Forsmark Nuclear Power Plant

F1

Active reactors ( gross ):

The Forsmark nuclear power plant is one of three located in the operating nuclear power plants in Sweden. It produces about one-sixth of the Swedish electricity.

The nuclear power plant consists of three power plant units with boiling water reactors: Forsmark -1 (1011 MW net electrical power, commissioning 1980), Forsmark -2 ( 951 MW net electrical capacity in 1981 put into operation ) and Forsmark -3 ( 1190 MW net electrical capacity in 1985 put into operation ). The annual production stood since 2000 from 19.0 to 25.0 TWh. Block 1 and 2 reactors of BWR 75th 3 is a block type reactor BWR 3,000.

Sweden covers about 50 percent ( 69.5 TWh ( e)) of its electricity from nuclear power from three nuclear power plants ( Forsmark, Oskarshamn, Ringhals ) with a total of ten reactor blocks. Two more plants together three reactors ( Ågesta and Barsebäck ) have already been permanently shut down.

Location

The village lies at Forsmark Upplands coast about halfway between Gävle and Norrtälje. The reactor is located north of the village on the Baltic coast.

Operator

Operator of the nuclear power plant at Forsmark is the Forsmark power Grupp AB, a company which is owned by Vattenfall AB ( 66%), Mellansvensk force Grupp ( 25.5%) and E.ON Sverige Kärnkraft (8.5%) is (as of 2012). Vattenfall and E.ON are working as a power company in Germany.

History

Uncovering the Chernobyl disaster

Due to the sensitive instruments of the Forsmark nuclear power plant was on April 27, 1986 one of the first places outside the Soviet Union, where signs of the Chernobyl disaster were noted. At the time when workers and on the premises of the power plant increased radiation was detected. First, the evacuation of Forsmark was initiated, since it was from an accident in your own power plant. When searching for the cause of the increased radiation, it turned out that this came from outside.

Incident in July 2006

A short circuit outside of the power plant Forsmark -1 led on 25 July 2006 on the isolation of the equipment from the power supply and automatic reactor scram. To dissipate the decay heat of the shut-down reactor, emergency cooling system should have an automatic start. However, failed parts of the emergency power supply for the emergency cooling system, only two of four Siemens diesel generators jumped on and supplied with the post-cooling energy. Because a part of the control system had failed by the current interruption, the operating team had more than twenty minutes a complete overview on the state of the reactor. Then they could start the two do not automatically tarnished emergency generators by hand.

Scope of the incident

What are the effects of the accident according to the state of the technology used in Forsmark -1 in the worst case could have and how close the system had come through the incident at a nuclear meltdown, was differently assessed because the scram and substantial parts of the emergency core cooling system worked. According to a former design director of the power plant, Lars- Olov Höglund, the power plant had been close to a meltdown by meltdown.

The Swedish Radiation Protection Authority SKI and the Finnish safety authority STUK considered this statement, however, be exaggerated. Acute meltdown could have been expected at any time of the accident, but had to take very seriously the incident.

This is largely ignored, that it was merely due to chance that two emergency subsystems (C and D) anliefen, while two sub- systems (A and B) had failed. The reason for not falling out of the subsystems C and D could not be clarified. Caused by short-circuit surge could paralyze not only the subsystems A and B, but also the sub-systems C and D. The non- switching of all emergency diesel would have worsened the situation drastically.

Consequences of the accident in Sweden

As a result of the incident, the affected reactor block 1 remained at Forsmark and the identical block 2, which was at the time of the accident shut down already for the annual audit and refueling, shut off until further notice, as well as two identical reactor units in the Oskarshamn nuclear power plant. The approval of these four boiling water reactors with the same technique has been withdrawn and had to be replaced before re-starting.

The Swedish Radiation Protection Authority SKI evaluated the error in a first reaction as an emergency (level two ) on the zero to seven -reaching International Review Nuclear Event Scale (INES ). Four weeks after the accident, the Chairman of the Nuclear Safety Committee of the SKI, Björn Karlsson, to that " significantly degraded by the clarification of details of the picture " did.

The electricity prices in Sweden rose to record levels.

After employees of Forsmark had a " forfeiture of the security culture" criticized Vattenfall admitted security lapses and the public prosecutor took on suspicion of a criminal delay the shutdown of the reactor on the investigation. After further technical problems that led to reactor shutdowns again, resigned in February 2007, the head of the nuclear power plant, Lars Fagerberg, back. The safety of the system will now be reviewed by the International Atomic Energy Agency.

Re-commissioning, subject to conditions

About two months after the accident, the Swedish Radiation Protection Authority SKI first refused a new operating license because of lack of security and imposed conditions to increase safety. On 28 September 2006, the SKI agreed to a restart of the reactor units 1 and 2. The operators had complied with the requirements of CIP, but needed to improve further and to develop an action plan security. Prior to the resumption of operations at Forsmark contingency plans had to revised plans for the training of personnel prepared and maintenance be improved.

Reactions to the incident in Germany

The partial failure of the emergency power supply raised questions about the safety of their nuclear installations and in other countries. In the German media, the incident of Forsmark initially remained largely unnoticed. He was ranked by the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety on 3 August 2006 as a " safety- serious event " - with the result that all nuclear power plants were checked again in Germany. Within days, ranged the competent supervisory authorities of the Länder reports of the nuclear power plant operators who had been examined by their experts at the Federal Environment Ministry on. The central question was for the Federal Environment Ministry, if it could come to similar incidents in the German nuclear power plants.

According to the Society for Plant and Reactor Safety ( GRS), the central professional institution in Germany in the field of nuclear safety, these reports are not sufficient. A whole series of mishaps caused the fault in the system. Therefore, the GRS demanded a more thorough review of German nuclear power plants.

Expiry of the fault has occurred and margins

Expiration

On 25 July 2006, the reactor Forsmark -1 was after a short circuit in connection with maintenance work in the substation, about the nuclear power plant 's electricity into the public grid feeds, automatically disconnected from the power supply. This led to a load shedding of the generator and the heat produced in the reactor could not be converted into electrical power. The reactor was followed using a scram at 25% of its rated power; That is, the nuclear chain reaction is reduced to the internal plant supply. However, the separation was not done by the short circuit in the usual short time of about 100 ms, it initially was therefore under-voltage and after the separation voltage peaks (transients) of 120 % for one second. The current for the control of the nuclear power plant and the feed pumps that need to remove decay heat, fell out in two of four internal network areas. The internal power supply was then switched to the emergency power system.

The safety systems of the power plant 1 is designed Forsmark quad redundant, i.e., the four sub- systems (A to D) are physically separated, and include electrical and mechanical safety devices. The factory internal 220 - V power supply should be powered at low voltage of four separate, battery-operated, as an uninterruptible power supply (UPS ) designed inverters ( instantaneous) and the 6- kV network of four diesel generators (after the run-up). Of the four systems, two UPS and two associated diesel systems ( subsystems C and D) were intended in operation, the other two UPS ( subsystems A and B) had turned itself off because of the interference; the associated diesel were indeed underway, were due to lack of UPS voltage but do not go into operation.

This lacked the power supply for a portion of the 220 ​​- V- powered instruments in the control room and other components:

• Sensors, transmitters, controllers and event logging
• Displays and monitoring equipment in the control room, eg display " control rods in the core " (for system A and B ), indication for neutron monitoring and for pressure and water level in the reactor pressure vessel
• Fine movement of the actuators for the control rods (all rods were retracted by the hydraulic scram )
• Motor-driven separation and pressure reducing valves had prolonged reaction times
• The motor drives for four circulators fell from

The pressure in the reactor pressure vessel has been reduced for a period of 30 min to 1.2 MPa. The water level in the pressure vessel was stabilized at 1.9 m above the core. The saturation temperature decreased with pressure. Such a strong temperature change has been pre-calculated and must not occur more than 25 times during the entire service life of the reactor pressure vessel.

The supply and the backup of the reactor by removal of decay heat needed two emergency generators, since each 50 percent of the required emergency power can deliver.

After 22 minutes, the maintenance staff made ​​the connection between the de-energized 500 V rails of diesel -based sub-systems A and B and the 6- kV system restore, which was supplied during the whole incident from the external 70 kV network. These manual operations put the total electrical supply to the power plant back into operation. The operating crew could see again that the control rods were all inserted into the reactor core. From now on all parts of the auxiliary feedwater system went into operation again and the reactor soon reached its nominal water level. The activated security systems were closed manually reset (standby) and the open relief valves. After a total of 45 minutes, the operation team was able to confirm that the reactor was in a safe and stable shutdown mode.

Causes

The critical situation had arisen from two causes:

A weakness of the safety concept of the plant was seen mainly in the fact that the start up of an emergency diesel generator depends on the correct function of the associated UPS. UPS and diesel generator to bring together in this way hardly greater security for the 500 V mains. Other power plants feed the control of the diesel ramp directly from batteries. That same error occurred in two of four systems, is classified by the Swedish authority SKI as an "error with a common cause," which reduces the safety design of the emergency power supply.

Status of corrective measures (14 September 2006)

Meanwhile, the power supply for the diesel down control on DC power from the battery system was switched at Forsmark 1, in the external 400 kV switching station a protection system was set up and tested. The other errors mentioned causes have been eliminated. As a longer-term measures, a review of the safety analysis report and plans for preventive maintenance are provided.

Security

In October 2012 results were known from a stress test, which the EU after the Fukushima nuclear disaster had be carried out. Among the most critical of nuclear power plants counted here next to the Olkiluoto nuclear power plant in Finland, the Forsmark nuclear power plant. Thus, for example, would remain the crews in these power plants less than an hour to restore a failed power supply to maintain the absolutely necessary reactor cooling, in Forsmark even just 35 minutes.

Bomb threats

After a bomb threat had to be evacuated down to a skeleton crew on 21 March 2007 the grounds.

Data of the reactor units

The Forsmark nuclear power plant has a total of three blocks: