Encyclopedia of Environmental Science and Engineering, Volume I and II

MANAGEMENT OF RADIOACTIVE WASTES 631

As long ago as 1959 fifty million gallons of High Level

wastes were stored in stainless steel tanks at Hanford (USA)

alone. The radionuclides in solution generate so much

decay heat that many of the tanks boil, making the provi-

sion of elaborate off-gas cleaning systems necessary. Some

high level waste tanks have ruptured, but since they are

constructed on a cup-and-saucer principle, with adequate

monitoring for spills, and spare tankage is kept available, no

unexpected contamination problems have arisen.

Gases from the dissolvers and storage tanks contain tritium,

bromides, iodines, xenon, krypton and smaller amounts of

less volatile elements such as ruthenium and cesium. After

storage for decay, scrubbing and filtration, off-gases can be

liberated from a tall stack. As mentioned in the section on

reactors, proliferation of fuel processing plants in the future

might conceivably lead to local or even eventual world-wide

atmospheric contamination if improved containment is not

provided in time at spent fuel processing sites.

Solid waste may include glasses or ceramics, used as a

means for fixing the activity in high-level liquid wastes, and

bitumen or concrete blocks containing less active material.

Products of waste processing such as sludges, evaporator

bottoms, incinerator ash, absorbers, filters and scrap fuel

cladding are usually in the medium level category. Worn and

failed equipment such as pipes, tanks and valves, unservice-

able protective clothing, cleanup material and even whole

buildings may have a variety of levels of contamination, by

numerous different radionuclides, which defies quantitative

assessment. This is not a serious difficulty, except for admin-

istrative and recording purposes when quantitative reports

have to be made, because most of these wastes have to be

contained in some way and none of them are dumped into

the environment.

The most difficult problem for the fuel processing industry

is not high or medium level waste, offgases or heterogeneous

contaminated scrap. The real problem is very low level liquid

waste, because it arises in such enormous volume. Coming

from numerous different sources—e.g. cooling and final wash

waters, laundry and decontamination center effluents, floor

drainage from cleanup operations, personnel shower drainage

and effluent from the final stages of liquid waste purification

plants—low level and “essentially uncontaminated but sus-

pect” waste adds up to billions of gallons per year. Although

some countries (Sweden and Japan, for example) evaporate

such effluents on a large scale they are usually discharged by

some route into the environment.

Research and Development

A wide variety of wastes arises in such research establishments

as Brookhaven (USA), Chalk River (Canada) or Harwell (UK)

and the include many of the types mentioned under the head-

ing of fuel processing. In addition the research reactors

usually produce very large quantities of radioisotopes which

may be processed onsite. However, the quantities involved are

very much lower, especially in the high level category, and

elaborate waste processing systems are seldom needed even at

large research centers unless they are situated in built-up areas

or immediately over important aquifers.

Hospitals and Biological Laboratories

Organic material and excreta makes wastes from these insti-

tutions difficult to handle. The radioactive content is usu-

ally small, and limited to a restricted list of radionuclides.

Those used as sealed sources seldom appear as waste, and

the rest are practically confined to^131 I,^32 P,^59 Fe,^51 Cr,^35 S and

(^24) Na. Other nuclides may be used in small amounts for spe-
cial purposes such as specific location in certain organs. The
nature and amount of radionuclides used in these institutions
are such that a high proportion of the waste can be handled
safely by the municipal sewage and garbage systems.
SPENT
FUEL
STACK
PURIFICATION
OFF-GASES
NITRIC ACID
DISSOLVER
HIGH LEVEL WASTE MEDIUM LEVEL WASTE LOW LEVEL WASTE
SEPARATION
OF
PLUTONIUM
AND
URANIUM
WASH WITH
ACID
ORGANIC
LAYER
EXTRACTS
Pu plus U
AQUEOUS
LAYER
ORGANIC
SOLVENT
FIGURE 2 Schematic diagram of fuel processing plant. Showing origins of main waste streams. Reactor fuel contains over
99.95% of the total radionuclides eventually disposed of as waste.
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