Nuclear Energy: Not a solution for energy crisis

Dr. Manabendra Nath Bera

1) Nuclear Physics: Radioactivity1) Nuclear Physics: Radioactivity

2) Nuclear Power Plants2) Nuclear Power Plants

3) Nuclear Fuel3) Nuclear Fuel

4) Nuclear Waste4) Nuclear Waste

5) Nuclear Safety5) Nuclear Safety

6) Conclusion6) Conclusion

Agenda

Nuclear Physics: Radioactivity

Nuclear Fission

The reaction:

¿235¿¿U ¿ ¿

235U + n

141Ba + 92Kr +3 n + Energy

144Cs + 90Rb +2n + Energy

Measuring Radioactivity

• Half-Life– The time for a radioactive source to lose 50% of its

radioactivity– For each half-life time period, radioactivity drops by

50%• 1/2; 1/4; 1/8; 1/16; 1/32; 1/64; 1/128; 1/256; …• A half-life of 1 year means that radioactivity drops to <1%

of its original intensity in seven years

• Intensity vs. half-life– Intense radiation has a short half life, so decays more

rapidly

Types of Radiation

http://www.uic.com.au/wast.htm

Health Effects of Radiation

• Radiation changes living cells– body repairs low dose rate damage– body cannot repair large acute doses– Cancer

• Degree of effect depends on dose intensity, length of exposure, and type of cell exposed

Nuclear Power Plants

Nuclear Heat

Heat

Steam produced

Steam

Turbine

Generator

Electricity

Nuclear Fuel

Creating Uranium Fuel

• 50,000 tonnes of ore from mine • 200 tonnes of uranium oxide concentrate (U3O8)

– Milling process at mine• 25 tonnes of enriched uranium oxide

– uranium oxide is converted into a gas, uranium hexafluoride (UF6),

– Every tonne of uranium hexafluoride separated into about 130 kg of enriched UF6 (about 3.5% U-235) and 870 kg of 'depleted' UF6 (mostly U-238).

– The enriched UF6 is finally converted into uranium dioxide (UO2) powder

– Pressed into fuel pellets which are encased in zirconium alloy tubes to form fuel rods.

Creating Uranium Fuel

Green house gases during these process

What Is the Nuclear Fuel Cycle?

• Mine the uranium

• Process the uranium to make the fuel

• Use it in the reactor

• Safely store the radioactive waste

• Decommission the reactor

Nuclear Waste

Spent Fuel rods

• After about 3-4 years of use, the Fuel rods become spent-level of fission drops beneath a certain level

• Rods are taken out of reactor stored nearby in water filled pools or dry casks

• Stored until they cool down enough to be shipped for permanent storage or to be recycled

• These storage facilities are next to the reactor plants, vulnerable to terrorist attack or accidents

Waste Burial

• Immobilize waste in an insoluble matrix– E.g. borosilicate glass, Synroc (or leave them as uranium oxide

fuel pellets - a ceramic)

• Seal inside a corrosion-resistant container– Usualy stainless steel

• Locate deep underground in stable rock• Site the repository in a remote location. • Most radioactivity decays within 10,000 years

– Remaining radioactivity similar to that of the naturally-occurring uranium ore, though more concentrated

http://www.uic.com.au/wast.htm

http://www.uic.com.au/opinion6.html

After 3 or 4 Years in a Reactor, Spent Fuel Rods Are Removed and Stored in Water

Dealing with Radioactive Wastes Produced by Nuclear Power Is a Difficult Problem

• High-level radioactive wastes – Must be stored safely for 1,000–24,000 years

• Where to store it– Deep burial: safest and cheapest option– Transportation concerns– Would any method of burial last long enough?– There is still no facility

Cooled in a spent fuel pool: 10 to 20 years

Onsite temporary dry storage: Until permanent site becomes available

Case Study: Experts Disagree about What to Do with Radioactive Wastes in the U.S.

• 1985: plans in the U.S. to build a repository for high-level radioactive wastes in the Yucca Mountain desert region (Nevada)

• Problems– Cost: $58–100 billion– Large number of shipments to the site: protection from

attack?– Rock fractures– Earthquake zone– Decrease national security

Nuclear Safety

List of dangers connected to NPPs

Release of radioactive element into environmentRadioactive isotope pollutionWater temperature increaseThe threat of nuclear accidentThreat of nuclear terrorismTransportation of the waste can be risky

During the operation of nuclear power plants, radioactive

waste is produced, which in turn can be used for the

production of nuclear weapons.

Worst Commercial Nuclear Power Plant Accident in the U.S.

• Three Mile Island– March 29, 1979– Near Harrisburg, PA, U.S.– Nuclear reactor lost its coolant– Led to a partial uncovering and melting of the

radioactive core – Unknown amounts of radioactivity escaped– People fled the area– Increased public concerns for safety

• Led to improved safety regulations in the U.S.

Cleanup lasted 14 years; cost $975 million51 US nuclear reactor orders canceled 1980-84.

• April 26, 1986

• Pripyat, Ukraine

• Catastrophic steam explosion -Destroyed reactor

-Plume of radioactive fallout spread far• USSR, eastern Europe, Scandinavia,

UK, eastern US

• Belarus, Ukraine, and Russia hit hardest

-56 direct deaths; ~4,000 long-term deaths

-350,000 people evacuated and resettled

http://en.wikipedia.org/wiki/Chernobyl_accident

Worst Nuclear Power Plant Accident in the World

What happened?

-Reactor No.4 was undergoing a test of the backup power supply in case of a power loss.

-The experiment involved shutting down the coolant pumps, which caused the coolant to rapidly heat up and boil.

-All control rods were ordered to be inserted. As the rods were inserted, they became deformed and stuck. The reaction could not be stopped.

-The rods melted and the steam pressure caused an explosion, which blew a hole in the roof. A fire also resulted from the explosion.

-To save money, the reactor was constructed with only partial containment, which allowed the radiation to escape. 13%-30% of the material escaped.

Evacuation-Following the accident hundreds of thousands of people had to be evacuated and between 1990 and 1995 an additional 210,000 people were resettled.

People evacuated:-May 2-3 (1 week later) 10 km area (45,000 people)

-May 4 30 km area (116,000

people)

http://library.thinkquest.org/3426/data/emergency/evacuation.html

-50,000 people from Pripyat, Ukraine were evacuated 2 days after the accident.

Effects of Radiation

Belarusian doctors identify the following effects from the Chernobyl disaster on the health of their people:

100% increase in the incidence of cancer and leukemia 250% increase in congenital birth deformities “Chernobyl AIDS”--the term doctors are using to describe illnesses

associated with the damage done to the immune system

Initial response• These were firemen who helped put out the fires and helped clean

up the radiation• Most did not realize the dangers of radiation.• Many later died from radiation, because they didn’t wear

protection.• An estimated 8,000-20,000 to date have died (20% from suicide)

Approximately 300,000 to 600,000 people were involved in the cleanup of the 30 km evacuation zone around the plant in the years following the meltdown.

Effects of Radiation

Victims

Victims

Fukushima

Cause and Effects

Can Nuclear Power Reduce Dependence on Imported Oil, Reduce Global Warming?

• Nuclear power plants: no CO2 emission

• Nuclear fuel cycle: emits CO2

• Opposing views on nuclear power and global warming– Nuclear power advocates– 2003 study by MIT researchers– 2007: Oxford Research Group

Conclusion: NPPs as an alternative source of energy

Fig. 15-21, p. 391

TRADE-OFFSConventional Nuclear Fuel Cycle

Large fuel supply Cannot compete economically without huge government subsidies

Advantages Disadvantages

Low net energy yieldHigh environmental impact (with major accidents)Emits 1/6 as much CO2 as

coal

Environmental costs not included in market price

Risk of catastrophic accidents

No widely acceptable solution for long-term storage of radioactive wastes

Moderate land use

Spreads knowledge and technology for building nuclear weapons

Subject to terrorist attacks and Earth quake

Fig. 15-22, p. 392

TRADE-OFFS

Coal vs. Nuclear

Coal NuclearAmple supply Ample supply of

uraniumHigh net energy yield

Low net energy yield

Very high air pollution

Low air pollution

High CO2 emissions Low CO2 emissions

Much lower land disruption from surface mining

High land disruption from surface mining

High land use Moderate land use

Low cost (with huge subsidies)

High cost (even with huge subsidies)

Thank you

Extra

Reactor Safety DesignContainment Vessel1.5-inch thick steel

Shield Building Wall3 foot thick reinforced concrete

Dry Well Wall5 foot thick reinforced concrete

Bio Shield4 foot thick leaded concrete with1.5-inch thick steel lining inside and out

Reactor Vessel4 to 8 inches thick steel

Reactor Fuel

Weir Wall1.5 foot thick concrete

Controlling Chain Reaction

Control rods

Fuel Assemblies

Withdraw control rods,reaction increases

Insert control rods,reaction decreases

Boiling Water Reactor

Human casualties

• 56 people lost their lives as a direct result of radiation poisoning or fire.

• Thyroid cancer from drinking milk 10-12 thousand.

Can Nuclear Power Reduces Dependence on Imported Oil, Reduce Global Warming?

• Nuclear power plants: no CO2 emission

• Nuclear fuel cycle: emits CO2

• Opposing views on nuclear power and global warming– Nuclear power advocates– 2003 study by MIT researchers– 2007: Oxford Research Group