Sec. 12.2- Nuclear Radiation: Harmful or Helpful?

Background Radiation Believe it or not, the general public (us) is exposed to radiation every year The amount of radiation a person is exposed to is called a “dose” The general public is approved to be exposed to a dosage of 172.5- 402.5 mR every year

The radiation the public is exposed to is called “background radiation” and is caused by natural and artificial sources of radioactive isotopes Natural: Rocks, ground (Radon), food, cosmic rays (The Sun) Artificial: CT Scans, Radiation Therapy, X-rays, Chest Scans, etc

Bodily Effects/Uses Acute effects of high dosage exposure: Radiation poisoning Effects of long term (or high dosage) exposure: Cancer Cancer Treatment: Cancer therapy Diagnosis: CT Scans, Stress Tests

Effects of Radiation Poisoning If a person is exposed to a high dosage of radiation at one time, acute effects of radiation poisoning are observed Large doses result in: Gastrointestinal problems (nausea, vomiting, etc) Difficulty fighting infections (due to depletion of white blood cells) Low platelet count- Can cause spontaneous internal bleeding Death within weeks of exposure

Extremely Large doses can also result in: Hair loss Burned Skin Neurological damage- headaches, dizziness, seizures Death within hours of exposure

Long term effects of radiation exposure (small dose over long period of time, or leftover effects from high dosage in short period of time): Skin mutations Tumors Cancer Infections/General Illness

Nuclear Radiation Causes Cancer Nuclear radiation of all types can cause cancer in the body What types of radiation did we talk about last section?

Cancer- results when DNA or enzymes that carry out DNA “orders” (replication, repair, etc) are damaged in such a way that they can no longer perform their duties correctly This can result in cells that continue to multiply and grow without regulation (tumors)

The level of damage to tissue is determined by: Type of radiation Amount of radiation absorbed (dose) Type of tissue exposed

Alpha Particles- very heavy and strongly charged compared to other types of radiation What was mass number? Charge? When an alpha particle hits any type of matter, it will pull away and absorb electrons from the matter and turn into regular Helium atoms These Helium atoms then move around in the atmosphere

When alpha particles collide with matter, they can also bump atoms out of molecules If an atom is bumped out of a strand of DNA or one of the enzymes it regulates, it could lead to cancer

Alpha particles are not able to penetrate through much matter- meaning they are easily blocked, which makes them “safer” Usually, the layer of dead skin we have protects us from alpha particles However, if the alpha particles are inhaled or ingested, they are able to damage exposed tissue

Beta particles- what are they? Due to small size/mass, and high speeds, beta particles are able to penetrate more human tissue than alpha particles, which makes them more dangerous Beta particles can make their way through about 1cm of our body

Gamma radiation can pass through entire human bodies, as well as buildings and cars When gamma rays come into contact with molecules, they will rip electrons away and cause the molecule to become charged- ionized Due to this “ionizing matter” process, gamma radiation is often called “ionizing radiation”

Once a molecule becomes ionized, it will fall apart and be unable to function correctly in our body Lead or thick concrete can block gamma radiation

Radioactive Elements Replace Others in the Body Some radioactive isotopes are able to replace other elements used in the body The molecules that use these elements are then unable to operate properly

Plutonium- plutonium (in an oxidized state) acts very similarly to iron ions in the body If oxidized plutonium is ingested/inhaled, it will kick out and replace the iron atoms in our body- this can the cause radiation poisoning from the inside out and/or cancer

Strontium-90- released in nuclear fallout after a nuclear bomb is detonated, and falls to ground in very fine dust Strontium-90 acts very similarly to the calcium found in our bones

If the strontium works its way through the environment and is incorporated into a person’s body, it will kick out and replace the calcium found in our bones Once strontium-90 is in bone, it will emit radiation from inside the body

Radiation- able to cause cancer Radiation in Medicine Radiation- able to cause cancer Radiation- can also be used to treat/get rid of cancer Radiation therapy- narrowly focused radiation used to destroy cancer cells Drawbacks- can also kill healthy cells, which causes patients to become ill and prone to infection

New radiation therapy techniques being developed to better target cancerous cells while minimizing damage to healthy cells Boron-10 (not normally radioactive) absorbed into cancerous tumor Beam of neutrons shot at tumor- the Boron-10 in tumor is hit with neutrons and releases an alpha particle

These Alpha particles collide with cancerous cells in tumor and destroy them without radiating out to healthy cells

Imaging with Radiation Radioactive isotopes can be injected into the body and absorbed by specific parts of the body a doctor wants to look at Isotopes used: short half-lives, emit gamma radiation Need to use gamma in order to see into the body- only radiation that could be detected from outside your body

These imaging processes can be used to monitor how the body metabolizes or moves fluids throughout certain spaces Iodine-131 used to monitor how the thyroid is operating Sodium-24 used to monitor blood flow- stress tests in heart Strontium-87 used to monitor bone growth

Using radioactive materials for imaging is associated with health risks Precautions are taken to minimize these risks and to ensure the benefits to the procedure outweigh the rewards

Radioactive isotopes are extremely useful for dating things Radioactive Dating Radioactive isotopes are extremely useful for dating things Any idea why? Carbon-14 is a radioactive isotope of carbon found in all organic substance (on Earth) and has a half-life of 5,730 years

Carbon-14 is actually produced in our atmosphere Nitrogen is hit with neutrons coming from the sun, which causes it to turn into Carbon-14

Carbon-14 found in plants, animals, you and me, along with carbon-12 Carbon-12- not radioactive, will not decay Living organisms maintain a constant ratio of carbon-14 to carbon-12 Once an organism dies, the carbon-14 found in its body will begin to decay

Since the amount of carbon-14 is decreasing in the dead organism, the ratio of carbon-14 to carbon-12 will change We can use the amount this ratio changes to find how old a dead organism is.

For objects that are extremely old, carbon-14 becomes difficult to use- Uranium-238 is used instead (half-life of 4.5x109 years) For fairly new materials, Hydrogen-3 (half- life of 12.3 years) is used

Nuclear Energy Nuclear reactions are accompanied by the release of extremely large amounts of energy We have an interest in harnessing this energy to generate power (electricity) No carbon emissions- relatively clean energy

Two types of nuclear reactions release energy: Fission Fusion

Fission is used in nuclear power plants to generate electricity Fission occurs when a large, heavy nucleus breaks down into multiple, smaller nuclei Fission can occur: Spontaneously By bombarding a heavy nucleus with neutrons Fission is used in nuclear power plants to generate electricity

Power plants use heavy elements like uranium- 235, uranium-233, and plutonium-239 Take the radioactive nucleus and shoot neutrons at it If a neutron sticks, it causes the nucleus to split into smaller nuclei When this occurs, the nucleus that splits typically also releases neutrons

These ejected neutrons then collide with more heavy nuclei and cause them to split This pattern repeats in a chain-reaction and allows for massive amounts of energy to be released

Drawbacks to fission: Generates nuclear waste This waste must be isolated and properly stored until it is no longer dangerous Problems with finding appropriate places to store waste safely

Fusion occurs when 2 small nuclei combine into one larger nucleus Our Sun performs hydrogen fusion- smashes 2 hydrogen atoms together at high speeds to produce a helium atom and releases extremely large amount of energy

Fusion is much more difficult to achieve than fission- the atoms must be hurled at each other at incredibly high speeds/energies Fusion has been achieved in weapons, but not for civil uses (power plants)

Fusion is being heavily pursued because it does not generate any harmful nuclear waste and also provides much more energy than fission does