Recent advances on containment iodine chemistry
Paper i proceeding, 2010

The 5th FWP EURSAFE Project highlighted iodine chemistry in the containment as one of the issues requiring further research in order to reduce source term uncertainties. Consequently, a series of studies was launched in the 6th FWP SARNET Project aimed at improving the predictability of iodine behaviour during severe accidents via a better understanding of the complex chemical phenomena in the containment. In particular, SARNET has striven to foster common interpretation of integral and separate effect test data, production of new or improved models where necessary, and compilation of the existing knowledge of the subject. The work has been based on a substantial amount of experimental information made available from bench-scale projects (PARIS and EPICUR), via intermediate-scale tests (CAIMAN) to large-scale facilities (SISYPHE, THAI and PHEBUS-FP). In the experimental field, particular attention has been paid to two specific issues: the effects of radiation on both aqueous and gaseous iodine chemistry, and the mass transfer of iodine between aqueous and gaseous phases. Comparisons between calculations and results of the EPICUR and CAIMAN experiments suggest that the aqueous phase chemistry is reasonably well understood, although there are still some areas of uncertainty. Interpretation of integral experiments, like PHEBUS-FPT2, indicated that radiation-induced conversion of molecular iodine into particulate species (IxOy) could be responsible for the gaseous iodine depletion observed in the long-term. However, the results of much simpler, small-scale experiments have shown that further improvements in understanding and modelling are still needed. Mass transfer modelling has been extended to cover evaporating sump conditions based on SISYPHE data; however, application of this model to the larger scale THAI experiments seems not to be straightforward. In addition to these two major issues, some specific studies have been carried out concerning the potential effect of passive autocatalytic hydrogen recombiners on iodine volatility. The RECI analytical experiments have shown that metal iodides (namely Csl and Cdl(2)) are not stable and yield gaseous iodine when heated, in a humid atmosphere, at temperatures representative of recombiner operation. Another important undertaking successfully carried out has been the compilation of an Iodine Data Book, which provides a critical review of the experimental data and modelling approaches that have been used in the development of iodine source term methodologies. This should assist in a proper use of such models, and inform their future development.

Författare

S. Dickinson

National Nuclear Laboratory

F. Andreo

Electricite de France (EDF)

T. Karkela

Teknologian Tutkimuskeskus (VTT)

J. Ball

Atomic Energy of Canada Limited - Chalk River Lab

L. Bosland

IRSN Institut de Radioprotection et de Surete Nucleaire

L. Cantrel

IRSN Institut de Radioprotection et de Surete Nucleaire

F. Funke

AREVA

N. Girault

IRSN Institut de Radioprotection et de Surete Nucleaire

Joachim Holm

Chalmers, Kemi- och bioteknik, Kärnkemi

S. Guilbert

IRSN Institut de Radioprotection et de Surete Nucleaire

L. E. Herranz

Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas

C. Housiadas

Research Centre Demokritos

G. Ducros

Le Commissariat à l’énergie atomique et aux énergies alternatives (CEA)

C. Mun

IRSN Institut de Radioprotection et de Surete Nucleaire

J. C. Sabroux

IRSN

G. Weber

Gesellschaft fur Anlagen- und Reaktorsicherheit mbH

Progress in Nuclear Energy

0149-1970 (ISSN)

Vol. 52 128-135

Ämneskategorier

Kemi

DOI

10.1016/j.pnucene.2009.09.009