Created in 2006, the European Technical Safety Organisations Network ETSON [1] aims to contribute to the harmonization of nuclear safety in Europe and beyond. Today, the network publishes four technical guides to promote and disseminate best practices for the assessment of nuclear safety.

Since the launch of the EUROSAFE initiative in 1999, the French institute IRSN, the German GRS and the Belgian Bel V (formerly AVN) pursued the objective of advancing the harmonization of nuclear safety in Europe by comparing their methods to assess safety. In 2004, they published a "Guide for Safety Evaluation" with practical methods for performing common safety assessments.

Pursuing this approach, the European Technical Safety Organisations Network ETSON releases today four technical guides to promote and disseminate best practices for the assessment of nuclear safety at European and global level. The preparation of these guides relied on twelve thematic working groups in which experts have analyzed the different methods of evaluation of nuclear safety implemented in European countries.

A general document (Safety Assessment Guide) defines the scope of the methodology used in Europe during safety assessments, presents different requirements for the assessment of nuclear safety and also the technical elements required to complete an evaluation. It is supplemented by the first three thematic technical guides: Deterministic severe accidents analysis, Event review and precursor analysis, Human and organizational factors in nuclear facilities design and modification processes.

Each ETSON members will appropriate the harmonised methods described in the TSAGs, decline them in their countries for their own safety studies assessment and, then, share the experience feedback.

Download the ETSON guides (PDF files) on the ETSON website www.etson.eu​

• Safety Assessment Guide
• Technical Safety Assessment Guide : Event review and precursor analysis
• Technical Safety Asessment Guide : Human and organisational factors in nuclear facilities design and modification processes
• Technical Safety Assessment Guide : Deterministic severe accidents analysis

Note:

1- The ETSON network currently comprises eight members (IRSN - France, GRS - Germany, Bel V – Belgium, UJV - Czech Republic, VTT – Finland, LEI – Lithuania, VUJE – Slovakia, PSI - Switzerland) and 3 associate members (JNES – Japan, SSTC - Ukraine, SEC NRS – Russia)

For several years, IRSN has been conducting researches on the economical costs of nuclear accidents involving radioactive releases in the environment. A short presentation of these studies took place during the Eurosafe Forum in November 2012.

Preparing for a nuclear accident implies understanding potential consequences. While many specialized experts have been working on different particular aspects, surprisingly little effort has been dedicated to establishing the big picture and providing a global and balanced image of all major consequences.

IRSN has been working on the cost of nuclear accidents, an exercise which must strive to be as comprehensive as possible since any omission obviously underestimates the cost. It therefore provides (ideally) an estimate of all cost components, thus revealing the structure of accident costs, and hence sketching a global picture.

On a French PWR, it appears that controlled releases would cause an “economical” accident with limited radiological consequences when compared to other costs; in contrast, massive releases would trigger a major crisis with strong radiological consequences. The two types of crises would confront managers with different types of challenges.

More information:

Download the paper by Patrick Momal and Ludivine Pascucci-Cahen presented during the Eurosafe Forum: Massive radiological releases profoundly differ from controlled releases (pdf)

On February 12, 2013, a roof and a section of wall of the turbine hall of the C​hernobyl reactors collapsed. IRSN publishes an information note about this event which, given the available evidence, has no impact on the environment.

The collapse was caused by an accumulation of snow on the roof structural steelwork. The area is near the sarcophagus that was installed over the damaged reactor in 1986. The photos below show a view of the outer wall of the turbine hall, locally destroyed, and a view of the roof partially collapsed.

Download the information note from IRSN

Following the accident that occurred on the Fukushima Daiichi nuclear power plant on 11th March 2011, the French prime minister asked the French nuclear safety authority (ASN) to carry out an audit on the safety of French nuclear facilities.

On 5th May 2011, ASN required the French nuclear operators to perform Complementary Safety Assessments (CSAs) of their facilities. The CSAs evaluate the capacity of French nuclear facilities to withstand extreme situations beyond design basis assumptions. In 2011, these evaluations included the power reactors in operation or under construction, as well as certain nuclear facilities considered by ASN to be priority.

The operators submitted their CSAs reports to ASN on 15th September 2011. IRSN’s review and of these reports was transmitted to ASN and to the Nuclear Safety Advisory Committees on 4th November 2011.

Based on IRSN's critical assessment, the Nuclear Safety Advisory Committees met the 8th, 9th and 10th November 2011 to review these Complementary Safety Assessments and the relevance of the improvements proposed by the operators to enhance the safety of their facilities in the event of extreme situations (earthquake, flood, loss of electrical power supply, loss of heat sinks).

On 17th November 2011, during a conference jointly organised by ASN and IRSN, IRSN presented its analysis and conclusions to the press and made public its CSAs report. And on 3rd January 2012, ASN’s report on the CSAs was submitted to the Prime Minister and made public.

The review conducted by IRSN of the CSAs reports submitted by operators revealed three main observations:

1. A small number of nuclear facilities have compliance gaps in terms of requirements, which weaken their safety within the framework of events taken into account for their design. Corrective actions are already in progress and are to be accelerated.
2. Developments in knowledge must lead to some requirements being re-examined in advance. This is especially the case with the integration of earthquakes, for which knowledge has advanced massively over the last years.
3. The issue of the behaviour of nuclear facilities in the event of a conceivable extreme natural disaster is raised since, in the current situation, this could have unavoidable consequences, ending up in core meltdown and radioactive release.

To confront these exceptional - but nonetheless conceivable - scenarios, IRSN recommends adopting an additional safety requirement level, entitled “hardened safety core”, which would guarantee that the vital basic functions of nuclear facilities are sustained over several days, thus enabling off-site resources to intervene.

More information:

IRSN information notice of 17th November 2011: IRSN analysis and conclusions following the expert review of the Complementary Safety Assessments submitted to ASN by the operators at the request of the Prime Minister after the Fukushima accident

Technical summary of IRSN review of CSAs report: Post-Fukushima Complementary Safety Assessments: behaviour of French nuclear facilities in the event of extreme situations and relevance of the proposed improvements