Nuclear Power Plant Beznau

Nuclear Power Plant Beznau
Reliable, environmentally compatible electricity production
Axpo – electricity for Switzerland
Nuclear Power Plant Beznau is part of the pool of power
giants operated by Axpo, the Swiss energy utility with
strong local roots and a presence in Europe. Axpo is
100 percent owned by the cantons of Northeastern
Switzerland, and together with partners supplies electricity to about 3 million people in Switzerland. Axpo is
active along the entire value chain, from electricity generation to transmission grids, trading, sales and services.
Axpo has an environmentally compatible pool of power
plants with largely CO2-free electricity production.
Nuclear power plants, river-based hydroelectric plants
and biomass power plants cover the base load of the
electricity supply. High-pressure pumped storage power
plants with their reservoirs are used to compensate
fluctuations and peaks in demand. This pool of power
plants is perfectly aligned with the requirements of safe
and cost-efficient electricity production.
• Axpo/Kantonswerke
• CKW
Schaffhausen
Basel
Delémont
Frauenfeld
Liestal
Herisau
Aarau
Solothurn
Neuchâtel
Zurich
St. Gallen
Appenzell
Vaduz
Zug
Lucerne
Berne
Sarnen
Fribourg
Schwyz
Glarus
Stans
Altdorf
Chur
Lausanne
Geneva
Sion
Bellinzona
Electricity for about 3 million people in Switzerland. Axpo/Cantonal power plants
Centralschweizerische Kraftwerke (CKW)
View of Beznau Island with the
nuclear power plant in the background.
Nuclear Power Plant Beznau
2 | 3
Electricity production around the clock
Nuclear Power Plant Beznau comprises two largely identical plants, Unit 1 and Unit 2, each with an output of
365 megawatts (MW). Both plants are designed for 8000
full-load hours or approximately 355 days a year. Together
they generate approximately 6000 gigawatt-hours (GWh)
a year. This corresponds to around twice the electricity
consumption of the city of Zurich.
First nuclear power plant with environmental
product declaration
Nuclear Power Plant Beznau is the first power plant in
Switzerland for which an EPD ®, Environmental Product
Declaration, has been drawn up in accordance with
ISO 14025. The key feature of the environmental product
declaration is a life cycle assessment. It enables the
quantification and estimation of emissions into the environment and also of the utilization of resources along the
entire process chain of electricity production. As further
environmental information, a survey was made of biodiversity in the area around the nuclear power plant, radiation exposure of the staff and the electromagnetic fields.
Together with the run-of-river hydroelectric plants,
Nuclear Power Plant Beznau is thus one of Switzerland’s
most environmentally compatible power plants.
Vital base load capacity
Apart from a few weeks each year during which refueling,
maintenance and annual inspections take place, the nuclear power plant produces electricity around the clock.
Nuclear power and river-based hydroelectric plants cover
the base load of the electricity supply. When the system
goes offline each summer for maintenance, the electricity
demand can be met by the hydroelectric plants.
Over 500 people work at the nuclear power plants. The
plants are monitored by a team of specialized operating
staff working in a three-shift pattern. In the control room,
the settings, values and changes relating to all components are indicated and displayed. The slightest deviations
from the defined set points are announced immediately,
both acoustically and visually, so that the correct precautions can be taken.
Containment building of Nuclear Power Plant Beznau.
Nuclear Power Plant Beznau
4 | 5
Electricity from kinetic energy
Nuclear power plants are basically steam power plants.
The heat necessary for evaporation of the water is not,
however, the result of a combustion process but is
obtained in a nuclear reactor. The steam is routed to a
turbine that drives a generator. In the process, the rotor
of the generator turns on the same shaft as the turbine,
at 3000 revolutions per minute. At this high speed,
its magnetic field generates an electrical voltage in the
windings of the fixed stator. As a result, the kinetic energy
is converted into electrical energy in exactly the same
way as in a bicycle dynamo. The generator voltage is
15.5 kilovolts (kV). It is increased to 220 kV by a transformer and thus rendered transportable. The electricity
is ultimately delivered to the high-voltage grid via a
switching station.
Transformers in operation.
Nuclear Power Plant Beznau
6 | 7
Machine hall with turbines and generator.
View inside the nuclear power plant
The two round containment buildings dominate the
image of Nuclear Power Plant Beznau. The primary systems, in which steam is generated from nuclear power,
are situated in these double-walled buildings with a
height of 67.5 m and a diameter of 38 m. They are surrounded by a gas-tight welded steel containment (3).
It is 30 mm thick. The steel containment is completely
enclosed by a concrete containment (1), which is 90 cm
thick, with an intermediate space of 1.5 m. The concrete
containment has on the inside a gas-tight steel liner (2),
which is 6 mm thick. The air from the cavity is sucked
into the interior of the steel liner where a vacuum is
created. This prevents air – and radioactivity – from accidentally escaping to the outside. Accommodated in the
machine hall are the secondary systems and the turbine
generator assemblies, which first convert the heat
generated into mechanical energy and then into electrical energy. The heat for the Refuna district heating
supply is also taken off here.
Nuclear Power Plant Beznau
8 | 9
1 Concrete containment
2 Steel liner
3 Steel containment
4 Reactor pressure vessel
5 Control rod drive
6 Steam generator
7 Reactor main coolant pump
8 High-pressure turbine
9 Moisture separator
reheate
10 Low-pressure turbines
11 Generator
12 Transformer
13 Condenser
14 Feedwater tank
1
2
3
Containment building
14
Machine hall
9
6
Fuel
store
12
Control room
Spent-fuel
storage pool
7
5
4
13
8
10
11
9
The energy cycle
1 Control rod drive
2 Reactor pressure vessel
3 Pressurizer
4 Control rods
5 Fuel assemblies
6 Reactor main coolant pump
7 Steam generator
8 High-pressure feedwater heater
9 Feedwater tank
10 Feedwater pump
11 Low-pressure feed heater
12 Condensate pump
13 Condenser
14 High-pressure turbine
15 Low-pressure turbines
16 Generator
17 Transformer
18 Moisture
separator reheater
19 Refuna steam cogeneration
20 Refuna heat exchanger
View into the open reactor pressure vessel.
Nuclear Power Plant Beznau
10 | 11
Kreislaufschema
Containment building
7
Refuna district
heating
Concrete containment
Steel liner
Steel containment shell
Machine hall
20
19
55 bar, 270°C
1
9
3
120°C
127°C
8
230 kV
18
2 bar, 247°C
155 bar, 300°C
15.5 kV
4
5
2
14
15
15
16
17
10
0.04 bar, 30°C
6
11
12
13
Cooling water
extraction
Cooling water
return
Steam generation
The two units at Nuclear Power Plant Beznau are equipped
with pressurized water reactors, i.e. they have two separate water circulation systems. The pressurizer system
ensures such a high pressure in the primary loop that the
water in the core cannot boil, despite a temperature of
312°C. In the steam generators, the water in the primary
loop releases the absorbed heat to the secondary loop.
The steam produced by the low pressure drives turbines
connected to steam generators. In the condenser, the
steam is converted back into water – ready for another
cycle of steam generation.
1 Flywheel
2 Pump motor
3 Pump impeller
4 Control rod drive
5 Pressure vessel lid
6 Control rod
7 Fuel assembly
8 Core support plate
9 Main steam outlet
10 Steam dryer
11 Manhole cover
12 Moisture separator
13 Main steam to turbines
14 Feedwater to steam generator
15 Feedwater inlet
16 U-tube bundle
17 Tube plate
18 Water chamber
Nuclear Power Plant Beznau
12 | 13
Steam generator
Pressurizer
9
10
11
13
12
14
1
2
Reactor pressure vessel
15
4
5
16
6
3
17
7
8
Reactor main coolant pump
18
Cooling by water from the River Aare
The steam must be cooled down in the condensers to
convert it back into water after passing through the
turbines. In full-load operation this means taking 40 m3
of cooling water per second from the River Aare. As the
drop between the headrace channel and the lower
course of the Aare is 6 m, the cooling water does not
need to be conveyed through the condensers using
pumps, as is usual in other nuclear power plants. In
Beznau it runs naturally from the headrace channel of
the hydroelectric power plant to the Aare riverbed
further down. This was one of the reasons why the site
on Beznau Island was chosen at the time.
Temperature increasedurch
due to
NPP Beznau
Temperaturerhöhung
KKB
nach
dem
after Durchmischung
mixing with themit
water
ofAarewasser
the River Aare
Monatsmaximum
Monthly maximum
Monthly minimum
Monatsminimum
24°
22°
20°
18°
16°
14°
12°
10°
8°
6°
4°
2°
0°
Jan. Feb. March Apr. May June July Aug. Sept. Oct. Nov. Dec.
Nuclear Power Plant Beznau
14 | 15
1 Unit 1
2 Unit 2
5
7
3 Cooling water inlets in the headrace channel
4 Cooling water outlets
in the natural riverbed
of the Aare
5 Hydroelectric power plant
6 Weir power plant
3
2
7 Substation (connection
to electricity transmission
network)
3
1
4
4
6
Following pages: In the
control room, electricity
production is monitored
continuously.
Safety first and foremost
For Axpo, safety takes top priority. Nuclear Power Plant
Beznau is protected against earthquakes, floods, and
airplane crashes. Critical systems and sections of buildings function independently, have multiple redundancies
built in and are spatially separated. In addition, Nuclear
Power Plant Beznau invests in safety technology and
replacement on an ongoing basis.
Six barriers
Radioactive products are created during nuclear fission.
These highly radioactive materials may not escape into
the environment. Several barriers ensure that this cannot
happen:
• The fission products are virtually unable to leave the
microstructure of the hard sintered fuel pellets.
• The gas-tight welded cladding tubes of the fuel as- semblies prevent fission products from escaping into the cooling water.
• The fuel assemblies are enclosed in the reactor pres-
sure vessel and water circulates around them. This
remains in the enclosed primary loop.
Nuclear Power Plant Beznau
18 | 19
• The entire primary loop is encased inside the steel
containment made of 30 mm thick steel plates that are
welded gas-tight.
• The vacuum in the space between the steel contain ment and the concrete containment prevents radio active gases from escaping.
• A steel liner seals off the inside of the concrete containment.
Shielding of the radioactive radiation
The 3 m thick biological shield and the shielding concrete
effectively prevent the escape of radioactive radiation.
The concrete containment has a wall thickness of 90 cm.
Operational safety
Maximum attention is paid to operational safety – not
just during normal operation but also in the event of any
extraordinary events, such as unforeseeable defects in
plant components. For this reason, the most important
plant components, such as controllers and alarm releasers, are present in duplicate or in multiple form.
If one fails, there is always a second or a third available
that can perform the same function.
Double-walled containment building
67.5 m high, 38 m outer diameter
Steel containment (3 cm)
Intermediate space
with vacuum
Fuel pellets
Cladding tube
Steel liner (0.6 cm)
Concrete containment
(90 cm)
Shielding concrete
Reactor pressure vessel
Biological
shield
Fuel assemblies
Uranium as a fuel
How long will uranium reserves last?
Uranium is the raw material that fuels today’s nuclear
power plants. It is a metal found nearly everywhere
in terrestrial volcanic rocks and in substantial quantities
in the oceans. The globally known uranium reserves,
which can be mined economically for a price of 130 US
dollars per kilo, are sufficient for the next 100 years
at current usage levels. Actual uranium reserves are substantially higher. A rise in market prices would make it
worthwhile to develop new deposits or use new means of
extraction. The available alternatives include extracting
uranium from phosphates or seawater, two approaches
that have already been proved. Under these conditions,
reserves should last for many centuries or even millennia.
Recycling of nuclear fuel by means of reprocessing and
increasingly enhanced utilization of the fuel in reactor
operation are reducing the consumption of fresh uranium
and thus significantly extending the ranges referred to.
Even a rise in price could be absorbed since uranium
costs amount to only 5 to 10 percent of the cost of generating electricity in a nuclear power plant.
Nuclear Power Plant Beznau
20 | 21
Higher energy content
One metric tonne of ore yields on average approximately
1 to 5 kilos of natural uranium. The uranium’s high energy content – one metric tonne of uranium can generate
the same amount of energy as 10,000 metric tonnes of
crude oil – even makes it profitable to develop deposits
with a relatively low uranium content. Natural uranium
consists mainly of a mixture of two atoms that differ
merely in their physical properties. Only uranium 235,
which is present in natural uranium in a concentration of
0.7 percent, is fissile in light water reactors. The remainder consists of nonfissile uranium 238. To be able to operate nuclear reactors, the proportion of fissile uranium 235
must be increased from 0.7 percent to 3 to 5 percent,
i.e. it must be enriched.
Once extracted, the ore is crushed. The uranium is
leached from the ore using acid and subsequently processed into uranium concentrate (U3O8). This is also
referred to as “yellow cake” because of its yellowish color.
The next processing step is conversion of the uranium
concentrate into gaseous uranium hexafluoride (UF6).
From enrichment to fuel assembly
Gas centrifuges are used primarily for the next refining
step – enrichment. After enrichment, the uranium hexafluoride is converted into powdered uranium dioxide
(UO2), pressed into pellets and sintered at 1700°C, i.e.
transformed into ceramic material. To manufacture fuel
rods, the pellets are loaded into zirconium tubes. The
fuel rods are welded gas-tight, grouped into assemblies
of different sizes depending on the type of power plant
and, after a rigorous outgoing inspection by a plant representative, delivered to the power plant. There they can
be used to produce energy without further processing.
Two fuel pellets of uranium dioxide (UO2) will supply electricity for a
four-person household for one year.
.
Careful waste handling
At Nuclear Power Plant Beznau waste is produced with
varying levels of radioactivity. 99 percent of the radioactivity remains in the irradiated fuel assemblies which are
stored in the water-cooled spent-fuel storage pool for at
least six months. They are then removed to storage containers and taken to the interim storage facility of Nuclear
Power Plant Beznau (Zwibez). Here low-level waste is
Control panel of the NPP Beznau interim storage facility for
low-level waste.
Nuclear Power Plant Beznau
22 | 23
stored before being carted away to a geological repository. Solid radioactive nuclear waste is transported to
the central interim storage facility in Würenlingen (Zwilag)
where it is incinerated or melted down. This process
reduces the volume and improves final disposability
through vitrification.
View onto the low-level waste in the NPP Beznau interim storage facility.
Wastewater
Ion-exchange resins
Combustible material
Fusible objects
From operation,
laboratory, showers,
laundry etc.
From chemical water
purification
Preservatives, cleaning
materials etc.
Pumps, valves, pipes,
insulating materials etc.
Incineration in the
incineration and melting
plant in Zwilag
Melting down in the
incineration and melting
plant in Zwilag
At least six months’ storage in the water-filled
spent-fuel storage pool
Ash solidified with
glass in molds, placed
into canisters
Melt solidified in molds,
placed into canisters
Transport to the Zwibez
for interim storage
Cleaning with chemical
precipitation, centrifuging, microfiltration
Spent-fuel assemblies
Solidified with synthetic
polymer, placed
into canisters
Residue (sludge) solidified with concrete,
placed into canisters
Each year the operation of NPP Beznau produces approximately one hundred 200-liter canisters of
solidified low-level residues amounting to a volume of around 20 m3. They are carted away to geological
repositories in NPP Beznau or put into interim storage in Zwilag.
Highly radioactive
residues are vitrified and
placed in special flasks –
around 1.5 m3 per year
from NPP Beznau
District heating for the region
Das Refunda
Refuna Fernwärme-Leitungsnetz
Das
Fernwärme-Leistungsnetz
Hot feed
Cooled-down return
The Regionale Fernwärme Unteres Aaretal (Refuna) supplies 11 municipalities in the region and around 15,000
residents with heat from the Nuclear Power Plant Beznau.
The connected load in 2010/11 was approximately 81 MW.
This means that 12,000 tonnes of fuel oil can be saved
annually. In winter 1983/84 the Paul Scherrer Institute
(PSI) was connected to the environmentally compatible
heating system. The first private customers followed a
year later. Today, the length of the main network is 31 km
and that of the local network 103 km.
Leuggern
Klingnau
Kleindöttingen
Döttingen
A a re
Nuclear Power
Plant Beznau
Main pumping station
Paul Scherrer
Institute (PSI)
Endingen
Villigen
Aar
Würenlingen
e
Siggenthal station
Stilli
Rüfenach
Riniken
Lim m
Heat is extracted between the high- and low-pressure
section of the turbine where steam with a temperature of
127°C is extracted and routed to a heat exchanger.
There, the heat contained in the steam is transferred to
the district heating network, whose water heats up in the
process to 120°C. As each of the two power plants has
such a heat extraction system, district heating is available
at all times, including during the annual inspection.
The power station’s electrical output decreases by up to
7.5 MW during heat extraction.
Standby heating plants
Booster pump stations
ABB Turgi
at
The main lines are 31 km long and the local lines
are 103 km long.
Refuna pipe bridge over the Aare Canal.
Nuclear Power Plant Beznau
24 | 25
EnergiemitallenSinnen!
Axporama Visitor Center
Visitor Center
Axpo | Axporama
Schlossweg 16 | CH-5315 Böttstein
T +41 56 250 00 31 | F +41 56 250 00 35
axporama@axpo.com
www.axpo.com/erleben
Axporama opening times
Monday to Friday
9 a.m. – 5 p.m.
Saturday, Sunday,
holidays
11 a.m. – 5 p.m.
Unrestricted viewing for individuals and families. Free
entry. Guided tours for booked groups are also possible
outside the opening hours. Please contact the center in
good time.
Plant tour of Nuclear Power Plant Beznau
Visitor groups may tour NPP Beznau with an experienced
guide. Please contact the Axporama visitor center if you
are interested. Your application should be made at least
two weeks prior to the desired date.
Nuclear Power Plant Beznau
26 | 27
Axporama
8I9
Axporama_Imagebroschuere_100715.indd 8
15.07.10 18:08
8
The Axporama visitor center is
situated close to NPP Beznau.
The exhibition offers an exciting insight into the world of
energy and provides extensive
information about the energy
mix of Axpo.
11.2012 | 3000
Axpo | Nuclear Power Plant Beznau
Beznau | CH-5312 Döttingen
T +41 56 266 71 11 | F +41 56 266 77 01
www.axpo.com