NUCLEAR REACTOR : RISKS & BENEFITS

BY SARTH

ROLL NO. 46

T.E. AUTO (2013-2014)

INTRODUCTION

• This is a presentation showing the real effects of Nuclear Power Plants how harmful it actually is compared to other forms of energy.

• After this presentation we evaluate the risks and benefits of Nuclear Energy generation.

TYPES OF RADIATION

• What is radiation?

• Transmitted Energy

• Types of radiation

• Electromagnetic (radio, visible, x-rays, γ rays)

• Charged particles (electrons, protons, α particles)

• Other (neutrons, neutrinos, other exotic beasts)

• Categorized as either ionizing or non-ionizing

• Depending on whether they can ionize other particles (i.e., rip off electrons from the atom)

• All 3 types of radiation can be ionizing depending on their energies. Ionization Interaction

EFFECTS OF RADIATION

Chronic Dose Dose delivered over an extended period of time.

Acute Dose Dose delivered over a short period of time. An acute dose is generally more damaging than a chronic dose of the same size, because the body’s repair mechanisms have less opportunity to act.

Immediate Effects (hours to days)

– Skin reddening, inflammation – Immune suppression – Sterility – Blood chemistry changes – Loss of hair – Gastrointestinal syndromes – Central nervous system syndromes

Long term effects (months to years)

– Cancer / leukemia – Cataracts – Genetic defects – Blood disorders – Lifespan shortening

THE FUEL

Natural uranium consists of mainly 3 isotopes :

Isotope % Abundance Half Life (years)

U-238 99.284 4.5billionU-235* 0.711 704million

U-234 0.005 245thousand

*Must be enriched up to about 3-5% for commercial fuel

The good stuff!!

As we can see, from the total ore mined, only a small fraction is used for actual energy generation. Thus extraction and enrichment of uranium ore is an expensive process and increases the cost of energy production.

The most commonly used fuel for production of energy by Nuclear Fission is Uranium.

THE REACTOR

• The reactor is where the energy is generated.

• Neutrons produced in a chain reaction split uranium-235 atoms into smaller atoms, converting the mass difference into pure energy as given by Einstein's equation E = mc2. The reaction has to be controlled and kept running continuously. The reactor is a very complex generator which is expensive to build and requires precision engineering.

Pressurized Water Reactor ( Light water Thermal Reactor)

NUCLEAR WASTE

• Nuclear waste is one of the major issues in Nuclear power production today.

• Even though a very tiny amount of waste is created in nuclear power production, the spent fuel rods are hot and highly radioactive with half life of billions of years.

• Nuclear waste cannot be disposed easily due to the risk of radioactive contamination in organisms which can cause mutations and last for generations.

• There is currently no full proof method of dealing with these spent fuel rods. Burial deep into the earth (Deep Geological Repository) is the most commonly employed method, but it suffers the risk of earthquakes and natural calamities and being unearthed by future generations.

REACTOR SAFETY FUNDAMENTALS

• What is the biggest risk to the public that is unique to nuclear power reactors? – Release of radioactive materials.

• Release is prevented by Multiple-Barrier Design

– Pellet – Cladding – Reactor Primary Coolant System – Containment / Safety Systems

MAJOR REACTOR ACCIDENTS

1. SL-1 (Idaho)

• Criticality Accident - Destroyed reactor and killed three operators. Little release of contamination in spite of the fact that SL-1 did not have containment.

• Fatalities - 3

2. Three Mile Island (Pennsylvania)

• 50-80% of fuel in core melted. Reactor core and vessel were total losses. Containment held.

• Fatalities - 0

3. Chernobyl (Russia)

• Super Critical Power Excursion which created a steam explosion and destroyed the plant. “Containment” was destroyed

4. Fukushima (Japan) • Natural disaster of tsunami overwhelmed emergency

systems. Suspect reactor core damage. • No known fatalities.

RADIATION STANDARDS

• The main source of radiation for general public is the background radiation which lies in the range of 1mSv to 13mSv/yr.

• Studies have shown that low level radiation can be beneficial to biological life forms.

• Public dose limits for exposure from uranium mining or nuclear plants are usually set at 1mSv/yr above background.

• Radiation from Grand Central Station (NYC) is 5.25mSv/yr, from St. Peter Square (Vatican) 8mSv/yr and from eating a banana 0.1μSv/yr (Banana equivalent Dose).

• Anything below 0.25Sv (250mSv) has no observable effects.

HORMESIS

Hormesis is a biological process where cells react differently to small doses of otherwise harmful toxins.

• The stress of low dose exposure causes cell to “learn” (or evolve) to efficiently repair radiation damage.

• Possible effects of Hormesis :

• Increased cell growth/fertility

• Reduction in cancer incidence

CASUALTIES COMPARISON TO OTHER ENERGY SOURCES

Deaths from Accidents from Generating Electricity per Billion Mwe-h

Hydro

Coal

101

39

Gas

Nuclear

10

1*

*Includes Chernobyl

400-page study of 4,290 energy-related accidents:• 15,000 deaths related to Oil• 8,000 related to Coal• 5,000 related to Gas

Paul Scherrer Institute , Switzerland. (2001)

ECONOMICS

• It is not possible to accurately estimate costs on a global basis.

• 0.453592kg (1 Lb.) of Uranium 235 produces energy equivalent to 260,000,000 kilograms

• The capital cost for construction of a nuclear facility and manufacturing of fuel rods is quite high, but once running, the nuclear power plant produces more energy pre dollar compared to other conventional sources.

CONCLUSIONS

The major hurdle of Waste Disposal and Accidents can be overcome in the future through research and better engineering. We must keep an open mind and not be afraid of new technology.

"A day without sunlight is a day without radiation." - Proffessor Larry Foulke

(Department of Mechanical Engineering and Materials Science)(University of Pittsburgh)

Much fear and paranoid is observed among the people towards newer technologies like Nuclear Power, Genetically Modified Food, Artificial Intelligence, etc. This irrational attitude towards new technology is what Arthur Clarke called “The Frankenstein Complex”.

With the world’s energy needs growing, there is a dire need of energy that is constantly available.

Nuclear energy can provide such energy and fulfil most of our current energy needs.