Objective
The extent and mechanism(s) of organic iodide formation contribute to an important uncertainty in the calculation of the iodine source term. Organic iodine is, compared with other volatile iodine forms, relatively immune to the accident management measures designed to reduce the iodine concentration in the containment gas phase (sprays) and in the vent gas (filters). Variations in the estimated organic iodide concentrations are therefore reflected more or less directly in source term predictions, irrespective of the accident sequence under consideration.
Most large-scale tests such as ACE and Phebus have shown that, whilst the absolute amount of organic iodide formed under PWR accident conditions is very small, it is often the major volatile form. However, the processes leading to the formation of organic iodides are not well understood, so it is not possible to predict reliably whether these observations are generally applicable. Furthermore, in BWR accident conditions, the quantities of organic iodide formed could be much greater.
Although experimental studies of the reactions of iodine with paint have been made in the past, few of these programmes were designed to yield results which could be used in modelling the formation of organic iodides. Furthermore, recent results have indicated that the interaction mechanisms change significantly at temperatures above 80øC, so that results obtained at lower temperatures may not be applicable to reactor containment conditions. To help clarify the phenomenology, and to increase confidence in the modelling of iodine behaviour in containment, an integrated programme of assessment, experiments and analysis is proposed involving the key European laboratories working in the field. A comprehensive review and assessment of the international literature on organic iodide formation and destruction will be carried out in order to determine the critical data requirements. These will then be addressed in experimental studies which will be designed specifically to produce data which can be used in model development.
The major objectives of this work are:
(i) identification of the principle mechanism(s) of organic iodine production,
(ii) development of modelling to simulate the process, and (iii)harmonisation of the treatment of organic iodide formation in iodine chemistry models at a European level/ leadinq to closure issue.
Programme(s)
Call for proposal
Data not availableFunding Scheme
CSC - Cost-sharing contractsCoordinator
DT2 8DH Dorchester
United Kingdom