the european stress test for nuclear power plants

Recommendation No. 2: 


Comprehensiveness of documentation 


Under the given scope of the “Stress test“, as defined by ENSREG, the description of the plants’ defence-in-depth-concept in the country reports should cover all operational states of the reactor and include spent fuel pools and should document the following issues:48 

Defence in depth level 1 (normal operation): 

  • Description of the existing ageing management program 
  • Description of the existing operating experience feedback program 
  • Quality of the pressure retaining boundary (e.g. material, tolerated flaw indications, status of fatigue analyses) 
  • Status report including an evaluation on number, types and trends of plant specific incidents during the last ten years. 

Defence in depth level 2 (abnormal events): 

  • List of postulated initiating events allocated to this Defence in Depth level 
  • Applied acceptance criteria allocated to these events. 
  • Applied requirements for analytical methods, model and boundary conditions for the analyses 
  • Applied requirements for the systems, structures and components (SSCs) needed to fulfil the acceptance criteria in case of these events. 
  • Degree of independence of the SSCs from SSCs of other levels of the Defence in Depth including the reactor auxiliary and support systems (e. g. electrical power supply, cooling systems). 

Defence in depth level 3 (postulated accidents) 

  • List of postulated initiating events allocated to this Defence in Depth level
  • Applied acceptance criteria allocated to these events
  • Applied requirements for analytical methods, model and boundary conditions for the analyses (conservative vs. best-estimate approach).
  • Applied requirements for the systems, structures and components (SSCs) needed to fulfil the acceptance criteria in case of these events.
  • Degree of independence of the SSCs from SSCs of other levels of Defence in Depth (including the reactor auxiliary and support systems (e. g. electrical power supply, cooling systems).
  • Applied requirements for accident procedures (EOPs) needed to fulfil the acceptance criteria in case of these events.

Defence in depth level 4 (very rare events, multiple failure events and severe fuel damage events)

  • List of considered events/states
  • Applied acceptance criteria allocated to these events/states
  • Applied requirements for analytical methods, model and boundary conditions for the analyses.
  • Applied requirements for the systems, structures and components (SSCs) needed to fulfil the acceptance criteria in case of these events/states.
  • Degree of independence of the SSCs from SSCs of other levels of Defence in Depth.
  • Applied requirements for accident management procedures (SAMGs)





48 See e.g. fn..69