Regulations and Improvements in Hungary Related to Severe Accidents and Filtered Venting

At that time when Paks NPP was designed and commissioned (1982–1987), the beyond design basis events had not been analyzed, so there were no analyses if these events can lead to a severe accident situation or not, as this was not required at that time. The requirements regarding to the beyond design basis events appeared just 15 years later in the domestic nuclear safety regulations. The most important regulations (without being exhaustive) related to severe accidents and containment for existing power plants are the following which can be found in the Nuclear Safety Codes Volume 3: 3.2.2.0300. The following categories of the extended design basis shall be distinguished: (a) DEC1: complex accident not resulting in melting of the fuel in the active core and the spent fuel pool; (b) DEC2: a severe accident resulting in a considerable melting of fuel. 3.2.2.3930. The DEC analyses and designs shall identify all reasonably achievable measures by which severe accidents can be prevented. Irrespective of the success of the identified measures, preparations shall also be made for severe accidents. As part of the analyses and design, all reasonably implementable solutions by which the consequences of severe accidents can be limited shall also be identified.