LAB 14 RADIOACTIVITY

Physics Lab 14, Wednesday June 30, 2010 Name _____________
Dr Dave Menke, Instructor

I Title: Radioactivity
II Purpose: In this laboratory, students will study radioactive decay. One sample will emit alpha particles. Another, beta particles. Finally, gamma rays will blast from the third sample.
The relationship for radioactive decay is: A = Ao e-t/t
III Equipment
Radiation Detector
The radiation detector is a model Monitor 4/4EC, made by SE International, Inc. Summertown, Tennessee. The units listed are: CPM and mR/hr.
CPM is “Counts per minute,” and it is a measure of radioactive decay. It is the number of atoms within a given radioactive sample that are detected to have decayed in one minute of time.
There is also a term, DPM, which is decays per second. We will use this later.
Seeing “mfR/hr” tells us the number of Roentgens. The Roentgen is a unit of measurement for ionizing radiation, usually for x-rays and g-rays. The unit of 1.0 R is approximately 2 billion units. Also, 1.0 R = 2.58×10−4 C/kg (from 1 esu ≈ 3.33564 × 10−10 C and the standard atmosphere air density of ~1.293 kg/m³)
Also noted on the equipment is the Curie, Ci. The curie is a unit of radioactivity defined as 3.7×1010 decays per second (DPS)
A commonly-used measure of radioactivity is the micro-curie, mCi. In this case, 1.0 μCi = 3.7×104 disintegrations per second = 2.22×106 disintegrations per minute
The typical human body contains roughly 0.1 μCi of naturally occurring something.
Set of 3 samples of radioactive substances:
Sample 1: Polonium-210, emits an Alpha particle, a, at the rate of 0.1 mCi, with a half-life of t = 138.4 days
Polonium-210 decays into two “lighter” elements. One is the Helium nucleus, 2He4. This nucleus is often called an “Alpha” particle, or just using the Greek letter, a. A single gram of 210Po can generate 140 watts of power.
Sample 2: Cobalt-60, emits a Gamma Ray, g, at the rate of 0.1 mCi, and has a half-life of t = 5.27 years.
Due to its short half-life, it is not found in nature. It is created artificially by being bombarded by neutrons, and as a result, Cobalt-60 gives off a beta particle, b-, to become another element which then emits two gamma rays, with energies of 1.17 MeV and 1.33 MeV. Cobalt-60 nuclear bombs leave behind many insidious radioactive isotopes, thus, it is called a “dirty” bomb.
Sample 3: Strontium-90, emits beta particles at the rate of 0.1 mCi, and with a half-life of t = 28.8 years
Strontium-90 is a radioactive isotope which decays to another element while giving off a beta particle, and this new element, in turn, decays quickly (with a t = 64 hours) to become yet another element, giving off more beta particles.
Strontium-90 is a by-product of nuclear fission as fallout from testing nuclear bombs. Along with Cesium-134 and Cesium-137, Strontium-90 were the most important radioactive fallout of the Chernobyl Disaster.
Accidental mixing of radioactive sources containing strontium with metal scrap can result in production of radioactive steel. Discarded radioisotope thermoelectric generators are a major source of 90Sr contamination in the area of the former Soviet Union.
IV Procedure
Turn on Radiation Detector
Sing “Just Dance” by Lady Gaga
Adjust the Detector to get the correct reading of 1x or 10x or 100x.
Use the x-ray glasses to observe your lab partner, who will appear nude
Repeat with Sample 2
Repeat with Sample 3
Determine and write the Chemical Formula for the decay of Sample 1.
Repeat for Sample 2
And for Sample 3
Put away your toys

V Data, Observations, and Calculations go here


VI Results

VII Error

VIII Quests
If you started with 100 grams of Polonium-210 today, how many children would you have in 5 years?

If you started with 100 grams of Cobalt-60 today, how much would remain after 5 years?

If you started with 100 grams of Strontium-90 today, how much would remain after 5 years?

Describe the Chernobyl Disaster