Nuclear hazards

• Nuclear energy can be both beneficial and harmful, depending on the way in which is it used.

• Approximately 17% of the electrical energy generated in the world comes from nuclear power plants.

• The radioactive wastes from nuclear energy have caused and continue to cause, serious environmental damage.

Processing of nuclear fuel:

• Uranium ore which contains 0.2% uranium by weight, is obtained by surface or underground mining.

• After it is mined the ore goes through milling process where it is crushed and treated with a solvent to concentrate the uranium and produces ‘yellow cake’, a material containing 70-90% uranium oxide.

Uranium contains only 0.7% of fissionable U-235,which is not high enough for most types of reactors.

The enrichment process increases the U-235 content from 0.7-3%.

Fuel fabrication then coverts the enriched material into a powder, which is compacted into pallets.

These pallets ate sealed in metal fuel rods about 4m into a powder, which is compacted into pellets.

As fission occurs, the concentration of U-235 atoms decreases. after about three year, a fuel rod must be replaced by new ones.

These spent rods are still very radioactive, containing about 1% U-235 and 1% plutonium.

An incident which changed people’s attitudes towards nuclear power plants was the Chernobyl Disaster that occurred in 1986.

Chernobyl is a small city in Ukraine, near the border with Belarus, north of Kiev. At 1.00 am April 25, 1986, a test to measure the amount of electricity that the still-spinning turbine would produce if stream were shut off was being conducted at the Chernobyl Nuclear Power Sation-4.

The amount of Stream being produced was reduced by lowering the rods into reactor.

The operator failed to program the computer to maintain power at 700mW and the output 30mW.

Rapidly increases the power and many of the control rods were withdrawn.

Xenon had accumulated on the fuel rods. Slowed the rate of power increases. To obtain more power, the operators the withdrew all the

control rods (safety violation).

At 1.00 am, the operators shut off emergency warning signals. In spite of the warning, the operators blocked the automatic reactor

shutdown and began the test. As the test continued the power output increases. The operator s activated the emergency system designed to put

the control rods back into the reactor and stop the fission but the core had already been deformed and the rods would not fit properly

In 4.5 seconds the energy level of the reactor increased 2000 times!

Explosion blew the 1000 metric tons concrete roof from the reactor In 1996, ten years after the accident, it was clear that one of the

long-term effects was the increased frequency of thyroid cancer in children.

There was also a spurt in genetic anomalies as doctors began observing clusters of children born displaying monoadactyly (fingers fused together to from a paddle) and polydactyly (more than 5 digits on the hands and feet).

What is Noise Pollution ?

• Noise is undesirable and unwanted sound.• Not all sound is noise.• Sound is measured in a unit called the

‘decibel’ (dB).• Noise emanating from factories, vehicle,

and playing of loudspeakers.

Effects of Noise Pollution On physical health:

• The temporary or permanent hearing loss often called a ‘temporary threshold shift’ (TTS).

• Permanent hearing loss usually called ‘noise-induced permanent threshold shift’ (NIPTS)

• Below a sound levels between 80 and 130 dB hearing loss does not occur at all.

• About 50% of the People exposed to 95 dB sound levels at work will develop NIPTS

• A sound level of 150 dB or more can physically rupture the human eardrum.

Effect of noise pollution on mental health:

• Noise can also cause emotional or psychological effects such as irritability, anxiety and stress.

• Lack of concentration and mental fatigue are significant health effects of noise.

Noise-Control techniques:There are four fundamental ways in which noise can be

controlled:• Reduce noise at the source• Block path of noise• Increase the path-length• Protect the recipient

The best control method is reduce noise at the source