In 2014 WENRA published the revised Safety Reference Levels (SRL) as a result of a review in the light of the learning from the TEPCO Fukushima Daiichi NPP accident. The first task for WENRA countries was to implement the new SRL into their national regulation. Afterwards WENRA’s Reactor Harmonization Working Group (RHWG) started to discuss options for a benchmarking process on the implementation of SRL at the Nuclear Power Plants.

During its fall meeting 2017, WENRA advised that RHWG should combine the following tasks into a single task:

• Implementation of the 2014 RLs at the plants,
• Safety improvements for implementation of the VDNS.

This should look at the implementation of a subset of RLs at a representative sample of existing plants per country covering the range of reactor designs in WENRA countries. WENRA suggested that RHWG should review implementation of Issue F for plant faults with emphasis on severe accident management. The task should also look at:

• Implementation of NSD articles 8(a) to 8(c) – especially 8(a),
• Benchmarking on specific safety improvements.

Concerning the original task defined by WENRA, RHWG selected SRLs F4.8 to F4.18 as candidates. A RHWG subgroup was founded. Countries were asked to give feedback on the technical solutions (improvements) that are or will be installed in their NPPs for compliance with these SRLs. SRLs have been selected as ones that would provide the most fruitful insight, are linked to Articles 8a, are particularly associated with preventing early and large releases.

In January 2019 it was decided to conduct a pilot study with two SRLs to prove the chosen approach of RHWG to fulfil the task mentioned above. The following SRL were selected:

• F4.10 – The threats due to combustible gases should be managed.
• F4.17 – Adequate power supplies during DEC shall be ensured considering the necessary actions and the timeframes defined in the DEC analysis, taking into account external hazards.

The objectives of the pilot study are:

• to prove the chosen approach,
• to show the harmonization status in WENRA countries with regard to the selected SRL,
• to share information on different technical solutions to implement the SRLs at the NPPs and to learn from each other,
• to address the timeliness of the safety improvements,
• to present lessons learned.

On the basis of country feedbacks, lists of technical solutions were compiled for both SRLs. Various technical solutions have been given for each of the selected SRLs. These technical solutions may be needed altogether for SRL fulfilment, or may describe alternative ways to fulfil the SRL, or can be seen as supplementary measures. Depending on the SRL, the lists are different for the different reactor types to be considered in WENRA countries.

Nuclear power plants in WENRA observer countries are included in the exercise to the extent these countries wish to be.

It has to be pointed out, that when compiling the lists of technical solutions, the details of their design and the implementation status reflect the position of the corresponding national authority.

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WENRA SRL 2014 - Impl. at NPPS, reasonably practicable improv.