IRSN sees problems in assessing passive safety systems

Further research is needed to properly assess the performance and reliability of passive safety systems to be used in new nuclear power reactors designs, according to France's Institute for Radiological Protection and Nuclear Safety (IRSN).

Passive safety systems aim to bring a reactor to a safe shutdown state and maintain this state for a long period of time without the need for human intervention and with limited reliance on support functions. The IRSN noted that while those reactors currently operating in France are equipped with such systems, some new reactor designs "make more extensive use" of them.

The IRSN has today published a report presenting the main characteristics of passive safety systems and outlining the main difficulties associated with assessing their performance and reliability. It also identifies priority research areas to be developed in order to overcome these difficulties.

The IRSN said its evaluation so far has identified a number of "intrinsic difficulties" in assessing their performance and reliability. It says this requires a very good understanding of the physical phenomena underlying their operation, as well as the necessary simulation capabilities for such phenomena.

Specific development approaches appear to be required in order to evaluate properly the reliability of such systems, with particular emphasis on assessing the failure probabilities of thermal-hydraulic mechanisms they use.

The IRSN concluded that further research is required in order to properly assess the performance and reliability of passive safety systems. This research, it said, will focus on understanding the physical phenomena influencing their operation; simulation capabilities for such phenomena; and testing for validation of simulation software.

IRSN said it has established a working group for technical exchanges with Areva, EDF and the French Alternative Energies and Atomic Energy Commission (CEA) in order to identify priority research areas.

It is also participating in the NUSMOR (NUgenia Small Modular Reactor with passive safety systems) project to be proposed as part of the Horizon 2020 EU framework program.

Researched and written
by World Nuclear News