Encyclopedia of Environmental Science and Engineering, Volume I and II

628 MANAGEMENT OF RADIOACTIVE WASTES

better information on the probable consequences of a major

nuclear accident which leads to high radiation exposure.

In other words we can, within rather broad limits, estimate

the risks.

The situation is different in most other industries. The

consequences of acute doses of cyanide, lead, fluoride or

carbon tetrachloride are well known, and there is some evi-

dence for the effects from low doses received over a lifetime,

but who knows what effect to expect in humans from benz-

pyrene or nitrous oxide emitted from smoke stacks or from

the low levels of polychlorodiphenyls and mercury com-

pounds that are liberated into the environment? They affect

every age group in the population and are a potential life-

long hazard. But nothing is known about the probability that

they will eventually do harm, and it is difficult to see how

such knowledge could be obtained in a human population.

Every human activity is associated with some risk,

however small. Normally we do not solemnly calculate the

risk, weigh it against the benefit we expect to obtain, and

then decide for or against the activity. Yet to decide to do

something—such as driving a car, getting up in the morn-

ing, or going mountain climbing—must involve some sort of

conscious or unconscious weighing of risk against benefit.

In deciding upon a particular waste management system,

or in deciding to license a particular kind of nuclear power

station, a much more deliberate weighing of cost vs. benefit

must be undertaken. There is, however, a fundamental dif-

ficulty which up to now has made it impossible to express

such a judgment in numbers. It is characteristic of a ratio

that the numerator and the denominator must be in the same

units. It should be possible to express most of the benefits of

nuclear power, for example, in dollars, but if we regard part

of the cost of nuclear power as an increase in the probability

that people will develop cancer or that they will experience a

shortened lifetime, how can that be expressed in dollars?

One benefit of nuclear power is the difference between

death and injury among uranium miners and processors and

the corresponding figure for equivalent energy production

by the coal mining industry. This, again, cannot be expressed

in dollars. To work out a true COST/BENEFIT ratio is thus

little better than a dream, and the people responsible for

approving a waste management system or a new power sta-

tion are therefore faced in the last analysis with a value judg-

ment, which is at least to some extent subjective. It is not

a scientific decision. In the broadest sense, the decision is

political.

Controls

The responsibility for making decisions on matters related to

“dealing in”—i.e. having anything to do with—radioactive

materials, machines capable of producing electromagnetic

radiation (expect for medical purposes) and certain scheduled

materials such as heavy water, usually rests with a national

atomic energy authority. Typically, regulations are issued by

the authority that have the force of law. Assistance is given

to the authority in assessing hazards of reactors and other

installations—including waste management systems—by

an independent advisory committee which can call on the ser-

vices of an expert staff.

In most countries regulations lay down the maximum per-

missible exposure to radiation for workers in nuclear industry

and also for the general population. Maximum permissible

doses (MPDs) have been recommended by the International

Commission on Radiological Protection (ICRP), which have

received worldwide acceptance as the fundamental basis for

national regulations. The ICRP has derived from the MPDs

a list of maximum permissible concentrations (MPCs) in air

and water on the basis that if workers were to breathe air, or

drink water, at the MPC for any particular radionuclide over

a lifetime they would not suffer any unacceptable harm.

“Unacceptable” means “detectable”, in the sense that it

could reasonably be regarded as caused by the radiation. The

ICRP has also laid down rules for calculating the MPC for

mixtures of more than one radionuclide.

The MPDs are constantly under review by the ICRP,

which consists of people who have devoted their profes-

sional lives to assessment of radiation hazards. They drawn

upon the work of large numbers of scientists throughout the

world, many of whom are actively engaged in research on

somatic and genetic effects of radiation. Changes have been

made from time to time in details of the ICRP recommenda-

tions but it is remarkable that in such a rapidly developing

field the necessary changes have been so few.

The ICRP has consistently emphasized that the MPD

and its associated MPs are maximum permissible figures.

The Commission has made another recommendation equal

in force and status to those on maximum permissible doses.

This states that exposure to radiation must always be held

down to the lowest PRACTICABLE dose. The world “prac-

ticable” was carefully chosen, after considerable debate. If

“possible” had been used it could have been claimed that a

single contaminated rat must be buried in a platinum box. It

is our mission to see that all practicable steps are taken to

protect mankind from exposure to radiation, and we can do

that very effectively.

SOURCES OF WASTES

Uranium Mining and Milling

Apart from the normal hazards associated with hard-rock

mining, the workers in uranium mines are exposed to radon

and the decay products which arise from the radium content of

the ore. These hazards can be controlled by sealing old work-

ings and general “good house-keeping”, but more particularly

by installation of an efficient ventilation system and, where

necessary, the use of respirators. The ventilation air contains

radioactive material and dust, some of which can be removed if

necessary by filtration, but the radon remains. The large volume

of air used for mine ventilation is ejected at high velocity from

a stack, which ensures adequate dilution into the atmosphere.

The end products of the mill are uranium oxide and “tail-

ings”. The tailings, together with mine drainage water, contain

most of the radium originally present in the ore. Radium is

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