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APPENDIX H: Relative Hazard from Absorption of
Various Radioisotopes into the Body(a)
Hazard Classes for Various Radioisotopes
(b) |
Activity Ranges (c)
Low.........Medium.......High
Level.........Level.........Level |
Very High Hazard
A. Po-210, Ac-227, Th-228, Th-230, Np-237, Pu-238, Pu-239, Pu-240,
Pu-241, Pu-242, Cm-242, transuranium elements
*B. Pb-210, Ra-226, Ra-248, Am-241 |
Up to 100 uCi |
10 uCi to 10 mCi |
Over 1 mCi |
High hazard
A. Ca-45, Sr-90, I-129, Bi-210, Ra-224, U-233, Na-22, Sc-46, Co-60,
Ru-106, I-125, I-131, Cs-137, Ce-144 |
Up to 1 mCi |
100 uCi to 100 mCi |
Over 10 mCi |
Medium Hazard
A. C-14, Si-31, P-32, S-35, Cl-36, Sc-47, Fe-55, Sr-89, Y-90, Tl-204,
Rn-220, U-235
*B. Na-24, K-42, V-48, Cr-51, Mn-54, Mn-56, Fe-59,
Cu-64, Zn-65, Rb-86, Mo-99, Cd-109, Sn-113, Ba-140, Ir-190, Au-198,
Rn-222 |
Up to 10 mCi |
1 mCi to 1 Ci |
Over 100 mCi |
Low Hazard
A. H-3, F-18, Ni-59, Zn-69, Ge-71, U-238, Natural Th, Natural U,
Noble Gases
*B. Be-7 |
Up to 100 mCi |
10 mCi to 10 Ci |
Over 1 Ci |
*Emits gamma radiation in amounts significant for external exposure
(a) Adapted from NBS handbook #92, "Safe
Handling of Radioactive Materials", March 1964.
(b) The estimated relative hazards of radionuclides
are based on their physical properties and their maximum permissible
concentrations in air and water. The classifications above are for soluble
forms of the radionuclides and take into account the types of compounds
in which the nuclides are encountered, their specific activity, their
volatility, and the maximum permissible dose limits.
(c) The levels within the activity ranges
refer to the degree of protection required against internal deposition
for the quantity of radioisotope present. The ranges overlap at the
upper and the lower end of each level, indicating that there are no
sharp transitions between the quantity levels, group classifications,
or associated protection techniques. Modifying factors may be applied
to the quantities handled, according to the complexity of the handling
operation. The following table indicates how the quantities listed above
might be modified, according to the type of operation:
Use |
Modifying Factor |
Storage only |
x100 |
Simple wet operation |
x10 |
Normal chemical operation |
x1 |
Complex chemical operation with high spill risk |
x0.1 |
Simple dry operation |
x0.1 |
Dry, dusty operation |
x0.01 |
The amount of activity handled and the type of operation performed
will affect the protective techniques designed into a laboratory, such
as floor, wall, and work bench finishes, ventilation, fume hoods, and
other items including shielding and glove boxes.
As an example of how the table might be used, consider the following
situation:
Suppose the "Health Physicist"
has determined that, in order for an individual to receive an Authorization
Number for a quantity of I-125 that corresponds to a high level of activity,
an individual’s lab must possess a charcoal filtered glove box.
Since the table indicates that the use of more than 10 mCi of I-125
is considered a high level of activity, the "Health
Physicist"
would require a researcher planning to use 20 mCi of I-125 in normal
chemical operations to have a charcoal filtered glove box. If, on the
other hand, the researcher plans only to store the 20 mCi of I-125,
a glove box would not be required because the modifying factor of 100
for storage raises the activity equivalent to a high level to more than
1 Ci.
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