Nuclear power gives us large radiation dosages.
Figure 1- Proportion of an average yearly radiation dosage based on the American Institute of Physics handbook. All figures are in mSv.
In actual fact, the proportion of the average dose rate from the nuclear fuel cycle is on the order of a tenth of a percent. Figures vary from 10µSv to 0.1µSv yearly from the nuclear fuel cycle. This compares with a yearly natural background radiation dosage of 1000µSv to 4000µSv. Natural radiation accounts for over 80% on average. The vast bulk of manmade dosage comes from non-nuclear industrial and agricultural operation, medical exposure and jet air travel. The effects of fallout from weapons testing also dwarfs civil nuclear power, although it is still less than 1% of total dosage. Actual numbers vary greatly in different locations, but generally the proportions are similar. Figure 1 shows an example.
An interesting fact is that the Capitol Building in Washington is made on masonry so radioactive, it could not be licensed as a nuclear facility. Also interesting is that radiation dosage to local population from a coal power station is 2-3 times greater because of all the radioactive particulates dispersed into the atmosphere from burning coal. Radiation is everywhere. The strictly regulated practises of the nuclear industry give an insignificant contribute to overall dosage to the population.
Nuclear power stations regularly discharge radioactive material into the air and water.
Reactor cores themselves contain all radioactive materials apart from occasionally a trace of tritium (in light water reactors) and radioactive noble gases, and even more rarely iodine-131, should there be an unwanted build up of these materials. The amount discharged is so insignificant as to be negligible and discharges only happen infrequently in any case. The noble gases for examples are stored for a short time to allow them to decay (they are generally very short-lived) before being vented as harmless, inert gases. All discharges are strictly regulated with far more rigour than many other toxic substances. The hazard posed is negligible.
The origin of discharges into water claim no doubt comes from the fact that any thermal heat engine takes in water from a river or sea for cooling and then returns the water to the source. In nuclear power stations, this water is isolated from any contact with radioactive material that was not there to begin with and as such is returned to the source no more radioactive than when it entered. It's just a little warmer. Similar false claims about radioactivity in cooling water have been made about reactors cooled with cooling towers. Again, there is nothing abnormally radioactive about this water.
Cases of ground water contamination involving tritium and strontium-90 due to leakages from spent fuel pools were recently found at Indian Point, Perry and Braidwood. But again, this values were so small as to represent no risk to the population, even under worst case assumptions, something on the order of less than a nanosievert in the case of the Indian Point leak according to the report from the NRC. Radioactivity is easy to detect so any leaks can be plugged while the levels remain numerical curiosities rather than legitimate environmental hazards.
Greenpeace openly stated that nuclear power stations 'pump' radioactive pollution into the sea and air everyday. But this statement ranks between the marks of grossly misleading to downright dishonest. Any radioactive discharge is miniscule in quantity and overall potency and contributes nothing measurable to the dose rate of the population. The statement that radioactive pollution is pumped into the sea and air everyday conveys a completely false impression of the scale and frequency of these discharges.
Other fuel cycle facilities have made many a sea radioactive.
Reprocessing facilities used to make larger radioactive discharges, although they still were strictly regulated and the ensuing contamination was the subject of all manner of exaggerated hyperbole. Sellafield was the most notorious example, which had to repeatedly discharge technetium-99 into the Irish Sea as part of the reprocessing of Magnox fuel. However, new techniques have reduced that almost entirely. Other facilities were never as profligate as Sellafield, which has to bear the burden of its military heritage. Newer reprocessing techniques have made reprocessing much cleaner.
Somehow, nuclear facilities pose a cancer risk.
A recent report (pdf) from the Committee on Medical Aspects of Radiation in the Environment gave a clean bill of health to all generating station in the UK. Their studies looked at cancer incidence in children and found no statistically significant increase. Children were used because their weaker immune systems would be more revealing of any health problems and also because adults are more likely to have moved around, making epidemiological analysis more difficult. The report did find an increase around Sellafield and the shutdown fast reactor at Dounreay. However, the report was cautious about drawing conclusions about these cases. For Sellafield, but because the amount of radioactive discharge has been decreasing since the 1970s, they could not attribute causality entirely to the facility.
Dounreay was even more of a puzzle. The radioactive discharge has always been lower than Sellafield and such for COMARE to discover increased statistical significance is inconsistent. Furthermore, the excess from an earlier report in 1980s has not continued as expected. It was difficult to infer a causal relationship between the Dounreay facility and the increased incidence of clusters. The COMARE report highlighted population mixing as an explanation. It must also be considered that due to the small sample size around Dounreay, statistical analysis is even more prone to errors.
Over the entire life cycle, nuclear power produces as many emissions as a third of the life cycle emissions from natural gas.
The oft cited claim is based on a paper by Storm van Leeuwen and Smith entitled Is Nuclear Power Sustainable? There are a number of problems with the assumptions in this study and one big problem with the use of it in the debate over the construction of a new generation of reactors today. The latter problem is that the SLS paper assumes the use of low grade ore. Therefore it is not relevant for the current debate since there is sufficient high grade ore to last for the lifetime of the proposed new generation.
The way low grade ore is used in the paper is also erroneous, since it assumed it will be used in thermal uranium reactors in much the same way we do now. The economic situation brought about by the necessity to use low grade ore once high grade ore is depleted will drive a paradigm shift in the fuel cycle helped by advancing technology. The balance of technology will shift to fast reactors and to the use of thorium, available in abundance. Not only does the scenario laid out in SLS not apply now, it will never apply therefore the entire paper is invalid.
But even assuming it was, it is still plagued by problems of methodology. In life cycle analyses, carbon dioxide emissions are essentially a proxy for energy inputs. In order for SLS to obtain the figures, they make the assumption that all energy inputs are produced by fossil fuels, frequently coal. Derive the needed energy from non-carbon sources, as the situation changes. Enrichment facilities could be nuclear powered as they are in France, as could the ships used to transport the raw uranium ore. Mining and transport is based on oil products, but it could be based on alternative fuels such as hydrogen, which could be produced from nuclear reactors themselves.
Then there is the gross overestimating of the size of the energy inputs themselves. Early versions of the paper assumed diffusion enrichment although later versions tentatively corrected this. Mining is also assumed to be conventional with no regard for new technologies being implemented such as in situ leaching. A more detailed appraisal of these errors is found at the WNA.
Figure 2- Average life cycle greenhouse gas emissions for different energy sources from a 2000 IAEA study.
The SLS fails because:
- It assumes a scenario, where low grade ores are used in a similar fashion to today's fuel cycle, which will never exist.
- It assumes all energy inputs are from fossil fuels, whereas most of them can be directly or indirectly nuclear powered.
- It grossly inflates the energy inputs.
Multiple studies from Vattenfall in Finland, the IAEA, and the NEI, give figures that are significantly lower. One such example is shown in figure 2, although different studies of different scenarios give slightly different results. For high grade ores, carbon dioxide emissions, still assuming mostly fossil fuel energy inputs, but with realistic input figures, nuclear life cycle is less than 5% as carbon emitting as natural gas, perhaps rising to 6% if low grade ores were used as SLS suggest. Although figures vary regionally, on average, this is on par with wind power, sometimes higher, sometimes lower, and significantly less than photovoltaic.
Nuclear power stations have to discharge hot water into rivers or seas.
Discharging hot water is only done where there is open cycle cooling (ie without cooling towers). It is also done at any steam cycle based power station, nuclear or otherwise, which accounts for the majority of electricity generation. So it is not really a nuclear issue. It is however worth noting that improved thermodynamic efficiency of new plants - nuclear or coal - can reduce waste heat. In some places, the cooling water it piped to local buildings to be used as hot water in lieu of expending more electricity and gas in heating it on site. The use of cooling towers eliminates the problem and some facilities have built small helper towers on sites previously with strictly open cycle cooling to deal with increasing regulations on heat discharge. This involves an expense, but if through regulation or weather the current cooling system is insufficient to handle a full power load, forcing a power reduction or worse a shutdown, these modifications can quickly repay themselves by allowing the plant to operate at full revenue generating capability.
So this issue is not specifically nuclear, it is strictly regulated, and there is technical progress to minimise heat pollution to local water sinks.