One Thing the General Public are Concerned... (Uganda)

The Nuclear Industry Explained

Uranium is a slightly radioactive metal that occurs throughout the Earth's crust in most rocks and soils. For example, it is found in concentrations of about four parts per billion in granite which makes up 60% of the earth's crust. It is about 500 times more common than gold. However, there are only a limited number of places in the world where uranium is found in high enough concentrations for it to be deemed economically viable to extract it for use as nuclear fuel. Such concentrations are called uranium ore and they are present in Uganda.

Surveys by the Ugandan Ministry of Energy and Mineral Development (MEMD) show that the country has about 52,000 square kilometres of uranium deposits.

In the early 20th century, it was discovered that radioactive elements such as uranium released huge amounts of energy. A series of experiments over the following decades culminated in the announcement of self-sustaining nuclear chain reactions by Frederic Joliot-Curie in 1939. A nuclear reaction is defined as the process by which two nuclei, or a nucleus and a sub-atomic particle, collide to produce one or more nuclides that are different from those that started the process. A nuclear chain reaction occurs when one single nuclear reaction causes an average of one or more subsequent nuclear reactions, thus leading to the possibility of a self-propagating series of these reactions. Most importantly, the nuclear chain reaction releases several million times more energy per reaction than any chemical reaction - the potential in terms of power generation is enormous.

Figures from the World Nuclear Association indicate there are currently 437 operable civil nuclear power reactors around the world with a further 71 under construction. Out of the 30 countries currently generating power from nuclear reactors, the five with the highest number of reactors are:

USA - 99 reactors that generated 790.2 billion kWh in 2013 (19.4 % of total)

France - 58 reactors that generated 405.9 billion kWh in 2013 (73.3% of total)

Japan - 43 reactors that generated 13.9 billion kWh in 2013 (1.7% of total)*

Russia - 34 reactors that generated 161.8 billion kWh in 2013 (17.5% of total)

China - 26 reactors that generated 104.8 billion kWh in 2013 (2.1% of total)

Prior to the earthquake and tsunami of March 2011 Japan generated 30% of its electricity from nuclear and planned to increase that share to 40%. However, all of Japan's nuclear plants have now been closed or their operation suspended for safety inspections hence the figure of 1.7%.

According to President Museveni, a developed Uganda requires in excess of 50,000 megawatts of electricity which cannot be generated from the country's limited hydro and geo-thermal resources. The country therefore is looking at nuclear energy as a viable option and hopes to begin producing nuclear energy in about twenty years. Already, Uganda is conducting pre-feasibility studies which involve assessing the country's energy needs, proposing road maps, developing expertise and training human resources, establishing policy and regulatory frameworks and mobilizing funding. When that is completed, Uganda will then conduct other studies to establish the viability of setting up nuclear plants in the country.

Developing nuclear fuel

The nuclear fuel cycle is the series of industrial processes which lead to the production of electricity from uranium in nuclear power reactors. It involves the following stages:

Uranium mining:

depending on the nature of the uranium ore and adjoining rock, as well as safety, environmental and economic considerations, a variety of mining methods can be used. In the case of excavation it may be underground (for deep deposits) or open pit (where deposits are close to the surface). In situ leach (ISL) mining is also now commonly used where oxygenated groundwater is circulated through very porous rock to dissolve the uranium oxide and bring it to the surface.

Uranium milling is used to extract the uranium from the ore (or ISL leachate). The ore is crushed and ground to a fine slurry which is leached in sulphuric acid to separate the uranium from the waste rock - this waste rock or 'tailings' must be isolated from the environment. The uranium is then recovered from the solution and precipitated as uranium oxide (U3O8) concentrate - sometimes known a 'yellowcake'. This material is then dried and packaged ready for transport

Conversion:

Theuranium oxide productmust first be refined at a conversion facility into uranium dioxide (UO2) which can be fabricated into fuel rods for use in some reactors - notably the Canadian and Indian heavy water type. However, to get more energy out, most of the uranium dioxide goes through a further process called enrichment. This is where things get a little complicated.

Enrichment:

The aim of this process is to increase the proportion of 'fissile' material or material that is capable of undergoing fission (splitting up of the nucleus). This is the process by which energy is produced in a nuclear reactor. Only 0.7% (this is the concentration of the uranium-235 isotope - but we won't go into that here) of natural uranium is fissile. For most kinds of reactor the concentration of the fissile material needs to be increased - typically to between 3.5% and 5%. Firstly, the uranium dioxide mentioned above must be converted into gaseous uranium hexafluoride (UF6) by adding a highly toxic gas called hydrogen fluoride. The uranium hexafluoride is then passed through a series of rapidly spinning vertical tubes known as centrifuges to produce low-enriched uranium hexafluoride. Finally, this is reconverted back to produce enriched uranium oxide (UO2).

Note - Uranium enrichment is a critical component for civil nuclear power generation but also for military nuclear weapons. Weapons grade uranium typically contains 85% or more of 'fissile' uranium-235.

Fuel fabrication:

The final stage of the 'front end' is to press and bake the enriched uranium dioxide into ceramic pellets. The pellets are then encased in metal tubes to form fuel rods, which are arranged into a fuel assembly ready for introduction into a reactor. About 27 tonnes of this enriched fuel is required each year by a 1000 megawatt reactor.

Power generation:

Several hundred fuel assemblies make up the core of a reactor. In the reactor core, the fissile material (uranium-235) fissions or splits producing a huge amount of heat in a continuous nuclear chain reaction. As in fossil fuel burning plants such as coal, the heat is used to produce steam which drives a turbine and an electric generator. To maintain a high level of efficiency in the reactor, about one third of the spent fuel is replaced with fresh fuel every year or 18 months.

Waste from the nuclear fuel cycle can be in solid, liquid or gaseous form and is categorised as either high, medium or low-level depending on the amount of radiation it is giving off. One of the big issues is that at the present time there are no disposal facilities in operation in which the very highest level solid waste i.e. used fuel (not destined for reprocessing) and the waste from reprocessing can be placed. This highly radioactive waste presents many technical issues due to the extremely long periods of time that must pass before it stops being dangerous to humans and the environment. Having said this, the total volumes of such wastes are relatively small. For example, one year worth of high level waste from a 1000 megawatt reactor can be contained in five tonnes of borosilicate (Pyrex) glass, stored in stainless steel containers.

Handling radiation

One thing the general public are always concerned about, and rightly so, is the effect of radiation on people and the environment. Although radiation is naturally present in our environment, it can have either beneficial or harmful effects depending on its use and control. Since the beginning of time all living creatures have been, and are still being, exposed to radiation. Natural radiation comes from cosmic radiation (i.e. the sun and stars), terrestrial radiation (i.e. soil, rock, water, food and even air - all air contains radon which is responsible for most of the dose people get from background radiation) and internal radiation (i.e. mainly from radioactive potassium-40 and carbon-14 inside your body from birth). People who work with or near nuclear materials (i.e. fuel cycle facilities, power stations, medical radiology departments etc.) will be likely to receive some additional varying amounts of radiation depending on their specific jobs. However, note that this occupational exposure is tightly controlled by the regulatory authority of the country where the operations are taking place. Radiation can broadly be split into either ionising on non-ionising radiation depending on how it affects matter. Non-ionising radiation includes light, heat, microwaves and radio waves and does not have sufficient energy to break molecular bonds. Ionising radiation on the other hand is more energetic and when passing through a material it deposits enough energy to break molecular bonds and remove electrons from atoms causing changes in living cells of plants, animals and people.

A common example is the 1986 Chernobyl accident in Ukraine that caused the death of 30 people due to acute radiation poisoning.

In the second part of this series, we will explore in more detail the Ugandan context- how much uranium has been found to date, where it is in the country and how accessible it is. We shall discuss what this means for Uganda in the context of wider natural resources management and governance.

By Luke Williams. He is an Environment, Health and Safety professional.