RADIOACTIVE MATERIALS AND THEIR APPLICATIONS

RADIOACTIVE ELEMENTS – HALF LIFE

The radioactive elements decay, i.e., lose their activity with time. The decay is measured in half-life, i.e., the time required for the radioactivity to reduce to half. The half-life of some of the elements are shown below:

Element	Half life
Uranium-235	Billions of years
Carbon-14	5730 years
Strontium-90	28 years (beta)
Ce-137	30.2 years
Co-60	5.27 years

As the half-life of these and other radioactive elements are very long, contaminated areas, e.g., due to detonation of a dirty bomb, need to be cleaned or abandoned.
 

SOME PEACEFUL USES OF NUCLEAR ENERGY AND RADIOACTIVE ISOTOPES

There are many beneficial uses of ionizing radiation in medicine for diagnosis and treatment of many diseases. About 200 million x-rays given each year in the USA to diagnose and evaluate diseases or accidents. Because of the ability of radiation to kill cells, it has also been widely used in cancer therapy. Radioisotopes have found a large number of applications. They include:

• Generate electricity
• Power for desalination plants
• Power for spacecrafts
• Power for ocean vessels
• Wear testing (auto-engines, tires)
• Thickness gauges
• Sterilization of medical supplies
• Radioimmunoassay
• Medical diagnosis
• Synthesis of new elements
• Chemical analysis (by neutron activation)
• Sterilization of insects
• Preservation of food
• Smoke detectors
• Bomb detectors at airports
• Manufacture of semiconductors
• Manufacture of radioisotopes
• Radio-dating

A wide variety of radiation sources and radioactive elements are used for the above applications. For example more than 20 radioisotopes are used for medical applications.
 

SOME RADIOISOTOPES AND THEIR MEDICAL APPLICATIONS

Nuclear energy is used in a variety of ways in our lives. Some of the radioisotopes and their applications in medical field are listed below:

 

ISOTOPE	HALF-LIFE	USES
Carbon-11	20.3m	Brain scans
Chromium-51	27.8d	Blood Volume determination
Cobalt-57	270d	Measuring vitamin B12 uptake
Cobalt-60	5.26y	Radiation cancer therapy
Gadolinium-153	242d	Determining bone density
Gallium-67	78.1	Scan for lung tumors
Iodine-131	8.07d	Thyroid therapy
Iridium-192	74d	Breast cancer therapy
Iron-59	45d	Detection of anemia
Phosphorous-32	14.3d	Detection of skin cancer or eye tumors
Plutonium-238	86y	Power for pacemakers
Radium-226	1600y	Radiation therapy for cancer
Slenium-75	120d	Pancreas scans
Sodium-24	15.0h	Locating obstructions in blood flow
Technetium-99	6.0h	Imaging of brain, liver, none marrow, kidney, lung or heart
Thallium-201	73h	Detecting heart problems with treadmill stress test
Tritium	12.3y	Determining total body water
Xenon-133	5.27d	Lung imaging

Y = year, d = days, h = hours, and m = minutes

Other radioactive materials are available because we use them to destroy bacteria from food, sterilize pharmaceutical & medical products, kill cancer cells, inspecting welds/joints and explore for oil.  About 21,000 licensed organizations in the U.S. use radiation sources.
 

CLASSIFICATION OF RADIONUCLIDES ACCORDING TO RELATIVE HAZARD POTENTIAL

Radioactive materials are hazardous as they emit ionizing radiation. Hazardous radioactive elements are listed below:

VERY HIGH HAZARD POTENTIAL (HAZARD CLASS I)

Sr-90, Pb-210, Po-210, At-211, Ra-226, Ac-227, Th-228, Th-229, Th-230, Th-231, U-233, Pu-238, Pu-239, Am-241, Cm-242, Cf-252, other transuranic nuclides

HIGH HAZARD POTENTIAL (HAZARD CLASS II)

Ca-47, Fe-59, Co-60, Sr-85, Sr-89, Y-91, Ru-106, Cd-109, Cd-115, I-125, I-131, Ba-140, Ce-144, Sm-151, Eu-152, Eu-154, Tm-170, Hg-203, Bi-207, Th-232, natural thorium, natural uranium.

MODERATE HAZARD POTENTIAL (HAZARD CLASS III)

Na-22, Na-24, P-32, P-33, S-35, Cl-36, K-42, Ca-45, Sc-46, Sc-47, Sc-48, V-48, Mn-56, Fe-55, Co-57, Co-58, Ni-59, Ni-63, Cu-64, Cu-67, Zn-65, Ga-67, Ga-68, Ga-72, As-74, As-76, Br-82, Kr-85, Rb-84, Rb-86, Y-90, Zr-95, Nb-95, Mo-99, Tc-99, Rh-105, Pd-103, Ag-105, Ag-111, Sn-113, Te-127, Te-129, I-132, Xe-133, Cs-137, La-140, Pr-143, Pm-147, Ho-166, Lu-177, Ta-182, W-181, Re-183, Ir-190, Ir-192, Pt-191, Pt-193, Au-196, Au-198, Au-199, Tl-200, Tl-202, Tl-204, Pb-203, Hg-197

LOW HAZARD POTENTIAL (HAZARD CLASS IV)

H-3, Be-7, C-14, F-18, Cr-51, Ge-68, Ge-71, Sr-87m, Tc-99m, In-111, Tl-201