Beznau (Switzerland)

Map of Beznau

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2 * 350 MW PWR constructed by Westinghouse.
In operation since 1969 and 1971.
The site is near by the Swiss nuclear research center PSI.

Facilities in Beznau

plantreactor typconstruction startoperation startshut down
2010: Annual report of incidents

In 2010 42 notifiable incidents occurred in Swiss nuclear power plants. 41 of the events were classified as INES 0, one event as INES 2.
- Beznau: 4 incidents
- Gösgen: 11 incidents
- Leibstadt: 5 incidents
- Mühleberg: 14 incidents

The INES 2 event occured in the NPP Leibstadt during inspection works.



Radiation exposure of workers during revision

On July 31st 2009 reactor no. 2 of the NPP Beznau was shut down for revision. During the revision the pressure of the primary circuit was checked (has to be done once in ten years) - for that purpose two workers installed lamps in the chamber beneath the reactor pressure vessel (for the use of a camera later on).
Double-walled tubes for the the neutron sensors to controll the pressure vessel are installed in this chamber. While the employees were working in the chamber the inner tube of the double-walled tube was pulled out (from another chamber). The inner tubes normally are within the reactor pressure vessel and are therefore highly radioactive.

That way the radioactivity in the chamber rose immediatelly to about 1000 mSv/h (comment: normal dose outside a NPP about 0,5 microSievert/h).
The two workers were exposed to the following radiation doses: 37,8 mSv/25,4 mSv.


In the morning of the 31st Jan. 2008 an emergency shutdown of Beznau-2 took place after the electric power supply of several instruments failed. No increased radioactivity was released to the environment. A defect of the inverter of the electric power supply caused the problem.


During the annual examination of block 2 the external 50-kV-feeding of both blocks was shutdown. As the emergency power system of the still operating block 1 was supplied by this feeding the emergency Diesel generator was started up. The Diesel-generator overcharged and fell out after the 50-kV-feeding had been online again.


A feedwater pump failed resulting in an automatic reactor scram. This event was rated INES level 0.


During commissioning of a new resin refill unit, the resin tank was connected to the gas system resulting in a small gas volume excaping through an open valve into the surroundings. This event was rated INES level 0.


During a monthly test a trip breaker was opened before the associated trip bypass was inserted resulting in an immediate reactor scram. This was caused by maloperation. This event was rated INES 0.


A malfunctioning oil pressure relief valve caused an unduly high increase in system pressure. When checking the oil system significant deposits of foreign matter were found on all of the relief valve servomotors. This event was rated INES level 0.


Failure to start of a primary service water pump druing a test run. This event was rated INES level 0.


Except from the program the short revision of block 2 extends, because of the replacing of two seal units, which did not function correctly at one of the two reactor main pumps when starting. The revision lasts one week longer.


In 1994 the "Bundesrat" had given an operating grant to the Nordostschweizerischen Kraftwerke AG (NOK) for Beznau II until the 31st of December 2004. The NOK asked for abolition of this dead line in November 2000. Now several thousand persons, several organizations and associations as well as public bodies protested against this. More than 99 per cent of the objections are multiplied forms and come from Austria. In addition the Austrian Federal Ministry for foreign affairs submitted a statement supported by the "nuclear information agreement Switzerland-Austria" concerning the request of the NOK. One argument against the project is, that a permission without a time limit would mean that the power plant could not be controlled directly by the public any longer. An unlimited permission would not correspond to the practice of many years of the "Bundesrat". The statement says that the safety system of the power plant is outdated , and the protection against attacks of terror and the crash of large passenger planes is insufficient. Important components are appropriate only for an operation of 40 years.
According to the Swiss Federal Department of environment, traffic, energy and communication (Uvek) the objections are now submitted to the NOK in anticipation of a statement. The head department for security of nuclear installations (HSK) and the Swiss federal commission for security of nuclear installations (KSA) will examine the objections. The "Bundesrat" will presumably decide on the request in the second half of 2004.


A damaged measuring instrument belonging to an electrical current switch released a scram announcement in block 2. The measuring instrument including the isolating pipe was replaced. "The damage was slightly and connected with no personal injury, radioactivity did not escape", so the nuclear power plant management. After an 10-hour operating interrupt the plant was started again.


Reactor scram caused by a short-circuit in the power supply of the feedwater control valves. This event was rated INES level 0.


Manual reactor scram due to over-boration. This event was rated INES level 0.


Discovery of deformations on a containment penetration during leak testing. This event was rated INES level 0.


Unavailability of a safety injection pump during a functionality test. This event was rated INES level 0.


Failure to start of the emergency diesel motor during a functionality test. This event was rated INES level 0.


Non-availabiltiy of an emergency feedwater pump during a functionality test. This event was rated INES level 0.


Non-availabiltiy of an emergency feedwater pump during a functionality test. This event was rated INES level 0.


Non-availability of a residual heat removal pump during residual-heat-removal operation during a revision shut-down. This event was rated INES level 0.


Exceeding the test interval for measuring channels of the emergency instrumentation. This event was rated INES level 0.


Failure to start of the emergency safety-injection pump during a functionality test. This event was rated INES level 0.


Loss of the emergency diesel supply during testing of the short-circuit protection of the 50 kV external suply. This event was rated INES level 0.


Reactor scram caused by excessive water level in a steam generator. This event was rated INES level 0.


Failure to start of an emergency diesel generator during a monthly functionality test. This event was rated INES level 0.


Failure to open of a valve of the emergency core cooling system during a functionality test. This event was rated INES level 0.


NOK has ordered two replacement SG´s for Beznau-2 from Framatome. It is NOK´s second such order with the French vendor, which manufactured new SG´s for Beznau-1 several years ago. As in that 1993 the replacement itself will be carried out, in 1999, by a consortium of Siemens and Sulzer.
The replacement project, including the new SG´s, the removal and installation work, and associated plant upgrades, is estimated at 125 million Swiss francs (US$ 104 million currently).
Beznau-2, a two-loop Westinghouse PWR, began operation in 1971 and had achieved a lifetime 85% load factor at the end of 1994. The unit is still operating under a limited-time license issued in 1994 because NOK failed in its bid to obtain permission from the Swiss government for unlimited operation. The unit's 10-year license expires at the end of 2004, when the PWR will be 33 years old.
After three years, Beznau project leader Steffen Daemmig says,"we are happy with the (Framatome-built) SG´s," which have tubes of alloy 690. Beznau`s unit-1´s 1995 outage was the first in which NOK didn't have to open the SG´s for inspection.
The Beznau-2 order adds to the list of 20 replacement SG´s manufactured already at Framatome´s heavy components plant at Chalon-St. Marcelectrical 33 more SG´s are being fabricated or are on order, the French vendor said.


Beznau achieved an "excellent"rating from an IAEA Operational Safety Review Team (Osart) mission completed December 1. Beznau was commended for areas including and experienced, capable staff; highest work quality standards, with good condition and cleanliness of plant equipment. The team recommended more in-depth reviews of abnormal operating events; attention to human performance contribution; more careful guidelines on plant conditions before returning to power following reactor trips; stronger management safety policies and guidance to staff; and a more self-questioning attitude. The Osart cost the plant more than 1million Swiss Francs, including all internal cost of special reports, documentation and files, by Nordostschweizerische Kraftwerke AG (NOK) estimates.


Shutdown caused by failure of SG feed pump.


Cracks found in RPV head penetrations during annual outage. Cracks are in two of the CRD mechanism penetrations, one 28 mm long, 1 mm deep; the other 3 mm long and 1 mm deep near the weld.


Leak in one SG and leaking fuel element found.