Irradiation Vessel with Coupons, CNL

The NEA Behaviour of Iodine Project (BIP) was created to provide separate effects and modelling studies of iodine behaviour in a nuclear reactor containment building following a severe accident. This joint project complemented other national and international experimental programmes also studying this phenomenon. As part of the project, the results of three radioiodine test facility (RTF) experiments were provided by Atomic Energy of Canada Limited (AECL). AECL's capabilities include experienced personnel and a wide range of facilities and equipment for the study of all aspects of reactor safety. Key facilities included Co-60 irradiators (Gammacells), active laboratories for performing iodine-131 tracer studies, specialised surface science laboratories (capable of working on active or inactive samples) and extensive hot cell facilities.

BIP phases

First phase (2007-2011)

In the first phase of BIP, project participants sought to combine international resources to produce a consolidated understanding of the behaviour of iodine and other fission products in severe accidents.

The specific technical objectives were to:

• Quantify the relative contributions of homogeneous bulk aqueous phase processes, homogeneous aqueous phase processes in paint pores and heterogeneous processes on surfaces to organic iodine formation;
• Measure adsorption/desorption rate constants on containment surfaces as a function of temperature, relative humidity and carrier-gas composition;
• Provide RTF data to participants, for use in collaborative model development and validation.

The results provided in this phase were valuable to regulators and operators in the context of managing post-accident situations in a containment building.

Work during the first part of the project had concentrated on the specifications for the first tests of the test matrix. Within the framework of BIP, the group had successfully performed more than 50 tests dealing with the adsorption of iodine on surfaces and the formation of organic iodides from irradiated paint. 

At the end of the project, it was decided to start a follow-up project, BIP-2, to address remaining issues concerning organic iodine formation and iodine interaction with paintings.

The Data Package may be requested at BIP PROJECT, Behaviour of Iodine Project.

Second phase (2011-2014)

BIP-2 was a follow-up to the first phase that provided results from separate effects and modelling studies of iodine behaviour in a nuclear reactor containment building following a severe accident.

Atomic Energy of Canada Limited's Chalk River Laboratories in Canada was the primary research facility for the project. Key facilities included Co-60 irradiators (gamma cells), active laboratories for performing iodine-131 tracer studies, specialised surface science laboratories (capable of working on active or inactive samples) and extensive hot cell facilities. With these facilities, and within the framework of the BIP Project, the group had successfully performed more than 50 tests dealing with the adsorption of iodine on surfaces and the formation of organic iodides from irradiated paint.

The joint project complemented other national and international experimental programmes such as SARNET2, which were also studying this phenomenon. Project participants sought to combine international resources to produce a consolidated understanding of the behaviour of iodine and other fission products in severe accidents. The specific technical objectives for this follow-up project were to:

• Obtain a more detailed and mechanistic understanding of iodine adsorption/desorption on containment surfaces by means of new experiments with well-characterised containment paints and paint constituents and novel instrumentation (spectroscopic methods);
• Obtain a more detailed and mechanistic understanding of organic iodide formation by means of new experiments with well-characterised containment paints and paint constituents and novel instrumentation (chromatographic methods);
• Develop a common understanding on how to extrapolate confidently from small-scale studies to reactor-scale conditions.

An extensive analytical effort accompanied the experimental programme, mainly consisting of data interpretation, result evaluations and modelling for application to reactor situations.

Main outcomes of the BIP-2 project were presented at the International Iodine Workshop organised by the NEA in 2015 (pp. 37-38 and pp. 153-164 of the full proceedings). 

The Data Package may be requested at BIP-2, Behaviour of Iodine Project Phase 2.

BIP-2 Members' area (password protected | reminder)

Third phase (2016-2019)

BIP-3 was a follow-up to the first two phases that provided results from separate effects and modelling studies of iodine behaviour in a nuclear reactor containment building following a severe accident. While painted surfaces are a very important iodine sinks within containment, they represent a pathway that converts molecular iodine into organic iodine which is less easily trapped than molecular iodine by conventional iodine filtration methods (charcoal, wet scrubbers). Building on the earlier experiments performed by CNL (Canada), BIP-3 attempted to answer some outstanding questions raised during BIP and BIP-2 where the specific technical objectives were to:

• Perform experiments to resolve outstanding questions and improve the simulations of BIP and the Source Term Evaluation and Mitigation (STEM) Project results, including by improving the ability to simulate iodine adsorption and desorption on containment surfaces; predicting organic iodine behaviour (formation and degradation) under accident conditions; and investigating the effects of paint ageing on these processes;
• Further investigate the effects of contaminants (nitrous oxides, chlorine and other potential contaminants);
• Share simulation strategies involving all partners in, for example, a code comparison exercise.

The BIP and STEM projects had strong scientific links with complementary objectives and many common partners.

BIP-3 members' area (password protected | reminder)