urg:::Fw: [abolition-caucus] U and DU

[judy]

----- Original Message -----
From: "Jim Hoerner" <jim_hoerner@hotmail.com>
To: <Know_Nukes@yahoogroups.com>
Cc: <nucnews@yahoogroups.com>; <downwinders@yahoogroups.com>;
<abolition-caucus@yahoogroups.com>
Sent: Saturday, June 08, 2002 9:50 AM
Subject: [abolition-caucus] U and DU


> http://www.world-nuclear.org/info/inf14.htm
>
> Uranium and Depleted Uranium
>
> June 2002
>
>
> --------------------------------------------------------------------------
------
>
> The basic fuel for a nuclear power reactor is uranium - a very heavy metal
> containing abundant concentrated energy.
> It is mildly radioactive and occurs naturally in the Earth's crust.
> Depleted uranium is a by-product or waste product of uranium enrichment.
> The health hazards associated with any uranium are much the same as those
> for lead.
>
> --------------------------------------------------------------------------
------
> Uranium was apparently formed in super novae about 6.6 billion years ago.
> While it is not common in the solar system, today its radioactive decay
> provides the main source of heat inside the earth, causing convection and
> continental drift. As decay proceeds, the final product, lead, increases
in
> relative abundance.
> Uranium was discovered by Martin Klaproth, a German chemist, in 1789 in
the
> mineral pitchblende, and was named after the planet Uranus.
>
> Uranium (chemical symbol U) is slightly more abundant than tin and about
40
> times as common as silver. It occurs in most rocks in concentrations of 2
to
> 4 parts per million and is as common in the earth's crust as tin, tungsten
> and molybdenum. It is also found in the oceans, at an average
concentration
> of 1.3 parts per billion. There are a number of locations in different
parts
> of the world where it occurs in economically-recoverable concentrations.
> When mined, it yields a mixed uranium oxide product, (U3O8). Uraninite or
> pitchblende is the most common uranium mineral.
>
> Uses
>
> For many years from the 1940s, virtually all of the uranium that was mined
> was used in the production of nuclear weapons, but this ceased to be the
> case in the 1970s. Today the only substantial use for uranium is as fuel
in
> nuclear reactors, mostly for electricity generation. Uranium-235 is the
only
> naturally-occurring material which can sustain a fission chain reaction,
> releasing large amounts of energy.
>
> In the past, uranium was also used to colour glass (from as early as 79
AD)
> and deposits were once mined in order to obtain its decay product, radium.
> This element was used in luminous paint, particularly on the dials of
> watches and aircraft instruments, and in medicine for the treatment of
> disease.
>
> While nuclear power is the predominant use of uranium, heat from nuclear
> fission can be used for industrial processes. It is also used for marine
> propulsion (mostly naval). And nuclear reactors are important for making
> radioisotopes.
>
> The Uranium Atom
>
> On a scale arranged according to the increasing mass of their nuclei,
> uranium is the heaviest of all the naturally-occurring elements (Hydrogen
is
> the lightest). Uranium has a specific gravity of 18.7.
>
> Like other elements, uranium occurs in slightly differing forms known as
> 'isotopes'. These isotopes differ from each other in the number of neutron
> particles in the nucleus. 'Natural' uranium as found in the earth's crust
is
> a mixture largely of two isotopes: uranium-238 (U-238), accounting for
99.3%
> and U-235 about 0.7%.
>
> The isotope U-235 is important because under certain conditions it can
> readily be split, yielding a lot of energy. It is therefore said to be
> 'fissile' and we use the expression 'nuclear fission'.  [fissile means
> fissions with thermal (slow) neutrons - JH]
>
> Meanwhile, like all radioactive isotopes, it decays. U-238 decays very
> slowly, its half-life being the same as the age of the earth. This means
> that it is barely radioactive, less so than many other isotopes in rocks
and
> sand. Nevertheless it generates 0.1 watts/tonne and this is enough to warm
> the earth's mantle.
>
> Uranium fission
>
> The nucleus of the U-235 isotope comprises 92 protons and 143 neutrons (92
+
> 143 = 235). When the nucleus of a U-235 atom is split in two by a neutron,
> some energy is released in the form of heat, and two or three additional
> neutrons are thrown off. If enough of these expelled neutrons split the
> nuclei of other U-235 atoms, releasing further neutrons,a 'chain reaction'
> can be achieved. When this happens over and over again, many millions of
> times, a very large amount of heat is produced from a relatively small
> amount of uranium.
>
> It is this process, in effect "burning" uranium, which occurs in a nuclear
> reactor. In a nuclear reactor the uranium fuel is assembled in such a way
> that a controlled fission chain reaction can be achieved. The heat created
> by splitting the U-235 atoms is then used to make steam which spins a
> turbine to drive a generator, producing electricity.
>
> Nuclear power stations and fossil-fuelled power stations of similar
capacity
> have many features in common. Both require heat to produce steam to drive
> turbines and generators. In a nuclear power station, however, the
fissioning
> of uranium atoms replaces the burning of coal or gas. The chain reaction
> that takes place in the core of a nuclear reactor is controlled by rods
> which absorb neutrons. They are inserted or withdrawn to set the reactor
at
> the required power level.
>
> The fuel elements are surrounded by a substance called a moderator to slow
> the speed of the emitted neutrons and thus enable the chain reaction to
> continue. Water, graphite and heavy water are used as moderators in
> different types of reactors.
>
> Most nuclear reactors require natural uranium (having 0.7% U-235) to be
> enriched, so as to increase the proportion of the fissile isotope U-235
> about five- or six-fold. (see below)
>
> A typical 1000 megawatt (MWe) reactor can provide enough electricity for a
> modern city of close to one million people, about 7 billion kWh per year.
>
> Uranium and Plutonium
>
> Whereas the U-235 atom is 'fissile', the U-238 atom is said to be
'fertile'.
> This means that it can capture one of the neutrons which are flying about
in
> the core of the reactor and become (indirectly) plutonium-239, which is
> fissile. Pu-239 is very much like U-235, in that it fissions when hit by a
> slow neutron and this also yields a lot of energy.
>
> Because there is so much U-238 in a reactor core (most of the fuel), these
> reactions occur frequently, and in fact about one third of the energy
yield
> comes from "burning" Pu-239.
>
> But sometimes a Pu-239 atom simply captures a neutron without splitting,
and
> it becomes Pu-240. Because the Pu-239 is either progressively "burned" or
> becomes Pu-240, the longer the fuel stays in the reactor the more Pu-240
is
> in it. The significance of this is that when the spent fuel is removed
after
> about three years, the plutonium in it is not suitable for making weapons
> but can be recycled as fuel. See also Plutonium paper.
>
> From uranium ore to reactor fuel
>
> Uranium ore can be mined by underground or open-cut methods, depending on
> its depth. After mining, the ore is crushed and ground up. Then it is
> treated with acid to dissolve the uranium, which is then recovered from
> solution. Uranium may also be mined by in situ leaching (ISL), where it is
> dissolved from the orebody in situ and pumped to the surface.
>
> The end product of the mining and milling stages, or ISL, is uranium oxide
> concentrate (U3O8). Before it can be used in a reactor for electricity
> generation, however, it must undergo a series of processes to produce a
> useable fuel.
>
> For most of the world's reactors, the next step in making a useable fuel
is
> to convert the uranium oxide into a gas, uranium hexafluoride (UF6), which
> enables it to be enriched. Enrichment increases the proportion of the
U-235
> isotope from its natural level of 0.7% to 3 - 4%. This enables greater
> technical efficiency in reactor design and operation, particularly in
larger
> reactors, and allows the use of ordinary water as a moderator. A
by-product
> (or waste product) of enrichment is depleted uranium (about 89% of the
> original feed).
>
> After enrichment, the UF6 gas is converted to uranium dioxide (UO2) which
is
> formed into fuel pellets. These fuel pellets are placed inside thin metal
> tubes which are assembled in bundles to become the fuel elements for the
> core of the reactor.
>
> For reactors which use natural uranium as their fuel (and hence which
> require graphite or heavy water as a moderator) the U3O8 concentrate
simply
> needs to be refined and converted directly to uranium dioxide.
>
> Spent reactor fuel is removed and stored, either to be reprocessed or
> disposed of underground
>
> Reprocessed Uranium
>
> When spent nuclear fuel is reprocessed, both plutonium and uranium are
> recovered separately. Uranium comprises about 96% of that spent fuel.
>
> The composition of reprocessed uranium depends on the time the fuel has
been
> in the reactor, but it is mostly U-238. Typically it will have about 1%
> U-235 and small amounts of U-232 and U-236. The former is a gamma-emitter,
> making the material difficult to handle, even with trace amounts. The
> latter, comprising about 0.5% of the material, is a neutron absorber which
> means that if reprocessed uranium is used for fresh fuel it must be
enriched
> slightly more than is required for natural uranium. In the future, laser
> enrichment techniques may be able to remove these isotopes.
>
> Nuclear power
>
> Over 16% of the world's electricity is generated from uranium in nuclear
> reactors. This amounts to about 2400 billion kWh, as much as from all
> sources worldwide in 1960.
>
> It comes from over 430 nuclear reactors with a total output capacity of
more
> than 350 000 MWe operating in 31 countries. A further thirty reactors are
> under construction and another 70 are on the drawing board.
>
> Belgium, Bulgaria, Finland, France, Germany, Hungary, Japan, South Korea,
> Lithuania, Slovakia, Slovenia, Spain, Sweden, Switzerland and Ukraine all
> get 30% or more of their electricity from nuclear reactors. The USA has
over
> 100 reactors operating, supplying 20% of its electricity. The UK gets
about
> a quarter of its electricity from uranium.
>
> Sources of uranium
>
> Uranium is widespread in many rocks, and even in seawater. However, like
> other metals, it is seldom sufficiently concentrated to be economically
> recoverable. Where it is, we speak of an orebody. In defining what is ore,
> assumptions are made about the cost of mining and the market price of the
> metal. Uranium reserves are therefore calculated as tonnes recoverable up
to
> a certain cost.
>
> Australia's reserves are about 25% of the world's total, but Canada is the
> world's leading producer. Other countries with reserves include Canada,
USA,
> South Africa, Namibia, Brazil and Kazakhstan. China may also have
> substantial deposits of uranium. Many more countries have smaller deposits
> which could be mined.
>
> Uranium is sold only to countries which are signatories of the Nuclear
> Non-Proliferation Treaty, and which allow international inspection to
verify
> that it is used only for peaceful purposes.
>
> Radioisotopes
>
> Radioisotopes have become a vital part of modern life. Using relatively
> small special purpose nuclear reactors, a wide range of radioactive
> materials (radioisotopes) can be made at low cost. For this reason their
use
> has become widespread since the early 1950s, and there are now some 280
> "research" reactors in 56 countries producing them.
>
> Radioisotopes play an important part in the technologies that provide us
> with food, water and good health. They are produced by bombarding small
> amounts of particular elements with neutrons.
>
> In medicine, radioisotopes are widely used for diagnosis and research.
> Radioactive chemical tracers emit gamma radiation which provides
diagnostic
> information about a person's anatomy and the functioning of specific
organs.
> Radiotherapy also employs radioisotopes in the treatment of some
illnesses,
> such as cancer. More powerful gamma sources are used to sterilise
syringes,
> bandages and other medical equipment. About one in two people in Western
> countries is likely to experience the benefits of nuclear medicine in
their
> lifetime, and gamma sterilisation of equipment is almost universal.
>
> In the preservation of food, radioisotopes are used to inhibit the
sprouting
> of root crops after harvesting, to kill parasites and pests, and to
control
> the ripening of stored fruit and vegetables. Irradiated foodstuffs are
> accepted by world and national health authorities for human consumption in
> an increasing number of countries. They include potatoes, onions, dried
and
> fresh fruits, grain and grain products, poultry and some fish. Some
> prepacked foods can also be irradiated.
>
> Agriculturally, in the growing crops and breeding livestock, radioisotopes
> also play an important role. They are used to produce high yielding,
disease
> and weather resistant varieties of crops, to study how fertilisers and
> insecticides work, and to improve the productivity and health of domestic
> animals. Industrially, and in mining, they are used to examine welds, to
> detect leaks, to study the rate of wear of metals, and for on-stream
> analysis of a wide range of minerals and fuels.
>
> Most household smoke detectors use a radioisotope (Americium-241) derived
> from the plutonium formed in nuclear reactors. These alarms save many
lives.
>
> Environmentally, radioisotopes are used to trace and analyse pollutants,
to
> study the movement of surface water, and to measure water runoffs from
rain
> and snow, as well as the flow rates of streams and rivers.
>
> Other reactors
>
> There are also other uses for reactors. Over 200 small nuclear reactors
> power some 150 ships, mostly submarines, but ranging from icebreakers to
> aircraft carriers. These can stay at sea for very long periods without
> having to make refuelling stops. In most such vessels the steam drives a
> turbine directly geared to propulsion.
>
> The heat produced by nuclear reactors can also be used directly rather
than
> for generating electricity. In Sweden and Russia, for example, it is used
to
> heat buildings and elsewhere it provides heat for a variety of industrial
> processes such as water desalination. High-temperature reactors can also
be
> used for industrial processes such as thermochemical production of
hydrogen.
>
> Nuclear weapons
>
> Both uranium and plutonium were used to make bombs before they became
> important for making electricity and radioisotopes. But the type of
uranium
> and plutonium for bombs is different from that in a nuclear power plant.
> Bomb-grade uranium is highly-enriched (>90% U-235, instead of about 3.5%);
> bomb-grade plutonium is fairly pure (>90%) Pu-239 and is made in special
> reactors.
>
> Today a lot of military high-enriched uranium is becoming available for
> electricity production. It is diluted about 25:1 with depleted uranium
> before being used as reactor fuel.
>
> Depleted Uranium
>
> Every tonne of natural uranium produced and enriched for use in a nuclear
> reactor gives about 130 kg of enriched fuel (3.5% or more U-235). The
> balance is depleted uranium (U-238, with 0.25-0.30% U-235). This major
> portion has been depleted in its fissile U-235 isotope by the enrichment
> process. It is commonly known as DU.
>
> DU is stored either as UF6 or it is de-converted back to U3O8, which is
more
> benign chemically and thus more suited for long-term storage. It is also
> less toxic. Every year over 50,000 tonnes of depleted uranium joins
already
> substantial stockpiles in USA, Europe and Russia. World stock is about 1.2
> million tonnes.
>
> Some DU is drawn from these stockpiles to dilute high-enriched (>90%)
> uranium released from weapons programs, particularly in Russia, and
destined
> for use in civil reactors. This weapons-grade material is diluted about
25:1
> with depleted uranium, or 29:1 with depleted uranium that has been
enriched
> slightly (to 1.5% U-235) to minimise levels of (natural) U-234 in the
> product.
>
> Other uses are more mundane, and depend on the metal's very high density
> (1.7 times that of lead). Hence, where maximum mass must fit in minimum
> space, such as aircraft control surface and helicopter counterweights,
yacht
> keels, etc, it is often well suited. Until the mid 1970s it was used in
> dental porcelains. In addition it is used for radiation shielding, being
> some five times more effective than lead in this role.
>
> Also because of its density, it is used as solid slugs or penetrators in
> armour-piercing projectiles, alloyed with abut 0.75% titanium. DU is
> pyrophoric, so that upon impact about 30% of the projectile atomises and
> burns to uranium oxide dust. It was widely used in the Kuwait war (300
> tonnes) and less so in Kosovo (11 tonnes).
>
> Health aspects of DU
>
> Depleted uranium is not classified as a dangerous substance
radiologically,
> though it is a potential hazard in large quantities, beyond what could
> conceivably be breathed. Its emissions are very low, since the half-life
of
> U-238 is the same as the age of the earth (4.5 billion years). There are
no
> reputable reports of cancer or other negative health effects from
radiation
> exposure to ingested or inhaled natural or depleted uranium, despite much
> study.
>
> However, uranium does have a chemical toxicity about the same as that of
> lead, so inhaled fume or ingested oxide is considered a health hazard.
Most
> uranium actually absorbed into the body is excreted within days, the
balance
> being laid down in bone and kidneys. Its biological effect is principally
> kidney damage. WHO has set a Tolerable Daily Intake level for U of 0.6
> microgram/kg body weight, orally. (This is about eight times our normal
> background intake from natural sources.) Standards for drinking water and
> concentrations in air are set accordingly.
>
> Like most radionuclides, it is not known as a carcinogen, or to cause
birth
> defects (from effects in utero) or to cause genetic mutations. Radiation
> from DU munitions depends on how long the uranium has been separated
> chemically from its decay products. If thorium-234 and protactinium-234
has
> built up through decay of U-238, these will give rise to some beta
> emissions. On this basis, DU is "weakly radioactive" with an activity of
39
> Bq/mg quoted (15 Bq/mg if pure).
>
> In 2001 the UN Environment Program examined the effects of nine tonnes of
DU
> munitions having been used in Kosovo, checking the sites targeted by it.
> UNEP found no widespread contamination, no sign of contamination in water
of
> the food chain and no correlation with reported ill-health in NATO
> peacekeepers.
>
> Thus DU is clearly dangerous for people in vehicles which are military
> targets, but for anyone else - even in a war zone - there is little
hazard.
> Ingestion or inhalation of uranium oxide dust resulting from the impact of
> DU munitions on their targets is the main possible exposure route. See
also
> Appendix and WHO briefing on DU and WHO fact sheet on DU.
>
>
>
> --------------------------------------------------------------------------
------
>
> Sources:
> BNFL, Cogema, JNFL, SKB and ANSTO publications and papers.
> Bulletin of Atomic Scientists, Nov-Dec 1999.
> New Scientist 5 & 26/6/99, AFP 29/10/01.
> UNEP/UNCHS, 1999, Balkans Task Force report, Appendix 4.
> OECD NEA 2001, Management of Depleted Uranium.
> Burchall & Clark, Depleted Uranium, NRPB Bulletin #229, March 2001.
>
>
>
> --------------------------------------------------------------------------
------
> Appendix:
> Statement by Australasian Radiation Protection Society
> Potential Health Effects of Depleted Uranium in Munitions
> February 2001.
> Some military personnel involved in the 1991 Gulf War have complained of
> continuing stress-like symptoms for which no obvious cause has been found.
> These symptoms have at times been attributed to the use of depleted
uranium
> in shells and other missiles, which are said to have caused toxic effects.
> Similar complaints have arisen from the more recent fighting in the
Balkans,
> particularly the Kosovo conflict about a year ago.
>
> Depleted uranium (DU) is natural uranium which is depleted in the rarer
> U-235 isotope (see below). It is a heavy metal and, in common with other
> heavy metals, it is chemically toxic. It is also slightly radioactive and
> there is therefore said to be a hypothetical possibility that it could
give
> rise to a radiological hazard under some circumstances, e.g. if dispersed
in
> finely divided form so that it is inhaled.
>
> However, because of the latency period for the induction of cancer by
> radiation, it is not credible that any cases of radiation-induced cancer
> could yet be attributed to the Kosovo conflict. Furthermore, extensive
> studies have concluded that no radiological health hazard should be
expected
> from exposure to depleted uranium.
>
> The risk from external exposure is essentially zero, even when pure metal
is
> handled. No detectable increases of cancer, leukaemia, birth defects or
> other negative health effects have ever been observed from radiation
> exposure to inhaled or ingested natural uranium concentrates, at levels
far
> exceeding those likely in areas where DU munitions have been used. This is
> mainly because the low radioactivity per unit mass of uranium means that
the
> mass needed for significant internal exposure would be virtually
impossible
> to accumulate in the body - and DU is less than half as radioactive as
> natural uranium.
>
> (see full statement on ARPS web site)
>
>
> From National Radiation Protection Board (UK) Bulletin Editorial
> March 2001:
>
> Uses and Risks of DU
> DU is radioactive and doses from inhalation of dust or from handling bare
> spent rounds need to be assessed properly. However, the scientific
consensus
> at present is that the risks are likely to be small and easily avoidable,
> especially compared with the other risks the armed forces have to take in
> war.
> (see full statement pdf on NRPB web site)
>
>
> --
> Hold the door for the stranger behind you.  When the driver a
> half-car-length in front of you signals to get over, slow down.  Smile and
> say "hi" to the folks you pass on the sidewalk.  Give blood.  Volunteer.
>
>
>
>
>
>
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