Belgium Federal Agency for Nuclear Control (FANC) held a meeting in Brussels on August 16th last with several international nuclear regulators after the detection of flaws in the Doel-3 NPP vessel.
The Spanish Nuclear Safety Council (CSN) has released a statement to Power Engineering International (PEI) confirming that the international regulators attending the meeting were France, Germany, Sweden, Switzerland, The Netherlands, United Kingdom, United States and Spain.
In their statement the Spanish agency says that one of the relevant plants, the Cofrentes NPP vessel is not affected by the same defects as found in Belgium, but the authority is continuing to investigate for signs of deterioration.
The authority added that while Santa María de Garoña plant was built similarly to Doel 3, there are differences in size, dimension and thickness, as well as reactor type.
Most of these countries, like Belgium, have nuclear power plants which vessels have been manufactured by Dutch firm Rotterdam Droogdok Maatschappij.
These flaws, or fractures as reported in PEI, were found during the refuelling outage works and may come from the manufacturing process of the vessel.
The event has been classified by the Belgium regulator as a preliminary level 1 in the INES Scale.
The Spanish Nuclear Safety Council (CSN) is analyzing the documentation and the fabrication process of the Spanish reactors' vessels from the same manufacturer: Cofrentes and Santa María de Garoña. CSN is also in contact with the European Nuclear Safety Regulators Group (ENSREG) and with the regulators that attended the meeting to share further information.
“Cofrentes NPP vessel is not affected by the same defects detected in Belgium, as per the preliminary data and the processes and material used in its manufacturing. The vessel is composed by semicircular clasps welded vertically; meanwhile, Doel-3 vessel is composed by forged rings welded horizontally.
Regarding Santa María de Garoña, its vessel was constructed with the same process of Doel-3 but there are differences with the Belgium vessel like the size, thickness, dimension, number of forged pieces and the type of reactor. Garoña is a Boiling Water Reactor (BWR) and Doel-3 is a Pressurized Water Reactor (PWR). Therefore the defects from Doel-3 NPP cannot be extrapolated to Garoña NPP.
As part of its action plan, the Spanish regulator is reviewing the vessels manufacture and the parameters determining the possible appearance of these defects as well as the results of inspections carried out in different areas of the vessels of the above mentioned nuclear power plants.
Furthermore, CSN is waiting for more precise data analysis that, according to the FANC, will be available in the coming weeks.
CSN will carry out the necessary inspections to verify:
- The acceptance tests and trials in the manufacturing process.
- The characteristics of the steel used in the manufacturing process of the vessels.
- The results of the tests carried out in the inspection programs conducted under ASME Code. This Code sets the inspection criteria for U.S. designed plants, such as Santa María de Garoña and Cofrentes.
Once this process is finished, CSN will report on the results obtained.
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