Table of Contents
The Energy Challenge
Nuclear Power Facts
Nuclear Power Advantages
The Salient Points
Annex I: The DECADES Project
Annex II: Nuclear Power Case Studies
Limited Environmental Impacts
To assist energy planners, the IAEA has over the years carried out comparative assessments of the alternative energy sources. These assessments cover a broad range of technical, economic, environmental and health aspects (see Annex I - the DECADES Project). Extensive databases and analytical tools allow full energy chain analyses so that elements beyond the direct power generation stage can be examined. The comparative assessments permit an examination of nuclear power that is not in isolation. Studies of fossil fuels, nuclear power and renewable energy sources show that there are a wide variety of significant issues and impacts linked to energy options.
Emissions to the environment have been the principal focus of energy impact studies. Other significant impacts such as land disturbance and population displacement together with their economic and social implications are less emphasized. Major impacts such as depletion of natural resources and large fuel and transport requirements that influence a wide range of areas including occupational and public safety as well as national transport systems are generally ignored.
The multitude of factors for consideration are shown in the following compilation of potential environmental impacts:
Fossil fuels can have significant damaging impacts locally, regionally and globally. Hydroelectric, while relatively kind to the atmosphere, can be much less considerate to the earth and its inhabitants both locally and regionally. Renewables are not without their impact, although they are more local in nature. Nuclear power under normal operation is benign to the atmosphere and to the earth and its inhabitants locally, regionally and globally. As discussed below, owing principally to the small fuel requirements there are limited environmental impacts for the full energy chain from mining to waste disposal and decommissioning. A significant environmental impact arises only from potential abnormal events.
Energy density comparisons (fuel and land requirements)
The quantity of fuel used to produce a given amount of energy - the energy density - determines in a large measure the magnitude of environmental impacts as it influences the fuel extraction activities, transport requirements, and the quantities of environmental releases and waste. The extraordinary high energy density of nuclear fuel relative to fossil fuels is an advantageous physical characteristic.
One kilogram (kg) of firewood can generate 1 kilowatt-hour (kW·h) of electricity. The values for the other solid fossil fuels and for nuclear power are:
|1 kg coal:||3 kW·h|
|1 kg oil:||4 kW·h|
|1 kg uranium:||50 000 kW·h|
|(3 500 000 kW·h with reprocessing)|
Consequently, a 1000 MW(e) plant requires the following number of tonnes (t) of fuel annually:
|2 600 000 t coal:||2000 train cars|
|(1300 t each)|
|2 000 000 t oil:||10 supertankers|
|30 t uranium:||reactor core|
|(10 cubic metres)|
The energy density of fossil and of nuclear fuel allows relatively small power plant areas of some several square kilometers (km²). The low energy density of renewables, measured by land requirements per unit of energy produced, is demonstrated by the large land areas required for a 1000 MW(e) system with values determined by local requirements and climate conditions (solar and wind availability factors ranging from 20 to 40%):
|Fossil and nuclear sites:||1–4 km²|
|Solar thermal or photovoltaic
(a small city)
|Wind fields:||50–150 km²|
|Biomass plantations:||4000–6000 km²|
Owing to the vast fuel requirements, the quantity of toxic pollutants and waste generated from fossil fuel plants dwarfs the quantities from other energy options. In general, the pollution depends on the impurity level of the fuel, with natural gas cleaner than oil and oil cleaner than coal. A 1000 MW(e) coal plant without abatement technology produces annually an average of some 44 000 tonnes of sulphur oxides and 22 000 tonnes of nitrous oxides that are dispersed into the atmosphere. Additionally, there are 320 000 tonnes of ash containing 400 tonnes of heavy metals - arsenic, cadmium, cobalt, lead, mercury, nickel and vanadium - quantities which ignore energy chain activities such as mining and transportation.
Fossil fuel plants using modern abatement technology can decrease noxious gas releases as much as ten-fold, but significant quantities of solid waste can be produced in the process. Depending on the sulphur content, solid waste quantities from sulphur abatement procedures for a 1000 MW(e) plant are annually as much as 500 000 tonnes from coal, more than 300 000 tonnes from oil and some 200 000 tonnes from natural gas sweetening procedures [Fig.: Waste Generated Annually in Fuel Preparation and Plant Operation]. The waste, which contains small quantities of toxic substances, is commonly stored in ponds or used for landfill and other purposes. Regulatory bodies are increasingly categorizing such waste as hazardous.
A 1000 MW(e) nuclear power plant does not release noxious gases or other pollutants and produces annually only some 30 tonnes of discharged high level radioactive spent fuel along with 800 tonnes of low and intermediate level radioactive waste. Significant reductions in the volume of low level waste to be managed can be made through compaction. In the USA, low level solid waste from nuclear power plants has been reduced ten-fold over the past decade to 30 cubic metres annually of compacted waste per plant - a total of some 3000 cubic metres from all operating plants. For perspective, industrial operations in the USA are estimated to produce annually more than 50 000 000 cubic metres of solid toxic waste.
Although the amount of radioactive waste is small, future nuclear power designs and fuel cycles can be modified to even further decrease the quantities generated. Innovative actinide burning reactors might also in the future transmute long lived radioactive elements into short lived elements.
Greenhouse gas emissions
Efforts to reduce greenhouse gas emissions require attention to be given to the full energy chain emissions as significant fuel extraction, transport, manufacturing and construction activities can be involved. Full chain analyses require the identification of all emission sources [Fig.: Full Energy Chain CO2 Equivalent Emission Factors]. Burning natural gas which has a low carbon content produces less CO2; than burning coal or oil. But leakages during extraction and pipeline transport, which are more than 5% in some areas, can offset much of this advantage since the escaping methane is a more effective greenhouse gas. In terms of equivalent grams of carbon per kilowatt-hour, some natural gas chains could have emissions similar to coal energy chains.
Full chain hydroelectric assessments generally show comparatively low greenhouse emissions despite large construction activities. However, if methane gas released from decomposition of inundated organic material at the bottom of some water reservoirs is included, emissions could approach natural gas values. Nuclear power and wind are on the low side of full chain emissions, while solar photovoltaic releases are higher owing to various greenhouse gases released during silicon chip manufacturing. Although in many situations biomass is on the low side of emissions, the full chain analyses can be extremely complex and currently provide uncertain results as they involve non-energy byproducts as well as growth and harvesting time periods.
A single 1000 MW(e) coal plant emits around 6 000 000 tonnes annually of CO2. There is no economically viable technology to abate or segregate the large quantities emitted. Segregation and storage underground are theoretically possible, but technologies are only in the very early stages of study. Some may require high energy input and environmental impacts have not been assessed.
Countries with significant nuclear power and hydroelectric capacity have markedly lower CO2 emissions per unit of energy produced than countries with high fossil fuel shares [Fig.: CO2 Per Unit of Energy]. France over the past 30 years has, through a rapid expansion in nuclear power, lowered its CO2 emissions by more than 80% (see Annex II). In contrast, countries that have rejected or sharply curtailed nuclear power programmes have increased greenhouse gas emissions by turning to fossil fuels.
Globally, the use of nuclear power and hydroelectric as an alternative to fossil fuels over the past several decades has helped restrain CO2 emissions. Today, nuclear power and hydroelectric each avoid annually some 8% of global CO2 emissions from energy production [Fig.: Global CO2 Avoided Annually].
Comparisons of various CO2 emission reduction possibilities reported in the 1996 IPCC Technical Paper 1, Technologies, Policies and Measures for Mitigating Climate Change, demonstrate the large mitigation potential of nuclear.
Human Disruption Index
A general indicator of the impact on the global environment attributed to today's energy activities is the Human Disruption Index (HDI) (see Table 3). It is essentially a ratio of human generated additions to the natural baseline situation for energy related environmental factors such as CO2, SO2, NOx, cadmium, lead, mercury, toxic particles, oil to oceans and methane stock. It includes energy chain impacts such as manufacturing that demonstrate the influence of impacts beyond the production stage.
HUMAN DISRUPTION INDEX (ENERGY SUPPLY INPUT)
Flow Item Natural Baseline Flow Human Disruption Index Major Causes Lead 25 000 (t/a) 15 Fuel burning associated processesa Oil oceans 500 000 (t/a) 10 Oil processing and wastes Cadium 1 000 (t/a) 8 Assocaited processesa SO2 50 million (t/a) 1.4 Fuel burning Methane stock 0.8 ppm 1.1 Agricultural activities Mercury 25 000 (t/a) 0.7 Assocaited processesa Nitrous oxides 10 million (t/a) 0.4 Agricultural activities Particle 500 million (t/a) 0.25 Fuel burning; land activities CO2 280 ppm 0.25 Fuel burning
a - Associated processes include metals processing, manufacturing and refuse burning.
HDI values of 10 for oil into oceans, 15 for lead and 0.7 for mercury correspond to human generated movements of 5 million tonnes of oil annually into the oceans and also almost 400 000 tonnes of lead and 20 000 tonnes of mercury into the environment. In the context of a large natural inventory of radioactive material in the earth and a significant continuous release of natural radon gas to the atmosphere, additions from nuclear power activities have a negligible impact on the natural radioactive baseline situation.