The STEM Project was initiated with a first phase in 2011 to improve the general evaluation of the fission-product (FP) source term in the event of a severe accident of a water-cooled reactor in relation to two major FPs, iodine and ruthenium. The STEM Project is conducted at Institut de radioprotection et de sûreté (IRSN) facilities at Cadarache, France. The first phase of the project, which ended in 2015, addressed three main issues: experiments on radioactive-iodine release due to irradiation of iodine-bearing aerosols that would contribute to mid- and longer-term source in the containment; a literature survey on interactions between iodine and paints; and experiments on transport of volatile ruthenium species through steel pipes representing the reactor coolant system (RCS).
The second phase (STEM-2) pursues experimental investigations of iodine and ruthenium issues undertaking the following investigations concerning iodine:
Regarding ruthenium, experiments in more representative conditions than in STEM will be performed on simulations of ruthenium transport in the RCS. In particular, this means more representativity for the deposition surface, the use of stronger oxidising conditions characteristic of air radiolysis products (such as ozone and nitrous oxides) and the use of representative gaseous and/or aerosol “pollutants” (i.e. seed particles, silver aerosols, aerosol deposits) that could influence ruthenium behaviour.
STEM also has strong scientific links with the Behaviour of Iodine Project (BIP), including complementary objectives and many common partners.
STEM: Canada, Czech Republic, Finland, France, Germany, Korea and United States
STEM-2: Canada, Finland, France, Germany, Japan, Korea, Sweden, United Kingdom and United States.
STEM: July 2011 to Sept 2015
STEM-2: Jan 2016 to Dec 2019
STEM: EUR 3.5 million
STEM-2: EUR 2.5 million