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Transcript of Energy and Environment Environmental Impacts of Nuclear Energy Dr. Hassan Arafat Department of Chem....
Energy and Environment
Environmental Impacts of Nuclear Energy
Dr. Hassan ArafatDepartment of Chem. Eng.
An-Najah University
(these slides were adopted, with modification, from Ms. Paulina Bohdanowicz , KTH Institute, Sweden)
World Energy Consumption by Source, 2000
Hydro & Traditional Biomass
15%Nuclear
6%
New Renewables
2%Fossil Fuels77%
Source: IEA
World Electricity Generation by Type, 2000
Fossil Fuels 64%
Nuclear 17%
Source: IEA
Other Renewables 2%
Hydropower 17%
Europe – 35% of electricity production from nuclear
Lithuania – 79.9%
Nuclear energy in the world
• On December 2004:• 441 nuclear power plants in operation• 25 nuclear power plants under
construction (combined capacity of 20.9GW)
Nuclear power plants in the world
Source: International Nuclear Satefy Center Argonne National Laboratory, www.insc.anl.gov
Nuclear power
Source: European Environment Agency (EEA), Europe’s environment: the third assessment, Environmental assessment report, no.10, European Community, Copenhagen 2003
World Electrical Generating Capacity of Nuclear Power Plants, 1960-2003
0
100
200
300
400
1960 1970 1980 1990 2000
Source: Worldwatch
Gig
aw
atts
World Nuclear Reactor Construction Starts, 1955-2003
0
10
20
30
40
1955 1965 1975 1985 1995 2005
Source: Worldwatch
Gig
awat
ts
Nuclear Capacity of Decommisioned Plants, 1964-2003
0
10
20
30
40
1965 1975 1985 1995 2005Source: Worldwatch
Gig
awat
ts
Potential causes of concern associated with the nuclear power
• Misuse of fissile and other radioactive material by terrorists
• Radioactivity (routine release, risk of accident, waste disposal)
• Proliferation of nuclear weapons• Land pollution by mine tailings• Health effects on uranium miners
Source: Boyle G., Everett B., Ramage J., Energy systems and sustainability, Oxford 2003
Environmental impacts of nuclear power
• Uranium mining – uranium concentration ~3 mg/tonne of seawater,
~4 g/tonne of the granite, & up to 400 g/ tonne of coal
– naturally occurring uranium: more than 99 % of U-238
– uranium-235 has an abundance of 0.71 %, and U-234 of 0.01%
– large amounts of rock have to be mined to obtain the required uranium - average ore grades at operating uranium mines range from 0.03 % to as high as 10 % uranium, but are most frequently less than 1 %
– radioactive contamination of the environment (radon and other gases)
– noise, dust, sulphur dioxide fumes – overall relatively low polluting
Source: UIC – Uranium and Nuclear Power Information center, http://www.uic.com.au/index.htm 2003
Environmental impacts of nuclear power
• In-situ leaching - a leaching liquid solution - liquid ammonium carbonate, sodium carbonate, or sulphuric acid - forced through the underground ore body to dissolve the uranium => the uranium bearing solution - pumped back to the surface => precipitated => yellowcake U2O8
– can only be used for ore situated in permeable rocks, which are confined by non-permeable rocks
– possibility that the solution of sulphuric acid, oxidant, and uranium migrate beyond the deposit and contaminate the groundwater
– the effects of the leaching liquid on the host rock of the deposit are unpredictable
– impossible to restore the natural condition in the leaching zone after finishing the leaching operation
Source: UIC 2003
Tailings
• up to 1000 tonnes of slurry residues per tonne of uranium extracted
• contain chemically and biologically harmful materials and radioactivity (20 times that of uranium)
• the tails are covered permanently with enough water, clay and soil to reduce both gamma radiation levels and radon emanation rates to levels near those naturally occurring in the region. A vegetation cover can then be established
Environmental impacts of nuclear power
• Enrichment – Yellowcake U2O8
– gaseous diffusion enrichment, centrifugal enrichment, laser enrichment
– “enriched” uranium fuel – the content of the U-235 isotope from the natural level of 0.71% to about 3.5% or even more
– the enrichment process removes about 85% of the U-238 by separating gaseous uranium hexa-fluoride (UF6) into 2 streams:• Enriched : Depleted : in the weight ratio 1:6• Depleted uranium – treated as waste
Source: UIC 2003
Environmental impacts of nuclear power
• Transport– enriched UF6 - transported to a fuel fabrication
plant => converted to uranium dioxide (UO2) powder and pressed into small pellets => inserted into thin zircalloy tubes to form fuel rods
– possibility of an accident with the transporting vehicle, catching of fires => a leakage to the surroundings contaminating water, soil and air
– UF6 – weakly radioactive but highly toxic and corrosive
• Facility construction– Similar impacts as in case of fossil fuel power
plant of similar size
Environmental impacts of nuclear power
• Facility operation– Thermal pollution into the environment
(comparable with fossil fuel-fired plant) – sometimes utilised by district heating and agriculture• Thermal efficiency: coal 20-40%, average for
newer 32%; nuclear 29-38%, light water reactors – 34%
• A 8-10 oC increase in the temperature of the water - observed in the vicinity of the power plant
Environmental impacts of nuclear power
Facility operation -gaseous releases
• water vapour from cooling towers => heating and increasing humidity of the air around the plant– cooling towers are often required to reduce the thermal
impact if a river of a lake is the primary cooling source• ventilation exhaust from buildings that do not have
any processes with radioactivity – similar to any other building exhaust air
• diesel generators exhaust => the only source of GHG at a nuclear plant - the operation hours of diesels and turbines per year are very low
• gases and steam from the air ejectors => not radioactive at PWRs – unless leakage occurs; radioactive at BWRs - but passes through delay pipes, storage tanks & a hydrogen recombiner before being released
Environmental impacts of nuclear power
Facility operation -gaseous releases
• ventilation exhaust from buildings that do have processes with radioactivity
• gases removed from systems having radioactive fluids and gases (systems supporting the reactor cooling system) => removed, compressed and stored, periodically sampled and can only be released when the radioactivity is less than an acceptable level
• Small quantities of radioactivity may also be released by diffusion and through microscopic cracks in the fuel cladding (krypton-85, xenon-133, iodine-131)
Environmental impacts of nuclear power
Facility operation - liquid releases – radioactive tritium, 3H, may be released in the
discharged water– non-radioactive - water that has been used to cool
condenser, various heat exchangers (e.g. to cool oil, steam, water), used in the turbine-generator support processes, or that passes through the cooling towers, & water released from the steam generators => some or all of this water amount may be discharged to a river, sea or lake
– slightly radioactive• very low levels of leakage may be allowed from the
reactor cooling system to the secondary cooling system of the steam generator in any case where radioactive water may be released to the environment, it must be stored and radioactivity levels reduced through ion exchange processes below acceptable levels.
Environmental impacts of nuclear power
Facility operation – solid wastes– radioactive waste (clothes, rags, wood) =>
compacted and placed in drums, drums must be thoroughly de-watered and put on special landfills
– radioactive spent resin (can be very radioactive) => shipped in specially designed containers
– spent fuel => stored underwater in large cooling pools at the plant, when storage has become limited, dry cask storage on-site may be used
Environmental impacts of nuclear power
• Facility operation– Low level waste (~600m3 – from a 1000MW
PWR/annum)• laboratory equipment, clothing, dust swept from
laboratories, gases from fuel cladding stripping & other low irradiated bodies from plants and laboratories
• weak emitters of alpha, beta, and gamma particles, & generate little heat
• the disposal policy differs with the type of waste– gaseous products - released to the atmosphere – low activity liquids - piped out to sea– solid products - buried
Source: Ristinen R.A., Kraushaar J.J., Energy and the environment, USA 1999, Boyle et al. 2002
Environmental impacts of nuclear power
• Facility operation– Intermediate level waste (40m3)
• low level, long half-life wastes -fuel cladding, stream liquids, materials from decomissioning
• repositories – usually located around 300 meters underground
Source: Ristinen R.A., Kraushaar J.J., Energy and the environment, USA 1999, Boyle et al. 2002
Environmental impacts of nuclear power
• Facility operation– high level waste (25m3) - spent fuel with
long half-life (4m3), waste from reprocessing
– 1000 MWe reactor - ~30 tonnes of spent fuel => 1 tonne high-level waste
– isotopes of high activity and high heat generation (the fission products and actinides)
– 99.9% of the uranium and plutonium can be recovered
Source: Ristinen, Kraushaar, 1999; Boyle et al. 2002
Environmental impacts of nuclear power
• Facility operation – high level waste– stored on-site until radioactivity decays to below
1% of original level (50yrs), placed in containers made of stainless steel or copper, then buried in special storages -– i.e. Yucca mountain
• A 1000 MWe reactor –total radioactivity in its spent fuel• ~70MCi - a year after discharge• ~14MCi – 10 years• ~1.4MCi – 100 years• ~2000Ci – 100 000 years
– high-level waste from reprocessing - incorporated into solid blocks of borosilicate glass - vitrification
– risk of accident and excessive radiation
Source: Ristinen, Kraushaar, 1999; Boyle et al. 2002
Nuclear waste in the US
• As of 2003, the United States accumulated about 49 000 metric tons of spent nuclear fuel from nuclear reactors. In addition, there will be about 22000 canisters of solid defense-related radioactive waste for future disposal in a repository
• all the nuclear waste produced to date in the United States stacked side-by-side, end-to-end, would cover an area about the size of a football field to a depth of about ten feet
• by the year 2035 this amount will increase to an estimated 105 000 metric tons
Source: Office of Civilian Radioactive Waste Management, 2005, Ristinen, Kraushaar, 1999
Yukka Mountain project, US• Under current regulations, a total of
70 000 metric tons of spent nuclear fuel and solid high level radioactive waste will be placed in Yucca Mountain – believed to be achieved by 2030.
• Spent fuel assemblies placed in cylindrical steel canisters 5m long, 2m in diameter + stabilising material
• Tunnels 350m below the surface, 222m above the water level– On July 9, 2002, the U.S. Senate cast the
final legislative vote approving the development of a repository at Yucca Mountain.
The Yucca Mountain Project is currently focused on preparing an application to obtain a license from the U.S. Nuclear Regulatory Commission to construct a repository
Source: Office of Civilian Radioactive Waste Management, www.ocrwm.doe.gov 2005; Ristinen, Kraushaar, 1999
Yucca Mountain
• http://www.ocrwm.doe.gov/• Yucca Mountain: The Making of an
Underground Laboratory
• Safe Passage: An Overview of Plans for the Railroad to Yucca Mountain (5min)
Environmental impacts of nuclear power
• Reactor shutdown– Heat pollution– Immediately after shutdown, after the
fission reactions have ceased, about 7% of normal thermal power generation remains,
– 1 hour after shutdown, about 1% of the normal reactor heat output – may be sufficient to melt the core.
Source: Ristinen & Kraushaar 1999
Environmental effects of radiation
• Agricultural areas– Long-lived isotopes (Cs-137)
• Water– Nucleides settle down with time
• Forest– Reproductive functions
• Animals– Mutations
Health impacts of nuclear power
• Natural radiation:– Canada 0.5-1.1 mSv/yr, – Sydney 0.16-0.9 mSv/yr, – Perth 3.0mSv/yr, – Cornwall, UK 7mSv/yr, – India, Brazil, Sudan – up to 40mSv/yr, – Iran many times more
• Average individual annual dose from natural and medical sources – 1.6mSv
• Aircrew and frequent flyers – up to 5mSv/yr,• From nuclear power plants: UK citizens – 0.0003 mSv/yr
• International Comission for Radiological Protection acceptable radiation levels:– 1 mSv/yr for members of the public– 20 mSv/yr averaged over 5 yrs for radiation workers who
are required to work under closely monitored conditionsSource: Boyle et al. 2003
Health impacts of nuclear power • Single large doses in a short period
– >10 Sv – death within hours or days– 1-10 Sv – radiation sickness and disability for
weeks/months, ev. fatal– >1 Sv – symptoms decrease– 0.1 Sv – no immediately obvious effects
• Long-term effects of lower doses– 1-2 cancers per 100 person-sieverts– Total no of genetic effects down to about the 10th
generation – of the same order• Scientific evidence – no cancer risk or immediate effects at
doses below 50 mSv in a short time, and about 100 mSv/yr • Beta particles, gamma rays and X-rays deliver a radiation dose
of 1 Sv (sievert) in depositing 1J of energy per kg of tissue.• Alpha particles and neutrons deliver a radiation dose of 1 Sv in
depositing 0.1 J of energy per kg of tissue. Source: Boyle et al. 2003
Risks associated with nuclear accidents
Source: Clemens P. L., Mohr R. R., Concepts in risk management, USA 2002
Risk of accident
April 26, 1986 – Chernobyl disaster, Pripiat, Ukraine
Source: Y. Arhus Bertrand
Chernobyl – 200 plant personnel and firefighters – acute radiation sickness, out of them - 31 direct
fatalities
Deposition after Chernobyl accident
Source: EEA 2003
135000 evacuated within 30km radius
~47000 eventual excess cancer deaths in Europe & Asia may occur in the next 50yrs (background level of cancer deaths – 500million)
Source: Ristinen & Kraushaar 1999
Occupational hazards of electricity production by fuel,
no of deaths and diseases per GW-yr of output (including entire fuel cycle, excluding severe
accidents)
Source: Boyle et al. 2003
Fuel cycle
Occupational hazards per GWyr
Public (off-site) hazards per GWyr
Fatal Non-fatal
Fatal Non-fatal
Nuclear (LWR)
0.1-0.9 15 0.006-0.2
16
Gas 0.1-1.0 15 0.2-0.4 15
Oil 0.2-1.4 30 2.0-6.1 2000
Coal 0.2-4.3 63 2.1-7.0 2018
Estimated deaths from power generation per GW-year output
Source: Boyle et al. 2003
Occupational
accidents
Occupational
disease
Public Total
Nuclear (LWR)
0.14-0.6 0-0.9 0.067-0.2
0.4-1.7
Gas 0.21
Oil 1.63 1.3-130 3-130
Coal 0.46-0.93 0.13-93 0-320 1-330
Global Nuclear Arsenal, 1945-2002
0
20,000
40,000
60,000
80,000
1945 1965 1985 2005
Source: NRDC
Num
be
r of
Wa
rhe
ad
s
The following countries are not included, due to a high level of uncertainty regarding their stockpiles: Israel (estimated warheads: 100-200); India (30-35), Pakistan (24-48); North Korea (?)
Global Nuclear Warhead Tests, 1945-2003
0
50
100
150
200
Source: Ferm, Norris and Arkin, Arms Control Reporter
Num
ber
of T
ests
Nuclear Warhead Tests by Country, 1945-2003
0
40
80
120
160
200
Source: Ferm, Norris and Arkin, IDDS
Num
ber
of T
ests
Pakistan
India
China
France
United Kingdom
Soviet Union/RussiaUnited States
Positive impacts of nuclear power
• Not affected by the shortage of fossil fuels
• During operation do not emit CO2, CO or particulates into the atmosphere
Source:
Environmental impacts of fossil fuels
and nuclear energy
Fossil fuels• Air emissions• Water pollution• Thermal pollution• Waste generation• Impacts on human
health
Nuclear energy• Thermal pollution• Waste generation• Risk of radioactivity
release
And what about the renewables?
Are they a solution to sustainable development?
Are they environmentally neutral?