Nuclear power plant water use
- Like other thermal power plants, a nuclear power plant needs cooling water to cool and condense the turbine steam back into a liquid state. Groundwater is not used for cooling water, seawater is suitable in Estonian conditions.
- The water taken from the sea and discharged back into the sea is not exposed to radiation sources and is not radioactive.
- The main environmental impact of cooling is in the temperature of the water discharged back into the sea, which is a few degrees warmer.
- To avoid undue negative impacts on the aquatic environment, cooling water must be diverted away from the shore and into deeper water, where the warmed water is better dissipated into the environment. The protection of the aquatic environment must be ensured.
- There are a dozen thermal power plants around the Baltic Sea, whose impact on the aquatic environment is generally well known.
The future Estonian nuclear power plant will have two water cooling contours
The water cooling contour leaving the plant is not radioactive because it is not exposed to radiation sources.
First contour
REACTOR → TURBINE → CONDENSER → REACTOR
It is a closed system where water circulates through the reactor, turns into steam and condenses back into water without coming into contact with the outside environment. See water may be slightly radioactive, but as the system is sealed, it cannot escape.
The steam leaving the reactor condenses and returns to the reactor, without leaving the power plant.
Second contour
SEA → CONDENSER → (COOLING TOWERS) → SEA
It does not come into contact with radioactive material and uses natural bodies of water (e.g. sea, large river or lake, artificial bodies of water) as a source of cooling water. The water that enters and leaves the second contour is not radioactive.
The relevant construction and operating licences will only be granted if it has been thoroughly investigated and demonstrated that the construction and operation of the plant and the geological disposal of the waste will not affect groundwater in such a way as to endanger the environment, the quality of human drinking water or its availability.
Why the second contour is not radioactive
The nuclear power plant has two water systems or contours. In the first contour, water circulates, bringing thermal energy from the reactor to the turbine. This water is weakly radioactive, but it stays in a closed contour and does not come into contact with the water moving in the second contour.
The second contour cools the first contour through heat exchanger The aim is to turn the steam that has passed through the turbine and done its work back into liquid water that can be pumped around in the first contour. The second contour, or station cooling system, may be closed (e.g. in the case of cooling towers); or Open (e.g. for seawater use). Closed systems are used where water is limited, for example in inland locations in dry climates, or near lakes and rivers away from the sea. Open systems are used when the amount of water is not limited - for example, all the stations in Finland and Sweden near the sea.
All in all, station cooling can be thought of as. radiator in a swimming pool- hot water circulates inside, but cooler water around it, which is heated only by the radiator and does not mix with the hot water in the radiator.
Radionuclides in seawater
In order to ensure that the cooling water leaving the plants is free of radioactive substances in dangerous concentrations, monitoring is carried out both by the plants themselves during day-to-day operation and by national and international environmental monitoring agencies. Here are some of the highlights:
HELCOM, the Commission for the Protection of the Marine Environment of the Baltic Sea, brings together a wide range of marine research, including measurements of different radionuclides in seawater and sediments. Such surveys are also carried out by national environmental monitoring agencies and, in the case of nuclear power plants, separately by national nuclear safety regulators. The main radionuclides monitored are caesium, polonium, strontium and potassium. Of these tseesium and strontium are mainly man-made, while poloonium and potassium occur naturally.
Sometimes people also ask about natural and anthropogenic tritium levels and effects. Tritium (the hydrogen isotope) is a naturally occurring, weakly radioactive element with a relatively short half-life, which is also produced in small quantities in nuclear power plants, depending on the type of reactor used.
Tritium in the Baltic Sea, including. in the vicinity of nuclear power plants (<5-10 Bq/l) is lower than, for example, the reference value for drinking water (100 Bq/l).
It is worth pointing out that the tritium rules in force in the European Union. reference value in drinking water is 100 Bq/l, but this is not considered to be a limit for health risk, but rather a reference level to assess whether other radionuclides may also be present.
The WHO recommended limit for tritium is much higher (around 10 000 Bq/l), in Finland (30 000 Bq/l) - so 100 Bq/l is very conservative.
Source: Canada nuclear regulator
Nuclear power plants do not add significant amounts of tritium to the environment.
Cooling water volume and temperature
Cooling with sea water (open method)
If seawater is used to cool the second contour, then cold water is collected from the sea, it is moves through the capacitor and returns to the sea unchanged but up to about 10 degrees warmer. This temperature increase is in line with environmental requirements and its impact on the marine ecosystem is minimal and under continuous monitoring.
According to temperature measurements, the water discharged from Finland's Loviisa nuclear power plant raises the temperature of seawater by about 1-2.5 degrees Celsius within a radius of 1-2 kilometres from the discharge point.
Source: Fortum
In Estonia it is a low-capacity nuclear plant capacity, so the heat load is also lower.
| Baltic Sea water capacity: | 21 721 km³ |
| A nuclear power plant pumps from the sea: | 13 – 25 m³/s |
| The nuclear power plant returns to the sea: | as much as was pumped in |
| Temperature of the water after returning to the sea: | 6 - 10 °C above ambient temperature |
Cooling with cooling towers (closed method)
If the second contour is cooled by cooling towers, the cold water is collected from the sea. About half of the water evaporates in the cooling towers and returns to the atmosphere as pure water vapour, the other half returns to the sea.
| Baltic Sea water capacity: | 21 721 km³ |
| A nuclear power plant pumps from the sea: | 0,31 m³/s (0.14 m3/s evaporates) |
| The nuclear power plant returns to the sea: | 0,17 m³/s |
| Temperature of the water after returning to the sea: | 6 - 10 °C above ambient temperature |
Seawater-cooled nuclear plants in Estonia's vicinity
Today, there are a dozen thermal power plants around the Baltic Sea, about half of them nuclear. Continuous monitoring and assessment of cooling water impacts is part of the daily operation of nuclear power plants, as it is one of the most important environmental impacts of a plant. A good example is Website explaining the effects of cooling water from the Olkiluoto plant.
| Reactors | Seawater use m³/second | Sea water use m³ / year |
|---|---|---|
|
Loviisa 1 and 2 |
40 m³/s |
1,323 million m³ |
|
Olkiluoto 1 |
30 m³/s |
946 million m³ |
|
Olkiluoto 2 |
30 m³/s |
946 million m³ |
|
Olkiluoto 3 |
60 m³/s |
1,890 million m³ |
Where do today's shale power plants get their cooling water from?
Narva power plants used 1,300 million m³ of cooling water from the Narva River to condense boiler steam in 2012, which is discharged back into the river at a slightly higher temperature without changing the composition of the water.
Auvere power plant uses 520 million m³ of cooling water. The water is taken from surface water intakes in the EstonianJW intake canal (the Black River canal) and the Black River. Process water and rainwater used in the production process is discharged into the Black River.