Environmental Engineering Reference
In-Depth Information
• The equipment inside the core of the reactor is handled remotely. Employees are kept behind a physical
shield.
• The time that an employee is in areas where exposure might be an issue is limited.
• The individual dose exposure is monitored, and limits are very strict.
Radiation and Human Health
The potential exists for a large-scale disaster at nuclear power plants, like that at Chernobyl. High, short-term
exposure to radiation from a nuclear power plant accident leads to a very painful death. This was the case in
Chernobyl, where several employees and many technicians brought in to control the accident were exposed to
high levels of radiation and most of them died as a result. Most recently, the nuclear accident in Japan has not
yielded major health problems from immediate radiation exposure, but there may be long-term effects that are
not yet seen.
Scientists, policy makers, and the public also debate the safety of working in conditions of low-level radiation
in nuclear power plants over a long period of time. Employees at nuclear power plants (like employees who
may be exposed to radioactive material on the job, such as X-ray technicians, dentists, or scientists) wear dose
exposure badges that monitor and display radiation doses received by the employees. These dose exposures are
logged and there are limits on the dose that a person is allowed to receive in a year and in a lifetime. Reaching
dose limits is more likely to occur working near radioactive material outside a nuclear power plant than it is
working inside the plant itself.
Understanding Half-Life
If an isotope of an element is unstable, it experiences radioactive decay, or the process of losing energy from an
unstable nucleus. The isotope's half-life is the amount of time that it takes for half of the isotope to decay. To
be considered safe, a radioactive isotope must complete ten half-lives. Using an isotope's half-life, questions
can be answered about quantities that remain after a given period of time, and also questions of how much time
it takes to decay certain amounts of an isotope.
Calculating Using Half-Life Information
On the AP Environmental Science exam, there may be questions about half-life in both the multiple choice and
free response sections.
EXAMPLES:
1. How long must an isotope be stored to be considered safe for disposal?
This type of question requires simple calculation. If given the isotope's half-life (in years), multiply it by 10 to
find the number of years (or other unit) when the material will be considered safe. Below is a table of common
isotopes, their half-lives, and the number of years it will take to be considered safe.
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