Addressing Nuclides Not in the CAP88-PC Version-3 Library

Abstract

Versions of the computer program, CAP88, are widely used to calculate the radiological doses from radionuclides emitted into the air. CAP88-PC Version-3 includes an extensive library of radionuclides, but there are many more that are not included. Surrogates are often used to substitute for nuclides not in the library, though the results are usually overestimates. This paper addresses nuclides that are not in the library and describes methods to obtain more accurate results.

Methods to Account for CAP-88 PC-Omitted Nuclides in Radioactive Air Emissions From DOE Facilities

“…Air submersion DCs. Doses from external exposures will be of primary concern for radionuclides with short half-lives (<10 min) (McNaughton et al 2013). In this case, internal dose will be relatively insignificant and external dose will dominate.…”

“…The minimal surrogacy method involves using DCAL, a software code developed at Oak Ridge National Laboratory, to calculate DCs using ICRP respiratory and alimentary tract models and systemic biokinetic model for the element of interest but using established nuclear decay data for a few selected surrogate radionuclides. First, a small number of surrogate radionuclides are identified (e.g., using the ICRP nuclear decay database) based on criteria for nuclear decay data similar to those previously discussed (Moore 2008;McNaughton et al 2013;Boyd 2021). A separate DC is then calculated by DCAL (or other dose calculation software) using the nuclear data for each of the surrogate radionuclides.…”

“…Methods to account for omitted radionuclides in early versions of CAP-88 PC have also been published (McNaughton et al 2013) but are not included in the current work. Although all versions of CAP-88 PC are approved for use for the purpose of 40 CFR Part 61, Subpart H, compliance dose calculations, it is recommended to migrate to CAP-88 PC V4 or V4.1.…”

“…Once approved, the surrogate nuclide can be used in lieu of the CAP-88 PC-omitted nuclide. Criteria and radioisotope characteristics typically evaluated are listed as follows (Moore 2008;McNaughton et al 2013;Boyd 2021):…”

“…By selecting and including an appropriate radionuclide sufficiently similar to the radioisotope omitted from CAP-88 PC, compliance with the dose standard for members of the public can be demonstrated. In addition to the surrogate nuclide approach, there are alternate methods to account for omitted radionuclides (Leggett 2005; McNaughton et al 2013; Snyder and Eckerman 2017) and these may also be approved for use. Any use of surrogate radionuclides, DCs, or other methods of accounting for doses from radioactive emissions used for compliance reporting that are not in the CAP-88 PC radionuclide library require official approval from US EPA Headquarters or the appropriate region with regulatory oversight for the facility responsible for the emissions via a formal written request.…”