Sorption of fission product vapors on metallic surfaces and dust particles is an important safety aspect of HTR reactors. Safety analyses of these reactors are performed using computer codes, such as MELCOR, RADAX, SPECTRA. These codes have sorption models allowing to compute the sorption rates of different fission products on surfaces. The code users must supply the model coefficients applicable for the particular surface and isotope. This paper describes the work performed to find relevant experimental data and find the sorption coefficients that represent well the available data for iodine on different surfaces. The purpose of this work is to generate a set of coefficients that may be recommended for the computer code users. Calculations were performed using the computer code SPECTRA. The following data was analyzed: • Sorption of I-131 on graphite; • Sorption of I-131 on steel; • Sorption of I-131 on dust. The results are summarized as follows: • The available data is provided in form of Langmuir isotherms. • The Langmuir isotherms do not provide sufficient data to define all sorption coefficients. The Langmuir isotherm provides equilibrium data; the relaxation time (to get to equilibrium) needs to be guessed. In practice this means that one of the sorption coefficients must be guessed. In the present calculations the desorption coefficient was being guessed and then varied in sensitivity calculations. The calculations showed that surface concentration is not sensitive to the choice of the parameter. • The sorption model in SPECTRA is capable to correctly reproduce the sorption behavior given by the Langmuir isotherms. • Out of the calculated cases, the highest activity (surface concentration) is observed on the steel surface; the lowest on the graphite surfaces. • The present work may serve as a useful guide of how to convert the Langmuir isotherm data into the input parameters required for computer code calculations.

This content is only available via PDF.
You do not currently have access to this content.