1. B: Radioactive Decay

2. There are about 350 isotopes of 90 elements found in our solar system. Of these, about 70 are radioactive. Naturally occurring radioisotopes (elements with atomic nos. of 83 or less) emit background radiation in relatively small amounts.

3. B.2 Natural Radioactive Decay Alpha particles have two protons and two neutrons. They are massive— 8000 x heavier than beta particles, but can only cause damage over very short distances. They are easily blocked, even by skin.

4. Radium-226 loses two protons, so it’s atomic number drops from 88 to 86. Atoms of 2 elements, He and Rn can be formed.

5. Beta particles are fast- moving negatively charged particles released during radioactive decay. During beta decay, a neutron changes into a proton and an electron. The proton remains in the nucleus but the electron (beta particle) is ejected at high speed. A third particle called an antineutrino is also released.

6. A beta particle has a mass number of 0 and an atomic number (nuclear charge) of -1. The overall result of beta emission is that a neutron is converted into a proton. Notice that the atomic number increases and Radium turns into Actinium.

7. v Gamma emissions do not change the mass or charge balance in a nuclear equation because the rays have no mass or charge.

8. Of the three emissions: alpha, beta and gamma, alpha radiation is the most damaging at short range but easy to protect against. Beta and gamma do less damage over a long range but it’s harder to protect against them.

9. New isotopes created from radioactive decay can also be radioactive and undergo further decay. Eventually, the result will be a stable atom. In this case Uranium decays into stable lead—it just takes 14 steps to do so.

10. B.3 Ionizing Radiation—How Much is Safe? Radiation can be measured with a Geiger counter in counts per minute (cpm). It can also be measured in rems when evaluating its effect on humans. Rems stand for Roentgen equivalent man and measures the ability of radiation to cause ionization in human tissue. A third way to measure radiation levels is in Becquerels.

11. 1986 Nuclear Meltdown at Chernobyl The accident released 1.1 x 10 19 Becquerels of radioactive material (one Becquerel is one molecule undergoing radioactive decay per second). The accident released 1.1 x 10 19 Becquerels of radioactive material (one Becquerel is one molecule undergoing radioactive decay per second). About 116,000 people were evacuated from the area around the plant, and 134 were hospitalized for acute radiation sickness. The 31 deaths were mainly among fire fighters who fought the first fire without radiation protection. About 116,000 people were evacuated from the area around the plant, and 134 were hospitalized for acute radiation sickness. The 31 deaths were mainly among fire fighters who fought the first fire without radiation protection. The major health hazards came from iodine 131 (I-131), which accumulates in the thyroid gland, and cesium 137 (Cs-137), which gathers in bone. The accident released 1,760 * 10 15 Becquerels of I-131 and 85 * 10 15 Becquerels of Cs-137. The major health hazards came from iodine 131 (I-131), which accumulates in the thyroid gland, and cesium 137 (Cs-137), which gathers in bone. The accident released 1,760 * 10 15 Becquerels of I-131 and 85 * 10 15 Becquerels of Cs-137.

12. Radiation Damage Now and Later Ionizing radiation tears molecules apart by breaking chemical bonds. Damage to proteins and nucleic acids are particularly detrimental because of their importance in body functions and structures.

13. Nucleic acids in DNA can be damaged in two ways: Mutations result in the synthesis of altered proteins. Can result in killing the cell or if it’s a sperm or ovum, cause birth defects. If the exposure is high enough and proteins cannot be synthesized, death follows.

14. Sources of Radiation Cosmic rays Radioisotopes from rocks and soils Radioisotopes from the atmosphere Fallout from nuclear weapons testing Increased exposure to cosmic rays through air travel. Radioisotopes released from nuclear power technologies.

15. Radioisotopes in the Environment On average, people in the U.S. receive above 360 mrem per year, of which 82% is naturally occurring. Radiation standard by fed. Gov. is 500 mrem per year. Maximum exposure recommended by federal government is 5000 mrem (.5 rem) per year.

16. Radioisotopes in the Human Body ThyroidI-131 LungsRn-222U-238Pt-239Kr-85 MusclesK-40Cs-137 LiverCo-60 BonesRa-226Sr-90P-32C-14

17. Radon in Homes Radon is a decay product of uranium and is always present in the atmosphere. Some radon dissolves into groundwater from the soil. Inhaled radon gas goes through radioactive decay causing health problems such as lung cancer.