Reactor Harmonisation Working Group (RHWG)

Safety Reference Levels for Existing Plants 

The first task of the Reactor Harmonisation Working Group was to develop safety reference levels (RLs) for existing nuclear power plants. The methodology and results of the harmonisation study are presented in the report “Harmonization of Reactor Safety in WENRA Countries”  published by WENRA in January 2006.

The results of the study were also presented during a seminar in Brussels in February 2006 where stakeholders were invited by WENRA to provide comments on the report. As a result of the seminar, the RLs were updated in March 2007 and once again in January 2008, mainly to take into account the publication of the IAEA Safety Requirement GS-R-3. 

Following the nuclear accident at TEPCO Fukushima Dai-ichi nuclear power plant in Japan in March 2011, WENRA decided to revise the RLs to incorporate the lessons learned from the accident. For this purpose, three working groups were created to address technical issues for reviewing, revising (or developing) the RLs. The working groups each dealt with specific technical issues regarding natural hazards, containment in severe accidents, and accident management. The revised RLs were published in September 2014. 

Long Term Operation

RHWG has also discussed about the safety aspects of continued operation of nuclear power plants longer than foreseen by their original design (this is referred to as “long term operation” or LTO). WENRA published in 2011 an overview of the LTO practices in WENRA countries. The report discusses also the link between the periodic safety review and LTO. 

Safety Objectives for New Nuclear Power Plants 

After the reference levels were published for the existing nuclear power plants, RHWG initiated work with new reactors. In December 2009, WENRA published a statement concerning “Safety objectives for new nuclear power plants”. In order to achieve true harmonization of the safety approaches at the new plants, it is necessary to provide more specific guidance on issues that should be considered for meeting the commonly agreed safety objectives. As a follow-up to the WENRA statement, the RHWG presented a report outlining safety objectives for new NPPs in 2013. 


One of the key aspects of nuclear safety and continous improvement is the periodic safety review (PSR). According to the WENRA RLs, PSRs shall be made periodically, at least every ten years. The review shall confirm the compliance of the plant with its licensing basis and any deviations shall be resolved. In addition, the review must consider any issues that might limit the future life of the facility or its components and explain how they will be managed.

In light of the accident in Fukushima, in 2013 the RHWG presented a position paper regarding PSRs taking into account the lessons learned from the accident. 

RHWG Reports