Re: interesting article on nuclear
From: brianb (bri1600bv_at_hotmail.com)
Date: 07/27/04
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Date: 27 Jul 2004 16:17:24 -0700
longmuirg@aol.com (LongmuirG) wrote in message news:<20040727130241.16070.00001643@mb-m21.aol.com>...
> brianb titled this "interesting article on nuclear":
> >http://www.feasta.org/documents/wells/contents.html?two/fleming.htm
>
> Here is what the Irish dreamer says about nuclear, quoted in full:
> "Nuclear will contribute little."
>
> Come on Brian -- you can do better than this!
That link went to the main page. There is a subsection about nuclear
that talked about some things, difference b/w diffusion and
centrifuge, etc.
Why consider nuclear power in a book about the transition to renewable
energy? In my view, because nuclear is complementary to renewables in
moving to a sustainable and largely carbon-free energy future. The
reason I say this is that in most countries, the demand for
electricity has a very large continuous component - see Figure 1D1.
This requires a reliable supply of electricity which cannot be readily
met from intermittent wind or solar sources since their electricity
cannot be stored on a large scale.
Nuclear is simply the most appropriate technology for the job of
providing clean baseload power. (Hydrogen may one day be made on a
large scale from electricity, or directly from nuclear energy by
thermochemical means and then stored on a large scale for turning back
to electricity, but such developments are many years away. Even then
the hydrogen will be in higher demand for transport.)
ENERGY BALANCE
The economics of electricity generation are important. If the costs of
building and operating a power plant cannot profitably be recouped by
selling the electricity, it is not financially viable. But as energy
itself can be a more fundamental unit of accounting than money, it is
also essential to know which generating systems produce the best
return on the energy rather than the money invested in them. Determing
this involves Life Cycle Analysis (LCA).
Analysing the energy balance between inputs and outputs, however, is
complex because the inputs are diverse, and it is not always clear how
far back they should be taken. For instance, oil expended to move coal
to a power station, or electricity used to enrich uranium for nuclear
fuel, are generally included in the calculations. But what about the
energy required to build the train or the enrichment plant? And can
the electricity consumed during enrichment be compared with the fossil
fuel needed for the train? Many analysts convert kilowatt-hours (kWh)
to kilojoules (kJ), or vice versa, but this requires them to make
assumptions about the thermal efficiency of the electricity
production.
Some inputs are easily quantified, such as the energy required to
produce a tonne of uranium oxide concentrate at a particular mine, or
to produce a tonne of particular grade of uranium hexfluoride at a
uranium enrichment plant. Similarly, the energy required to move a
tonne of coal by ship or rail can be identified, although this will
vary considerably depending on the location of the mine and the power
plant. Moving gas long distances by pipeline is surprisingly
energy-intensive.
Other inputs are less straightforward such as the energy required to
build a 1000 MWe power plant of a particular kind, or even that to
construct and erect a wind turbine. But all such energy inputs need to
be amortised over the life of the plant and added to the operational
inputs such as fuel. Also the post-operational energy requirements for
waste management and decommissioning plants must be included. There is
no such thing as a free kilowatt-hour! As well as energy costs, the
environmental and health consequences of energy production that do not
appear in the financial accounts need to be considered as well. Recent
studies have plausibly quantified them in financial terms, and I will
comment on those at the end.
Many energy analysis studies done in the 1970s seem to have assumed
that if nuclear generating capacity was expanded very rapidly, it
would require so much energy for fuel production and construction
that, for a few years, inputs would exceed overall outputs. To
determine whether or not this would happen requires the dynamic
analysis of the whole energy system and is not attempted here. The
1970s studies were also driven by a perception that primary energy
sources including uranium would become increasingly difficult and
expensive to recover, and would thus require undue amounts of energy
to access them. This notion has since re-surfaced.
The figures in Figure 1D2 are based as far as possible on current
assumptions and current data for enrichment, mining and milling, etc.
Where current data are unavailable, that from earlier studies is used.
For nuclear power, enrichment is clearly the key energy input where
the older diffusion technology is used - it comprises more than half
of all the energy used in the lifetime of the plant. However, with
centrifuge technology, enrichment takes far less energy than the
construction of the plant itself. Indeed, the difference between the
two processes is so great that, overall, an input of only a third of
the energy is required to build and operate a nuclear plant using
centrifuge technology than one fuelled by the older diffusion method.
(Figure 1D2) Life Cycle Energy Requirements for a Nuclear Power Plant
GWh (e) TJ (th)
Annual PJ (th)
30 year
Inputs
Mining & Milling (180 t/yr U308 at Ranger) 37 1.26
Conversion (ConverDyn data) 5.63
Initial enrichment diffusion @ 2400 kWh/SWU 576 6.23
Urenco centrifuge @ 63 kWh/SWU 15 0.16
Reload enrichment diffusion @ 2400 kWh/SWU 201 2175 65.25
Urenco centrifuge @ 63 kWh/SWU 5.3 57 1.71
Fuel Fabrication (ERDA 76/1) 4.32
Construction & Operation (ERDA 76/1) 24.69
Fuel storage, Waste storage, Transport (ERDA 76/1, Perry
1977), Decommissioning allow 1.0
Total (diffusion enrichment) 108
Total (centrifuge enrichment) 39
Output: 7 TWh/yr 7000 75.670 2 270 PJ
Input percentage of lifetime output, thermal (diffusion) 4.8%
(centrifuge) 1.7%
Energy ratio (output/input), thermal (diffusion) 21
(centrifuge) 59
Assumptions:
Fuel Cycle: 1000 MWe, 30-year life, 80% capacity factor, enrichment
with 0.30% tails (3.0 SWU/kg for initial 80 t fuel load @ 2.3% U-235,
4.3 SWU/kg for 3.5% fresh fuel @ 19.5 t/yr), 45,000 MWd/t burn-up, 33%
thermal efficiency.
Calculations: Electrical inputs converted to thermal @ 33% efficiency
(x 10 800, kWh to kJ)
Other figures for front end: Cameco mines in Saskatchewan input 32 TJ
per 180 t U3O8 over 1992-2001 including some capital works. Urenco
enrichment at Capenhurst input 62.3 kWh/SWU for whole plant in 2001-
02, including infrastructure and capital works.
Other figures for construction (but not operation) of 1000 MWe PWR
power plant are: 13.6 PJ (Chapman 1975, recalculated), 14.76 PJ (Held
1977, if converted direct), 24.1 PJ (Perry et al 1977).
Energy payback period. If 30 PJ or 25 PJ is taken for diffusion and
centrifuge enrichment respectively as the energy capital cost of
setting up, then at 75 PJ/yr output the initial energy investment is
repaid in 5 months or 4 months respectively at full power.
Construction time for nuclear plants is 4-5 years.
The only data available for storage and disposal of radioactive
wastes, notably spent fuel, suggests that this is a minor contribution
to the energy picture. This is borne out by personal observation in
several countries - spent fuel sitting quietly in pool storage or
underground is about as passive as you can imagine. Decommissioning
energy requirements may be considered with wastes, or (as Vattenfall)
with plant construction.
As yet, no energy-input figures seem to have been published for the
fuel cycle that the UK has been using - the closed cycle involving
reprocessing at Sellafield, a point that some Irish observers find
upsetting. However, this probably uses less energy overall because,
although reprocessing requires extra energy, 25% less enrichment will
be required. It is also important to recognise that precise energy
figures for plant construction are not readily available, although
several studies use a factor converting monetary inputs to energy.
Recent studies have compared different means of generating electricity
in energy and greenhouse terms. Here are some of their results,
together with earlier data. The energy ratio is simply output divided
by input for the full life cycle. Unlike some others in use, the R3
energy ratio employs a convention which converts between electrical
and thermal energy, including a thermal efficiency factor, so is used
here. Nevertheless the reciprocal percentage, the input as a
percentage of a plant's lifetime output, may be more meaningful.
(Figure 1D3) Life Cycle Energy Ratios for Various Technologies
R3 Energy Ratio.
(output/input) Input % of lifetime
output
Hydro Uchiyama 1996 50 2.0
Held et al 1977 43 2.3
Quebec Gagnon et al 2002 205 0.5
Nuclear (centrifuge enrichment) see Table 1D2. 59 1.7
PWR/BWR Kivisto 2000 59 1.7
PWR Inst. Policy Science 1977* 46 2.2
BWR Inst. Policy Science 1977* 43 2.3
BWR Uchiyama et al 1991* 47 2.1
Nuclear (diffusion enrichment) see Table 1d. 21 4.8
PWR/ BWR Held et al 1977 20 5.0
PWR/BWR Kivisto 2000 17 5.8
Uchiyama 1996 24 4.2
PWR Oak Ridge Assoc.Univ. 1976* 15.4 6.5
BWR Oak Ridge Assoc.Univ. 1976* 16.4 6.1
BWR Uchiyama et al 1991* 10.5 9.5
Coal Kivisto 2000 29 3.5
Uchiyama 1996 17 5.9
Uchiyama et al 1991* 16.8 6.0
Inst. Policy Science 1977* 14.2 7.0
unscrubbed Gagnon et al 2002 7 14
Natural gas- piped Kivisto 2000 26 3.8
piped 2000 km Gagnon et al 2002 5 20
LNG Uchiyama et al 1991* 5.6 17.9
LNG (57% capacity factor) Uchiyama 1996 6 16.7
Solar Held et al 1997 10.6 9.4
Solar PV rooftop Uchiyama 1996 9 11.1
utility Uchiyama 1996 5 20.0
amorphous silicon Kivisto 2000 3.7 27
Wind Resource Research Inst. 1983* 12 8.3
Uchiyama 1996 6 16.7
Kivisto 2000 34 2.9
Gagnon et al 2002 80 1.3
Biomass forestry waste Gagnon et al 2002 27 3.7
plantation Gagnon et al 2002 5 20
* In IAEA 1994, TecDoc 753.
These figures show that energy ratios are clearly sensitive not only
to the amount of energy used to build the power source and supply it
with whatever it needs to run, but also to the proportion of the time
at which it is delivering power - in other words, its capacity factor.
This is particularly true where a significant amount of energy is
required to build the power plant. The higher the energy input to
build the plant, the more output is needed to amortise it. With
technologies such as wind, where a turbine will only be producing
whenever the wind blows, and then at a rate dependent on the wind
speed, a longer period is required to cover the inputs due to lower
capacity factors. Energy payback period for the construction of a
nuclear power plant is 3-4 months, which compares favourably with all
except gas combined cycle.
The Liquid Natural Gas (LNG) figures quoted are for natural gas
compressed cryogenically and shipped to Japan and used largely for
peak loads. The solar and wind figures relate to intermittent inputs
of primary energy, with inevitably low capacity utilisation and
relatively high energy costs in the plant (for silicon manufacture in
the case of solar cells, or steel and concrete for wind turbines).
The Swedish utility Vattenfall has undertaken a thorough life cycle
assessment of its Forsmark nuclear power station, which has three
boiling water reactors totalling 3100 MWe net. These started up in
1980-84 and run at 86.4% capacity. The energy analysis figures (input
as % of output, transport included, 40 yr plant life, with PJ figures
calculated from % on basis of 3272 PJ output) are shown in figure 1D4
below.
(Figure 1D4) Energy analysis of a Swedish nuclear power station
input as % of output PJ (calculated)
Mine 0.44 14
Refining & conversion 3.18 104
Enrichment (80:20 centrifuge:diffusion) 3.00 98
Fuel fabrication 1.34 44
Plant operation 0.28 9.2
Plant build & decommission 0.27 8.8
Waste management 0.11 3.6
Waste build & decommission 0.01
Total life cycle: 8.70% 285 PJ
The Vattenfall Life Cycle Analysis study tracks energy inputs further
back than others, and so is only comparable with data based on similar
methodology. Even so, some major variances are unexplained - notably
refining and conversion.
Uchiyama (1996) points out that hydro, nuclear and fossil fuel plants
have high energy ratios of output over inputs because of their higher
energy density as well as capacity factors. Wind and solar, however,
are under 10 because of their lower energy density, or output in
relation to plant volume and hence materials used.
LIFE CYCLE ANALYSIS: GREENHOUSE GASES
A principal concern of life cycle analysis for energy systems today is
their likely contribution to global warming. This is a major external
cost.
If all energy inputs are assumed to be from coal-fired plants that
release about one tonne of carbon dioxide per MWh, it is possible to
derive a greenhouse contribution from the energy ratio. With major
inputs, this is worth investigating further.
Uranium enrichment in USA is by diffusion and some of this capacity is
supplied by coal-fired plants. If a national average, allowing for
different sources of power, is applied, this input has a value of
around 650 kg CO2/MWh. This gives a greenhouse contribution for
nuclear power of about 40kg/MWh overall. In France, however, which has
the world's largest diffusion enrichment plant, electricity is
supplied by on-site nuclear reactors (which also supply the grid).
Because of this, the greenhouse contribution from any nuclear reactor
using Frenchenriched uranium is similar to a reactor using
centrifuge-enriched uranium -- less than 1kg /MWh for the enrichment
input, and less than 20 kg/MWh overall.
Rashad and Hammad conclude that the life cycle CO2emission coefficient
for nuclear power, on the basis of centrifuge enrichment, is 2.7% of
that for coal-fired generation. This is consistent with other figures
based on fossil fuel inputs.
Adding further confirmation to figures already published from
Scandinavia, Japan's Central Research Institute of the Electric Power
Industry has published life cycle carbon dioxide emission figures for
various generation technologies. Vattenfall (1999) has published a
popular account of life cycle studies based on the previous few years
experience and its certified Environmental Product Declarations (EPDs)
for Forsmark and Ringhals nuclear power stations in Sweden, and
Kivisto in 2000 reports a similar exercise for Finland. They show the
CO2 emissions in the table below.
The Japanese gas figures include shipping LNG from overseas, and the
nuclear figure is for boiling water reactors, with enrichment 70% in
USA, 30% France & Japan, and one third of the fuel to be MOX. The
Finnish nuclear figures are for centrifuge and diffusion enrichment
respectively, the Swedish one is for 80% centrifuge.
(Figure 1D5) Relative carbon dioxide emissions from different energy
sources
g/kWh CO2 Japan Sweden Finland
coal 975 980 894
gas thermal 608 1170 (peak-load, reserve) -
gas combined cycle 519 450 472
solar photovoltaic 53 50 95
wind 29 5.5 14
nuclear 22 6 10 - 26
hydro 11 3 -
OTHER EXTERNAL COSTS
The report of ExternE, a major European study of the external costs of
various fuel cycles, focusing on coal and nuclear, was released in
2001. The European Commission launched the project in 1991 in
collaboration with the US Dept of Energy (which subsequently dropped
out), and it was the first research project of its kind "to put
plausible financial figures against damage resulting from different
forms of electricity production for the entire EU".
The external costs are defined as those actually incurred in relation
to health and the environment and quantifiable but not built into the
cost of the electricity to the consumer and therefore which are borne
by society at large. They include particularly the effects of air
pollution on human health, crop yields and buildings, as well as
occupational disease and accidents. In ExternE they exclude effects on
ecosystems and the impact of global warming, which could not
adequately be quantified and evaluated economically.
The methodology measures emissions, their dispersion and ultimate
impact. With nuclear energy the (low) risk of accidents is factored in
along with high estimates of radiological impacts from mine tailings
and carbon-14 emissions from reprocessing (waste management and
decommissioning being already within the cost to the consumer).
The report shows that in clear cash terms nuclear energy incurs about
one tenth of the costs of coal. In particular, the external costs for
coal-fired power were a very high proportion (50-70%) of the internal
costs, while the external costs for nuclear energy were a very small
proportion of internal costs, even after factoring in hypothetical
nuclear catastrophes. This is because all waste costs in the nuclear
fuel cycle are internalised, which reduces the competitiveness of
nuclear power when only internal costs are considered. The external
costs of nuclear energy averages 0.4 euro cents/kWh, much the same as
hydro, coal is over 4.0 cents (4.1 - 7.3 cent averages in different
countries), gas ranges 1.3-2.3 cents and only wind shows up better
than nuclear, at 0.1-0.2 cents/kWh average.
The EU cost of electricity generation without these external costs
averages about 4 cents/kWh. If these external costs were in fact
included, the EU price of electricity from coal would double and that
from gas would increase 30%. These particular estimates are without
attempting to include possible impacts of fossil fuels on global
warming. See also web: http://externe.jrc.es/
Another European treatment of production and external costs,
specifically of power generation in Switzerland, has recently been
done by the Paul Scherrer Institut and shows that the damage costs
from fossil fuels range from 10% (gas) to 350% (coal) of the
production costs, while those for nuclear are very small. A summary is
accessible on the web: http://gabe.web.psi.ch/
An earlier European study (Krewitt et al, 1999) quantified
environmental damage costs from fossil fuel electricity generation in
the EU for 1990 as US$ 70 billion, about 1% of GDP. This included
impacts on human health, building materials and crop production, but
not global warming.
The ExternE report proposes two ways of incorporating external costs:
taxing the costs or subsidising alternatives. Due to the difficulty of
taxing in an EU context, the subsidy route is favoured. EC guidelines
published in February 2001 encourage member states to subsidise "new
plants producing renewable energy ... on the basis of external costs
avoided", up to 5 c/kWh. However, this provision does not extend to
nuclear power, despite the comparable external costs avoided. EU
member countries have pledged to have renewables (including hydro)
provide 12% of total energy and 22% of electricity by 2010, a target
that appears unlikely to be met. The case for extending the subsidy to
nuclear energy is obvious, particularly if climate change is to be
taken seriously.
Consideration of external costs leads to the conclusion that the
public health benefits associated with reducing greenhouse gas
emissions from fossil fuel burning could be the strongest reason for
pursuing them. Considering four cities - New York, Mexico, Santiago
and Sao Paulo - with total 45 million people, a 2001 paper in Science
presents calculations showing that some 64,000 deaths would be avoided
in the two decades to 2020 by reducing fossil fuel combustion in line
with greenhouse abatement targets. This is consistent with a 1995 WHO
estimate of 460,000 avoidable deaths annually from suspended
particulates, largely due to outdoor urban exposure.
The World Health Organisation in 1997 presented two estimates, of 2.7
or 3 million deaths occurring each year as a result of air pollution.
In the latter estimate: 2.8 million deaths were due to indoor
exposures and 200,000 to outdoor exposure. The lower estimate
comprised 1.85 million deaths from rural indoor pollution, 363,000
from urban indoor pollution and 511,000 from urban ambient pollution.
The WHO report points out that these totals are about 6% of all
deaths, and the uncertainty of the estimates means that the range
should be taken as 1.4 to 6 million deaths annually attributable to
air pollution.
OTHER CONCERNS ABOUT NUCLEAR POWER
In discussions of the relative merits of different means of producing
electricity, several concerns are commonly raised regarding nuclear
power. This is not the place to treat them comprehensively, but I will
attempt a paragraph on each of four:
RESOURCES
Uranium is abundant. The world's present measured resources of uranium
in the IAEANEA lower cost category (3.1 million tonnes) and used only
in conventional reactors, are enough to last for almost 50 years. This
represents a higher level of assured resources than is normal for most
minerals. Further exploration and higher prices will certainly, on the
basis of present geological knowledge, yield further resources as
present ones are used up. This is indicated in the figures if those
covering estimates of all conventional resources are considered 15.4
million tonnes, which is 240 years' supply at today's rate of
consumption. This figure still ignores unconventional resources such
as phosphate deposits (22 Mt) and seawater (up to 4000 Mt). But before
recourse to them, widespread use of the fast breeder reactor could
increase the utilisation of uranium sixty-fold or more. It is
well-proven but currently uneconomic due to low uranium prices. Using
uranium for electricity is responsible in relation to allowing for the
needs of future generations.
WASTES
Virtually all wastes from the civil nuclear fuel cycle are contained
and managed. Certainly none cause any harm to people or the
environment, nor pose any significant credible threat, with the
possible exception of reprocessing where high-level wastes are in
liquid form for a time. High-level wastes mainly comprise, or are
derived from, spent fuel. They must be shielded and cooled, neither of
which is difficult or complex. As spent fuel, they are in stable
ceramic form, and if reprocessed they end up thus. Storage under water
or in shielded concrete structures is simple and safe. For final
disposal some 50 years ex reactor, they will be encapsulated and
placed in deep repositories, well down towards where radiogenic decay
of uranium already heats the earth. The distinguishing feature of
radioactive wastes is that their toxicity decays, unlike most other
industrial wastes - after 40 years from reactor, the radioactivity of
spent fuel has decayed to one thousandth of its original level, and it
is producing less than one kilowatt of heat per tonne. Apart from
renewables, nuclear power is the only energy-producing industry which
takes full responsibility for all its wastes, and fully costs this
into the product.
SAFETY
>From the outset, the safety of nuclear reactors (where one has a very
high energy density) has been a high priority in their design and
engineering. About one third of the cost of a typical reactor is due
to safety systems and structures. The Chernobyl accident in 1986 was a
reminder of the need for this (normal safety provisions being largely
absent there), whereas the comparable Three Mile Island accident in
1979 showed that such safety measures work - noone was harmed. In
fact, and despite Chernobyl, the safety record of nuclear power is
better than for any other major industrial technology. And it is
improving with newer reactors.
WEAPONS PROLIFERATION
An early concern as nuclear technology emerged from its military
chrysalis was that civil nuclear power should not enable more
countries to acquire nuclear weapons. Under the Nuclear
Non-Proliferation Treaty a safeguards system was set up to detect and
deter any diversion of fissile material from civil to military use. It
is arguably the UN's most successful program, and early prospects of
20-30 countries with nuclear weapons have been averted. Today, the
flow of material is from weapons stockpiles to civil use, filling
about one fifth of world uranium demand. One in ten light globes in
the USA are now lit by ex- Russian military uranium. The WNA web site
www.world-nuclear.org has information papers on all these issues and
many more.
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