633 Technical project description

depleted uranium, re-enrichment of depleted uranium gen- erated in the uranium fuel enrichment process, and repro- cessing of spent fuel. In addition, there are some uranium stockpiles accumulated by investors operating on the raw material markets around the world. The amount of ura- nium fuel produced through reprocessing is estimated to increase up to twofold in the future.

Some depleted uranium generated in the uranium enrichment process is stored in Russia for re-enrichment because it can be utilized in the production of nuclear fuel in the future. Depleted uranium is also used for the produc- tion of mixed oxide fuel, a mixture of uranium oxide and plutonium oxide.

The plutonium separated during the reprocessing of spent nuclear fuel can be recycled into mixed oxide fuel, and the depleted uranium can be recycled to be re-used as nuclear fuel. While the plutonium can be immediately utilized in the production of mixed oxide fuel, the uranium has to be re-enriched in order to be recycled into nuclear fuel. There are reprocessing plants in France, Great Britain, Russia, and Japan. Mixed oxide fuel is produced in locations such as France and Great Britain.

The use of mixed oxide fuel is permitted in several Euro- pean countries and Japan. Fennovoima is planning to use reprocessed uranium as fuel. However, there are no plans to use mixed oxide fuel.

3.7.1.3 The future outlook of the uranium market

Following the Fukushima accident, the price of uranium has been in steady decline, and it is estimated to reach a low point at the time of the preparation of this report. From this point on, the price is estimated to rise moderately, without major price spiking in sight.

Unlike in the case of energy generated using fossil fuels, in nuclear power production fuel accounts for only a minor part of the overall production costs. The price of uranium constitutes less than one-third of the cost of uranium fuel. Therefore, even a significant increase in the price of uranium will have little effect on the production costs of nuclear power.

In the future, the current producer countries will remain the main sources of uranium.

3.7.1.4 Availability of suppliers relating to the various production phases of uranium fuel

There are six conversion companies in the world, with plants in locations such as France, Great Britain, Russia, and the USA. The plants are currently operating at less than full capacity. (WNA 2013)

The enrichment market is dominated by four providers: AREVA (France), Urenco (Great Britain, Germany, the Neth- erlands), Tenex (Russia), and USEC (the USA). There are major enrichment plants in France, Germany, Great Britain, and Russia, to name some locations. Additionally, there are numerous smaller plants, with countries such as Japan and China having enrichment capacity. Furthermore, it is possi- ble to increase the total enrichment capacity.

Zirconium, the material used in fuel rod cladding, is readily available. About five percent of the world’s total zirconium consumption is currently used for the produc- tion of uranium fuel.

There are five suppliers of fuel rod bundles. Production plants for fuel rod bundles suitable for light water reactors are located in countries such as Sweden, Germany, Spain, France, the USA, and Russia. While fuel for the 1,200 MW plant planned by Fennovoima is currently only produced in Russia, it is feasible that in the future, the fuel will be pro- duced in other locations as well.

3.7.2 The fuel production chain

When natural uranium is used, the phases of production of nuclear fuel will be as follows: mining and concentration of uranium ore, conversion into uranium hexafluoride (UF₆), enrichment for the U-235 isotope, the production of fuel pel- lets and fuel rods, and the manufacture of fuel rod bundles.

3.7.2.1 Mining and purification of uranium

Mining of uranium and concentration of ore belong to the scope of normal mining operations. Natural uranium is produced in underground mines and opencast quarries and through underground in-situ leaching. In 2012, under- ground mining accounted for 35 percent, opencast quarry- ing 20 percent, and in situ leaching 45 percent of the total production of natural uranium (WNA 2013). The selection of the mining method depends on factors such as the ura- nium content of the deposit and the geological properties and ground water conditions prevailing at the area.

In conventional mines, the ore is broken loose from the rock, crushed, and milled. In the case of uranium deposits located deep inside the rock, uranium is mined from under- ground tunnels. Mining waste, tailings and gangue, and waste water are generated in the course of mining operations.

The fine ore is taken to a concentration plant, where the uranium is separated from the ore, typically using sulfuric acid. Usually, 75–90 percent of the uranium contained in the ore can be recovered. The uranium contained in the acid solution is concentrated through extraction using a variety of solvents, after which the uranium is precipitated into U3O8 (triuranium octaoxide) using ammonia. The final

product of the extraction process is called uranium concen- trate (yellowcake, Figure 3-7).

In the in situ leaching method, holes are drilled in the ground for the purpose of circulating an acidic or alkaline solution in the soil (Figure 3-8). The uranium mineral is dis- solved into the circulating solution, which is circulated to a plant located on the surface and treated using either the sol- vent extraction or ion exchange method, depending on the acidity of the groundwater. The mixture recovered from the precipitation phase (U₃O₈) is dried at a high temperature. The in situ leaching method has been utilized for a long period of time in countries such as the USA and Kazakh- stan, and the method is gaining wider use in the production of uranium.

64 3 Technical project description

3.7.2.2 Conversion and enrichment

For enrichment, the uranium concentrate (yellowcake) is converted into a gaseous form, uranium hexafluoride (UF₆) through chemical processes at a conversion plant. The pro- cesses make use of a variety of chemicals and thermal energy.

Natural uranium contains 0.7 percent of the isotope U-235. The uranium used in light water reactors must con- tain approximately 3-5 percent of U-235. Enrichment is performed using either gaseous diffusion or, increasingly, the centrifuge method, which requires a substantially lower amount of energy. In centrifugal separation, the uranium isotopes, which have different atomic masses, are separated from each other by centrifugal force.

The enrichment process yields 10-15 percent of the origi- nal amount of uranium as enriched uranium and 80-90 per- cent as so-called depleted uranium. Depleted uranium can be mainly utilized in the dilution of uranium derived from military use for use in civilian reactors.

At the conversion plant, gaseous and liquid impurities are generated in the process of production of fluorine and the fluorination of the uranium compound, as well as the solution purification processes. The most significant gaseous

Figure 3-7. Uranium concentrate (yellow cake).

Figure 3-8. The under- ground in situ leaching method.

impurities monitored at conversion plants are hydrogen flu- oride (HF), fluorine (F2), and uranium isotopes (U).

The operation and maintenance of a centrifuge plant results in some gaseous radioactive emissions. For example, the wastewater from the gas scrubbers of the centrifuge plant is slightly radioactive.

3.7.2.3 The manufacture of fuel rod bundles

The production phases taking place at the fuel production plant are as follows: conversion of uranium hexafluoride into uranium dioxide, production of pellets, manufacture of fuel rods, and manufacture of fuel rod bundles (Figure 3-9).

The uranium dioxide is stored in drums at the fuel pro- duction plant. The uranium dioxide powder is compressed into pellets with a diameter of approximately 1 centimeter and a length of approximately 2 centimeters. The cylindrical pellets are loaded into cladding tubes made of zirconium alloy and with a length of 3-4 meters. The fuel rod thus formed is then filled with helium and sealed tightly. Dur- ing assembly, the fuel rods are composed into fuel rod bun- dles with an approximate diameter of 30 centimeters. The fuel rod bundles used in pressurized water reactors typically contain around 300 fuel rods.

Enriched uranium contains only minor amounts of the uranium decay products which are more harmful in terms of radiation, such as radium, radon, or polonium.

Exhaust air and wastewater led outside the produc- tion plant are decontaminated as necessary before they are released into the environment. The air exhausted from the plant is led through a filter.

65