Expert report of ENSI on the request of EKKM AG for a general license - Project 'New nuclear power plant to replace the Muehleberg plant'

The 'Ersatz Kernkraftwerk Muehleberg AG' (EKKM) Company submitted to the Swiss Federal Inspectorate of Nuclear Safety (ENSI) a request for a general license for a new power plant to be built near to the Muehleberg power plant. According to the law, all damage risks with a probability higher than 10-4/a must be taken into account through protection measures. The considered risks concern the power plant itself as well as the population in the neighbourhood and the environment. The purpose of the general license is to demonstrate that the site chosen for the foreseen power plant is acceptable and that the risks can be counteracted through adequate measures. The buildings of the power plant and their partition on the left side of the Aare River are briefly described. The reactor is a Light Water Reactor of third generation with a maximum electrical power of 1.6 GWel. The European Pressurized water Reactor, which is of the same power class, can be taken as an example for planning that will follow. The main cooling is provided by one or, if needed, two cooling towers using a hybrid system of water evaporation and air heating, what reduces the plume at the exit of the cooling towers. The population density in the neighbourhood of the power plant is low; it is demonstrated that, in the case of a very unlikely severe accident in the power plant, the people in the neighbourhood can be evacuated quickly. Then, numerous types of possible accidents in the neighbourhood of the power plant are analyzed in order to settle their possible negative influence on the operation of the power plant: bursting of gas containers on the neighbouring roads and railways, fires of all types of hydrocarbons, air pollution through chloride gas, etc. The check by ENSI of the EKKM studies on the potential danger for the power plant through neighbouring industrial plants, roads or railways demonstrated that none of the considered accidents presents an unacceptable risk for the power plant: on the one hand, these plants are located too far from the power plant, so that a sensible injury to the power plant safety can be excluded; on the other, the protection of the power plant can be guaranteed through appropriate technical measures. The power plant operation needs pumping water from the Aare River; it was demonstrated that the water flow rate in the Aare is sufficient even in the case of a long lasting drought. In case of emergency, pumping water from a groundwater well would provide a sufficient flow, but this point should be further investigated. A difficult point is that of the likelihood of an earthquake of large magnitude. The considered region is quiet from the seismic point of view, even though geological studies have brought to light geological faults in the large deepness. The electric power produced by the power plant is transmitted to the grid by means of two lines: the one at 220 kV and the other at 380 kV. In the case of power outage on the grid the power plant can be supplied through a 132 kV line; in the case the generator or the transformers fail, a small conventional emergency power generator can be activated. To fight a fire in the power plant the company will set up its own fireman team; it can also call for the fireman corps of the surrounding municipalities. The power plant must be able to withstand a large number of different rare accidental events: earthquakes, floods, airplane crashes, extreme winds and tornadoes, very low and very high air temperatures, strong rain, heavy snow fall, lightning, very low water flow rate, meteorite fall, power outage on the grid. Apart from the meteorite fall the probability of which is considered too small, all these events must be taken into account in the design of the power plant. The power plant must withstand the largest flood which can be expected once in 10,000 years as well as dam breaks up-stream on the river. In what regards airplane crashes the selected site is not worse than every other, because the probability of such an accident does not depend on the topography of a given site. With respect to storms and tornadoes the risks can be correctly taken into account through appropriate design of the buildings; but climate change must be considered in the request for the building license. From the very beginning EKKM will set up a team sufficient to operate the power plant safely. The power plant protection against sabotage, violent actions or embezzlement is based on well designed safeguards regarding building, technical, organisational and administrative measures. The volume of radioactive wastes which are produced during the operation of the power plant is evaluated; it is compatible with the project for the disposal of all radioactive wastes as accepted by the Swiss Federal Council. At the end of its operation period, the power plant can be entirely dismantled and the radioactive parts safely stored