Deliverable D1.1 released – Identification of improved safety systems of light water SMRs

Current and emerging light water cooled SMR designs are seen as particularly promising for deployment in EU countries. New and innovative design features can pose specific challenges when demonstrating the safety of such plants. The report D1.1 you can download below summarizes our work in the Work Package 1 of the ELSMOR project.

In this work package we have:

  • Briefly evaluated the existing rules and regulations, particularly the relevant EU directives as well as WENRA and ENSREG guidance, regarding their applicability on light water cooled SMRs and their impact on the safety demonstration and acceptability of a design.
  • Identified new and innovative design features of current and emerging light water-cooled SMR designs which could pose new challenges to existing safety demonstration approaches, including the concept of modular designs integral to most SMRs.
  • Evaluated emerging generic features against specific issues relevant to the safety demonstration and acceptability of new built plants.

We find that the existing high-level regulation is basically applicable to light water cooled SMR designs. Practical elimination of postulated severe accidents and subsequent definition of emergency planning zones is an area where consolidated demonstration methods are needed.

Regarding the designs, the main new features compared to existing larger-scale NPPs include so-called integral reactors in which steam generators, pressuriser, pumps and sometimes also the control rod drive mechanisms are installed inside the RPV. Decay heat removal is often performed mainly with passive safety systems. Finally, cores with high burnups and high excess reactivity are used to enlarge the cycle lengths to make the SMRs economically more interesting.

Based on these findings, we recommend further work on improving the safety demonstration methods and substantiating acceptance criteria for the Work Package 2 of ELSMOR. Main areas of interest should be:

  • the use of passive safety systems and related safety demonstration methods,
  • impact of multiple modules at a site including common systems and structures,
  • demonstrations for high burn-up cores including innovative materials and
  • mitigation strategies for postulated severe accidents including the demonstration of practical elimination and definition of emergency planning zones).

Download the report here

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