International Standard Problem (ISP) No.41; Computer code comparison exercise based on a Radioiodine Test Facility (RTF) experiment on iodine behaviour in containment under severe accident conditions

Ball, J.*; Glowa, G.*; Wren, J.*; Rydl, A.*; Poletiko, C.*; Billarand, Y.*; Ewig, F.*; Funke, F.*; Hidaka, Akihide   ; Gauntt, R.*; Cripps, R.*; Herrero, B.*; Royen, J.*

The ISP No.41 exercise resulted from a recommendation at the fourth iodine chemistry workshop held at PSI, Switzerland in 1996 for an International Standard Problem on iodine behavior models. The test selected for the comparison was a Radio Test Facility experiment. It was conducted in a stainless steel vessel at 25C and at a dose rate of 1.4 kGy/h to evaluate the effect of pH on irradiated aqueous solutions containing CsI. This paper discusses the results of ISP 41 exercise, with a primary focus on the evaluation and comparison of calculated results, and what they demonstrate about the aqueous iodine reaction subset within each model. The paper will also discuss the relative importance of mass transfer, surface adsorption and aqueous chemistry, and the sensitivity of each of the models to these phenomena. Finally, it will assess the applicability of the ISP 41 exercise to qualitative validation of the iodine models, and provide recommendations for continuing model evaluation.