GENERAL ARTICLE
CURRENT SCIENCE, VOL. 81, NO. 12, 25 DECEMBER 20011534
K. R. Rao lives at ‘Gokula’, 29/2, 11th Cross Road, III Main (Margosa)
Road, Malleswaram, Bangalore 560 003, India
e-mail: krrao@ias.ernet.in
Radioactive waste: The problem and its
management
K. R. Rao
Radioactive waste, arising from civilian nuclear activities as well as from defence-related nuclear-weapon
activities, poses a formidable problem for handling and protecting the environment
to be safe to the present and future generations. This article deals with this global problem in its
varied aspects and discusses the cause for concern, the magnitude of the waste involved and various
solutions proposed and being practised. As nuclear power and arsenal grow, continuous
monitoring and immobilization of the waste over several decades and centuries and deposition in
safe repositories, assumes great relevance and importance.
It’s very clear
Plutonium is here to stay
Not for a year
Forever and a Day.
In time the Rockies may tumble
Yucca may crumble
They’re only made of clay
But Plutonium is here to stay.
— Anonymous
‘The stuff we are dealing with can’t go away until it
decays. You can containerize it, solidify it, immobilize it
and move it, but you can’t make it go away’.
– James D. Werner, Scientific American, May 1996
BEGINNING with the Manhattan Project, during the
World War II, USA created a vast arsenal of nuclear
weapons based on plutonium. The inputs came from a
number of nuclear complexes spread across the country
and they included a number of nuclear reactors to produce
plutonium, reprocessing plants to extract plutonium
and weapon-research laboratories and production
plants. As an example, at Hanford (Washington State), a
typical nuclear weapons’ complex, there were 9 nuclear
reactors producing plutonium, 5 reprocessing plants and
200 tanks storing nearly 200,000 m3
of high-level radioactive
waste.
Nearly a thousand weapons were detonated by USA
for testing and the arsenal comprised of tens of thousands
of weapons. The leftovers from this cold war
legacy are believed to contain several large highlycontaminated
reprocessing plants, thousands of tons of
irradiated fuel in basins that act as ‘radioactive dustbins’,
hundreds of underground tanks each containing
hundreds of thousands of cubic metres of high-level
radioactive waste in hazardous state, dozens of tons of
unsecured plutonium and so on.
Reports from the European press state that the
erstwhile Soviet Union secretly dumped nuclear reactors
and radioactive waste into the bordering seas, indicating
more damaging nuclear legacy of the Cold
War than previously known. It is said that nuclear reactors
from at least 18 nuclear submarines and icebreakers
were dumped in the Barents Sea. The Russians are reported
to have dumped unprocessed nuclear waste into
The Sea of Japan. The latest in this scenario is that on
12 August 2000, the giant Russian nuclear submarine
Kursk, carrying a crew of 118, sank in the icy waters
of the Barents Sea after what Russian officials described
as a ‘catastrophe that developed at lightning
speed’.
It may not be wrong to guess that any other weaponproducing
complex in any other country also operates
in a similar manner. Only the scale of operation
may be large or small depending on the resources
that are pumped in. The secrecy, callousness in handling
the radioactive waste and the problems that each
nation faces would be qualitatively no different; quantitatively
they increase as weaponization takes deeper
roots.
Radioactive waste
Two basic nuclear reactions, namely fission of nuclei
like
235
U,
239
Pu and fusion of elements like hydrogen
result in release of enormous energy and radioactive
elements. Controlled vast releases of energy are possible
in nuclear power plant reactors through the fission
reaction. The dream of controlled vast releases of energy
through fusion reaction is still to be realized. Un-
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CURRENT SCIENCE, VOL. 81, NO. 12, 25 DECEMBER 2001 1535
controlled vast releases of energy through both these
reactions have been possible in ‘atom’ and ‘hydrogen’
(thermonuclear) bombs. As in many other industrial
processes, in the nuclear industry also, one gets unusable
and unwanted waste products; the residues turn out
to be hazardous.
Waste, by definition, is any material (solid materials
such as process residues as well as liquid and gaseous
effluents) that has been or will be discarded as being of
no further use. Note that what may be considered as
one’s waste may turn out to be another’s wealth. Reusable
plastics and other components in day-to-day
household waste are good examples in this context. This
concept holds good for radioactive waste also, in some
sense. Waste that emits nuclear radiation is radioactive
waste. (See Box 1 for basic concepts of radioactivity.)
Natural radioactivity
It is somewhat surprising that nature has been a large
producer of radioactive waste. Over the eons, the surface
of the Earth and the terrestrial crust happens to be
an enormous reservoir of primordial radioactivity.
Small amounts of radioactive materials are contained in
mineral springs, sand mounds and volcanic eruptions.
Essentially all substances contain radioactive elements
of natural origin to some extent or the other.
The second source of radioactive waste is a part of
industrial mining activity where, during mineral exploration
and exploitation, one excavates the primordial
material from the Earth that contains radioactivity, uses
part of it and rejects the radioactive residues as waste.
These are referred to as Naturally Occurring Radioactive
Materials (NORMs) and are ubiquitous as residual
wastes in processing industries that cover fertilizers,
iron and steel, fossil fuel, cement, mineral sands, titanium,
thorium and uranium mining as well as emanations
and waste from coal and gas-fired power plants.
One should note that in many industries, radiation
exposure to the workers and the general public would
be at least as high as those from nuclear installations
and in some cases it is even higher. It is also known that
certain mineral springs contain fairly large amounts of
222
radon. Monazite sand deposits in coastal areas may
result in radiation exposure to humans around an order
of magnitude in excess of the currently set international
exposure limits to radioactive waste disposal (one msv/
year) and volcanic deposits result in similar exposure.
There is no place on Earth that is free from natural radioactive
background; it may vary from place to place
all the way from the low to the high. The content of
Box 1. Radioactivity
Certain elements that compose matter emit particles and radiations spontaneously. This phenomenon is referred
to as ‘radioactivity’, it cannot be altered by application of heat, electricity or any other force and remains
unchangeable.
Three different kinds of rays, known as alpha, beta and gamma rays are associated with radioactivity. The
alpha rays consist of particles (nuclei of helium atoms) carrying a positive charge, beta rays particles have
negative charge (streams of electrons) and gamma rays are chargeless electromagnetic radiation with shorter
wavelengths than any X-rays. These ‘rays’ can penetrate living tissues for short distances and affect the tissue
cells. But because they can disrupt chemical bonds in the molecules of important chemicals within the cells,
they help in treating cancers and other diseases. Every element can be made to emit such rays artificially. If
such radioactive elements are placed in the body through food or by other methods, the rays can be traced
through the body. This use of tracer elements is extremely helpful in monitoring life processes. Geologists use
radioactivity to determine the age of rocks. As atoms lose particles as heavy as nuclei of helium, they become
atoms of some other element. That is, the elements change or ‘transmute’ into other elements until the series
ends with a stable element.
Radioactive elements decay at different rates. Rates are measured as half-lives – that is, the time it takes
for one half of any given quantity of a radioactive element to disintegrate. The longest half-life is that of the
‘isotope’ 238
U of uranium. It is 4.5 billion years. Some isotopes have half-lives of years, months, days, minutes,
seconds, or even less than millionths of a second.
Measurement units and permissible dosages
Radioactivity is measured in Becquerel (Bq) units. 1 Bq = 1 decay or disintegration per second. Curie (Ci) was
used earlier and 1 Ci = 37 billion Bq (3.7 × 1010
disintegrations per second) or 37 Bq = 1 nano-Ci.
To measure the health risk through ionization, in the US the most commonly used unit is rem or mrem (millirem).
In Europe, the most commonly used measuring unit for this purpose is Sv (Sievert) or mSv (milli-Sv).
Conversion of rem to Sieverts: 1 rem = 0.01 Sv = 10 mSv.
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CURRENT SCIENCE, VOL. 81, NO. 12, 25 DECEMBER 20011536
radioactivity in the seas is estimated to be nearly 10,000
exabecquerel (Ebq = 1018
Bq). The residual waste tailings
from past mining and milling operations are estimated
to be around several million tons at many places
and the radioactivity contained may be nearly
0.001 EBq. Thousands of such sites are scattered all
around the world.
At OKLO, located in Gabon in the West African rainforest,
there exists uranium ore that formed an active
natural reactor over some billion years ago. A study of
this site has shown that the actinide fission products
migrated, under highly unfavourable conditions, only a
few tens of metres during this long duration.
Artificial radioactivity
Radioactivity was discovered about a hundred years
ago. Following the Second World War and discovery of
the fission process, human activity added radioactivity
artificially to the natural one. Two main sources have
been: (a) the civilian nuclear programmes, including
nuclear power production, medical and industrial applications
of radioactive nuclides for peaceful purposes,
and (b) the military nuclear programme, including atmospheric
and underground nuclear-weapon testing and
weapon production (see Box 2 for the nature of artificial
radioactive isotopes produced).
Nuclear fuel cycle
As stated earlier, civilian nuclear operations lead to radioactivity.
The story of uranium from its mining to its
use in reactors and thence of chemical processing and
accumulation of radioactive waste is covered by what is
referred to as ‘nuclear fuel cycle’ (see Box 3 for a
schematic fuel cycle). The ore that is mined in uranium
mines is sent to a uranium mill, where a small uraniumcontaining
fraction is separated from the ore, leaving
behind virtually almost the entire ore in the tailings.
The uranium fraction is processed to recover pure uranium
in metallic form. Uranium metal consists of the
isotope 235
U to the extent of 0.7%, the remaining 99.3%
being 238
U. 235
U fissions on absorption of thermal neutrons,
while 238
U does not. Hence this small fraction of
235
U is ‘enriched’ for use in light-water reactors for deriving
power. Highly enriched 235
U is used for nuclear
weapons also. In CANDU-type heavy-water reactors,
one can use natural uranium itself as fuel, without any
enrichment. (Except for the reactors at Tarapore and the
fast-breeder test reactor at Kalpakkam, the other Indian
power and research reactors use natural uranium as
fuel.) Fresh fuel made of uranium (sometimes containing
plutonium, in addition) is weakly radioactive. The
fuel, after sufficient use in reactors, is referred as ‘spent
fuel’; the ‘ash’ after ‘burning’ the fuel contains fissionfragment
debris from spontaneous or neutron-induced
Box 2. Common radioactive isotopes produced during nuclear reactions
Isotope Half-life Isotope Half-life Isotope Half-life
Relatively short half-life
Strontium-89 54 days Zirconium-95 65 days Niobium-95 39 days
Ruthenium-103 40 days Rhodium-103 57 minutes Rhodium-106 30 seconds
Iodine-131 8 days Xenon-133 8 days Tellurium-134 42 minutes
Barium-140 13 days Lanthanum-140 40 h Cerium-141 32 days
Year to century-scale half-life*
Hydrogen-3 12 years Krypton-85 10 years Strontium-90 29 years
Ruthenium-106 1 year Cesium-137 30 years Cerium-144 1.3 years
Promethium-147 2.3 years Plutonium-238 85.3 years Americium-241 440 years
Curium-224 17.4 years
Longer half-life
Technecium-99 2 × 106
years Iodine-129 1.7 × 107
years Plutonium-239 24000 years
Plutonium-240 6500 years Americium-243 7300 years
*Half-lives of the order of years to decades of isotopes of elements that can seek tissues or organs biologically
(being akin to other elements chemically) are the most hazardous from point of view of radiation. For example,
90
Sr, being chemically akin to Ca, can seek the bone and lodge itself there for years causing radioactive damage
to surrounding tissues.
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CURRENT SCIENCE, VOL. 81, NO. 12, 25 DECEMBER 2001 1537
Box 3. Nuclear fuel cycle: The activities comprising mining, processing, fuel fabrication and ultimately use of
fuel in nuclear reactors result in power generation. Reprocessing spent fuel helps in recycling plutonium for
fuel fabrication. The byproducts in this activity are enriched fissile material useful for fuel as well as for weapons,
depleted uranium used for DU shells, the actinides and radioactive waste.
fission of uranium and actinides, actinide elements and
unutilized uranium. This irradiated fuel is highly radioactive.
Transuranic actinides (principally neptunium,
plutonium, americium and curium) are created by absorption
of neutrons in non-fissioned uranium and by
sequential absorption of neutrons in the consequently
formed daughter elements. Although nearly 200 radionuclides
are produced during the burn-up of the fuel,
the great majority of them are relatively short-lived and
decay to low levels within a few decades (see Box 2).
Hence the spent fuel is often allowed to ‘cool’ in spentfuel
bays of water, to allow short-lived radioactivity to
Uranium mining Processing Uranium Uranium plant Waste
DU Shells for Tanks Depleted uranium Enrichment plant Fuel Nuclear reactor
235
UWeapons
From uranium mining to nuclear reactor
Thorium sands Processing Thorium Nuclear reactor Irradiated thorium
Reprocessing233
UFuelNuclear reactor
Weapon Waste
From thorium mining to nuclear reactor
Nuclear reactor Spent fuel Reprocessing plant Plutonium Fuel
Nuclear reactorWeaponsHigh level
radioactive residue
Nuclear power
Actinides Processing Waste
Nuclear reactor to nuclear power, spent fuel and reprocessing
GENERAL ARTICLE
CURRENT SCIENCE, VOL. 81, NO. 12, 25 DECEMBER 20011538
decay. Often such fuel is stored for indefinite time in
the fuel pools without any further processing, or in dry
‘coffins’. The short-lived radionuclides therefore do not
pose a big problem for long-term disposal.
The spent fuel, when subjected to chemical processing,
yields uranium and plutonium fractions apart from
the rest of the ‘ash’. In this article we do not deal with
the chemistry involving a variety of highly toxic chemicals
or the complex chemical processes that one employs,
either in fuel reprocessing or in radioactive waste
management. Beginning with dissolution of cladded
burnt fuel to retrieving useful fissile elements is an
enormous activity involving chemical engineering, remote
handling, monitoring, etc. As opposed to the socalled
‘once-through fuel cycle’ wherein no material is
recycled, in the ‘closed-cycle fuel cycle’, uranium is
recycled for fuel production and plutonium for either
fuel production or for weapons. Normally, the irradiated
uranium is dissolved in an acid medium and treated
with organic solvents to recover plutonium and remnants
of uranium. The byproduct is a highly acidic liquid,
a high-level radioactive waste containing fission
fragments and transuranic elements. The transuranic
elements can be separated further, as they constitute
rare, precious and often fissile materials themselves.
This is the ‘wealth’ from the waste we referred to in the
beginning.
The cause for concern
Radioactive waste, whether natural or artificial, is a
potential harbinger of radioactive exposure to humans
through many channels. The routes are direct exposure
to materials that are radioactive, inhalation and ingestion
of such materials through the air that one breathes
or food that one consumes. The quantum of exposure
(dose × duration of exposure) decides the deleterious
effects that may result. Exposure may occur to particular
organs locally or to the whole body. Sufficiently
high exposure can lead to cancer (see Box 4). The radiotoxicity
of a particular radionuclide is quantified in
terms of what is referred to as ‘potential hazard index’
that is defined in terms of the nuclide availability, its
activity, maximum permissible intake annually and its
half-life. This depends on a variety of factors like
physical half-life, biological half-life, sensitivity of the
organ or tissue where the nuclide is likely to concentrate,
ionizing power of the radiation from the nuclide
that depends on the energy of the radiation emitted from
the radionuclide, etc. It is from such considerations that
one concludes that radioactive nuclides of elements like
137
Cs or 90
Sr or 131
I are the most hazardous on the scale
of a human beings’ lifetime. Other long-life nuclides
like 239
Pu, 241
Am, 237
Np pose a long-term hazard, on the
other hand, to future generations.
Box 4. Radiation effects.
Every inhabitant on this planet is constantly exposed to naturally occurring ionizing radiation called background
radiation. Sources of background radiation include cosmic rays from the Sun and stars, naturally occurring
radioactive materials in rocks and soil, radionuclides normally incorporated into our body’s tissues, and
radon and its products, which we inhale. We are also exposed to ionizing radiation from man-made sources,
mostly through medical procedures like X-ray diagnostics. Radiation therapy is usually targeted only to the
affected tissues.
Much of our data on the effects of large doses of radiation comes from survivors of the atomic bombs
dropped on Hiroshima and Nagasaki in 1945 and from other people who received large doses of radiation,
usually for treatment. Only about 12% of all the cancers that have developed among those survivors are estimated
to be related to radiation.
Ionizing radiation can cause important changes in our cells by breaking the electron bonds that hold molecules
together. For example, radiation can damage our genetic material (DNA). But the cells also have several
mechanisms to repair the damage done to DNA by radiation.
Potential biological effects depend on how much and how fast a radiation dose is received. An acute radiation
dose (a large dose delivered during a short period of time) may result in effects which are observable
within a period of hours to weeks. A chronic dose is a relatively small amount of radiation received over a long
period of time. The body is better equipped to tolerate a chronic dose than an acute dose as the cells need
time to repair themselves.
Radiation effects are also classified in two other ways, namely somatic and genetic effects. Somatic effects
appear in the exposed person. The delayed somatic effects have a potential for the development of cancer
and cataracts. Acute somatic effects of radiation include skin burns, vomiting, hair loss, temporary sterility or
subfertility in men, and blood changes. Chronic somatic effects include the development of eye cataracts and
cancers. The second class of effects, namely genetic or heritable effects appears in the future generations of
the exposed person as a result of radiation damage to the reproductive cells, but risks from genetic effects in
humans are seen to be considerably smaller than the risks for somatic effects.
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Although nature’s sources are to be as much feared as
those from artificial sources, the (atomic) bomb’s legacy
has set a certain perception in the public mind, of
the dangers inherent or implicit in the use and abuse of
nuclear facilities, operations and waste. The recent emphasis
arises because of concern to the effects on the
environment over a very long period of time. High-level
radioactive waste is potentially toxic for tens of thousands
to millions of years; it is also the most difficult to
be disposed safely because of its heat and radiation output.
Thermal, chemical and radiological gradients operate
on the environment over periods as long as 500,000
years.
Some of the concerns being expressed border on
over-reaction to a problem that exists. It is not that one
should wish away the problem. But on the other hand,
the reaction or concern is often inflated. As Tanner
asked ‘Are not we kidding ourselves when we claim to
be so concerned about the far-out possibility that a nuclear-waste-disposal
site may begin to leak 10,000 or
1,000,000 years from now? In what other area of life do
we show such foresight?’ (Phys. Today, January 1998,
p. 86.)
We are confronted with a dilemma. On one side, 50–
100 years hence, our fossil fuel sources may be reaching
the rock-bottom of availability and the renewable
sources of energy (solar, wind, geothermal, etc. power
sources) may not meet the demands of society. Till alternate
energy sources are developed, the only source
available to mankind is the nuclear power.
To set the scenario in proper perspective, it should be
noted that nuclear power plants are managed subject to
several radiation protection control practices. Secondly,
one may also note that ‘a 1000 MW electric coal-fired
power plant releases into the environment nearly 6 million
tonnes of greenhouse gases, 500,000 tons of mixtures
of sulphur and nitrogen oxides and about 320,000
tonnes of ashes’. These ashes containing NORMs are
potentially capable of subjecting humanity to a collective
dose of radiation higher than that attributable to
wastes discharged into the environment by nuclear
power plants generating the same amount of electricity.
In spite of this ground reality, public perception about
nuclear wastes is rather skewed against nuclear power
in several countries.
Quantifying natural and artificial nuclear waste
The level of radioactive waste is quoted in terms of volume
(in cubic metres) or in tonnage. Another way is to
quote the radioactivity contained in such waste in bequerels
(Bq). Both the units are useful because one
needs to know the volume or weight of the waste to be
handled for disposal purposes and also the radioactivity
contained therein.
We have already noted that nuclear waste from natural
sources, including mining and related operations,
could have resulted in production of radioactive waste
of a few EBq and the sea is repository of several thousand
EBq of radioactivity.
Compared to this it is estimated that in the military
nuclear operations, the cold-war era resulted in release
of more than 1000 EBq of nuclear debris in the atmosphere.
Production of weapon-grade material resulted in
about 1000 EBq of residual waste and ‘accidents and
losses’ of nuclear submarines and nuclear-powered satellites
might have resulted in waste of a few EBq.
In the civilian regime, it is estimated that the nuclear
waste, as a result of nuclear power production around
the world over the past 50 years, is of the order of
1000 EBq and is growing at the rate of approximately
100 EBq/year. Typically, a large nuclear power plant of
generating capacity of 1000 MW electricity produces
‘around 27 tonnes of high-level radioactive waste, 310
tonnes of intermediate-level and 460 tonnes of lowlevel
radioactive waste’.
Classification of radioactive waste
Nuclear waste can be generally classified as either ‘lowlevel’
radioactive waste or ‘high-level’ radioactive
waste.
Low-level radioactive waste
Basically all radioactive waste that is not high-level
radioactive waste or intermediate-level waste or transuranic
waste is classified as low-level radioactive
waste. Volume-wise it may be larger than that of highlevel
radioactive waste or intermediate-level radioactive
waste or transuranic waste, but the radioactivity contained
in the low-level radioactive waste is significantly
less and made up of isotopes having much shorter halflives
than most of the isotopes in high-level radioactive
waste or intermediate-level waste or transuranic waste.
Large amounts of waste contaminated with small
amounts of radionuclides, such as contaminated equipment
(glove boxes, air filters, shielding materials and
laboratory equipment) protective clothing, cleaning
rags, etc. constitute low-level radioactive waste. Even
components of decommissioned reactors may come under
this category (after part decontamination proce-
dures).
The level of radioactivity and half-lives of radioactive
isotopes in low-level waste are relatively small.
Storing the waste for a period of 10 to 50 years will
allow most of the radioactive isotopes in low-level
waste to decay, at which point the waste can be disposed
of as normal refuse.
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It may come as a surprise that several investigations
have shown that exposure of mammals to low levels of
radiation may indeed be beneficial, including, ‘increased
life span, greater reproductive capacity, better
disease resistance, increased growth rate, greater resistance
to higher radiation doses, better neurological
function, better wound healing and lower tumour induction
and growth’ (Devaney, J. J., Phys. Today, January
1998, p. 87). Beneficial effects on plants include accelerated
growth and development and increased harvests.
Low-level radioactive waste, therefore, seems to be be-
nign.
High-level radioactive waste
High-level radioactive waste is conceptualized as the
waste consisting of the spent fuel, the liquid effluents
arising from the reprocessing of spent fuel and the solids
into which the liquid waste is converted. It consists,
generally, material from the core of a nuclear reactor or
a nuclear weapon. This waste includes uranium, plutonium
and other highly radioactive elements created during
fission, made up of fission fragments and
transuranics. (Note that this definition does not specify
the radioactivity that must be present to categorize as
high-level radioactive waste.) These two components
have different times to decay. The radioactive fission
fragments decay to different stable elements via different
nuclear reaction chains involving α, β and γ emissions
to innocuous levels of radioactivity, and this
would take about 1000 years. On the other hand, transuranics
take nearly 500,000 years to reach such levels.
Heat output lasts over 200 years. Most of the radioactive
isotopes in high-level waste emit large amounts of
radiation and have extremely long half-lives (some
longer than 100,000 years), creating long time-periods
before the waste will settle to safe levels of radioactiv-
ity.
As a thumb-rule one may note that ‘volumes of lowlevel
radioactive waste and intermediate-level waste
greatly exceed those of spent fuel or high-level radioactive
waste’. In spite of this ground reality, the public
concerns regarding disposal of high-level radioactive
waste is worldwide and quite controversial.
Approaches to radioactive waste disposal
Waste disposal is discarding waste with no intention of
retrieval. Waste management means the entire sequence
of operations starting with generation of waste and ending
with disposal.
Solid waste disposal, of waste such as municipal garbage,
is based on three well-known methods, namely
landfills, incineration and recycling. Sophisticated
methods of landfills are adapted for radioactive waste
also. However, during incineration of ordinary waste,
fly ash, noxious gases and chemical contaminants are
released into the air. If radioactive waste is treated in
this manner, the emissions would contain radioactive
particulate matter. Hence when adapted, one uses fine
particulate filters and the gaseous effluents are diluted
and released. Recycling to some extent is feasible. We
have already dealt with the reprocessing approach,
whereby useful radioactive elements are recovered for
cyclic use. But it still leaves some waste that is a part of
the high-level radioactive waste.
Radioactive waste management involves minimizing
radioactive residues, handling waste-packing safely,
storage and safe disposal in addition to keeping sites of
origin of radioactivity clean. Poor practices lead to future
problems. Hence choice of sites where radioactivity
is to be managed safely is equally important in addition
to technical expertise and finance, to result in safe and
environmentally sound solutions.
The International Atomic Energy Agency (IAEA) is
promoting acceptance of some basic tenets by all countries
for radioactive waste management. These include:
(i) securing acceptable level of protection of human
health; (ii) provision of an acceptable level of protection
of environment; (iii) while envisaging (i) and (ii),
assurance of negligible effects beyond national boundaries;
(iv) acceptable impact on future generations; and
(v) no undue burden on future generations. There are
other legal, control, generation, safety and management
aspects also.
Next we review some approaches for radioactive
waste disposal.
To begin with, the radioactive waste management
approach is to consider the nature of radioactive elements
involved in terms of their half-lives and then
choose the appropriate method of handling. If the concentrations
of radioactive elements are largely shortlived,
then one would resort to what is referred to as
‘delay and decay’ approach; that is, to hold on to such a
waste for a sufficiently long time that the radioactivity
will die in the meanwhile. A second approach is to ‘dilute
and disperse’ so that the hazard in the environment
is minimized. But when the radioactivity is long-lived,
the only approach that is possible is to ‘concentrate and
contain’ the activity. In order to carry out concentrating
the waste (generally the sludge), chemical precipitation,
ion exchange, reverse osmosis and natural or steam
evaporation, centrifuging, etc. are resorted to. The resulting
solids are highly concentrated in radioactivity.
In the following we shall discuss some of the approaches
that are being advocated or are currently in
practice.
However, to the extent that the mining operations
result in ‘bringing the radioactivity to the surface and
change its chemical and physical form that may increase
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CURRENT SCIENCE, VOL. 81, NO. 12, 25 DECEMBER 2001 1541
its mobility in the environment’, they assume importance
in radioactive waste management. Long-lived isotopes
like
230
Th,
226
Ra, the decay products of uranium
are part of the tailings and hence the tailings have to be
contained.
Low-level radioactive waste and even transuranic
waste is often buried in shallow landfills. One has to
pay attention to any groundwater contamination that
may result due to this.
The highly radioactive liquid effluents are expected
to be ultimately solidified into a leach-resistant form
such as borosilicate glass, which is fairly robust in the
sense that it is chemically durable, resistant to radiolysis,
relatively insensitive to fluctuations in waste composition
and easy to process remotely. (Immobilization
in cement matrices or bitumanization or polymerization
are also some of the other options that are practised to
some extent.) However, it must be noted that plutonium
does not bind strongly to the matrix of the glass and
‘thus can be loaded only in trace amounts to prevent the
possibility of criticality or recovery for clandestine purposes’.
This glass in turn is placed in canisters made of
specific alloys. Choice of the canister material would
depend on the ultimate site where the waste will be disposed-off.
For example, if the ultimate disposal is in the
oceans, the alloy chosen must have low corrosion rates
under the environmental temperature, pressure, oxygen
concentration, etc. Studies have been carried out in this
respect. For example, it is found that in oxygenated
sea water at 250o
C, 7 mega Pascals pressure and
1750 ppm of dissolved oxygen, the corrosion rates of
1018 mild steel, copper, lead, 50 : 10 cupro-nickel,
Inconel 600 and Ticode 12 are 11.0, 5.0, 1.0, 0.7, 0.1
and 0.06 mm/year, respectively.
One seeks to dispose-off the high-level radioactive
waste packages contained in multiple metal-barrier canisters
within natural or man-made barriers, to contain
radioactivity for periods as long as 10,000 to 100,000
years. ‘The barrier is a mechanism or medium by which
the movement of emplaced radioactive materials is
stopped or retarded significantly or access to the radioactive
materials is restricted or prevented’. It is obvious
that recourse to multiple barriers may assure safety of
emplaced radioactivity over long periods of time. The
man-made barriers, namely the form to which waste is
reduced, for example, in the glassy form, and the canister
along with overpackaging, go along with natural
barriers. As far as the choice of natural barriers is concerned,
land-based mined depositories over fairly stable
geologic formations are preferred over disposal in the
oceans. However several social and environmental concerns
have prevented the land-route being adopted in
counties like USA even after 50 years of accumulation
of radioactive waste. Therefore proposals have been
made to take to the ocean-route and there also the
choice varies from just placement of the canisters over
the seabed to placement within the sub-seabed sediments
and even within the basement rocks.
In the US, as spent fuels have reached levels of radioactivity
of the order of 50,000 MCi (excluding military
sources), there is dearth of space to store additional
irradiated fuel removed from operating reactors. Legally,
the Department of Energy (DOE) is expected to
take charge of all commercial spent fuel. However, the
DOE has run into a dead-end. On one hand it is unable
to use spent fuel and on the other, its attempts to develop
a permanent repository at Yucca Mountain in Nevada
are met by social and State challenges as well as
lack of complete study of the site itself. Presidential
consent has not been forthcoming to any legislation in
this connection.
Options being aired for disposing radioactivity
Triet Nguyen, Department of Nuclear Engineering,
University of California, Berkeley, has written in an
article ‘High-level Nuclear Waste Disposal’, 14 November
1994 that ‘High-level nuclear waste from both
commercial reactors and defence industry presents a
difficult problem to the scientific community as well as
the public. The solutions to this problem are still debatable,
both technically and ethically ... . There are many
proposals for disposing high-level nuclear wastes. However
the most favoured solution for the disposal of these
wastes is isolating radioactive waste from man and
biosphere for a period of time such that any possible
subsequent release of radionuclides from the waste
repository will not result in undue radiation exposure.
The basic idea behind this is to use stable geological
environments that have retained their integrity for millions
of years to provide a suitable isolation capacity for
the long time-periods required. The reason for relying
on such geological environments is based on the following
main consideration: ‘Geological media is an entirely
passive disposal system with no requirement for continuing
human involvement for its safety. It can be
abandoned after closure with no need for continuing
surveillance or monitoring. ...The safety of the system
is based on multiple barriers, both engineered and natural,
the main one being the geological barrier itself.’
One way of disposing high-level nuclear waste materials
which meets the above condition is the concept of
disposing of these wastes by burial in suitable geologic
media beneath the deep ocean floor, which is called
seabed disposal.
The following options have been aired sometime or
the other. Each one of the options demands serious
studies and technical assessments:
• Deep geological repositories
• Ocean dumping
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CURRENT SCIENCE, VOL. 81, NO. 12, 25 DECEMBER 20011542
• Seabed burial
• Sub-seabed disposal
• Subductive waste disposal method
• Transforming radioactive waste to non-radioactive
stable waste
• Dispatching to the Sun.
Major problems due to legal, social, political and financial
reasons have arisen in execution due to
• Environmental perceptions
• Lack of awareness and education
• ‘Not-in-my-backyard’ syndrome
• ‘Not-in-the-ocean’ syndrome
• Lack of proven technology.
Geologic disposal
Geologic disposal in deep geological formations –
whether under continental crust or under seabed – as a
means of radioactive waste disposal has been recognized
since 1957, for handling long-lived waste. Quite
often, contrary to views expressed by environmentalists,
it is ‘not chosen as a cheap and dirty option to get the
radioactive waste simply “out of site and out of mind”’.
The deep geological sites provide a natural isolation
system that is stable over hundreds of thousands of
years to contain long-lived radioactive waste. In practice
it is noted that low-level radioactive waste is generally
disposed in near-surface facilities or old mines.
High-level radioactive waste is disposed in host rocks
that are crystalline (granitic, gneiss) or argillaceous
(clays) or salty or tuff. Since, in most of the countries,
there is not a big backlog of high-level radioactive
waste urgently awaiting disposal, interim storage facilities,
which allow cooling of the wastes over a few decades,
are in place.
Ocean-dumping
For many years the industrialized countries of the world
(e.g. USA, France, Great Britain, etc.) opted for the
least expensive method for disposal of the wastes by
dumping them into the oceans. Before 1982, when the
United States Senate declared a moratorium on the
dumping of radioactive wastes, the US dumped an estimated
112,000 drums at thirty different sites in the Atlantic
and Pacific oceans.
Though this practice has been banned by most of the
countries with nuclear programmes, the problem still
persists. Russia, which currently controls sixty per cent
of the world’s nuclear reactors, continues to dispose of
its nuclear wastes into the oceans. According to Russia’s
Minister of Ecology, it will continue to dump its
wastes into the oceans because it has no other alternative
method. It will continue to do so until it receives
enough international aid to create proper storage facilities.
In response, the United States has pledged money
to help Russia, but the problem continues.
Although radioactive waste has known negative effects
on humans and other animals, no substantial scientific
proof of bad effects on the ocean and marine life
has been found. Hence some nations have argued that
ocean-dumping should be continued. Others argue that
the practice should be banned until further proof of no
harm is available.
Oceanic Disposal Management Inc., a British Virgin
Islands company, has also proposed disposing of nuclear
and asbestos waste by means of Free-Fall Penetrators.
Essentially, waste-filled missiles, which when
dropped through 4000 m of water, will embed themselves
60–80 m into the seabed’s clay sediments. These
penetrators are expected to survive for 700 to 1500
years. Thereafter the waste will diffuse through the
sediments. This was a method considered by the Scientific
Working Group (SWG) of the Nuclear Energy
Agency (NEA) during the eighties.
Penetrator disposal is potentially both feasible and
safe, its implementation would depend on international
acceptance and the development of an appropriate international
regulatory framework. Neither of these exists,
nor are they likely to in the foreseeable future. The
penetrator method has also been further constrained by
a recent revision of the definition of ‘dumping’, by the
London Dumping Convention, to include ‘any deliberate
disposal or storage of wastes or other matter in the
seabed and the subsoil thereof’.
Sub-seabed disposal
Seabed disposal is different from sea-dumping which
does not involve isolation of low-level radioactive
waste within a geological strata. The floor of deep
oceans is a part of a large tectonic plate situated some
5 km below the sea surface, covered by hundreds of
metres of thick sedimentary soft clay. These regions are
desert-like, supporting virtually no life. The Seabed
Burial Proposal envisages drilling these ‘mud-flats’ to
depths of the order of hundreds of metres, such boreholes
being spaced apart several hundreds of metres.
The high-level radioactive waste contained in canisters,
to which we have referred to earlier, would be lowered
into these holes and stacked vertically one above the
other interspersed by 20 m or more of mud pumped in.
The proposal to use basement-rock in oceans for radioactive
waste disposal is met with some problems:
variability of the rock and high local permeability. Oceanic
water has a mixing time of the order of a few thousand
years which does not serve as a good barrier for
long-lived radionuclides.
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CURRENT SCIENCE, VOL. 81, NO. 12, 25 DECEMBER 2001 1543
Since experiments cannot be conducted to assure
safety of seabed disposal on the basis of actual canisters
deposited in the seabed over periods of interest, namely
over hundreds of thousands of years, model calculations
have been performed to predict the capabilities of such
a disposal option.
The model approach has started with selection of
sites and acquisition of site-specific data using marine
geological methods. These sites are away from deep-sea
trenches, mid-oceanic ridges or formation zones where
geological activities are high. These sites are also far
away from biologically productive areas in the oceans.
The sediments in chosen sites are fine-grained and are
called ‘abyssal red clay’. These sites are believed to
have desirable barrier properties with ‘continuous stable
and depositional histories’. Therefore these potential
waste repositories are geologically stable over periods
of the order of 107
years and are likely not to have human
activities, as they are not resources of fishes or
hydrocarbons or minerals.
Core samples from most Pacific and Atlantic sites
have been studied to investigate thermal, chemical and
radiological effects. It is found that when sea water and
sample sediment mixtures are heated at 300
o
C at high
pressure, the solution pH changes from 8 to 3. Calculations
suggest that ‘less than 2 cubic metres of untreated
sediment would be needed to neutralize all the acid
generated in the thermally perturbed region of about
5.5 m
3
’. The canister material has to be compatible with
this type of environment for periods of at least 500
years by which time fission fragment activity would
become acceptable. Similarly, other calculations have
taken into account sediment–nuclide interactions to determine
ion concentration around a buried source as a
function of time.
Experimental work has already established that clays
have the property of holding on to several radioactive
elements, including plutonium; hence, seepage of these
elements into saline water is minimal. Rates of migration
of these elements over hundreds of thousands of
years would be of the order of a few metres. Hence,
during such long times, radioactivity will diminish to
levels below the natural radioactivity in sea water due
to natural radioactive decay. The clays also have plastic-like
behaviour to form natural sealing agents. Finally,
the mud-flats have rather low permeability to
water; hence, leaching probability is rather low.
It may be noted that the method depends on standard
deep-sea drilling techniques routinely practised and
sealing of the bore-holes. These two aspects are welldeveloped,
thanks to the petroleum industry and also
because of an international programme called the Ocean
Drilling Programme. Core samples from about half a
dozen vastly separated sites in the Pacific and Atlantic
oceans have ‘showed an uninterrupted history of geological
tranquillity over the past 50–100 million years’.
However there are questions that remain to be an-
swered:
• Whether migration of radioactive elements through
the ocean floor is at the same rate as that already
measured in the laboratories?
• What is the effect of nuclear heat on the deep oce-
anic-clays?
• What is the import on the deep oceanic fauna and
waters above?
• In case the waste reaches the seabed-surface, will
the soluble species (for example, Cs, Tc, etc.) be diluted
to natural background levels? If so, at what
rate?
• What happens to insoluble species like pluto-
nium?
• What is the likelihood of radioactivity reaching all
the way to the sea surface?
• In problems of accidents in the process of seabed
burial leading to, say, sinking ships, to loss of canisters,
etc. how does one recover the waste-load under
such scenarios?
• What is the likelihood that the waste is hijacked
from its buried location?
Added to these technical problems are others:
• International agreement to consider seabed-burial as
distinct from ‘ocean-dumping’.
• This method would be expensive to implement, but
its cost would be an impediment to any future plutonium-mining
endeavour.
Although the world trend is toward the option of
land-based disposal, it is doubtful whether restricting
repositories to land-based sites really helps prevention
of sea pollution. If radionuclides from a land-based repository
leached out to the surface, they would be
quickly transported to the sea by surface water. What is
essential is to isolate radionuclides from the biosphere
as reliably as possible. If sub-seabed disposal results in
more reliable isolation, sub-seabed disposal is the better
safeguard against sea pollution. This method takes into
consideration technological feasibility, protection of
marine environments, and availability of international
understanding.
The United Nation’s Convention on the Law of the
Sea delineates that a coastal state is granted sovereign
rights to utilize all resources in water and under the
seabed within its exclusive economic zone (EEZ),
which can extend from the coast line up to 200 nautical
miles (about 370 km) offshore. A repository is proposed
to be constructed in bedrock 2 km beneath the seabed.
To utilize sub-seabed disposal within the EEZ, it is also
proposed that waste packages would be transported
through a submarine tunnel connecting land with the
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CURRENT SCIENCE, VOL. 81, NO. 12, 25 DECEMBER 20011544
sub-seabed repository. Sea pollution by an accident during
disposal work would be improbable, because waste
would never go through sea water during the work. The
proposed method is a variation of geologic disposal.
Long-term monitoring is also possible by maintaining
the access tunnel for some time after constructing artificial
barriers.
While sub-seabed disposal of nuclear waste-filled
canisters thrown from vessels apparently is regulated by
the London Convention, it is not prohibited or regulated
by the London Convention when accessed via landbased
tunnels. Sweden has been practising this method
of sub-seabed disposal since 1988, when a repository
for reactor wastes was opened sixty metres below the
Baltic seabed. This project has been widely cited by
politicians from other countries as a great example of
solving the nuclear waste problem. Because of Sweden’s
initiative, nuclear waste is already being deposited
under the seabed. Other countries could follow
Sweden’s example and dispose-off nuclear waste under
the seabed via land-based tunnels.
Subductive waste disposal method
This method is the state-of-the-art in nuclear waste disposal
technology. It is the single viable means of disposing
radioactive waste that ensures non return of the
relegated material to the biosphere. At the same time, it
affords inaccessibility to eliminated weapons material.
The principle involved is the removal of the material
from the biosphere faster than it can return. It is considered
that ‘the safest, the most sensible, the most economical,
the most stable long-term, the most
environmentally benign, the most utterly obvious places
to get rid of nuclear waste, high-level waste or lowlevel
waste is in the deep oceans that cover 70% of the
planet’.
Subduction is a process whereby one tectonic plate
slides beneath another and is eventually reabsorbed into
the mantle. The subductive waste disposal method
forms a high-level radioactive waste repository in a
subducting plate, so that the waste will be carried beneath
the Earth’s crust where it will be diluted and dispersed
through the mantle. The rate of subduction of a
plate in one of the world’s slowest subduction zones is
2.1 cm annually. This is faster than the rate (1 mm annually)
of diffusion of radionuclides through the turbidite
sediments that would overlay a repository
constructed in accordance with this method. The subducting
plate is naturally predestined for consumption
in the Earth’s mantle. The subducting plate is constantly
renewed at its originating oceanic ridge. The slow
movement of the plate would seal any vertical fractures
over a repository at the interface between the subducting
plate and the overriding plate.
Transmutation of high-level radioactive waste
This route of high-level radioactive waste envisages that
one may use transmutational devices, consisting of a
hybrid of a subcritical nuclear reactor and an accelerator
of charged particles to ‘destroy’ radioactivity by neutrons.
‘Destroy’ may not be the proper word; what is
effected is that the fission fragments can be transmuted
by neutron capture and beta decay, to produce stable
nuclides. Transmutation of actinides involves several
competing processes, namely neutron-induced fission,
neutron capture and radioactive decay. The large number
of neutrons produced in the spallation reaction by
the accelerator are used for ‘destroying’ the radioactive
material kept in the subcritical reactor. The scheme has
not yet been demonstrated to be practical and cost-
effective.
Solar option
It is proposed that ‘surplus weapons’ plutonium and
other highly concentrated waste might be placed in the
Earth orbit and then accelerated so that waste would
drop into the Sun. Although theoretically possible, it
involves vast technical development and extremely high
cost compared to other means of waste disposal. Robust
containment would be required to ensure that no waste
would be released in the event of failure of the ‘space
transport system’.
Other options and issues
In its 1994 report entitled ‘Management and Disposition
of Excess Weapons’ Plutonium’, the National Academy
of Sciences set forth two standards for managing the
risks associated with surplus weapons-usable fissile
materials. First, the storage of weapons should not be
extended indefinitely because of non-proliferation risks
and the negative impact it would have on armsreduction
objectives. Second, options for long-term disposition
of plutonium should seek to meet a ‘spent-fuel
standard’ in which the plutonium is made inaccessible
for weapons use.
One of the chosen options of DOE is for dealing with
surplus plutonium, its use as a Mixed Oxide Fuel
(MOX) to be burned in reactors such as the CANDU.
The United States policy is not to encourage the civil
use of plutonium. The Nuclear Control Institute regards
the vitrification approach as posing fewer risks than the
MOX approach with regard to diversion or theft of warhead
material, reversal of the disarmament process, and
other adverse effects on international arms control and
non-proliferation efforts. A decision to dispose-off warhead
plutonium by means of vitrification or other immobilization
technology would be an essential step
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CURRENT SCIENCE, VOL. 81, NO. 12, 25 DECEMBER 2001 1545
toward achievement of such a regime. Proponents of
MOX disposition claim that vitrification technology is
immature, speculative and cannot be ready soon
enough. On the other hand, the MOX option, though it
does not necessarily involve further reprocessing, would
clearly encourage civilian use of plutonium, which in
some countries like Japan even includes plans for reprocessing
irradiated MOX fuel. In the opinion of the
Nuclear Control Institute, ‘the MOX option’ sends the
wrong signal in three ways.
First, this option effectively declares that plutonium
has an asset value, and that the energy contained within
it should be viewed as a ‘national asset’ (as the US
DOE expressed it) or even ‘national treasure’ (as the
Russians put it), when, in fact, plutonium fuel has been
shown to be an economic liability. Second, the MOX
option suggests that a commercial plutonium fuel cycle
can be effectively safeguarded, when, in fact, it is becoming
obvious that large-throughput plutonium plants
face daunting safeguard problems. Third, the MOX option
would be portrayed as giving credibility to the
claim that plutonium recycle in light water reactors
(LWRs) is essential to nuclear waste management, at a
time when direct disposal of spent fuel is looking increasingly
attractive to utilities.
There are other arguments that relate to proliferation
using high-level radioactive waste. It is believed that
the technologies of Laser Isotope Separation and the
Large Volume Plasma Process may permit the mining
of weapons materials from any matrix.
There are many international transporting-related
issues. It is not uncommon that reprocessing of one
country’s spent fuel or waste is taken up in a different
country. Such movement is often via one or more countries
or over the international waters. Regulatory
mechanisms, both national and international, have to be
in place to guarantee safety of the waste under these
conditions.
Radioactive waste management in India
Just as per capita consumption of electricity is related to
the standard of living in a country, the electricity generation
by nuclear means can be regarded as a minimum
measure of radioactive waste that is generated by a
country and hence the related magnitude of radioactive
waste management. On the scale of nuclear share of
electricity generation, India ranks fourth from the bottom
in about 30 countries. As of the year 2000, India’s
share of nuclear electricity generation in the total electricity
generation in the country was 2.65% compared to
75%, 47%, 42.24%, 34.65%, 31.21%, 28.87%, 19.80%,
14.41% and 12.44% of France, Sweden, the Republic of
Korea, Japan, Germany, UK, USA, Russia and Canada,
respectively. The reactors in operation produce in net
Gigawatts (one billion (10
9
) watts) (E) in the latter
countries nearly 63, 9,13, 44, 21, 13, 97, 20 and 10,
respectively; India’s reactors in operation yield 1.9 on
this scale (both data are as per IAEA Report of 2000).
Hence the magnitude of radioactive waste management
in India could be miniscule compared to that in other
countries, especially when one takes into account the
nuclear arsenal already in stockpile in the nuclear
weapons countries. As more power reactors come onstream
and as weaponization takes deeper routes the
needs of radioactive waste management increase and in
this context the experience of other countries would
provide useful lessons.
Radioactive waste management has been an integral
part of the entire nuclear fuel cycle in India. Low-level
radioactive waste and intermediate-level waste arise
from operations of reactors and fuel reprocessing facilities.
The low-level radioactive waste liquid is retained
as sludge after chemical treatment, resulting in decontamination
factors ranging from 10 to 1000. Solid radioactive
waste is compacted, bailed or incinerated
depending upon the nature of the waste. Solar evaporaBox
5. Characteristics of liquid and solid waste generated in India
Liquid waste Solid waste
Average annual Specific Average annual Radiation
Source generation (m3
) activity (Bq/ml) generation (m3
) field (mCi/l)
Research reactor 16000 1–3 20–25 0.01–1000
Power reactor
BWR 26800 50–100 80 0.05–1000
PHWR 26800 0.1–1 100 0.01–1000
Fuel-reprocessing facility 34300 4–20 130 0.01–500
R&D lab 12000 1–4 50 0.01–7000
GENERAL ARTICLE
CURRENT SCIENCE, VOL. 81, NO. 12, 25 DECEMBER 20011546
tion of liquid waste, reverse osmosis and immobilization
using cement matrix are adopted depending on the
form of waste. Underground engineered trenches in
near-surface disposal facilities are utilized for disposal
of solid waste; these disposal sites are under continuous
surveillance and monitoring. High efficiency particulate
air (HEPA) filters are used to minimize air-borne radioactivity.
Over the past four decades radioactive waste
management facilities have been set up at Trombay,
Tarapore, Rawatbhata, Kalpakkam, Narora, Kakrapara,
Hyderabad and Jaduguda, along with the growth of nuclear
power and fuel-reprocessing plants. Multiplebarrier
approach is followed in handling solid waste.
Box 5 shows the characteristics of liquid and solid
waste generated in India.
After the commissioning of the fast breeder test reactor
at Kalpakkam, one is required to reprocess the burnt
carbide fuel from this reactor. As the burn-up of this
fuel is likely to be of the order of 100 MWD/kg, nearly
an order of magnitude more than that of thermal reactors
and due to short cooling-time before reprocessing,
specific activity to be handled will be greatly enhanced.
The use of carbide fuel would result in new forms of
chemicals in the reprocessing cycle. These provide new
challenges for fast-reactor fuel reprocessing.
Concluding remarks
The problems associated with radioactive waste management
on a long-term are major ones that humanity
has not been able to come to terms with so far. The
problem of radioactive waste management has been
compared to a Gordian knot. The Gordian knot should
not be just sliced through quick and deftly. As American
Ambassador Rich III put it, ‘The obstacles cannot
be over soon or ignored. We must untie the Gordian
knot carefully and painstakingly, using all of our
resources and democratic institutions wisely and well’.
It is nearly 45 years since the IAEA was founded.
Over these years the Agency has deliberated on various
issues that confront radioactive waste management and
has been providing guidelines and forums for technical
and non-technical debates and discussions. As time
passes by, new issues crop up, which need to be discussed.
One example is how does one ‘plan for retirement
of nuclear facilities’, sometimes referred to as
‘decommissioning of facilities’. Similarly changes in
concepts of long-term issues on health and safety need
to be addressed – ‘dose and risk for a remote time in the
future are not believable, since habits of human populations
are impossible to be predicted’.
All options have not been examined in totality. ‘The
value of learning by holistic studies of so-called natural
analogues is getting appreciated. These are natural systems
(such as ore bodies, clay beds and alkaline
springs) or archaeological artifacts (Roman glasses,
ancient metallic objects and so on) that exhibit some of
the key features that repository analysts need to understand.
By studying how these systems have evolved
over geological time scales, one can gain insights into
future repository evolution... The problems will not be
solved by throwing unlimited money at them. Some
processes take their own time to fructify…’.
1. IAEA Bull., 2000, vol. 42, contains a large number of articles
related to radioactive waste management. This publication gave
an impetus for writing this review.
2. Special issue on Radioactive Waste – Five articles in Phys.
Today, June 1997 and subsequent letters.
3. Articles in ‘Confronting The Nuclear Legacy’ in three parts, Sci.
Am., 1996–1998.
4. Natarajan, R., in IANCAS Bull., July 1998, p. 27.
5. Kumra, M. S. and Bansal, N. A., in Facets of Nuclear Science and
Technology, Department of Atomic Energy, Mumbai, 1993.
6. Surender Kumar, et al., IAEA-SM-357/38, 1999.
7. Many resources on the world-wide-web.
Received 25 May 2001; revised accepted 27 September 2001