International projectModelling the behaviour of overhead crane bridges during an earthquake: call for participation in an international benchmark
From June 2020, IRSN and EDF organise an international benchmark, under the aegis of the OECD/NEA, to compare the models used to simulate the behaviour of overhead crane bridges during an earthquake. The failure of this equipment widely used in the nuclear industry can, for certain scenarios, contribute significantly to the probability of reactor core meltdown. Assessing their behaviour in the event of an earthquake is therefore a major safety issue. This assessment involves modelling the mechanical behaviour of these devices during an earthquake, which represents a scientific challenge due to the importance of contact dissipative phenomena.
The objective of the SOCRAT (Seismic simulation of Overhead CRAne on shaking Table) benchmark is to identify the best modelling practices of the behaviour of overhead crane bridges and the most relevant failure criteria. It will thus be possible, in the medium term, to define seismic fragility curves taking into account the physics of the phenomena involved.
The first step of the benchmark will consist in describing the models used by the participants and calibrating them on a set of data collected during a test campaign conducted in 2015 on the largest vibration table in Europe (TAMARIS/AZALEE, CEA Saclay, France). In a second step, the prediction capabilities of the models will be assessed during blind non-linear simulations at high seismic intensities.
Participation in the SOCRAT benchmark is open to experts from research organisations, technical support organizations, regulatory authorities, consulting firms, and more generally to all accepting to perform computational simulation of the tested crane bridges. The SOCRAT benchmark will end at the end of 2021 with a restitution workshop leading to recommendations on best modelling practices.
In November 2019, IRSN and the University of Tokyo signed a Memorandum of Understanding seeking to further our knowledge of the interactions that take place between droplets and solid aerosols. This has already involved around ten tests carried out at IRSN's TOSQAN facility, the most recent of which was completed on February 14, 2020.
This scientific collaboration is possible thanks to research carried out at the University of Tokyo and at IRSN on ways to mitigate aerosol dispersion in view of preparations to remove corium from the reactors at Fukushima Daiichi complex, for which IRSN is also working on the characterization of aerosols from the laser cutting of corium. This involves proposing and assessing strategies designed to reduce the risk of radioactive aerosols being released to the environment when cutting the corium.
The agreement between IRSN and the University of Tokyo has involved sharing scientific information and personnel, including for experimental studies conducted at the TOSQAN facility on aerosol collection using water mist. The agreement, which covers a period of 5 years, includes the publication of papers co-authored by the two bodies.
European Radiation Dosimetry Group (EURADOS) network convenes for its annual meeting in Florence, Italy, from January 27 to 30
The EURADOS network comprises over 70 European institutions and 630 members who work together to help harmonize practices and support technical and scientific research in the field of ionizing radiation dosimetry at both European and global level.
As a member of the network, the IRSN is represented by around 20 experts across the eight working groups, together with Isabelle Clairand and Jean-François Bottollier-Depois who are members of the council.
Our teams also will host a stand at the event, representing the Department for the Measurement of Exposure to Ionizing Radiation (SMERI) and providing an opportunity for attendees to discuss areas specifically relating to dosimetry for workers.
European IVMR research program on corium retention delivers its final results
Partners involved in the IVMR (In-Vessel Melt Retention) program, led by the IRSN, present their findings at a seminar held at the Juan les Pins (southern France) conference center from January 21 to 23, 2020.
Concluding in November last year, this four-year research program provided the opportunity to develop new knowledge and tools to assess whether the measures designed to stabilize and retain corium* in the vessel (IVR) in the event of a core meltdown accident might be effective for 1,000 MWe nuclear reactors. The program brought together 23 European organizations, joined in 2018 by a further nine from countries outside Europe (four Korean, two Russian, one Chinese, one Ukrainian and one Japanese).
A number of reactors with this power level (or higher) are currently in the construction or design phase across the globe, and this option, considered to be effective for reactors with a lower power, could be beneficial in stabilizing the corium before it reaches the containment building, the final barrier before releases into the environment.
The program enabled researchers to improve the methods and analytical tools used to assess IVR and the risks of vessel perforation for these reactors, and concluded that this strategy would be suitable for medium-power reactors, provided that certain key design elements were respected.
The IRSN played an active role in acquiring knowledge on in-vessel corium retention, particularly by carrying out experiments to determine the critical heat flux that can be extracted from a bath of corium surrounded by debris. The Institute also made improvements to its core meltdown accident simulation tools, by creating new models for its ASTEC (Accident Source Term Evaluation Code) software.
Finally, the new methodology proposed by the IRSN and its partners to assess the IVR strategy in high-power reactors made it possible to harmonize the different approaches used, taking account of the gradual erosion of the vessel and the transient stratification phenomena in the corium, which had previously been neglected.
* a mixture resulting from the melting of fuel, cladding and support structures
54 thesis proposals for 2020!
This year, IRSN is proposing 54 topics in all scientific disciplines, for PhD theses that will start in October 2020. A full description of each thesis project is available online, in the "Theses" section of the IRSN website, enabling applications to be filed directly with the thesis supervisor.
More than 100 doctoral students work continuously in its laboratories, covering a wide range of scientific disciplines, in innovative areas of physics, biology and social sciences, helping protect the population and the environment from nuclear and radiological risks. Each doctoral student benefits from specific training to master the intricacies of writing a scientific article or dissertation, learn about networking, open access and eco-design practices, familiarize him/herself with good intellectual property practices, or be informed of openness to society.
Every year, doctoral students practice presenting their research work to their peers as part of a four-day residential seminar called "Thesis Days." During this convivial event, doctoral students discuss and present the state of their research as they would at a conference. They can put their ability to summarize to the test during the "3 minutes for a thesis" competition, IRSN's own version of "My thesis in 180 seconds." The competition's participants also have the opportunity to work with a cartoonist to transpose their research in the form of a comic strip.
Lastly, the Ad'i[N] and ASTHEC doctoral student associations enable students to establish strong ties and create professional networks through the organization of scientific, cultural and sports events.
To receive funding for a thesis, applicants must have a Master's or equivalent degree allowing them to enroll in a doctoral school before October of the current year. In cases of diploma equivalence, authorization to enroll in the doctoral school associated with the topic shall be verified before the application is put together. Unless an exception is granted, applicants must be under 26 years of age when submitting their application and have graduated with honors.
For each thesis topic, additional information – description, tutor, laboratory, etc. – is available by clicking on the topic. The first step in the application process consists in sending a CV and cover letter to the thesis tutor (address in email@example.com format).
Final selection of the topics and applicants will take place in May-June 2020.