In nuclear power plants, nuclear energy is converted into thermal energy to boil water into steam, which in turn drives a turbine. The kinetic energy from the turbine is converted into electrical energy in the generator. The resulting radioactive emissions are reported in millisieverts, mSv, as this unit of measurement shows the consequences of the emission for people in the vicinity of the plant. The emissions may not exceed one tenth of the normal background radiation, i.e. a radiation dose of 0.1 mSv per year.

Radioactive gaseous fission products are formed in the fuel. These can escape in the steam. When the steam is condensed in the turbine condenser, the fission products are sucked away and transferred to an exhaust system where the activity can decay. In addition, small airborne particles accompany the steam and enter the turbine's delay system. When these are discharged through the stack, their activity is measured in units of Bequerel, Bq. The same applies to the quantities of water discharged. As process plants cannot be completely sealed, a leakage collection system is used for water coming from the process. The water is collected in tanks. When radioactivity is sufficiently low, through decay or filtration, the tanks are emptied into the sea after measuring the activity.

Knowing the fission products released and their activity, as well as their impact on the environment, allows the radiation dose to be calculated. To find out the impact of the releases on the environment, potential radiation doses to the people most likely to be affected are calculated. These potential people are called the critical group. They are an imaginary group around the power plant who mainly live on what they can get from farming, animal husbandry, hunting and fishing. They would then receive the highest permitted radiation dose, i.e. a maximum of 0.1 mSv per year. At OKG, we are working to reduce emissions to as low levels as reasonably possible.

Waste in the form of garbage, scrap, ion exchange resins and spent fuel is sorted into different groups according to its activity content. How the radioactive waste is managed depends on the form in which it is found and how much activity it contains. Simpevarp has a landfill for low-level waste built using the latest disposal technology.

Low-level waste: The vast majority of radioactive waste has a low activity content and emits a very small amount of radiation. This can include rags, old overalls, mixed scrap, used paper towels, packaging materials, plastics and stationery. Oil, mainly turbine oil from controlled areas, may also contain radioactive particles. This oil is purified in a centrifuge, measured and if limits are met, the oil can be reused for energy recovery in an approved incinerator.

All waste from controlled areas is measured and sorted. Scrap metal is often so low in activity after cleaning that it can be classified for free use and, for example, recycled in the metal industry.

Intermediate level waste: The major part of intermediate level waste is made up of filter masses, used to purify the water in reactor systems, condensate systems and fuel pools. Used pipes, replaced machine parts and used protective clothing are also classified as intermediate-level waste. When working with such waste, some radiation shielding is needed. However, no special cooling of the material is needed. The concrete containers with intermediate-level waste are temporarily stored in a special rock cavern on the Simpevarp peninsula. The canisters are then transported by special vehicles to the port of Simpevarp for loading onto the ship M/S Sigrid. The transport goes to SFR, the final repository for radioactive waste, outside the nuclear power plant at Forsmark.

A small part of the intermediate level waste consists of spent core components that are either transported to Clab in the same way as the high level waste or stored in steel tanks that are temporarily stored in a rock cavern at OKG pending final disposal in SFL (final repository for long-lived low and intermediate level waste).

High-level waste: The high-level waste consists of the spent fuel. The spent fuel is highly radioactive and generates large amounts of heat. In total, about 80 tons of high-level waste are received per year at OKG.

High-level waste management: During the annual overhaul shutdown, about 20 percent of the spent fuel in the reactor core is replaced by new fuel. The spent fuel is first stored for about a year in a fuel pool known as a cooling pool. From there, it is transported in radiation-shielded transport containers by special vehicles to interim storage in Clab (central interim storage facility for spent nuclear fuel) pending final disposal.

Interim storage will take place for about 40 years. During that time, activity and heat release will have decreased by about 90%. The responsibility for this entire process lies with SKB, Svensk Kärnbränslehantering AB.

Hot water discharge: The cooling water is heated to approximately 10°C in the turbine condenser. The cooling water is taken in through large tunnels, passing through the plant, before being discharged into Hamnefjärden on the north side of the peninsula. In fact, the amount of heat is so large that it accounts for about two-thirds of the total energy produced.

Biological monitoring: To find out the impact of this large amount of heat on marine life, extensive biological monitoring has been carried out since 1962. They show that the cooling water from OKG heats up about 15 km² along the coastline by one degree or more. Measurements and monitoring of temperatures, physical and chemical properties of the water, the size, composition and health of fish stocks, and benthic fauna and algae are carried out on an ongoing basis.

Impacts on the marine environment and wildlife: In the vast majority of cases, the impacts are positive. Nutrient availability is good in the heated water, as is oxygen availability. This has meant that both plants and animals grow faster here than in other parts of the Baltic Sea.

Energy consumption: The plants are heated mainly by waterborne heat generated from electricity, steam from turbines and waste heat from the reactor water. Electricity is mainly used for machinery and lighting.

Water management and water discharge: For domestic and process water, OKG takes 75 000 m³ of water per year from the nearby Lake Götemaren. All water used on the Simpevarp peninsula, except for seawater for process cooling, goes through the company's own waterworks. Here, purification takes place just like at the ordinary municipal waterworks. In addition, fire and process water is produced for the plants. Water emissions mainly come from the sanitary treatment plant and OKG's laundry in the form of fertilizers (nitrogen, phosphorus) and oxygen-consuming substances.

Conventional waste: OKG is a large workplace with a large number of different activities. There are people working on production, repairs, inspection, service, office work, food preparation, transportation and much more. Naturally, this means that a lot of conventional waste is produced and must be dealt with. OKG is actively working to reduce the amount of unsorted waste through source separation. OKG sorts combustible waste, food, paper, corrugated cardboard, plastics, metals, cables and hazardous waste at source.

Hazardous waste: OKG, like other process industries, uses chemicals, oils and other substances that become by-products and residues. The largest quantities are waste oils, oil separation waste, acids and bases. This group also includes solvents, lead-acid batteries, fluorescent lamps, paints, varnishes, adhesives and laboratory waste. The waste is sent to OKG's environmental station where it is stored until it is taken care of by various approved companies specializing in the handling and transport of this type of substance.

How does heated cooling water affect the sea?

Cooling water is a necessary condition for operating a nuclear power plant. The cooling water from O3 is discharged into the nearby Hamnefjärden. The temperature rises by about 10°C from the time the seawater enters the plant until OKG releases it. The seawater is used to cool the process water in a heat exchange system but has no contact with the process water.

The increase in temperature affects the marine flora and fauna near Simpevarp. Through a monitoring program, the environmental effects in Simpevarp are compared with a reference area near Valdemarsvik, about 12 miles north of Simpevarp. The monitoring is carried out by SLU (Swedish University of Agricultural Sciences).

Impact on fish

For fish species that benefit from the warmer water, such as perch, roach and blackfish, there is a strong positive growth effect. Some reproductive disturbances in some fish species have been observed, but at the same time there are more and larger fish in the area. Fish have the ability to move to the temperature zones that suit them best. Fish enter the strainer stations at the cooling water intakes and the survivors are returned to the sea.

Impact on birds

The good availability of fish, but also the fact that Hamnefjärden is ice-free in winter, makes it an important feeding ground for seabirds. The environmentally sensitive white-tailed eagle also thrives in the Simpevarp area.

Impact on benthic fauna and algae

In Hamnefjärden, benthic fauna and algae are strongly affected by the cooling water, for example, the bay is overgrown and periodically there is a lack of oxygen for the benthic fauna. Outside Simpevarp, however, the algae and seaweed communities are rich in species. The area's seaweed belts are among the richest in Kalmar County. The distribution of cooling water on the seabed in the Simpevarp archipelago will not change significantly with an increase in power. Thus, bottom-dwelling animals and bottom vegetation will not be affected compared to the current situation.

LCA and LCC are two modern concepts that are increasing in demand today with regard to environmental impact. This is because consumers are now demanding more basic information about the products they buy in relation to their environmental impact. At the same time as the labeling of goods and products is developing and increasing, legislation is also tightening, especially within the EU.

LCA - Life Cycle Assessment is a method for producing an overall picture of the total environmental impact of a product's entire life cycle. This means from raw material extraction, through manufacturing, use until the product becomes waste, in these different stages, transportation and energy consumption in the intermediate stages are also included.

LCC - Life Cycle Cost Analysis is an analysis based on an economic aspect such as costs and benefits over the life of the product.

LCA and LCC are two concepts that are handled in parallel. From an environmental perspective, it usually becomes an economic issue and vice versa.

Three aspects

When performing an LCA for nuclear power, there are three key aspects that play a main role.

Fuel supply and waste management

Environmental impact from uranium ore mining to finished fuel. Waste management includes the handling of radioactive waste and spent fuel. Also included in the analysis are the chemicals needed in the various fuel production processes.

Operation of the facilities

The environmental impact of the operation, maintenance and reinvestment of the nuclear power plant is included. Also included is the production of spare parts, replacement materials and the chemicals needed for operation.

Construction and demolition

Environmental impact from construction and demolition of facilities. Transport to obtain construction materials and transport to remove demolition waste during plant demolition are included.

If you want to read more about life cycle assessments for energy production and nuclear power, follow the links:

IAEA www.iaea.org

NEA Nuclear Energy Agency www.nea.fr