(1) Ninety five percent of the total radioactivity in the process of nuclear ele
ID: 116253 • Letter: #
Question
(1) Ninety five percent of the total radioactivity in the process of nuclear electricity generation is due to high level waste produced by the nuclear reactor. High level waste is highly radioactive and hot, so requires cooling and shielding; it has both long-lived and short-lived components. All radioisotopes contained in the waste have a half-life. Half-life is the time it takes for any radioactive isotope to lose half of its radioactivity. During this time half of the radioactive isotope turns into non-radioactive and stable isotopes. Certain radioactive elements (such as plutonium-239) in nuclear reactor waste will remain hazardous to humans and other creatures for hundreds of thousands of years. Others remain hazardous for millions of years. Thus, these wastes must be shielded for centuries and isolated.
One of the waste byproducts of a nuclear reactor using uranium-235 is strontium-90 with half-life of about 28 years. If we have 100 pounds of this radioactive waste:
(a) How long is five half-life?
(b) How much of radioactive strontium is left after five half-life?
(2) Regarding fission nuclear reactors:
(a) List at least three safety and health risks associated with such reactors.
(b) Offer at least two methods of reducing such risks in such reactors.
Explanation / Answer
1) Half-life of about 28 years. If we have 100 pounds of this radioactive waste:
(a) How long is five half-life?
= 5* 28 years =140 years
b) How much of radioactive strontium is left after five half-life?
=100*(1/2)^5 = 100/32 = 3.125 pounds
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