Encyclopedia of Environmental Science and Engineering, Volume I and II

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MANAGEMENT OF RADIOACTIVE WASTES

RADIOACTIVE WASTE

Radioactive waste may be defined as solid, liquid, or gaseous

material of negligible economic value containing radionu-

clides in excess of threshold quantities. High level wastes

(HLW) are produced in the first cycle of reprocessing spent

nuclear material and are strongly radioactive. Intermediate level

wastes (ILW) can be divided into short lived, with half lives of

twenty years or less, and long lived, in which the half lives

of some constituents may be thousands of years. Low level

wastes (LLW) contain less than 4 GBq/ton of alpha emitters

and less than 12 GBq/ton of beta and gamma emitters. Very

low level waste (VLLW) contains activity concentrations

less than 0.4 MBq/ton.

ACTIVITY AND EXPOSURE

The Becquerel (Bq) is the activity of one radionuclide having

one spontaneous disintegration per second. One Curie (Ci)

is defined as 3.7 
 10 10 disintegrations per second. The

Becquerel is the more commonly used unit. The unit of ion-

izing radiation which corresponds to energy absorption of

100 ergs per gram is the rad (roentgen-absorption-dose).

The newer unit is the Gray (Gy), which is equal to 100 rads.

The amount of radiation which produces energy dissipation

in the human body equivalent to one roentgen of X-rays is

the rem (roentgen-equivalent-man). One Sievert is equal to

100 rems and is the commonly accepted unit.

Philosophy

The group of people engaged in management of radioac-

tive wastes has evolved from a small body of operators who,

originally with little or no expert knowledge, were engaged

in day-to-day solution of unpleasant problems. They now

form a recognized profession, extending from whole-time

research scientists to field workers who in some countries

are conducting a profit-making industry.

The members of the profession came mainly from Health

Physics and brought with them the caution and “conserva-

tive” attitude to radiation hazards characteristic of Health

Physicists. They regard their mission as being to ensure that

members of the public, as well as workers in the field of

nuclear energy, will not be harmed by the radioactive mate-

rial for which they are responsible. With their Health Physics

background this sometimes leads to an attitude which indus-

try regards as overrestrictive, although recent controversies

have tended to cast them ironically in the role of particularly

dangerous polluters of the environment.

It is clear that any human activity that involves conversion

of something into something different must produce waste.

Conversion of energy from one from to another is no excep-

tion. It is sometimes possible for an industry to recycle its

waste products and to convert part of them to a useful form,

but there is always some minimal residue which cannot be

retained within the system. This must find some place within

the environment. Usually the cheapest procedure is to dis-

charge it in some way that will ensure a sufficient dilution

to make it innocuous. If this is impracticable for technical or

political reasons it must be confined, but usually the more

effective the confinement, the higher the cost. To say that a

process must be conducted with now waste is equivalent to

saying that the process may not be conducted at all, and to

demand a certain level of confinement or restriction of wastes

implies an acceptance of the cost of the waste management

system as a necessary part of the cost of the process.

Discharge of potentially noxious materials into the envi-

ronment involves some risk, which may or may not be mea-

surable. Within very broad limits research in nuclear hazards

enables us to forecast the effects of exposure of large groups

of people, for extended periods, to low doses of radiation.

We can also estimate, with less accuracy, the probability that

an individual will suffer some harm from such exposure, and

we can say with much greater confidence what will happen

if an individual is exposed to larger doses—say 50 rem and

upwards—in a single dose. The nuclear industry, then, can

provide some information on the probable consequences of

environmental contamination extended over a lifetime, and

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