Environmental Engineering FOURTH EDITION

Radioactive Waste 325

per 10 mSv (1 rem) per million liveborn offspring in the first generation affected, and

between 10 and 200 per 10 mSv per million liveborn at equilibrium. The spontaneous

rate of human genetic abnormality is presently estimated to be about 50,000 per million

liveborn in the first generation.

Health risk from ionizing radiation may be summarized as follows: there is a

documented risk from ionizing radiation, but it is apparently small, clearly uncertain,

and depends on a number of factors. These include:

the magnitude of the absorbed dose,

the type of ionizing radiation,

penetrating power of the radiation,

the sensitivity of the receiving cells and organs,

the rate at which the dose is delivered,

the proportion of the target organ or organism exposed, and

the possibility of a threshold below which there is no discernible damage.

The risk from various radionuclides affecting health in various ways is summarized
in an excellent reference, the Handbook of Health Physics and Radiological Health.
To protect public health, the environmental engineer must do what he or she can to
minimize unnecessary radioactive exposure of both the general public and those who
work with ionizing radiation, including handling and disposal of radioactive waste.

SOURCES OF RADIOACTIVE WASTE

The nuclear fuel cycle, radiopharmaceutical manufacture and use, biomedical research
and application, nuclear weapons manufacture, and a number of industrial uses gen-
erate radioactive waste. The behavior of the radionuclides in waste (as in any other
form) is determined by their physical and chemical properties; radionuclides may exist
as gases, liquids, or solids and may be soluble or insoluble in water or other solvents.
Until 1980, there was no classification of radioactive wastes. The U.S. Nuclear
Regulatory Commission (NRC) has classified radioactive wastes and other materials
into the following categories:

High-level waste (HLW). HLW includes spent nuclear fuel from commercial
nuclear reactors and the solid and liquid waste from reprocessing spent or irradiated
fuel.6 The NRC reserves the right to classify additional materials as HLW as necessary.
Uranium mining and mill'tailings. The pulverized rock and leachate fromuranium
mining and milling operations.
Transuranic waste (TRU). Radioactive waste that is not HLW but contains more
than 3700 Bq (100 nCi) per gram of elements heavier than uranium (the elements with
atomic number higher than 92). Most TRU waste in the United States is the product
of defense reprocessing and plutonium production.

6"Reprocessing" is the chemical treatment of irradiated fuel to recover plutonium and fissile uranium.