Forsmark (Sweden)

Map of Forsmark

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2* BWR 970 MW by Asea Atom; grid connection in 1980/81;
Unit 3: 1100 MW BWR by Asea Atom; grid connection in 1985

Facilities in Forsmark

plantreactor typconstruction startoperation startshut down

The Swedish Radiation Safety Authority (SSM) criticized Forsmark NPP for slack security as it found out that an emergency cooling system vent had been shut since their last inspection a year ago. In case the regular cooling system stops working the vent in question is used to keep the reactor core cool.

The Forsmark plant is already under special supervision due to the several incidents in 2006.


The Swedish power group Vattenfall announced on Tuesday that an inspection had revealed that one control rod of Forsmark-3 was broken and that there were cracks in about 30 percent of other control rods. 100 out of 169 rods have already been inspected at that time.
The unit has been shut since Oct. 21 for inspections after the discovery of a broken control rod at the Oskarshamn 3 reactor.

Forsmark 1 and 2 stop operations

Due to a possible problem with a rubber sealing inside the containment the management of the Forsmark plant has decided to stop operations of Forsmark 1 and 2. A part of the sealing at Forsmark 1 when examined showed possible degradation and since the two reactors have similar construction the decision was taken to stop operation to ensure the function of the systems.

Possible violation of law by Forsmark

SKI last Monday (29th of Janauary) decided to go to prosecutor for an investigation on wether the management of Forsmark power plant violated law by not bringing the reactor to a cool shut down fast enough after incident the 25 th of July last summer.

Report about incident on 2005-06-25

The German GRS together with the German Institute for Applied Ecology published a renewed assessment about the incident at Forsmark-1 on the 25th of July 2006. Several reasons for the incident are identified in this report, but not everything could be totally clarified. In this report it is stated that if the other two diesel generators would also have failed to start up this common cause failure could have become an event that is not considered in the safety report of the plant.
These reports can be downloaded at


"Due to identical design and construction of the safety trains between Forsmark unit 1 and Forsmark unit 2, in particular the set points in the uninterrupted power supply systems and power supply to the speed measurement device on the diesel generators, the inverters and rectifiers of the UPS have been modified and the power supply of the speed measurement device on all diesel generators have been changed.

For further details on the actual occurred event please read the previously reported INES-event at Forsmark unit 1 "Two emergency diesel generators did not start when the unit was disconnected from the ordinary off site grid".

The event of July the 25th at Forsmark 1 has been rated INES 2. Since there was no initiating event at Forsmark 2 the rating has accordingly been determined to INES rating 1."

Incident - INES level 2

The Swedish Nuclear Power Inspectorate SKI described the incident at Forsmark-1 as follows: After an electricity failure caused by the short circuit in the switchyard the Forsmark 1 reactor was scrammed and a number of safety systems were activated. The reactor being shut down could be concluded by the surveillance systems but the indication of the position of the control rods was unclear due to lack of power supply. The emergency cooling system did for a short period of time pump water into the reactor vessel. Also the water spraying system in the containment was activated. The personnel kept watch over the water level and were prepared to activate further safety actions in case the water level should decrease further. After 23 minutes the two remaining diesel generators were started and the water spraying was terminated."
Safety systems that should have been independent of one another were not sufficiently separate. The incident was labelled INES level 2.

Incidents during 2005 at Forsmark 1

During the year 2005 two events occured at Forsmark-1 below INES labelling: Problems with the neutron flux measurement, and a fuel defect. Details can be found in the SKI Report 2006:15.

Incidents during 2005 at Forsmark 2

During the year 2005 four events occured at Forsmark-2 below INES labelling: Problems with the neutron flux measurement, a fire in a rectifier, a fault in a valve position indicator in the steam line and a fuse failure. Details can be found in the SKI Report 2006:15.

Incident - INES level 1

An inner containment isolation valve was leaking at Forsmark-2 because of debris entering the valve from the containment sump. This event was labelled INES 1.

Fuel defect at Forsmark-3

ABB will replace operating systems for the main recirculation pumps at the three Forsmark reactors, under a contract worth 100-million kronor (U.S. $13-million). The work, which will begin in 1999 and run through 2001, is part of the Swedish plant´s modernization program set to run well into the next century.