Regarding the article published on 15.09.2015 on the website of the “Terra Mileniul III” organization, which quotes a so-called study performed by a group of NGOs regarding the results of the stress tests performed at Cernavoda Nuclear Power Plant (“Cernavoda NPP”) and the measures for improvement resulted from this analysis, SN Nuclearelectrica SA makes the following statements:
Regarding the accuracy of the information comprised in the article:
- Such a study requires an extremely high level of expertise in the evaluation of systems, equipment, components and of the emergency response in the case of a nuclear installation. The published article represents a pseudo-follow up-evaluation of the reports resulted after the performance of the stress tests at Cernavoda NPP. As it results from the information presented in the article, there are serious misunderstandings of the power plant project, the purpose and nature of the stress tests performed at Cernavoda NPP, false interpretations of the data published in the reports related to the stress test, lack of knowledge of the operations systems and of the cause-effect relations between them and of the data which stood at the foundation of the official reports of the experts who evaluated the power plant. The article is a compilation of causally uncorrelated information, without technical-scientific ground and serious interpretations mistakes of the data from the official reports drawing conclusions and specifying measures which not only that they do not have any real correspondent, but represent unverified and ungrounded accusations.
- Cernavoda NPP was evaluated by a group of international experts, with the observation of the provisions of the European Commission and the European Council, elaborated after the Fukushima accident. The evaluations and analysis considered the behavior of the NPP in the case of extreme beyond design basis events such as: earthquake, flood, partial or total loss of the cooling source, total station blackout, sever accident management. The results of these stress tests are available in the reports published on the website of CNCAN and the conclusions of these evaluations revealed, beyond any doubt, that Cernavoda NPP holds a sufficient safety margin in order to withstand accidents and beyond design basis events, international experts appreciating the nuclear safety of the power plant, as well as the measures initiated after the Fukushima accident.
Regarding the technical accuracy, based on the information presented in the article
- Regarding the possibility of a powerful earthquake to trigger a serious accident, as the article mentions:
The technical basis regarding the choice of Cernavoda NPP site took into consideration the strongest possible earthquake which can affect the area and the structures and equipment were designed to resist to such an earthquake including a significant design margin. After the Fukushima event, the re-assessments and studies conducted by the Romanian Institute of Earth Physics specialists and validated by the experts of the European Commission confirmed that Cernavoda NPP would withstand even a hypothetical earthquake based on which it was assessed in compliance with the methodology of the stress tests. As well, the re-assessment of the seismicity of the site done for the approval to complete Cernavoda NPP Units 3&4 Project was verified and validated by a mission of the International Atomic Energy Agency (IAEA). Taking this into consideration, without invoking probabilistic considerations, it has been proved that a severe accident caused by seismic activity is not possible.
2. Regarding the possibility of flooding at Cernavoda NPP. We quote from the article: “The stress tests have further revealed that the protection against floods is also insufficient. A significant number of safety equipment are located in underground chambers of the power plant which requires the fitting of flood resistant, sealed doors……Instead of viable technical measures sand bags are employed”
SN Nucleatrelectrica states and supports with analytical data, resulted following a study done with last generation technologies (aerial scanning and dynamic modelling of the area) that the safety margin of the nuclear power plant in regard to external floods, caused by the Danube, does not allow such an event which could lead to a loss of the nuclear safety functions. As it regards the pluviometric regime, the calculations have proved that in case of rain with a flow ten times higher than the historic maximum flow, the maximum level of water on the nuclear power plant site cannot reach the level of the building floor. Even if these results prove that the project is robust from the point of view of flooding, in compliance with the stress tests, pure hypothetical conditions were taken into consideration that could exceed these levels and external and internal doors, resistant to flooding, were installed in all the locations that store safety equipment.
3. We quote from the article: “There is a further need of improvement in the area of the spent fuel pool, which is located outside the isolated area, thus, in case of severe accident a major leakage of radioactive substances might have dangerous consequences. The majority of intervention actions in case of a severe accident in the storage pool area are programmed to be effectuated using mobile equipment, equipment that was purchased and tested, but which was not stored in safety and does not present the guarantee that it is sufficient”
The results of the stress tests prove that there are no issues regarding potential radioactive leakages from the spent fuel pool similar to those at Fukushima where problems occurred to the temporary fuel storage pool, discharged during the shutdown, pools which in the case of the Cernavoda CANDU project do not exist, being unnecessary. The spent fuel pools of Cernavoda NPP, in which spent fuel is constantly discharged, are located on ground level eliminating the risk of major leakage of radioactive substances and facilitating water supply using mobile equipment. The mobile emergency response equipment is stored in adequate conditions and periodically inspected by both the nuclear power plant staff and the CNCAN inspectors. Their functionality is proved by a periodic testing program.
4. We quote from the article: “The improvements in the case of station blockout” (a significant power blackout) are also insignificant and the measures taken debatable”. We mention that the correct term is “station black-out”
In case of total loss of alternative current, scenario known as “station black-out”, the equipment with safety functions will be supplied from two different sets of electro generators: a backup set which enters automatically into function and an emergency set, seismically qualified, that will be used in case the backup generators are rendered unavailable by the earthquake. In addition to the initial project, as per the international practices post Fukushima, Cernavoda NPP purchased 4 mobile electro generator groups that will supply the essential equipment of the power plant. At the loss of all supply sources, including the own sources, the reactors automatically shut down, by the activation of the two independent emergency shut down systems – which do not need electricity. The cooling of the fuel is ensured by thermosiphonation of the heavy water from the Primary Circuit, and the heat is transferred through the steam generators into the atmosphere. The necessary water level in the steam generators is ensured by means of gravity from the emergency dousing tank.
5. We quote from the article: “The operator concluded an agreement with the local and national authorities involved in the emergency response coordination so that the nuclear power plant has priority to reconnect to the grid, meaning that other important consumers such as hospitals, traffic systems or other important institutions of local interest are left without electricity for a large period of time”
This is a tendentious information because the mentioned protocol refers only to the order of supplying the industrial consumers and is not of the nature to affect the public utilities but, on the contrary, to support them with power input from the nuclear power plant after start up. We mention that Cernavoda NPP does not require immediate reconnection to the national power system, to the deficit of other consumers, because it is capable to ensure from internal sources the safety functions for at least 72 hours after which external support is provided by means of the existing protocols and contracts.
6. We quote from the article: “All these are added to the fact that the CANDU type reactors design is an old one, built in the 70s. A great deal of weak points in the design of the reactors cannot be corrected, especially those related to a potentially high variation of energy in case of safety systems failure and the vulnerability against external risks. Moreover, the degradation of the pressure tubes caused by the ageing of the power plants is a persistent problem in CANDU type reactors and signs of these problem occurring at Cernavoda NPP are already visible”.
Most of the nuclear technologies used at present in the nuclear industry in Europe and around the world were developed in the 70s, but during the course of the years, a series of improvements and modifications were implemented in order to increase the safety margins in operation close to the new generation of reactors. By consequence, the assertion that CANDU reactors are obsolete proves, at first, a lack of knowledge regarding the technical innovation trends in the industry and of the measures implemented at Cernavoda NPP. Contrary to the information presented in the article, the stress tests revealed that the strong points of the power plant are, especially, the robustness of the technology, the redundancy and diversity of the systems, the resistance to severe accidents. Moreover, in 2015, during the latest meeting in Brussels with the purpose of evaluating the implementation status of the national action plans post – Fukushima, Romania, represented by the National Regulatory Body, did not receive any additional recommendations or suggestions considering the series of improvements achieved until the current date by Nuclearelectrica in order to reduce the risk of severe accidents.
The degradation of the pressure tubes in CANDU NPPs is an anticipated ageing phenomenon, well analyzed and strictly controlled by the period inspection program. This phenomenon determines the life span of a CANDU unit and does not effect, in any way, the operation safety.
The conclusions of the report performed by national experts and European Commission experts reveal the fact that a nuclear event similar to the one which happened at Fukushima NPP is not possible at Cernavoda NPP. The report complies with the requirements and criteria provided by the Western European Nuclear Regulators Association (WENRA) and by the European Nuclear Safety Regulatory Group (ENSREG), authorities which are responsible for controlling and monitoring the European organizations with activity in the nuclear field. The report contains almost 400 pages and details the response of the NPP’s systems and of the organization in case of sever conditions. The report shows that both units of Cernavoda NPP, as designed, maintained and operated, comply with the requirements stipulated in the original project and moreover, have a sufficient safety margin in case of hypothetical earthquakes, floods, total loss of energy supply and loss of cooling sources and combinations of the above, beyond design basis.
With a capacity factor of 91,4% since in service, Romania occupies the first position in the world wide top of 392 nuclear units, belonging to 181 nuclear power plants in 28 states. These performances were obtained by maintaining the highest level of nuclear safety, as the international evaluation missions of IAEA and WANO which took place over the past years at Cernavoda NPP concluded.