Encyclopedia of Environmental Science and Engineering, Volume I and II

640 MANAGEMENT OF RADIOACTIVE WASTES

the concrete are water-sealed and the base of the work is laid

well above the maximum height of the water table. Since the

facility will be used for reception of quite high-level waste the

approaches must be suitable for trucks and mobile cranes.

Concrete trenches are unsuitable for reception of small,

intensely radioactive objects such as spent teletherapy

sources because of the inconvenience of scattered radiation

fields. They can be accommodated on concrete-lined holes

fitted with removable shielding plugs. Canadian practice

is to construct these from sections of concrete drain pipe,

painted on the outside with bitumen, which is also used to

seal joints between sections (Figure 10).

There are many different versions of the types of dis-

posal facility just described. Some are in the open, some

within buildings, but all are designed to prevent access of

water to the contents.

It is often convenient to delay the passage of radionu-

clides contained in high volume low-level wastes before

discharge into the environment in order to take advantage

of radioactive decay. If the local soil and ground water

regime are suitable this can often be done by discharge

into seepage. In 1969 the Hanford (USA) laboratories dis-

charged 5000 million gallons of low-level waste into the

ground, containing nearly 4000 Ci of radionuclides. More

than 99.9% of this activity is held on the sediments imme-

diately below the disposal facilities.

METHODS FOR “SMALL USERS”

The International Atomic Energy Agency has issued a code

of practice on management of radioactive wastes by hospitals,

research institutes and industry when no special facilities are

available on the site. It gives a review of the scope and nature

of the necessary control, particularly in the establishment of

permissible limits for discharge into the environment. These

institutions rely heavily upon the public sewers and garbage

disposal systems, depending upon the fact that in practice there

are levels of radioactivity below which things are not regarded

as radioactive. Sometimes this is the level at which measure-

ment becomes practical and sometimes legal limits exist.

The ICRP and the IAEA both recognize 10^ ^4 m Ci/ml as

the concentration in the sewer of an institution below which

no restrictive action is required, irrespective of the nature

of the radionuclide. This assumes that since large dilutions

will occur before ingestion by the public, the individual at

risk is the sewer worker. Plumbers can also encounter haz-

ards in traps and filters, and they must be made aware of the

situation. Similarly, although very low-level discharges to

public disposal areas are usually acceptable, the waste man-

agement authorities must know of the practice so that they

can warn their staff or undertake special procedures such as

tip-and-fill operations. It is particularly important that scav-

enging should be prevented, because a very small source,

normally innocuous, can be hazardous if carried for a long

time in a pocket.

Apart from the use of public facilities, radioactive waste

disposal for the “small user” does not differ in principle from

the methods available to the larger producer of waste. A good

deal of common sense and sense of proportion are required

in dealing with the problem, aided by technical advice such

as that in the IAEA report. It is also useful to remember that

an ordinary illuminated wristwatch gives a count of several

thousand per minute on a Geiger counter from the face side

and almost zero from the back.

SEA DISPOSAL

In 1983 the London Dumping Convention passed a

non-binding resolution which imposed an international

moratorium on sea dumping of radioactive wastes. In 1993

a binding resolution against sea disposal of these wastes

was passed by the LDC. A scientific evaluation of this ban

will be conducted about the year 2019.

THE FUTURE

The accidents at Three Mile Island and Chernobyl have

focused public attention on the potential for disaster. After the

Chernobyl incident the WHO (World Health Organization)

European Office set up a Working Group to consider har-

monization of response to any similar incident which might

occur in the future. The accident has proved conclusively that

some nuclear accidents will have consequences for removed

from the accident sites. Thus, it makes little sense for one

nation to take measures in isolation. The report produced by

the WHO European Office sets forth not only the effects of

Chernobyl but also presents an excellent discussion of the

4 DISPOSAL FLASKS

PER BUNKER

ASPHALT

CONCRETE

PLUG

PIT FILLED TO

CAPACITY &

FILLED IN &

COVERED

LOCATING PIN

15" CONCRETE

PIPE

6"

6'-0"

12'-10"

CONCRETE TILE HOLES

FIGURE 10 Concrete Holes, constructed from drain pipe

painted with bitumen, provide will-shielded receptacles for high-

level solid waste.

C013_001_r03.indd 640C013_001_r03.indd 640 11/18/2005 10:38:21 AM11/18/2005 10:38:21 AM