Karlsruhe. This weekend, Block 1 of the Philippsburg nuclear power plant (KKP 1) was taken off the grid and shut down by its operator, EnBW Kernkraft GmbH. A fuel element exchange will take place during the shutdown. EnBW’s safety measures are a key factor in this.
The inspection during the summer, which involved ongoing operational measurements of activity in the reactor’s cooling circuit, showed evidence of a defect in a fuel element. The operator, EnBW Kernkraft GmbH, reported this in a timely manner to the regulatory agency bureau – the Baden-Württemberg Ministry for the Environment, Conservation and Transit – on June 17, 2010, and temporarily classified the event as Category N (normal report) and INES 0 (little or no safety-related significance). EnBW also informed the public of the event on the same day.
Since then, the measurement values have been regularly monitored both through the continuous operational measurements and through a supplementary measurement program, and have been evaluated with regard to further measures. Although the activity levels and the balanced exhaust-air removal still remain well below the permissible threshold values, EnBW Kernkraft GmbH decided, because of the further development of the defect in the fuel element, to shut down the plant as a precautionary safety measure and to inspect the fuel elements and carry out a fuel element exchange.
The regulatory agency has been informed of this plan.
Reactor cooling circuit and controlled area: the reactor’s cooling circuit is in the system’s “controlled area.” The systems and components of this safety area directly create nuclear heat, and they are separated from the rest of the plant and the outside environment by various structural and technical barriers.
Fuel element: Components known as fuel elements are installed in the reactor’s pressure vessel for generating power – there are 592 in KKP 1. In turn, these contain fuel rods that are installed vertically. In KKP 1, one fuel element consists of 96 fuel rods. The fuel rods contain uranium dioxide tablets. During operations, water flows along the underside of the fuel rods and is heated. The water moves upward out of the reactor core, transporting the heat created by the reactor core. During a fuel element exchange, fuel elements are replaced and changed over in order to optimize fuel use, taking the physical aspects of the reactor into consideration.
INES scale: The global standard for evaluating the safety of events in nuclear power plants is the seven-step international INES scale. Furthermore, users of nuclear plants in Germany report events that fall below this scale. The INES 0 step describes events that did not have any negative impact on people, the environment or plant operations. The idea behind this scale is to make the engineering of safety-related exchanges in the plants transparent among the users, open, and compliant with fixed formal guidelines. This is an indication of the high level of safety culture in German nuclear power plants.
The present event was temporarily classified as INES 0 (little or no safety-related significance). Thus it lies below the INES scale and had no negative effects on people, the environment or plant operations.
KKP 1: Block 1 of the Philippsburg nuclear power plant is a boiling-water reactor with an electrical capacity of 926 megawatts. The plant began operations in 1979 and produced approximately six-and-a-half billion kilowatt hours of electricity in 2009.