In 2014 WENRA published the revised Safety Reference Levels (SRLs) as the result of a review in light of the learning from the TEPCO Fukushima Daiichi NPP accident. The first task for WENRA countries was to implement the new SRLs into their national regulations. Following this WENRA’s Reactor Harmonization Working Group (RHWG) started to discuss options for a benchmarking process on the implementation of SRLs at the Nuclear Power Plants (NPPs).
During its fall meeting in 2017, WENRA advised that RHWG should combine the following tasks into a single task:
- Implementation of the 2014 SRLs at the plants,
- Safety improvements for implementation of the Vienna Declaration on Nuclear Safety (VDNS).
It was agreed that the task should look at the implementation of a subset of SRLs at a representative sample of existing NPP per country, covering the range of reactor designs in WENRA countries. WENRA suggested that RHWG should review the implementation of Issue F for plant faults with emphasis on severe accident management. The task should also look at:
- Implementation of the European Union Nuclear Safety Directive (NSD) articles 8(a) to 8(c) - especially 8(a),
- Benchmarking on specific safety improvements.
Concerning the task defined by WENRA, RHWG started its work in January 2018 by selecting SRLs F4.8 to F4.13 and F4.15 to F4.18 as candidates. These SRLs were selected as the ones that would provide the most fruitful insights, are linked to Article 8a and are particularly associated with preventing early and large releases.
The chosen approach provided an overview of the current status of the implementation of the chosen SRLs in the NPPs. Different technical solutions to fulfil a SRL were compiled in order to allow learning from each other. It became clear that many safety improvements to comply with the selected SRLs had been implemented long before the NSD or VDNS. Due to the positive feedback from the pilot study, the task was continued for the other SRLs and benchmarking of the related underlying national self-assessments was performed in parallel.
The objectives of the benchmarking process that started in May 2020 were:
- to share information on approaches to implement the SRLs in the NPPs and to enable learning across WENRA members;
- to evaluate the compliance with the safety objective of the SRL in the related NPPs.
Benchmarking exclusively concerned the SRLs F4.8 to F4.13 and F4.15 to F4.18 without consideration of the remaining SRLs of Issue F. The SRLs, however, need to be considered as a whole set. Thus, it should be clear that the benchmarking that was performed cannot be seen as an in-depth review of the technical or analytical aspects of the various SRL related safety relevant aspects, nor can conclusions be drawn on the overall safety of the NPP. This kind of review and assessment is the duty of national safety authorities.
The benchmarking was done by mutually checking the information given in the national self-assessments, by reviewing whether this information was considered as detailed enough, comprehensible and consistent with the understanding of the safety functions to be fulfilled by the different technical solutions, and, finally, sufficient to confirm that the SRL as a whole is implemented in the related NPPs.
The benchmarking results are based on the information provided by the participating countries. However, it should be noted that the situation in the plants themselves has not been verified.
