The standards of safety of nuclear power plants in Europe are “generally high” but further improvements in the safety features of almost all European nuclear power plants are recommended, the European Commission said on October 4 2012, reporting on the results of stress tests ordered after the 2011 Fukushima nuclear power station disaster.
Nevertheless, the European Commission said, European national safety authorities came to the conclusion that “no closure of nuclear power plants was warranted”.
The stress tests had found that not all safety standards promoted by the International Atomic Energy Agency (IAEA) and not all international best practices are applied in all EU member states.
“The Commission will follow closely the implementation of the recommendations and will at the same time propose legislative measures to further enhance nuclear safety in Europe.”
European Commissioner Günther Oettinger said: “The stress tests have revealed where we are good at and where we need to improve. The tests were serious, and they were a success. Generally, the situation is satisfactory but there is no room for complacency. All authorities involved must work to ensure that the highest safety standards are in force in every single nuclear power plant in Europe. For the safety of our citizens”.
In addition to recommending numerous of plant specific technical improvements, the stress tests have shown that international standards and practices have not been applied everywhere. In addition, lessons from Fukushima need to be drawn. In particular, these include:
- Earthquake and flooding risk. Current standards for risk calculation are not applied in 54 reactors (for earthquake risk) and respectively 62 reactors (for flooding risk) out of the 145 checked. The risk calculation should be based on a 10 000 year time frame, instead of the much shorter time periods sometimes used.
- On-site seismic instruments to measure and alert of possible earthquakes should be available at every nuclear power plant. These instruments should be installed or improved in 121 reactors.
- Containment filtered venting systems to allow safe depressurizing of the reactor containment in case of an accident, should be in place. 32 reactors are not yet equipped with these systems.
- Equipment to fight severe accidents should be stored in places protected even in the event of general devastation and from where it can be quickly obtained. This is not the case for 81 reactors in the EU.
- A backup emergency control room should be available in case the main control room becomes inhabitable in case of an accident. These are not yet available in 24 reactors.
The European Commission said that national action plans with timetables for implementation will be prepared by national regulators and will be made available by the end of 2012.
The action plans will go through peer reviews in early 2013, in order to verify that the stress tests recommendations are consistently implemented in a transparent way throughout Europe. The Commission intends to report on the implementation of the stress test recommendations in June 2014, in full partnership with national regulators.
In addition to the specific technical findings and recommendations, the Commission has reviewed the existing European legal framework for nuclear safety and will present a revision of the current nuclear safety directive in early 2013. The proposed amendments will focus on safety requirements, the role and powers of nuclear regulatory authorities, transparency, as well as monitoring.
This will be followed by further proposals on nuclear insurance and liability and on maximum permitted levels of radioactive contamination in food and feedstuff. The stress test process has also highlighted the need for further work on nuclear security (prevention of malevolent acts), where the main responsibility lies with the EU member states.
- On Bulgaria, the technical report said:
− Adequacy of paleoseismological studies should be further analysed throughout the periodic updates of the seismic PSA and in the PSR, on the basis of the information available and verified, to evaluate the need of re-assessment of the seismic hazard on site.
− Implementation of the complementary improvement measures for beyond design basis conditions identified in the Action Plan (such as improvement of the leak tightness of certain rooms below ground level) should be monitored.
− A combination of extreme weather conditions still needs to be considered.
− Although the batteries have 10 hours discharge time, a possibility of their recharging from a mobile DG should be considered.
− Concerning SAM, there is still an open issue under which conditions is the implementation of different SAM measures feasible, e.g. due to possible lacking some hardware provisions for mitigation of severe accidents. It is recommended that additional improvements for SAM covered by the “Program for Implementation of
Recommendations Following the Stress Tests Carried out on Nuclear Facilities at Kozloduy NPP plc.” is pursued.
− During the country visit it was noticed that periodic and frequent walk downs on SAMGs provisions are performed, this is considered as a good practice.
Safety improvements implemented or planned (non-exhaustive list):
Some examples of measures for improvement of plant robustness related to the two operating units 5 & 6 at Kozloduy NPP are, as follows:
− Studying the possibilities for alterative options for Units 5 and 6 decay heat removal using the existing SG emergency makeup system (EMS) of Units 3 and 4.
− Securing the availability of at least one tank of the SG Emergency Feedwater System in shutdown mode in order to provide for the use of the SG as an alternative for the residual heat removal.
− Two new mobile DGs will be delivered, and the existing one will be maintained in standby conditions for the remaining structures at the NPP area; Power supply from a mobile DG is provided for charging the accumulator batteries of the safety systems.
− Implementation of the symptom based EOPs for the shutdown states with open reactor, and implementation of SAMGs.
− Development of technical means for direct water supply to the steam generators, SFPs and the containment using mobile fire equipment.
− Installation of additional hydrogen recombiners in the containment.
− Installation of instrumentation for monitoring of steam and oxygen concentrations in the containment, and for monitoring the temperature in the reactor vessel
− Updating on-site and off-site emergency plans, taking into account (a) difficulties in accessing the emergency control rooms of Units 5+6; possible drying out of the SFS basin
compartments, with subsequent increase of dose rates; and (c) providing alternative routes for evacuation, transport of fuels and materials and access of staff.
− Construction of a new Emergency Management Centre, outside the Kozloduy site.
(Main photo: Les Powell)