IRSN, Institut de radioprotection et de sûreté nucléaire

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Safety approaches

​​IRSN's safety assessment relies on risks knowledge, especially acquired through research programs as well as analysis of operating experience, on existing regulation, but also on a set of approaches ensuring robustness and transversality to its technical statements.​

In this context, the Institute develops and publishes elements of approaches to enhance nuclear safety, security and the protection against ionizing radiation.


The break preclusion approach

Date of publication: July 2020

The break preclusion approach is based on the principle of not considering a break in a vessel or piping as a single initiating event to be studied in the safety demonstration. Its application should be duly justified and associated to specific reference documents. Break preclusion approach relies on reinforced requirements intended notably to ensure high quality levels.

IRSN publishes a report related to its recommendations with regards to implementation of break preclusion approach for a pressurized water reactor (PWR). This report completes ASN guide n° 22 produced jointly with IRSN and related to design of PWR and specifies some of its elements.

On this basis of insights of the fleet of nuclear power plants, including EPR reactor of Flamanville, IRSN has established a list of conditions needed, in order to allow a break preclusion approach to be acceptable for mechanical equipment. Among these conditions, the applicant shall justify the expected safety benefits of break preclusion implementation from the early project phases.

Download the document "The break preclusion approach" (PDF, 316 Ko)


Principles relating to the digital instrumentation and control design approach

Date of publication: January 2018

The implementation of digital systems in the instrumentation and control of nuclear facilities offers increasing capabilities enabling to carry out advanced functions or to provide operators with improved interfaces. However, it raises questions about their “complexity” and introduces sources of failure other than random hardware failures, which the implementation of appropriate design principles makes possible to take into account.

IRSN publishes a document presenting the main challenges associated with the design of the digital instrumentation and control, as well as the general principles to follow to demonstrate that a satisfactory safety level has been achieved.

Download the document "Principles relating to the digital instrumentation and control design approach" (PDF, 785 Ko)


The “practical elimination” approach of accident situations for water-cooled nuclear power reactors

Date of publication: January 2018
Update in March 2021​

The implementation of the defence in depth principle leads applicants to define provisions to prevent accidents, including severe accidents, and to limit their consequences should they occur. Some severe accident situations potentially lead to large early radiological releases, for which it appears impossible to define realistic and demonstrable provisions to limit their consequences according to current knowledge and the techniques available: applicants shall then use the “practical elimination” approach.

IRSN publishes an orientation document which defines “practical elimination” approach and its place in safety demonstration for nuclear power plants involving pressurized water reactors.

Download the document "The practical elimination approach of accident situations for water-cooled nuclear power reactors" (PDF, 438 Ko)



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