Environmental Encyclopedia

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Environmental Encyclopedia 3

Radioactive waste

release of millions of curies of radioactive material into the

Columbia River, Washington from 1944 through at least

the 1960s. In 1956, 450,000 gal (1.7 million l) of high-

level waste were accidently spilled on the Hanford grounds.

Through the 1950s, additional millions of gallons of waste

were dumped into the ground. Residents in the area and

along the river were never notified about any of the radioac-

tive discharges that took place at Hanford.

In 1988, the

U.S. Department of Energy

reported

that radioactive wastes from Hanford were contaminating

some underground water supplies; Hanford was shut down

a year later. At present, a farm of deteriorating storage tanks

at Hanford containing approximately 57 million gal (216

million l) of radioactive and toxic waste is being monitored

for leaks. Officials are not even sure what

chemicals

lie in

some of these tanks. Federal officials estimate that cleaning

up Hanford and the U.S. government’s other weapons facili-

ties (at Fernald, Ohio; Rocky Flats; Colorado; Savannah

River, Georgia; and other locations) may cost over $200

billion.

Nuclear power plants also contribute to radioactive

pollution. Spent nuclear fuel from these plants, a high-level

waste, must be kept from human contact for hundreds or

thousands of years, yet no completely reliable disposal

method exists. At present, most high-level waste has simply

been left in pools at power plant sites while the government

seeks a location for permanent disposal. Most low-level waste

(anything that is not spent fuel or transuranic waste) gener-

ated by nuclear power plants has been landfilled throughout

the country. Three such

landfill

sites (Maxey Flats, Ken-

tucky; West Valley, New York; and Sheffield, Illinois) have

been shut down due to leakage of radioactive liquid into the

ground.

Nuclear power plants also

discharge

wastes directly,

as a result of malfunctions or intentional dumping. During

the decade from 1979 to 1989, the

Nuclear Regulatory

Commission

recorded 33,000 mishaps at power plants in

the United States, 1,000 of which it classified as “particularly

significant.” Though the vast majority of these incidents

resulted in no release of radioactive material, some accidents,

such as the Three Mile Island partial meltdown and the

Chernobyl explosion, have caused significant discharges of

radioactivity into the

environment

. A sampling of incidents:

the Vermont Yankee power plant, a power station with a

poor safety record, was fined $30,000 for dumping 83,000

gal (314,000 l) of radioactive water into the Connecticut

River in July 1976;

the accident at Three Mile Island, Pennsylvania in 1979

released 2.5 million curies of radioactive noble gases and

a small quantity of radioactive iodine into the atmosphere;

in one of a series of 21 unreported leaks occurring up to

March 1981, radioactive material from the Tsuruga nuclear

1157

power plant in Japan was dumped into Tsuruga Bay after

warning alarms were shut off; operators of the plant later

admitted that they intentionally dumped wastes regularly;

in October 1982, heavy rains caused a flood at the Cofrentes

nuclear power plant in Spain which released 154 gal (580

l) of radioactive waste;

in December 1985, a power failure at the Rancho Seco,

California plant resulted in a release of a small quantity of

radiation into the air; in 1989 the NRC fined the facility

$100,000 for violating waste disposal regulations from 1983

to 1986;

at the Douglas Point, Canada, station in January 1986, it

was discovered that

high-level radioactive waste

had

been leaking from a spent-fuel “storage pond” at a rate of

16 gal (60 l) per hour.

The health effects of radioactive leaks are still debated.

While the harmful effects of Chernobyl are probably beyond

question, analysis of the Three Mile Island incident has not

detected a long-term increase in cancer or diseases as a

result of the discharge there. Studies conducted in England,

however, reveal increased rates of

leukemia

in areas sur-

rounding the nuclear plants at Hinkley Point, Dounreay,

and Windscale.

[Linda Rehkopf and Jeffrey Muhr]

ESOURCES

OOKS

Brill, A. Bertrand. Low-Level Radiation Effects: A Fact Book. New York:

Society of Nuclear Medicine, 1985.

Caufield, Catherine. Multiple Exposures. New York: Harper & Row, Pub-

lishers, 1989.

Dresser, Peter D., ed. Nuclear Power Plants Worldwide. Detroit: Gale Re-

search, 1993.

Gore, Al. Earth in the Balance. New York: Houghton Mifflin, 1992.

Jagger, J. The Nuclear Lion: What Every Citizen Should Know About Nuclear

Power and Nuclear War. New York: Plenum, 1991.

Jones, R. R., and R. Southwood, eds. Radiation and Health. New York:

Wiley, 1987.

Regenstein, Lewis. How to Survive in America the Poisoned. Washington,

DC: Acropolis Books Ltd., 1986.

Shulman, S. The Threat at Home: Confronting the Toxic Legacy of the U.S.

Military. Boston: Beacon Press, 1992.

ERIODICALS

Goldsmith, E., et al. “Chernobyl: The End of Nuclear Power?” The Econo-

mist 16 (1986): 138–209.

Radioactive waste

Radioactive waste is the “garbage” left as a result of the use

of nuclear materials by human societies. Such waste can be

categorized as low-level, intermediate-level, or high-level

waste. The term transuranic waste is also used to describe

Environmental Encyclopedia 3

Radioactive waste management

materials consisting of elements heavier than

uranium

the periodic table.

The term

low-level radioactive waste

usually refers

to materials that contain a small amount of

radioactivity

dispersed in a large volume of material. Such materials are

produced in a great variety of industrial, medical, and re-

search procedures. A common practice is to store these mate-

rials in sealed containers until their level of radioactivity is

very low and then to dispose of them by shallow burial or

in other traditional

solid waste

disposal systems.

The assumption is that the level of radiation released

by these wastes is too low to cause any harmful environmental

effects. That assumption has been challenged by some scien-

tists who believe that enough is not yet known about the

long-term effects of radiation. They suggest that safer meth-

ods of disposal for such wastes need to be developed.

Intermediate-level wastes, as the name suggests, con-

tain a higher level of radioactivity than low-level wastes, but

a lower level than high-level wastes. These materials cannot

be discharged directly into the

environment

. An important

source of such wastes is the re-processing of nuclear fuels.

At one time, large quantities of intermediate-level wastes

were dumped into the deepest parts of the Atlantic Ocean.

That practice has been discontinued and intermediate-level

wastes are now being stored on land until a permanent

disposal system is developed.

High-level radioactive wastes consist of materials that

contain a large amount of radioactivity that will remain at

dangerous levels for hundreds or even thousands of years.

These materials pose the most difficult disposal problem of

all since they must be completely isolated and stored for

very long periods of time. The primary sources of high-

level wastes are nuclear

power plants

and research and

development of

nuclear weapons

A number of methods for the storage of high-level

wastes have been suggested. Among these are burial in large

chunks of concrete, encapsulation in glass or ceramic, projec-

tion of them inside rockets into outer space, and burial in

the Antarctic ice sheet. Various countries around the world

have developed a variety of methods for storing their high-

level wastes. In Canada, such wastes have been stored in

water-filled pools for more than 25 years. France, with one

of the world’s largest

nuclear power

establishments, has

developed no permanent storage system but plans to build

a large underground vault for its wastes by the early twenty-

first century.

In the United States, Congress passed the Nuclear

Waste Policy Act in 1982, outlining a complete program

for the construction of a high-level waste repository in the

early twenty-first century. In 1987,

Yucca Mountain

, Ne-

vada, was selected as the location for that site. Current plans

call for a huge vault 1,000 ft (305 m) underground as the

1158

site for long-term, high-level waste storage at this location.

See also Nuclear fission; Nuclear Regulatory Commission

(NRC); Ocean dumping; Office of Civilian Radioactive

Waste Management (OCRWM); Radioactive decay; Radio-

active waste management

[David E. Newton]

ESOURCES

OOKS

Bartlett, D. L., and J. B. Steele. Forevermore: Nuclear Waste in America.

New York: W. W. Norton, 1985.

Carter, L. J. Nuclear Imperatives and Public Trust: Dealing With Radioactive

Waste. Baltimore: Resources for the Future, 1987.

League of Women Voters. The Nuclear Waste Primer. Washington, DC:

League of Women Voters, 1985.

Managing the Nation’s Nuclear Waste. Washington, DC: Office of Civilian

Radioactive Waste Management, March 1990.

Resnikoff, M. Deadly Defense: Military Radioactive Landfills. New York:

Radioactive Waste Campaign, 1988.

ERIODICALS

Hunt, C. B. “Disposal of Radioactive Wastes.” Bulletin of the Atomic Scien-

tists (April 1984): 44–46.

Radioactive waste management

Radioactive waste

materials are produced as by-products of

research,

nuclear power

generation, and

nuclear weapons

manufacture. Radioactive waste is classified by the U.S. gov-

ernment into five groups: high-level, transuranic (chemical

elements heavier than

uranium

), spent fuel, uranium mill

tailings

, and

low-level radioactive waste

The management and disposal of radioactive waste

receives attention at all levels of state and local governments,

but the regulations sometimes conflict or are confusing. The

U.S. Congress passes relevant legislation, the

Environmen-

tal Protection Agency

(EPA) sets applicable environmental

standards, and the

Nuclear Regulatory Commission

(NRC) develops regulations to implement the standards.

For

high-level radioactive waste

, the

U.S. Department

of Energy

(DOE) is responsible for the design, construction

and operation of suitable disposal facilities. And courts have

recently gotten into the act, ordering states to arrange to

have necessary disposal facilities designed, constructed and

operated for management of low-level wastes.

The principal federal laws related to the management

and disposal of radioactive waste include the Atomic Energy

Act (1954), the Uranium Mill Tailings Radiation Control

Act (1978), the Low-Level Radioactive Waste Policy Act

(1980), the Nuclear Waste Policy Act (1982), the Low-

Level Radioactive Waste Policy Amendments Act (1985),

and the Nuclear Waste Policy Amendments Act (1987). In

Environmental Encyclopedia 3

Radioactive waste management

A map of the United States showing radioactive waste disposal site locations. (McGraw-Hill Inc. Reproduced by

permission.)

addition, the Federal Facility Compliance Act (1992) forces

the military to clean up its waste sites.

One of the more difficult aspects of the regulatory

quagmire is the problem of dealing with waste, especially

spent nuclear fuel and contaminated material such as worn-

out reactor parts. Today, the official policy objective for

nuclear waste is to dispose of it so that it will never do any

appreciable damage to anyone, under any circumstances, for

all time. However, for some radioactive waste, “for all time”

is measured in thousands of years.

Although radioactive waste carries some hazard for

many years,

radioactive decay

removes most of the hazard

after a few hundred years. A well-designed waste storage

system can be made safe for a long time, some scientists

and policy-makers insist, provided that engineers ensure that

erosion

groundwater

, earthquakes, and other unpredict-

able natural or human activities do not breach safety barriers.

Disposal methods for radioactive wastes have varied.

Over the past 50 years, low-level wastes have been flushed

down drains, dumped into the ocean, and tossed into land-

fills. Uranium mill tailings have been mounded into small

1159

hills at sites throughout the western United States. Storage

tanks and barrels at DOE sites hold millions of gallons of

radioactive waste and toxic

chemicals

, the by-products of

plutonium

production for nuclear weapons.

Over 80% of the total volume of radioactive waste

generated in the United States is considered low-level. There

is now a shift away from the most common disposal method

of shallow land burial. Because of public demand for disposal

methods that provide the greatest safety and security, dis-

posal methods now include above- and below-ground vaults

and earth-mounded concrete bunkers.

However, the country’s 17,000 laboratories, hospitals,

and nuclear

power plants

that produce low-level radioactive

byproducts could become de facto disposal sites. The federal

low-level radioactive waste policy enacted in 1980 was de-

signed to remedy the inequity of shipping all the nation’s

low-level radioactive waste to three states (Illinois, Kentucky,

and New York) which never agreed to serve as the nation’s

sole disposal facilities. Its intent was to require every state

to either build its own low-level repository or compact with

other states to build regional facilities by 1986. The 1980

Environmental Encyclopedia 3

Radioactive waste management

federal act was amended in 1985, when it became clear that

the 1986 target would not be met, and the deadline was

postponed to 1993. As of late 1992, however, few states had

even determined sites for such facilities. And after 1996, the

institutions generating low-level wastes will be held liable

for all low-level wastes they produce.

The principal sources of high-level radioactive waste

are nuclear power plants, and programs of the U. S. Depart-

ment of Defense and DOE, especially those dealing with

nuclear weapons. These wastes include spent fuel removed

from nuclear plants, and fission products separated from

military fuel that has been chemically processed to reclaim

unused uranium and plutonium. In the United States, com-

mercial nuclear power plant fuel removed from those facili-

ties is stored on-site until a geologic repository is completed.

The expected completion date for the repository is 2010.

Typically, waste fuel is stored at the power station in

a pressurized

buffer

storage tube for 28 days, then the fuel

rod is broken down to component parts. Irradiated fuel

elements then are stored for 80 days in a water-filled pond

to allow for further decay. For the nonreusable radioactive

waste that remains, about 2.5%, there is no totally safe

method for disposal.

Radioactive waste from one of the first nuclear bomb

plants is so volatile that the clean-up problems have stymied

the experts. The plant at the DOE’s

Hanford Nuclear

Reservation

near Richland, Washington, is the nation’s

largest repository of nuclear waste. There, 177 tanks contain

more than 57 million gal (26 million l) of radioactive waste

and toxic chemicals, byproducts of plutonium production for

nuclear weapons. The DOE and Westinghouse Corporation

(the contractor in charge of Hanford’s clean-up) are still not

sure exactly what mixture of chemicals and radioactive waste

each tank contains, but a video taken inside one tank shows

the liquid bubbling and roiling from chemical and nuclear

reactions. Corrosive, highly radioactive liquids have eaten

through Hanford’s storage tanks and are being removed to

computer-monitored, carbon-steel storage tanks. The clean-

up at Hanford could cost as much as $57 billion. The only

other country known to have had a waste problem as large

as the one at Hanford is the former Soviet Union, where a

nuclear waste dump exploded in the nuclear complex at

Chelyabinsk in 1957, contaminating thousands of square

miles of land.

As the military starts massive clean-up efforts, it has

identified 17 nuclear facilities as among the worst of the

more than 20,000 suspected toxic sites. For example, since

the 1970s, about 77,000 barrels of low-level radioactive

wastes have been stored at the

Oak Ridge, Tennessee

nu-

clear reservation. Today, some barrels are rusting and leaking

radioactivity

. Other identified radioactive waste sites in-

clude California’s Lawrence Livermore National Laboratory

1160

and Sandia National Laboratory, Colorado’s

Rocky Flats

nuclear plant

, and New Mexico’s Los Alamos National

Laboratory. The Savannah River nuclear plant in South

Carolina has been called especially dangerous. Both the

Sa-

vannah River site

and the Hanford site pose the risk of

the kind of massive nuclear waste explosion that occurred

at Chelyabinsk.

One new technology in development for the treatment

of hazardous and radioactive waste is in situ vitrification

(ISV), which utilizes electricity to melt contaminated mate-

rial in place. This technology was developed primarily to treat

radioactive waste, but it also has applications to hazardous

chemical wastes. The end-result glass formed by ISV is

unaffected by extremes of temperature, is not biotoxic,

should remain relatively stable for one million years, and

passes government tests that measure the speed of contami-

nant

leaching

over time. The process permits treatment of

mixtures of various wastes including organic, inorganic, and

radioactive. The fact that it is not necessary to excavate the

waste prior to treatment is seen as a major advantage of

the technology, since excavation along with

transportation

increases health risks. The technology is currently being used

in the United States at Superfund sites.

Incineration

is also used for disposal of low-level ra-

dioactive waste, but incomplete

combustion

can produce

dioxins and other toxic ash and aerosols. Although finding

a site for ash disposal is difficult, the ash is considered a

better form for burial than the original waste. It is biologically

and structurally more stable, and many of the compounds

it contains are insoluble. The residual waste produced by

incineration also is less susceptible to leaching by rain and

groundwater.

Although progress is slow and the situation is often

chaotic in the United States, the state of radioactive

waste

management

in much of the rest of the world is even

less advanced. The situation is particularly acute in Eastern

Europe and the former Soviet Union, since these countries

have generated huge quantities of radioactive waste. In many

cases the information-gathering necessary to plan clean-up

efforts has not begun or is barely underway, and most, if

not all, of the actual clean-up remains. See also Eastern

European pollution; Ocean dumping; Radiation exposure;

Radiation sickness; Radioactive pollution; Waste Isolation

Pilot Plant; Yucca Mountain, Nevada

[Linda Rehkopf]

ESOURCES

OOKS

Deadly Defense: Military Radioactive Landfills. New York: Radioactive

Waste Campaign, 1988.

Moeller, D. W. Environmental Health. Cambridge: Harvard University

Press, 1992.

Environmental Encyclopedia 3

Radioactivity

Shulman, S. The Threat at Home: Confronting the Toxic Legacy of the U.S.

Military. Boston: Beacon Press, 1992.

The Nuclear Waste Primer. Washington, DC: League of Women Voters,

1985.

ERIODICALS

Hammond, R. P. “Nuclear Wastes and Public Acceptance.” American Scien-

tist 67 (March–April 1979): 146–50.

Shulman, S. “Operation Restore Earth: Cleaning Up After the Cold War.”

E Magazine 4 (March–April 1993): 36–43.

Radioactivity

In 1896, the French physicist Henri Becquerel accidentally

found that an ore of

uranium

, pitchblende, emits an invisible

form of radiation, somewhat similar to light. The phenome-

non was soon given the name radioactivity and materials like

pitchblende were called radioactive.

The radiation Becquerel discovered actually consists

of three distinct parts, called alpha, beta, and gamma rays.

Alpha and beta rays are made up of rapidly moving parti-

cles—helium nuclei in the case of alpha rays, and electrons

in the case of beta rays. Gamma rays are a form of electro-

magnetic radiation with very short wavelengths.

Alpha rays have relatively low energies and can be

stopped by a thin sheet of paper. They are not able to

penetrate the human skin and, in most circumstances, pose

a relatively low health risk. Beta rays are more energetic,

penetrating a short distance into human tissue, but they can

be stopped by a thin sheet of

aluminum

. Gamma rays are

by far the most penetrating form of radiation, permeating

wood, paper, plastic, tissue, water, and other low-density

materials in the

environment

. They can be stopped, how-

ever, by sheets of

lead

a few inches thick.

Radioactivity is a normal and ubiquitous part of the

environment. The most important sources of natural radio-

activity are rocks containing radioactive isotopes of uranium,

thorium, potassium, and other elements. The most common

radioactive

isotope

in air is carbon-14, formed when neu-

trons from cosmic ray showers react with

nitrogen

in the

atmosphere

. Humans, other animals, and plants are con-

stantly exposed to low-level radiation emitted from these

isotopes, and they do suffer to some extent from that expo-

sure. A certain number of human health problems—cancer

and genetic disorders, for example—are attributed to damage

caused by natural radioactivity.

In recent years, scientists have been investigating the

special health problems related to one naturally occurring ra-

dioactive isotope, radon-226. This isotope is produced when

uranium decays, and since uranium occurs widely in rocks,

radon-226 is also a common constituent of the environment.

Radon-226 is an alpha-emitter, and though the isotope does

have a long

half-life

(1,620 years), the alpha particles are not

1161

energetic enough to penetrate the skin. The substance, how-

ever, is a health risk because it is a gas that can be directly

inhaled. The alpha particles come into contact with lung tis-

sue, and some scientists now believe that radon-226 may be

responsible for a certain number of cases of lung

cancer

. The

isotope can be a problem when homes are constructed on land

containing an unusually high concentration of uranium. Ra-

don-226 released by the uranium can escape into the base-

ments of homes, spreading to the rest of a house. Studies by

the

Environmental Protection Agency

(EPA) have found

that as many as eight million houses in the United States have

levels of radon-226 that exceed the

maximum permissible

concentration

recommended by experts.

Though Becquerel had discovered radiation occurring

naturally in the environment, scientists immediately began

asking themselves whether it was possible to convert normally

stable isotopes into radioactive forms. This question became

the subject of intense investigation in the 1920s and 1930s,

and was finally answered in 1934 when Ire

ne Curie and Fre

ric Joliot bombarded the stable isotope aluminum-27 with

alpha particles and produced phosphorus-30, a radioactive

isotope. Since the Joliot-Curie experiment, scientists have

found ways to manufacture hundreds of artificially radioactive

isotopes. One of the most common methods is to bombard a

stable isotope with gamma rays. In many cases, the product

of this reaction is a radioactive isotope of the same element.

Highly specialized techniques have recently been de-

vised to meet specific needs. Medical workers often use

radioactive isotopes with short half-lives because they can be

used for diagnostic purposes without remaining in a patient’s

body for long periods of time. But the isotope cannot have

such a short half-life that it will all but totally decay between

its point of manufacture and its point of use.

One solution to this problem is the so-called “molyb-

denum cow.” The cow is no more than a shielded container

of radioactive molybdenum-99. This isotope decays with a

long half-life to produce technetium-99, whose half-life is

only six hours. When medical workers require technetium-

99 for some diagnostic procedure, they simply “milk” the

molybdenum cow to get the short-lived isotope they need.

Artificially radioactive isotopes have been widely em-

ployed in industry, research, and medicine. Their value lies

in the fact that the radiation they emit allows them to be

tracked through settings in which they cannot be otherwise

observed. For example, a physician might want to know if

a patient’s thyroid is functioning normally. In such a case,

the patient drinks a solution containing radioactive iodine,

which concentrates in the thyroid like stable iodine. The

isotope’s movement through the body can be detected by a

Geiger counter or some other detecting device, and the speed

as well as the extent to which the isotope is taken up by the

thyroid is an indication of how the organ is functioning.

Environmental Encyclopedia 3

Radiocarbon dating

Artificially radioactive isotopes can pose a hazard to

the environment. The materials in which they are wrapped,

the tools with which they are handled, and the clothing

worn by workers may all be contaminated by the isotopes.

Even after they have been used and discarded, they may

continue to be radioactive. Users must find ways of disposing

of these wastes without allowing the release of dangerous

radiation into the environment, a relatively manageable

problem. Most materials discarded by industry, medical

facilities, and researchers are

low-level radioactive waste

The amount of radiation released decreases quite rapidly,

and after isolation for just a few years, the materials can be

disposed of safely with other non-radioactive wastes.

The same cannot be said for the

high-level radioac-

tive waste

produced by nuclear

power plants

and defense

research and production. Consisting of radioactive isotopes,

such wastes are produced during fission reactions and release

dangerously large amounts of radiation for hundreds or thou-

sands of years.

Nuclear fission

was discovered accidentally in the

1930s by scientists who were trying to produce artificial

radioactive isotopes. In a number of cases, they found that

the reactions they used did not result in the formation of

new radioactive isotopes, but in the splitting of atomic nuclei,

a process that came to be known as nuclear fission.

By the early 1940s, nuclear fission was recognized as

an important new source of energy. That energy source was

first put to use for destructive purposes, in the construction

nuclear weapons

. Later, scientists found ways to control

the release of energy from nuclear fission in nuclear reactors.

The most serious environmental problem associated

with fission reactions is that their waste products are largely

long-lived radioactive isotopes. Attempts have been made

to isolate these wastes by burying them underground or

sinking them in the ocean. All such methods have proved

so far to be unsatisfactory, however, as containers break open

and their contents leak into the environment.

The United States government has been working for

more than four decades to find better methods for dealing

with these wastes. In 1982, Congress passed a Nuclear Waste

Policy Act, providing for the development of one or more

permanent burial sites for high-level wastes. Political and

environmental pressures have stalled the implementation of

the act and a decade after its passage, the nation still has no

method for the safe disposal of its most dangerous radioactive

wastes. See also Ecotoxicology; Hazardous waste; Nuclear

fusion; Nuclear winter; Radiation exposure; Radiation sick-

ness; Radioactive fallout; Radioactive pollution; Radioactive

waste management

[David E. Newton]

1162

ESOURCES

OOKS

Gofman, J. W. Radiation and Human Health. San Francisco: Sierra Club

Books, 1981.

Inglis, D. R. Nuclear Energy: Its Physics and Social Challenge. Reading, MA:

Addison-Wesley, 1973.

Jones, R. R., and R. Southwood, eds. Radiation and Health. New York:

Wiley, 1987.

Wagner, H. N., and L. E. Ketchum. Living With Radiation. Baltimore:

Johns Hopkins University Press, 1989.

Radiocarbon dating

Radiocarbon dating is a technique for determining the age

of very old objects consisting of organic (carbon-based) ma-

terials, such as wood, paper, cloth, and bone. The technique

is based on the fact that both stable and radioactive isotopes

carbon

exist. These isotopes behave almost identically

in biological, chemical, and physical processes.

Carbon-12, a stable

isotope

, makes up about 99% of

all carbon found in

nature

. Radioactive carbon-14 is formed

in the

atmosphere

when neutrons produced in cosmic ray

showers react with

nitrogen

atoms.

Despite the fact that it makes up no more than 0.08%

of the earth’s crust, carbon is an exceedingly important ele-

ment. It occurs in all living materials and is found in many

important rocks and minerals, including limestone and mar-

ble, as well as in

carbon dioxide

. Carbon moves through

the atmosphere, hydrosphere, lithosphere, and

biosphere

in a series of reactions known as the

carbon cycle

. Stable

and radioactive isotopes of the element take part in identical

reactions in the cycle. Thus, when green plants convert car-

bon dioxide to carbohydrates through the process of

photo-

synthesis

, they use both stable carbon-12 and radioactive

carbon-14 in exactly the same way. Any living material con-

sists, therefore, of a constant ration of carbon-14 to car-

bon-12.

In the mid-1940s, Willard F. Libby realized that this

fact could be used to date organic material. As long as that

material was alive, he pointed out, it should continue to take

in both carbon-12 and carbon-14 in a constant ratio. At its

death, the material would no longer incorporate carbon in

any form into its structure. From that point on, the amount

of stable carbon-12 would remain constant. The amount

of carbon-14, however, would continuously decrease as it

decayed by beta

emission

to form nitrogen. Over time, the

ratio of carbon-14 to carbon-12 would grow smaller and

smaller. That ratio would provide an indication of the length

of time since the material had ceased being alive.

Radiocarbon dating has been used to estimate the age

of a wide variety of objects ranging from charcoal taken from

tombs to wood found in Egyptian and Roman ships. One

Environmental Encyclopedia 3

Radioisotope

of its most famous applications was in the dating of the

Shroud of Turin. Some religious leaders had claimed that

the Shroud was the burial cloth in which Jesus was wrapped

after his crucifixion. If so, the material of which it was made

would have to be nearly 2,000 years old. Radiocarbon dating

of the material showed, however, that the cloth could not

be more than about 700 years old.

Radiocarbon dating can be used for objects up to

30,000 years of age, but it is highly reliable only for objects

less than 7,000 years old. These limits result from the fact

that eventually carbon-14 has decayed to such an extent that

it can no longer be detected well or, eventually, at all in a

sample. For older specimens, radioisotopes with longer half-

lives can be used for age determination. See also Half-life;

Radioactive decay

[David E. Newton]

ESOURCES

OOKS

Taylor, R. E., et al., eds. Radiocarbon Dating: An Archaeological Perspective.

Orlando: Academic Press, 1987.

———. Radiocarbon After Four Decades: An Interdisciplinary Perspective.

New York: Springer Verlag, 1992.

Radioisotope

The term radioisotope is shorthand for radioactive

isotope

Isotopes are forms of an element whose atoms differ from

each other in the number of neutrons contained in their

nuclei and, hence, in their atomic masses. Hydrogen-1, hy-

drogen-2, and hydrogen-3 are all isotopes of each other.

Isotopes may be stable or radioactive. That is, they

may exist essentially unchanged forever (stable), or they may

spontaneously emit an

alpha particle

beta particle

and/

or a

gamma ray

, changing in the process into a new sub-

stance. Hydrogen-1 and hydrogen-2 are stable isotopes, but

hydrogen-3 is radioactive.

The first naturally occurring radioisotopes were dis-

covered in the late 1890s. Scientists found that all isotopes

of the heaviest elements—uranium, radium,

radon

, tho-

rium, and protactinium, for example—are radioactive. This

discovery raised the question as to whether stable isotopes

of other elements could be converted to radioactive forms.

By the 1930s, the techniques for doing so were well

established, and scientists routinely produced hundreds of

radioisotopes that do not occur in

nature

. As an example,

when the stable isotope carbon-12 is bombarded with neu-

trons, it may be converted to a radioactive cousin, carbon-

13. This method can be used to manufacture radioisotopes

of nearly every element.

1163

Naturally occurring radioisotopes are responsible for

the existence of

background radiation

. Background radia-

tion consists of alpha and beta particles and gamma rays

emitted by these isotopes. In addition to the heavy isotopes

mentioned above, the most important contributors to back-

ground radiation are carbon-14 and potassium-40.

Synthetic radioisotopes have now become ubiquitous

in human society. They occur commonly in every part of

nuclear power

plant operations. They are also used exten-

sively in the health sciences, industry, and scientific research.

A single example of their medical application is

cancer

therapy. Gamma rays emitted by the radioisotope cobalt-60

have been found to be very effective in treating some forms

of cancer. Other gamma-emitting radioisotopes can also be

used in this procedure.

The potential for the release of radioisotopes to the

environment

is great. For example, medical wastes might

very well contain radioisotopes that still emit measurable

amounts of radiation. Stringent efforts are made, therefore,

to isolate and store radioisotopes until their radiation has

reached a safe level.

These efforts have two aspects. Some radioisotopes

have short half-lives. The level of radiation they emit drops

to less than 1% of the original amount in a matter of hours

or days. These isotopes need only be stored in a safe place

for a short time before they can be safely discarded with

other solid wastes.

Other radioisotopes have half-lives of centuries or mil-

lennia. They will continue to emit harmful radiation for

thousands of years. Safe disposal of such wastes may require

burying them deep in the earth, a procedure that still has

not been satisfactorily demonstrated. In spite of the potential

environmental hazard posed by radioisotopes, they do not

presently pose a serious threat to plants, animals, or humans.

The best estimates place the level of radiation from artificial

sources at less than five percent of that from natural sources.

See also Half-life; Radioactive decay; Radioactive waste man-

agement; Radioactivity

[David E. Newton]

ESOURCES

OOKS

Baker, P., et al. Radioisotopes in Industry. Washington, DC: U.S. Atomic

Energy Commission, 1965.

Corless, W. R., and R. L. Mead. Power from Radioisotopes. Washington,

DC: U.S. Atomic Energy Commission, 1971.

Kisieleski, W. E., and R. Baserga. Radioisotopes and Life Processes. Washing-

ton, DC: U.S. Atomic Energy Commission, 1967.

Environmental Encyclopedia 3

Radiological Emergency Response Team

Some radioisotopes associated with nuclear

power. (McGraw-Hill Inc. Reproduced by permission.)

Radiological Emergency Response

Team

The Radiological Emergency Response Team (RERT) of

the federal

Environmental Protection Agency

(EPA) re-

sponds to emergencies that involve the release of radioactive

materials. The team responds to emergencies such as acci-

dents at nuclear

power plants

, accidents involving the ship-

ment of radioactive material, and acts of nuclear terrorism.

RERT works with the EPA Superfund Program, as well as

federal, state, and local agencies to develop and enforce

strategic plans.

RERT is based in the EPA Office of Radiation and

Indoor Air in Washington, D.C., and at two national labora-

tories.

Environmental monitoring

and assessment is per-

formed by employees at the National Air and Radiation

Environmental Laboratory in Montgomery, Alabama, and

the Radiation and Indoor Environments National Labora-

tory in Las Vegas, Nevada. Approximately 75 RERT mem-

bers were stationed in Washington and at the laboratories

in the spring of 2002.

In an emergency, an RERT field team goes to the site

where radioactive material was released. The team’s duties

include taking environmental measurements and doing labo-

ratory work. In addition, RERT works with state and local

1164

authorities to protect the public from exposure to harmful

radiation levels. Team equipment ranges from a mobile radi-

ation laboratory to the personal dosimeter used to measure

the radiation dose in an individual.

[Liz Swain]

Radionuclides

Radionuclides are radioactive elements.

Radioactivity

can

be defined as the release of

alpha and beta

particles from

atoms, and/or

gamma rays

that takes place when the nuclei

of certain unstable substances spontaneously disintegrate. It

is during this disintegration process that they emit radiation.

The two main types of radiation released during such pro-

cesses are termed

ionizing

, or of sufficient strength to forc-

ibly eject electrons from their orbit around an atoms nucleus,

producing ions, and

non-ionizing

, of less strength and inca-

pable of displacing electrons and forming ions.

Ionizing

radiation

is highly significant because when it occurs within

the atoms of molecules in living things, it is capable of

causing biological damage such as the death of cells or the

unnatural reproduction of cells. We term this unnatural re-

production of cells

cancer

Radionuclides occur in the

environment

both natu-

rally and as a result of human industry. Some naturally-

occurring radionuclides exist all over the earth and have been

present since its formation 4.5 billion years ago. But most

elements can be made artificially radioactive by bombarding

them with high-energy particles such as neutrons. Each

radionuclides forms and behaves in unique ways, with its

own method and rate of decay. Such decay is measured by

what is called

half-life

, or the time it takes for a group of

atoms to decay to half of their original number.

One of the substances that occurs naturally in the

earth’s crust is

uranium

, a radionuclide used often as fuel

to produce

nuclear power

. Uranium is the heaviest element

found on earth with the exception of tiny amounts of an

element called neptunium. When the German chemist Mar-

tin H. Klaproth discovered uranium in 1789, he named

it in honor of the recently discovered planet Uranus. The

scientific community showed little interest in uranium until

1896, when Henri Becquerel discovered radioactivity, and

uranium was named as one of only two known radioactive

elements of the time. In 1938, scientists discovered

nuclear

fission

, a reaction that produces energy. In fact, uranium

can produce energy at nearly three million times that of

coal

(1 lb of uranium can produce the same amount of energy

produced by 3 million lb [1.4 million kg] of coal).

The most abundant form (

isotope

) of uranium boasts

half-life

nearly identical to that of the earth itself. This

allows scientists to use the substance’s disintegration to date

Environmental Encyclopedia 3

Radionuclides

other geological features of the earth by comparison. How-

ever, uranium use also has many drawbacks. Most notably,

use of the substance produces nuclear waste that must be

carefully transported and stored. In addition, easily obtain-

able supplies of uranium on Earth are limited, therefore the

costs of locating and refining uranium can be extremely high.

Radium occurs as a result of uranium disintegration.

Marie Curie, the first woman to win a Nobel Prize, and

one of the few scientists to ever receive the Nobel prize twice,

along with her husband Pierre, discovered the substance. She

had followed up on Becquerel’s observations on uranium’s

radioactive properties for her doctoral dissertation in the late

1890s. The Curies began refining pitchblende, a waste ore

that was commonly found around uranium mines, known

to emit radiation. The Curies first discovered the radioactive

salt they named polonium, and then radium, found to be

thousands of times more radioactive than any other substance

discovered to date.

Radium is found in water,

soil

, plants, and food, but

at low concentrations. Drinking water holds the highest

potential for human exposure to radium. When humans are

exposed to radium orally, they are at risk for lung, bone,

brain and nasal passage tumors. Chronic exposure has led

to acute

leukemia

and other complications. Radium has

been classified by the

Environmental Protection Agency

(EPA) as a human

carcinogen

. Today, radium is still con-

sidered among the most radioactive metals on Earth, and

requires careful attention and handling. Its use has been

limited in many products, but the substance still helps treat

cancers through radiation therapy and aids in some forms

of research. As evidence of the validity of the EPA’s finding,

its discoverer, Marie Curie died at the age of 67 of leukemia,

caused by her prolonged exposure to radiation.

Radon

is a gas that can diffuse out of uranium (from

radium) in the ground from uranium and thorium present

in minerals, ores and rocks. A German physics professor

named Friedrich Dorn discovered radon in 1900, after he

followed the experiments of Marie Curie. He found that

radium emitted a radioactive gas he termed

radium emana-

tion

. Dorns discovery was important because it showed that

an element could be transmuted from metal to gas as part

of the

radioactive decay

process. The hazards of radon

were not discovered until late in the twentieth century, and

since that time, testing houses for the gas has become an

important precaution. Radon has shown the capability of

seeping into

groundwater

and contaminating public drink-

ing supplies.

As Radon is colorless and odorless, it can prove partic-

ularly dangerous. Radon exposure occurs mostly through

inhalation of the gas in indoor locations such as schools,

homes, or office buildings. Chronic exposure produces seri-

ous respiratory effects, and smokers are at particular risk for

1165

lung cancer, estimated at 10–20 times the risk of nonsmok-

ers. Although hazardous, radon has been useful in predicting

earthquakes. In 1918, the discovery by a group of Chinese

scientists that radon levels in groundwater rise just before

earthquakes led to the prediction of several earthquakes by

monitoring radon concentrations in well water. Radon has

also proves useful in detecting leaks, inspecting metal welds,

and measuring flow rates. However, radons high risk status

as a carcinogen outweighs its beneficial uses.

Plutonium

is an example of an artificial radioactive

substance. It was discovered around the early 1940s during

experiments on nuclear fission conducted by a number of

scientists. Plutonium is used in breeder reactors when ura-

nium undergoes nuclear fission to produce energy and occurs

as a waste product of uranium. Like uranium, plutonium

produces large amounts of energy and its properties were

put to the test in the first

nuclear weapons

test in New

Mexico in 1945.

Knowledge of the properties and risks of all radionu-

clides have made it necessary for people all over the world

to become more aware of the inherent dangers they possess

and the necessary preventative measures needed for protec-

tion. People that work in factories that process uranium or

with phosphate fertilizers are at increased risk of exposure

to radionuclides, as are those living in close proximity to

uranium mines. Tests can measure radioactivity levels in the

body and elimination of radium and radon in exhaled breath.

Uranium, radon, and radium levels can be measured in

the urine.

One of the greatest challenges facing scientists and

policymakers throughout the world is the safe transport and

disposal of the

hazardous waste

resulting from radionu-

clides. The subject has been steeped in controversy for many

years, as no place seems safe enough to handle storage of a

substance that lives for millions of years. However, scientists

continue to develop new methods for storage of nuclear

byproducts. In early 2001, a Los Alamos National Labora-

tory team announced that certain ceramic materials held up

against radiation damage and could potentially offer new

solutions to resist

leaching

and radiation for thousands of

years.

A consortium of international agencies promotes in-

ternational cooperation in managing nuclear waste, since

nearly every developed country has some sort of nuclear

power or weaponry project in place. Most of these countries

have developed plans to safely dispose of nuclear waste early

in the twenty-first century. The United States leads most

countries in storage efforts, with the 1982 passage of the

Nuclear Waste Policy Act. The act identified objectives for

developing geologic repositories for high-level nuclear waste.

The federal government identified

Yucca Mountain

in Nevada for deep underground storage of wastes to replace

Environmental Encyclopedia 3

Radiotracer

storage that now lies at commercial nuclear

power plants

and research reactor sites in 43 states. The EPA continues

to develop public health and environmental standards to set

safe limits for the long-term storage of highly

radioactive

waste

. However, a coalition of environmental groups also

continues to watch and question the agency to ensure that

the radiation standard remains protective enough. Like the

Waste Isolation Pilot Plant

(WIPP) storage facility in

southern New Mexico, the Yucca Mountain site will no

doubt remain controversial for some time.

The EPA provides printed fact sheets on radionuclides

that warn of environmental and occupational exposure to

the substances and acceptable levels of contact for humans.

According to the agency, uranium is present in rocks and

soil and throughout the environment, and although exposure

can occur through air, higher levels generally occur in food

or drinking water. Chronic long-term exposure to uranium

and radon has been linked to both lung and kidney diseases.

The EPA is currently in the process of promulgating new

drinking water standards (the first update since 1976) regard-

ing (non-Radon) radionuclides. These standards will become

effective December 8, 2003, and will affect only Community

Water Systems (CWSs), or those systems that serve more

than 25 residents regularly all year.

[Joan M. Schonbeck]

ESOURCES

OOKS

Alexander, D. E., and R. W. Fairbridge. Encyclopedia of Environmental

Science. Dordrecht, The Netherlands: Kluwer Academic Publishers, 1999.

Clayman, Charles. The American Medical Association Home Medical Encyclo-

pedia. New York: Random House, 1998.

Emsley, J. The Elements. New York: Clarendon Press, 1998.

THER

Environmental News Network. [cited July 2002]. <http://wwww.enn.com>.

RGANIZATIONS

Alliance for Nuclear Accountability, 1914 N. 34th St., Ste. 407, Seattle,

WA USA 98103 (206) 547-3175, Fax: (206) 547-7158, Email:

ananuclear@earthlink.net, <http://www.ananuclear.org>

Environmental Protection Agency Office of Air and Radiation, Ariel Rios

Building, 1200 Pennsylvania Ave. NW, Washington, DC USA 20460

(202) 564-7400, <http://www.epa.gov/air/oarofcs.html>

Radiotracer

A radioactive

isotope

progressing through a biological or

physical system can be followed by several tracking proce-

dures. For example,

fertilizer

containing radioactive

phos-

phorus

can be added to

soil

. Plants grown in this soil then

take up the radioactive phosphorus just as they do non-

radioactive phosphorus. If one of these plants is placed on

1166

a photographic plate, radiation from the radioactive phos-

phorus exposes the plate. The plant “takes its own picture,”

showing where the phosphorus concentrates in the plant.

Radiotracers are a highly desirable research technique as they

do not require the destruction of an organism for its study.

Radon

Although it has received attention as an environmental haz-

ard only recently, radon is a naturally occurring radioactive

gas that is present at low concentrations everywhere in the

environment

. Colorless and odorless, radon is a decay prod-

uct of radium; radium is a decay product of the radioactive

element

uranium

, which occurs naturally in the earth’s crust.

Radon continues to break down into products called radon

progeny. Radon is measured in units called picocuries per

liter (pCi/L), and it becomes a health concern when people

are exposed to concentrations higher than normal back-

ground levels. Some geologic formations, such as the Read-

ing Prong in New Jersey, are naturally very high in radon

emissions.

During their normal decay process, radioactive ele-

ments emit several kinds of radiation, one of which is alpha

radiation. The health effects of radon are associated with

these alpha particles. These particles are too heavy to travel

far and they cannot penetrate the skin, but they can enter

the body through the lungs during inhalation. Studies of

miners exposed to high concentrations of radon have shown

an increased risk of lung

cancer

, and this is the health effect

most commonly associated with radon. Background levels

are usually estimated at 1 pCi/L. It is estimated that a person

exposed to this concentration for 18 hours a day for five

years increases their risk of developing cancer to one in 1000.

At radon levels of 200 pCi/L, the increased risk of lung

cancer after five years of exposure at 18 hours per day rises

to 60 in 1,000. Because cancer is a disease that is slow to

develop, it may take five to 50 years after exposure to radon

to detect lung cancer.

In the outdoor environment, radon gas and its decay

products are usually too well-dispersed to accumulate to

dangerous levels. It is indoors without proper ventilation, in

places such as basements and ground floors, where radon

can seep from the

soil

and accumulate to dangerous concen-

trations. The most common methods of reducing radon

buildup inside the home include installing blowers or simply

opening windows. Plugging cracks and sealing floors that

are in contact with soil also reduces the concentration. In

the United States, environmental and public health agencies

have instituted free programs to test for radon concentra-

tions, and they also offer assistance and guidelines for reme-