internal dosimetry programs be conducted for declared pregnant workers likely to receive an intake or intakes resulting in a dose equivalent to the embryo/fetus of more than 50 mrem from conception to birth.