IRSN, Institut de radioprotection et de sûreté nucléaire

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Research programme

First EPICUR tests

March 2006 Since its commissioning in May 2005, the new EPICUR installation has already been used to conduct eight experiments for the SOURCE TERM international research programme. This programme aims to reduce uncertainties in the evaluation of releases of radioactive products into the environment in the event of a core meltdown accident in a water reactor.

The first four tests, carried out between May 2005 and February 2006, were part of a programme to study iodine: also called EPICUR (Experimental Programme on Iodine Chemistry Under Radiation), the programme concerns the study of the behaviour of radioactive iodine in the containment of an accident-affected reactor. More precisely, this entails quantifying and characterising the fraction of volatile iodine likely to be released into the environment, this being the "source term’. The first three tests were aimed at validating the models of the radiolytic oxidation of iodine which is in the water in the reactor sump. Aqueous solutions of stable iodine in boric acid and tagged with iodine 131 were irradiated at different temperatures and iodine concentrations in order to study the effects of those parameters. The iodine emanations emitted by the solutions were trapped in selective Maypack filters and measured by gamma spectrometry.
The fourth test, conducted in February, consisted in irradiating a sample of paint, plunged in an aqueous solution tagged with iodine 131, simulating the painted surfaces of the sump. The purpose of this test was to validate the models of the production/destruction of organic iodines. Six other tests are planned to be conducted by the end of 2006, and about 30 are scheduled to be carried out by the end of 2009.
In the other four tests, performed between 28 February and 21 March 2006, the behaviour of ruthenium was examined in the ambient conditions of an accident-affected reactor containment. These tests were carried out for the purposes of a thesis which had the objective of quantifying the fraction of volatile ruthenium likely to be released into the environment, which was also the aim of the study on iodine. These tests used either an aqueous solution of stable ruthenium in boric acid or ruthenium-charged painted steel test coupons, representing the conditions existing in the sump water and on the surface of the containment of an accident-affected water reactor. The samples are being analysed to determine whether volatile ruthenium was formed by irradiation from the surfaces or solutions. Six other tests are to be conducted by the end of June, and the thesis is to be completed by the end of year.

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