urg:::Background - N-fuel chain & DU
judy
judab@iinet.net.au
Tue, 11 Jun 2002 11:12:07 +0800
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----- Original Message -----=20
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
>=20
> Uranium and Depleted Uranium
>=20
> June 2002
>=20
>=20
> =
-------------------------------------------------------------------------=
-------
>=20
> The basic fuel for a nuclear power reactor is uranium - a very heavy =
metal=20
> 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=20
> for lead.
>=20
> =
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> Uranium was apparently formed in super novae about 6.6 billion years =
ago.=20
> While it is not common in the solar system, today its radioactive =
decay=20
> provides the main source of heat inside the earth, causing convection =
and=20
> continental drift. As decay proceeds, the final product, lead, =
increases in=20
> relative abundance.
> Uranium was discovered by Martin Klaproth, a German chemist, in 1789 =
in the=20
> mineral pitchblende, and was named after the planet Uranus.
>=20
> Uranium (chemical symbol U) is slightly more abundant than tin and =
about 40=20
> times as common as silver. It occurs in most rocks in concentrations =
of 2 to=20
> 4 parts per million and is as common in the earth's crust as tin, =
tungsten=20
> and molybdenum. It is also found in the oceans, at an average =
concentration=20
> of 1.3 parts per billion. There are a number of locations in different =
parts=20
> of the world where it occurs in economically-recoverable =
concentrations.=20
> When mined, it yields a mixed uranium oxide product, (U3O8). Uraninite =
or=20
> pitchblende is the most common uranium mineral.
>=20
> Uses
>=20
> For many years from the 1940s, virtually all of the uranium that was =
mined=20
> was used in the production of nuclear weapons, but this ceased to be =
the=20
> case in the 1970s. Today the only substantial use for uranium is as =
fuel in=20
> nuclear reactors, mostly for electricity generation. Uranium-235 is =
the only=20
> naturally-occurring material which can sustain a fission chain =
reaction,=20
> releasing large amounts of energy.
>=20
> In the past, uranium was also used to colour glass (from as early as =
79 AD)=20
> and deposits were once mined in order to obtain its decay product, =
radium.=20
> This element was used in luminous paint, particularly on the dials of=20
> watches and aircraft instruments, and in medicine for the treatment of =
> disease.
>=20
> While nuclear power is the predominant use of uranium, heat from =
nuclear=20
> fission can be used for industrial processes. It is also used for =
marine=20
> propulsion (mostly naval). And nuclear reactors are important for =
making=20
> radioisotopes.
>=20
> The Uranium Atom
>=20
> On a scale arranged according to the increasing mass of their nuclei,=20
> uranium is the heaviest of all the naturally-occurring elements =
(Hydrogen is=20
> the lightest). Uranium has a specific gravity of 18.7.
>=20
> Like other elements, uranium occurs in slightly differing forms known =
as=20
> 'isotopes'. These isotopes differ from each other in the number of =
neutron=20
> particles in the nucleus. 'Natural' uranium as found in the earth's =
crust is=20
> a mixture largely of two isotopes: uranium-238 (U-238), accounting for =
99.3%=20
> and U-235 about 0.7%.
>=20
> 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]
>=20
> 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=20
> that it is barely radioactive, less so than many other isotopes in =
rocks and=20
> sand. Nevertheless it generates 0.1 watts/tonne and this is enough to =
warm=20
> the earth's mantle.
>=20
> Uranium fission
>=20
> The nucleus of the U-235 isotope comprises 92 protons and 143 neutrons =
(92 +=20
> 143 =3D 235). When the nucleus of a U-235 atom is split in two by a =
neutron,=20
> some energy is released in the form of heat, and two or three =
additional=20
> neutrons are thrown off. If enough of these expelled neutrons split =
the=20
> nuclei of other U-235 atoms, releasing further neutrons,a 'chain =
reaction'=20
> can be achieved. When this happens over and over again, many millions =
of=20
> times, a very large amount of heat is produced from a relatively small =
> amount of uranium.
>=20
> It is this process, in effect "burning" uranium, which occurs in a =
nuclear=20
> reactor. In a nuclear reactor the uranium fuel is assembled in such a =
way=20
> that a controlled fission chain reaction can be achieved. The heat =
created=20
> by splitting the U-235 atoms is then used to make steam which spins a=20
> turbine to drive a generator, producing electricity.
>=20
> Nuclear power stations and fossil-fuelled power stations of similar =
capacity=20
> have many features in common. Both require heat to produce steam to =
drive=20
> turbines and generators. In a nuclear power station, however, the =
fissioning=20
> of uranium atoms replaces the burning of coal or gas. The chain =
reaction=20
> that takes place in the core of a nuclear reactor is controlled by =
rods=20
> which absorb neutrons. They are inserted or withdrawn to set the =
reactor at=20
> the required power level.
>=20
> The fuel elements are surrounded by a substance called a moderator to =
slow=20
> the speed of the emitted neutrons and thus enable the chain reaction =
to=20
> continue. Water, graphite and heavy water are used as moderators in=20
> different types of reactors.
>=20
> Most nuclear reactors require natural uranium (having 0.7% U-235) to =
be=20
> enriched, so as to increase the proportion of the fissile isotope =
U-235=20
> about five- or six-fold. (see below)
>=20
> A typical 1000 megawatt (MWe) reactor can provide enough electricity =
for a=20
> modern city of close to one million people, about 7 billion kWh per =
year.
>=20
> Uranium and Plutonium
>=20
> Whereas the U-235 atom is 'fissile', the U-238 atom is said to be =
'fertile'.=20
> This means that it can capture one of the neutrons which are flying =
about in=20
> the core of the reactor and become (indirectly) plutonium-239, which =
is=20
> fissile. Pu-239 is very much like U-235, in that it fissions when hit =
by a=20
> slow neutron and this also yields a lot of energy.
>=20
> Because there is so much U-238 in a reactor core (most of the fuel), =
these=20
> reactions occur frequently, and in fact about one third of the energy =
yield=20
> comes from "burning" Pu-239.
>=20
> But sometimes a Pu-239 atom simply captures a neutron without =
splitting, and=20
> it becomes Pu-240. Because the Pu-239 is either progressively "burned" =
or=20
> becomes Pu-240, the longer the fuel stays in the reactor the more =
Pu-240 is=20
> in it. The significance of this is that when the spent fuel is removed =
after=20
> about three years, the plutonium in it is not suitable for making =
weapons=20
> but can be recycled as fuel. See also Plutonium paper.
>=20
> From uranium ore to reactor fuel
>=20
> Uranium ore can be mined by underground or open-cut methods, depending =
on=20
> its depth. After mining, the ore is crushed and ground up. Then it is=20
> treated with acid to dissolve the uranium, which is then recovered =
from=20
> solution. Uranium may also be mined by in situ leaching (ISL), where =
it is=20
> dissolved from the orebody in situ and pumped to the surface.
>=20
> The end product of the mining and milling stages, or ISL, is uranium =
oxide=20
> concentrate (U3O8). Before it can be used in a reactor for electricity =
> generation, however, it must undergo a series of processes to produce =
a=20
> useable fuel.
>=20
> For most of the world's reactors, the next step in making a useable =
fuel is=20
> to convert the uranium oxide into a gas, uranium hexafluoride (UF6), =
which=20
> enables it to be enriched. Enrichment increases the proportion of the =
U-235=20
> isotope from its natural level of 0.7% to 3 - 4%. This enables greater =
> technical efficiency in reactor design and operation, particularly in =
larger=20
> reactors, and allows the use of ordinary water as a moderator. A =
by-product=20
> (or waste product) of enrichment is depleted uranium (about 89% of the =
> original feed).
>=20
> After enrichment, the UF6 gas is converted to uranium dioxide (UO2) =
which is=20
> formed into fuel pellets. These fuel pellets are placed inside thin =
metal=20
> tubes which are assembled in bundles to become the fuel elements for =
the=20
> core of the reactor.
>=20
> For reactors which use natural uranium as their fuel (and hence which=20
> require graphite or heavy water as a moderator) the U3O8 concentrate =
simply=20
> needs to be refined and converted directly to uranium dioxide.
>=20
> Spent reactor fuel is removed and stored, either to be reprocessed or=20
> disposed of underground
>=20
> Reprocessed Uranium
>=20
> When spent nuclear fuel is reprocessed, both plutonium and uranium are =
> recovered separately. Uranium comprises about 96% of that spent fuel.
>=20
> The composition of reprocessed uranium depends on the time the fuel =
has been=20
> in the reactor, but it is mostly U-238. Typically it will have about =
1%=20
> U-235 and small amounts of U-232 and U-236. The former is a =
gamma-emitter,=20
> making the material difficult to handle, even with trace amounts. The=20
> latter, comprising about 0.5% of the material, is a neutron absorber =
which=20
> means that if reprocessed uranium is used for fresh fuel it must be =
enriched=20
> slightly more than is required for natural uranium. In the future, =
laser=20
> enrichment techniques may be able to remove these isotopes.
>=20
> Nuclear power
>=20
> Over 16% of the world's electricity is generated from uranium in =
nuclear=20
> reactors. This amounts to about 2400 billion kWh, as much as from all=20
> sources worldwide in 1960.
>=20
> It comes from over 430 nuclear reactors with a total output capacity =
of more=20
> than 350 000 MWe operating in 31 countries. A further thirty reactors =
are=20
> under construction and another 70 are on the drawing board.
>=20
> Belgium, Bulgaria, Finland, France, Germany, Hungary, Japan, South =
Korea,=20
> Lithuania, Slovakia, Slovenia, Spain, Sweden, Switzerland and Ukraine =
all=20
> get 30% or more of their electricity from nuclear reactors. The USA =
has over=20
> 100 reactors operating, supplying 20% of its electricity. The UK gets =
about=20
> a quarter of its electricity from uranium.
>=20
> Sources of uranium
>=20
> Uranium is widespread in many rocks, and even in seawater. However, =
like=20
> other metals, it is seldom sufficiently concentrated to be =
economically=20
> recoverable. Where it is, we speak of an orebody. In defining what is =
ore,=20
> assumptions are made about the cost of mining and the market price of =
the=20
> metal. Uranium reserves are therefore calculated as tonnes recoverable =
up to=20
> a certain cost.
>=20
> Australia's reserves are about 25% of the world's total, but Canada is =
the=20
> world's leading producer. Other countries with reserves include =
Canada, USA,=20
> South Africa, Namibia, Brazil and Kazakhstan. China may also have=20
> substantial deposits of uranium. Many more countries have smaller =
deposits=20
> which could be mined.
>=20
> Uranium is sold only to countries which are signatories of the Nuclear =
> Non-Proliferation Treaty, and which allow international inspection to =
verify=20
> that it is used only for peaceful purposes.
>=20
> Radioisotopes
>=20
> Radioisotopes have become a vital part of modern life. Using =
relatively=20
> small special purpose nuclear reactors, a wide range of radioactive=20
> materials (radioisotopes) can be made at low cost. For this reason =
their use=20
> has become widespread since the early 1950s, and there are now some =
280=20
> "research" reactors in 56 countries producing them.
>=20
> Radioisotopes play an important part in the technologies that provide =
us=20
> with food, water and good health. They are produced by bombarding =
small=20
> amounts of particular elements with neutrons.
>=20
> In medicine, radioisotopes are widely used for diagnosis and research. =
> Radioactive chemical tracers emit gamma radiation which provides =
diagnostic=20
> information about a person's anatomy and the functioning of specific =
organs.=20
> Radiotherapy also employs radioisotopes in the treatment of some =
illnesses,=20
> such as cancer. More powerful gamma sources are used to sterilise =
syringes,=20
> bandages and other medical equipment. About one in two people in =
Western=20
> countries is likely to experience the benefits of nuclear medicine in =
their=20
> lifetime, and gamma sterilisation of equipment is almost universal.
>=20
> In the preservation of food, radioisotopes are used to inhibit the =
sprouting=20
> of root crops after harvesting, to kill parasites and pests, and to =
control=20
> the ripening of stored fruit and vegetables. Irradiated foodstuffs are =
> accepted by world and national health authorities for human =
consumption in=20
> an increasing number of countries. They include potatoes, onions, =
dried and=20
> fresh fruits, grain and grain products, poultry and some fish. Some=20
> prepacked foods can also be irradiated.
>=20
> Agriculturally, in the growing crops and breeding livestock, =
radioisotopes=20
> also play an important role. They are used to produce high yielding, =
disease=20
> and weather resistant varieties of crops, to study how fertilisers and =
> insecticides work, and to improve the productivity and health of =
domestic=20
> animals. Industrially, and in mining, they are used to examine welds, =
to=20
> detect leaks, to study the rate of wear of metals, and for on-stream=20
> analysis of a wide range of minerals and fuels.
>=20
> Most household smoke detectors use a radioisotope (Americium-241) =
derived=20
> from the plutonium formed in nuclear reactors. These alarms save many =
lives.
>=20
> Environmentally, radioisotopes are used to trace and analyse =
pollutants, to=20
> study the movement of surface water, and to measure water runoffs from =
rain=20
> and snow, as well as the flow rates of streams and rivers.
>=20
> Other reactors
>=20
> There are also other uses for reactors. Over 200 small nuclear =
reactors=20
> power some 150 ships, mostly submarines, but ranging from icebreakers =
to=20
> 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=20
> turbine directly geared to propulsion.
>=20
> The heat produced by nuclear reactors can also be used directly rather =
than=20
> for generating electricity. In Sweden and Russia, for example, it is =
used to=20
> heat buildings and elsewhere it provides heat for a variety of =
industrial=20
> processes such as water desalination. High-temperature reactors can =
also be=20
> used for industrial processes such as thermochemical production of =
hydrogen.
>=20
> Nuclear weapons
>=20
> Both uranium and plutonium were used to make bombs before they became=20
> important for making electricity and radioisotopes. But the type of =
uranium=20
> and plutonium for bombs is different from that in a nuclear power =
plant.=20
> Bomb-grade uranium is highly-enriched (>90% U-235, instead of about =
3.5%);=20
> bomb-grade plutonium is fairly pure (>90%) Pu-239 and is made in =
special=20
> reactors.
>=20
> Today a lot of military high-enriched uranium is becoming available =
for=20
> electricity production. It is diluted about 25:1 with depleted uranium =
> before being used as reactor fuel.
>=20
> Depleted Uranium
>=20
> Every tonne of natural uranium produced and enriched for use in a =
nuclear=20
> reactor gives about 130 kg of enriched fuel (3.5% or more U-235). The=20
> 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=20
> process. It is commonly known as DU.
>=20
> DU is stored either as UF6 or it is de-converted back to U3O8, which =
is more=20
> benign chemically and thus more suited for long-term storage. It is =
also=20
> less toxic. Every year over 50,000 tonnes of depleted uranium joins =
already=20
> substantial stockpiles in USA, Europe and Russia. World stock is about =
1.2=20
> million tonnes.
>=20
> Some DU is drawn from these stockpiles to dilute high-enriched (>90%)=20
> uranium released from weapons programs, particularly in Russia, and =
destined=20
> for use in civil reactors. This weapons-grade material is diluted =
about 25:1=20
> with depleted uranium, or 29:1 with depleted uranium that has been =
enriched=20
> slightly (to 1.5% U-235) to minimise levels of (natural) U-234 in the=20
> product.
>=20
> Other uses are more mundane, and depend on the metal's very high =
density=20
> (1.7 times that of lead). Hence, where maximum mass must fit in =
minimum=20
> space, such as aircraft control surface and helicopter counterweights, =
yacht=20
> keels, etc, it is often well suited. Until the mid 1970s it was used =
in=20
> dental porcelains. In addition it is used for radiation shielding, =
being=20
> some five times more effective than lead in this role.
>=20
> Also because of its density, it is used as solid slugs or penetrators =
in=20
> armour-piercing projectiles, alloyed with abut 0.75% titanium. DU is=20
> pyrophoric, so that upon impact about 30% of the projectile atomises =
and=20
> burns to uranium oxide dust. It was widely used in the Kuwait war (300 =
> tonnes) and less so in Kosovo (11 tonnes).
>=20
> Health aspects of DU
>=20
> Depleted uranium is not classified as a dangerous substance =
radiologically,=20
> 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=20
> U-238 is the same as the age of the earth (4.5 billion years). There =
are no=20
> reputable reports of cancer or other negative health effects from =
radiation=20
> exposure to ingested or inhaled natural or depleted uranium, despite =
much=20
> study.
>=20
> However, uranium does have a chemical toxicity about the same as that =
of=20
> lead, so inhaled fume or ingested oxide is considered a health hazard. =
Most=20
> uranium actually absorbed into the body is excreted within days, the =
balance=20
> being laid down in bone and kidneys. Its biological effect is =
principally=20
> 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=20
> background intake from natural sources.) Standards for drinking water =
and=20
> concentrations in air are set accordingly.
>=20
> Like most radionuclides, it is not known as a carcinogen, or to cause =
birth=20
> defects (from effects in utero) or to cause genetic mutations. =
Radiation=20
> from DU munitions depends on how long the uranium has been separated=20
> chemically from its decay products. If thorium-234 and =
protactinium-234 has=20
> built up through decay of U-238, these will give rise to some beta=20
> emissions. On this basis, DU is "weakly radioactive" with an activity =
of 39=20
> Bq/mg quoted (15 Bq/mg if pure).
>=20
> In 2001 the UN Environment Program examined the effects of nine tonnes =
of DU=20
> munitions having been used in Kosovo, checking the sites targeted by =
it.=20
> UNEP found no widespread contamination, no sign of contamination in =
water of=20
> the food chain and no correlation with reported ill-health in NATO=20
> peacekeepers.
>=20
> 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.=20
> Ingestion or inhalation of uranium oxide dust resulting from the =
impact of=20
> DU munitions on their targets is the main possible exposure route. See =
also=20
> Appendix and WHO briefing on DU and WHO fact sheet on DU.
>=20
>=20
>=20
> =
-------------------------------------------------------------------------=
-------
>=20
> 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.
>=20
>=20
>=20
> =
-------------------------------------------------------------------------=
-------
> 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=20
> continuing stress-like symptoms for which no obvious cause has been =
found.=20
> These symptoms have at times been attributed to the use of depleted =
uranium=20
> in shells and other missiles, which are said to have caused toxic =
effects.=20
> Similar complaints have arisen from the more recent fighting in the =
Balkans,=20
> particularly the Kosovo conflict about a year ago.
>=20
> Depleted uranium (DU) is natural uranium which is depleted in the =
rarer=20
> U-235 isotope (see below). It is a heavy metal and, in common with =
other=20
> heavy metals, it is chemically toxic. It is also slightly radioactive =
and=20
> there is therefore said to be a hypothetical possibility that it could =
give=20
> rise to a radiological hazard under some circumstances, e.g. if =
dispersed in=20
> finely divided form so that it is inhaled.
>=20
> However, because of the latency period for the induction of cancer by=20
> radiation, it is not credible that any cases of radiation-induced =
cancer=20
> could yet be attributed to the Kosovo conflict. Furthermore, extensive =
> studies have concluded that no radiological health hazard should be =
expected=20
> from exposure to depleted uranium.
>=20
> The risk from external exposure is essentially zero, even when pure =
metal is=20
> handled. No detectable increases of cancer, leukaemia, birth defects =
or=20
> other negative health effects have ever been observed from radiation=20
> exposure to inhaled or ingested natural uranium concentrates, at =
levels far=20
> exceeding those likely in areas where DU munitions have been used. =
This is=20
> mainly because the low radioactivity per unit mass of uranium means =
that the=20
> mass needed for significant internal exposure would be virtually =
impossible=20
> to accumulate in the body - and DU is less than half as radioactive as =
> natural uranium.
>=20
> (see full statement on ARPS web site)
>=20
>=20
> From National Radiation Protection Board (UK) Bulletin Editorial
> March 2001:
>=20
> Uses and Risks of DU
> DU is radioactive and doses from inhalation of dust or from handling =
bare=20
> spent rounds need to be assessed properly. However, the scientific =
consensus=20
> at present is that the risks are likely to be small and easily =
avoidable,=20
> especially compared with the other risks the armed forces have to take =
in=20
> war.
> (see full statement pdf on NRPB web site)
>=20
>=20
> --
> Hold the door for the stranger behind you. When the driver a=20
> half-car-length in front of you signals to get over, slow down. Smile =
and=20
> say "hi" to the folks you pass on the sidewalk. Give blood. =
Volunteer.
>=20
>=20
>=20
>=20
>=20
>=20
> _________________________________________________________________
> Chat with friends online, try MSN Messenger: http://messenger.msn.com
>=20
>=20
> To subscribe to the Abolition Global Caucus, send an email from the =
account you wish to be subscribed to: =
"abolition-caucus-subscribe@egroups.com"
>=20
>=20
> Do not include a subject line or any text in the body of the message.=20
>=20
> Your use of Yahoo! Groups is subject to =
http://docs.yahoo.com/info/terms/=20
>=20
>=20
>=20
>=20
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<DIV>----- Original Message -----=20
<DIV>From: "Jim Hoerner" <<A=20
href=3D"mailto:jim_hoerner@hotmail.com">jim_hoerner@hotmail.com</A>></=
DIV>
<DIV>To: <<A=20
href=3D"mailto:Know_Nukes@yahoogroups.com">Know_Nukes@yahoogroups.com</A>=
></DIV>
<DIV>Cc: <<A=20
href=3D"mailto:nucnews@yahoogroups.com">nucnews@yahoogroups.com</A>>; =
<<A=20
href=3D"mailto:downwinders@yahoogroups.com">downwinders@yahoogroups.com</=
A>>;=20
<<A=20
href=3D"mailto:abolition-caucus@yahoogroups.com">abolition-caucus@yahoogr=
oups.com</A>></DIV>
<DIV>Sent: Saturday, June 08, 2002 9:50 AM</DIV>
<DIV>Subject: [abolition-caucus] U and DU</DIV></DIV>
<DIV><BR></DIV>> <A=20
href=3D"http://www.world-nuclear.org/info/inf14.htm">http://www.world-nuc=
lear.org/info/inf14.htm</A><BR>>=20
<BR>> Uranium and Depleted Uranium<BR>> <BR>> June 2002<BR>> =
<BR>> <BR>>=20
-------------------------------------------------------------------------=
-------<BR>>=20
<BR>> The basic fuel for a nuclear power reactor is uranium - a very =
heavy=20
metal <BR>> containing abundant concentrated energy.<BR>> It is =
mildly=20
radioactive and occurs naturally in the Earth's crust.<BR>> Depleted =
uranium=20
is a by-product or waste product of uranium enrichment.<BR>> The =
health=20
hazards associated with any uranium are much the same as those <BR>> =
for=20
lead.<BR>> <BR>>=20
-------------------------------------------------------------------------=
-------<BR>>=20
Uranium was apparently formed in super novae about 6.6 billion years =
ago.=20
<BR>> While it is not common in the solar system, today its =
radioactive decay=20
<BR>> provides the main source of heat inside the earth, causing =
convection=20
and <BR>> continental drift. As decay proceeds, the final product, =
lead,=20
increases in <BR>> relative abundance.<BR>> Uranium was discovered =
by=20
Martin Klaproth, a German chemist, in 1789 in the <BR>> mineral =
pitchblende,=20
and was named after the planet Uranus.<BR>> <BR>> Uranium =
(chemical symbol=20
U) is slightly more abundant than tin and about 40 <BR>> times as =
common as=20
silver. It occurs in most rocks in concentrations of 2 to <BR>> 4 =
parts per=20
million and is as common in the earth's crust as tin, tungsten <BR>> =
and=20
molybdenum. It is also found in the oceans, at an average concentration =
<BR>>=20
of 1.3 parts per billion. There are a number of locations in different =
parts=20
<BR>> of the world where it occurs in economically-recoverable=20
concentrations. <BR>> When mined, it yields a mixed uranium oxide =
product,=20
(U3O8). Uraninite or <BR>> pitchblende is the most common uranium=20
mineral.<BR>> <BR>> Uses<BR>> <BR>> For many years from the =
1940s,=20
virtually all of the uranium that was mined <BR>> was used in the =
production=20
of nuclear weapons, but this ceased to be the <BR>> case in the =
1970s. Today=20
the only substantial use for uranium is as fuel in <BR>> nuclear =
reactors,=20
mostly for electricity generation. Uranium-235 is the only <BR>>=20
naturally-occurring material which can sustain a fission chain reaction, =
<BR>> releasing large amounts of energy.<BR>> <BR>> In the =
past,=20
uranium was also used to colour glass (from as early as 79 AD) <BR>> =
and=20
deposits were once mined in order to obtain its decay product, radium. =
<BR>>=20
This element was used in luminous paint, particularly on the dials of =
<BR>>=20
watches and aircraft instruments, and in medicine for the treatment of =
<BR>>=20
disease.<BR>> <BR>> While nuclear power is the predominant use of =
uranium,=20
heat from nuclear <BR>> fission can be used for industrial processes. =
It is=20
also used for marine <BR>> propulsion (mostly naval). And nuclear =
reactors=20
are important for making <BR>> radioisotopes.<BR>> <BR>> The =
Uranium=20
Atom<BR>> <BR>> On a scale arranged according to the increasing =
mass of=20
their nuclei, <BR>> uranium is the heaviest of all the =
naturally-occurring=20
elements (Hydrogen is <BR>> the lightest). Uranium has a specific =
gravity of=20
18.7.<BR>> <BR>> Like other elements, uranium occurs in slightly =
differing=20
forms known as <BR>> 'isotopes'. These isotopes differ from each =
other in the=20
number of neutron <BR>> particles in the nucleus. 'Natural' uranium =
as found=20
in the earth's crust is <BR>> a mixture largely of two isotopes: =
uranium-238=20
(U-238), accounting for 99.3% <BR>> and U-235 about 0.7%.<BR>> =
<BR>>=20
The isotope U-235 is important because under certain conditions it can =
<BR>>=20
readily be split, yielding a lot of energy. It is therefore said to be =
<BR>>=20
'fissile' and we use the expression 'nuclear fission'. [fissile =
means=20
<BR>> fissions with thermal (slow) neutrons - JH]<BR>> <BR>> =
Meanwhile,=20
like all radioactive isotopes, it decays. U-238 decays very <BR>> =
slowly, its=20
half-life being the same as the age of the earth. This means <BR>> =
that it is=20
barely radioactive, less so than many other isotopes in rocks and =
<BR>> sand.=20
Nevertheless it generates 0.1 watts/tonne and this is enough to warm =
<BR>>=20
the earth's mantle.<BR>> <BR>> Uranium fission<BR>> <BR>> =
The=20
nucleus of the U-235 isotope comprises 92 protons and 143 neutrons (92 + =
<BR>> 143 =3D 235). When the nucleus of a U-235 atom is split in two =
by a=20
neutron, <BR>> some energy is released in the form of heat, and two =
or three=20
additional <BR>> neutrons are thrown off. If enough of these expelled =
neutrons split the <BR>> nuclei of other U-235 atoms, releasing =
further=20
neutrons,a 'chain reaction' <BR>> can be achieved. When this happens =
over and=20
over again, many millions of <BR>> times, a very large amount of heat =
is=20
produced from a relatively small <BR>> amount of uranium.<BR>> =
<BR>> It=20
is this process, in effect "burning" uranium, which occurs in a nuclear =
<BR>>=20
reactor. In a nuclear reactor the uranium fuel is assembled in such a =
way=20
<BR>> that a controlled fission chain reaction can be achieved. The =
heat=20
created <BR>> by splitting the U-235 atoms is then used to make steam =
which=20
spins a <BR>> turbine to drive a generator, producing =
electricity.<BR>>=20
<BR>> Nuclear power stations and fossil-fuelled power stations of =
similar=20
capacity <BR>> have many features in common. Both require heat to =
produce=20
steam to drive <BR>> turbines and generators. In a nuclear power =
station,=20
however, the fissioning <BR>> of uranium atoms replaces the burning =
of coal=20
or gas. The chain reaction <BR>> that takes place in the core of a =
nuclear=20
reactor is controlled by rods <BR>> which absorb neutrons. They are =
inserted=20
or withdrawn to set the reactor at <BR>> the required power =
level.<BR>>=20
<BR>> The fuel elements are surrounded by a substance called a =
moderator to=20
slow <BR>> the speed of the emitted neutrons and thus enable the =
chain=20
reaction to <BR>> continue. Water, graphite and heavy water are used =
as=20
moderators in <BR>> different types of reactors.<BR>> <BR>> =
Most=20
nuclear reactors require natural uranium (having 0.7% U-235) to be =
<BR>>=20
enriched, so as to increase the proportion of the fissile isotope U-235 =
<BR>>=20
about five- or six-fold. (see below)<BR>> <BR>> A typical 1000 =
megawatt=20
(MWe) reactor can provide enough electricity for a <BR>> modern city =
of close=20
to one million people, about 7 billion kWh per year.<BR>> <BR>> =
Uranium=20
and Plutonium<BR>> <BR>> Whereas the U-235 atom is 'fissile', the =
U-238=20
atom is said to be 'fertile'. <BR>> This means that it can capture =
one of the=20
neutrons which are flying about in <BR>> the core of the reactor and =
become=20
(indirectly) plutonium-239, which is <BR>> fissile. Pu-239 is very =
much like=20
U-235, in that it fissions when hit by a <BR>> slow neutron and this =
also=20
yields a lot of energy.<BR>> <BR>> Because there is so much U-238 =
in a=20
reactor core (most of the fuel), these <BR>> reactions occur =
frequently, and=20
in fact about one third of the energy yield <BR>> comes from =
"burning"=20
Pu-239.<BR>> <BR>> But sometimes a Pu-239 atom simply captures a =
neutron=20
without splitting, and <BR>> it becomes Pu-240. Because the Pu-239 is =
either=20
progressively "burned" or <BR>> becomes Pu-240, the longer the fuel =
stays in=20
the reactor the more Pu-240 is <BR>> in it. The significance of this =
is that=20
when the spent fuel is removed after <BR>> about three years, the =
plutonium=20
in it is not suitable for making weapons <BR>> but can be recycled as =
fuel.=20
See also Plutonium paper.<BR>> <BR>> From uranium ore to reactor=20
fuel<BR>> <BR>> Uranium ore can be mined by underground or =
open-cut=20
methods, depending on <BR>> its depth. After mining, the ore is =
crushed and=20
ground up. Then it is <BR>> treated with acid to dissolve the =
uranium, which=20
is then recovered from <BR>> solution. Uranium may also be mined by =
in situ=20
leaching (ISL), where it is <BR>> dissolved from the orebody in situ =
and=20
pumped to the surface.<BR>> <BR>> The end product of the mining =
and=20
milling stages, or ISL, is uranium oxide <BR>> concentrate (U3O8). =
Before it=20
can be used in a reactor for electricity <BR>> generation, however, =
it must=20
undergo a series of processes to produce a <BR>> useable =
fuel.<BR>>=20
<BR>> For most of the world's reactors, the next step in making a =
useable=20
fuel is <BR>> to convert the uranium oxide into a gas, uranium =
hexafluoride=20
(UF6), which <BR>> enables it to be enriched. Enrichment increases =
the=20
proportion of the U-235 <BR>> isotope from its natural level of 0.7% =
to 3 -=20
4%. This enables greater <BR>> technical efficiency in reactor design =
and=20
operation, particularly in larger <BR>> reactors, and allows the use =
of=20
ordinary water as a moderator. A by-product <BR>> (or waste product) =
of=20
enrichment is depleted uranium (about 89% of the <BR>> original=20
feed).<BR>> <BR>> After enrichment, the UF6 gas is converted to =
uranium=20
dioxide (UO2) which is <BR>> formed into fuel pellets. These fuel =
pellets are=20
placed inside thin metal <BR>> tubes which are assembled in bundles =
to become=20
the fuel elements for the <BR>> core of the reactor.<BR>> <BR>> =
For=20
reactors which use natural uranium as their fuel (and hence which =
<BR>>=20
require graphite or heavy water as a moderator) the U3O8 concentrate =
simply=20
<BR>> needs to be refined and converted directly to uranium =
dioxide.<BR>>=20
<BR>> Spent reactor fuel is removed and stored, either to be =
reprocessed or=20
<BR>> disposed of underground<BR>> <BR>> Reprocessed =
Uranium<BR>>=20
<BR>> When spent nuclear fuel is reprocessed, both plutonium and =
uranium are=20
<BR>> recovered separately. Uranium comprises about 96% of that spent =
fuel.<BR>> <BR>> The composition of reprocessed uranium depends on =
the=20
time the fuel has been <BR>> in the reactor, but it is mostly U-238.=20
Typically it will have about 1% <BR>> U-235 and small amounts of =
U-232 and=20
U-236. The former is a gamma-emitter, <BR>> making the material =
difficult to=20
handle, even with trace amounts. The <BR>> latter, comprising about =
0.5% of=20
the material, is a neutron absorber which <BR>> means that if =
reprocessed=20
uranium is used for fresh fuel it must be enriched <BR>> slightly =
more than=20
is required for natural uranium. In the future, laser <BR>> =
enrichment=20
techniques may be able to remove these isotopes.<BR>> <BR>> =
Nuclear=20
power<BR>> <BR>> Over 16% of the world's electricity is generated =
from=20
uranium in nuclear <BR>> reactors. This amounts to about 2400 billion =
kWh, as=20
much as from all <BR>> sources worldwide in 1960.<BR>> <BR>> It =
comes=20
from over 430 nuclear reactors with a total output capacity of more =
<BR>>=20
than 350 000 MWe operating in 31 countries. A further thirty reactors =
are=20
<BR>> under construction and another 70 are on the drawing =
board.<BR>>=20
<BR>> Belgium, Bulgaria, Finland, France, Germany, Hungary, Japan, =
South=20
Korea, <BR>> Lithuania, Slovakia, Slovenia, Spain, Sweden, =
Switzerland and=20
Ukraine all <BR>> get 30% or more of their electricity from nuclear =
reactors.=20
The USA has over <BR>> 100 reactors operating, supplying 20% of its=20
electricity. The UK gets about <BR>> a quarter of its electricity =
from=20
uranium.<BR>> <BR>> Sources of uranium<BR>> <BR>> Uranium is =
widespread in many rocks, and even in seawater. However, like <BR>> =
other=20
metals, it is seldom sufficiently concentrated to be economically =
<BR>>=20
recoverable. Where it is, we speak of an orebody. In defining what is =
ore,=20
<BR>> assumptions are made about the cost of mining and the market =
price of=20
the <BR>> metal. Uranium reserves are therefore calculated as tonnes=20
recoverable up to <BR>> a certain cost.<BR>> <BR>> Australia's =
reserves=20
are about 25% of the world's total, but Canada is the <BR>> world's =
leading=20
producer. Other countries with reserves include Canada, USA, <BR>> =
South=20
Africa, Namibia, Brazil and Kazakhstan. China may also have <BR>> =
substantial=20
deposits of uranium. Many more countries have smaller deposits <BR>> =
which=20
could be mined.<BR>> <BR>> Uranium is sold only to countries which =
are=20
signatories of the Nuclear <BR>> Non-Proliferation Treaty, and which =
allow=20
international inspection to verify <BR>> that it is used only for =
peaceful=20
purposes.<BR>> <BR>> Radioisotopes<BR>> <BR>> Radioisotopes =
have=20
become a vital part of modern life. Using relatively <BR>> small =
special=20
purpose nuclear reactors, a wide range of radioactive <BR>> materials =
(radioisotopes) can be made at low cost. For this reason their use =
<BR>> has=20
become widespread since the early 1950s, and there are now some 280 =
<BR>>=20
"research" reactors in 56 countries producing them.<BR>> <BR>>=20
Radioisotopes play an important part in the technologies that provide us =
<BR>> with food, water and good health. They are produced by =
bombarding small=20
<BR>> amounts of particular elements with neutrons.<BR>> <BR>> =
In=20
medicine, radioisotopes are widely used for diagnosis and research. =
<BR>>=20
Radioactive chemical tracers emit gamma radiation which provides =
diagnostic=20
<BR>> information about a person's anatomy and the functioning of =
specific=20
organs. <BR>> Radiotherapy also employs radioisotopes in the =
treatment of=20
some illnesses, <BR>> such as cancer. More powerful gamma sources are =
used to=20
sterilise syringes, <BR>> bandages and other medical equipment. About =
one in=20
two people in Western <BR>> countries is likely to experience the =
benefits of=20
nuclear medicine in their <BR>> lifetime, and gamma sterilisation of=20
equipment is almost universal.<BR>> <BR>> In the preservation of =
food,=20
radioisotopes are used to inhibit the sprouting <BR>> of root crops =
after=20
harvesting, to kill parasites and pests, and to control <BR>> the =
ripening of=20
stored fruit and vegetables. Irradiated foodstuffs are <BR>> accepted =
by=20
world and national health authorities for human consumption in <BR>> =
an=20
increasing number of countries. They include potatoes, onions, dried and =
<BR>> fresh fruits, grain and grain products, poultry and some fish. =
Some=20
<BR>> prepacked foods can also be irradiated.<BR>> <BR>>=20
Agriculturally, in the growing crops and breeding livestock, =
radioisotopes=20
<BR>> also play an important role. They are used to produce high =
yielding,=20
disease <BR>> and weather resistant varieties of crops, to study how=20
fertilisers and <BR>> insecticides work, and to improve the =
productivity and=20
health of domestic <BR>> animals. Industrially, and in mining, they =
are used=20
to examine welds, to <BR>> detect leaks, to study the rate of wear of =
metals,=20
and for on-stream <BR>> analysis of a wide range of minerals and=20
fuels.<BR>> <BR>> Most household smoke detectors use a =
radioisotope=20
(Americium-241) derived <BR>> from the plutonium formed in nuclear =
reactors.=20
These alarms save many lives.<BR>> <BR>> Environmentally, =
radioisotopes=20
are used to trace and analyse pollutants, to <BR>> study the movement =
of=20
surface water, and to measure water runoffs from rain <BR>> and snow, =
as well=20
as the flow rates of streams and rivers.<BR>> <BR>> Other =
reactors<BR>>=20
<BR>> There are also other uses for reactors. Over 200 small nuclear =
reactors=20
<BR>> power some 150 ships, mostly submarines, but ranging from =
icebreakers=20
to <BR>> aircraft carriers. These can stay at sea for very long =
periods=20
without <BR>> having to make refuelling stops. In most such vessels =
the steam=20
drives a <BR>> turbine directly geared to propulsion.<BR>> =
<BR>> The=20
heat produced by nuclear reactors can also be used directly rather than =
<BR>>=20
for generating electricity. In Sweden and Russia, for example, it is =
used to=20
<BR>> heat buildings and elsewhere it provides heat for a variety of=20
industrial <BR>> processes such as water desalination. =
High-temperature=20
reactors can also be <BR>> used for industrial processes such as=20
thermochemical production of hydrogen.<BR>> <BR>> Nuclear =
weapons<BR>>=20
<BR>> Both uranium and plutonium were used to make bombs before they =
became=20
<BR>> important for making electricity and radioisotopes. But the =
type of=20
uranium <BR>> and plutonium for bombs is different from that in a =
nuclear=20
power plant. <BR>> Bomb-grade uranium is highly-enriched (>90% =
U-235,=20
instead of about 3.5%); <BR>> bomb-grade plutonium is fairly pure =
(>90%)=20
Pu-239 and is made in special <BR>> reactors.<BR>> <BR>> Today =
a lot of=20
military high-enriched uranium is becoming available for <BR>> =
electricity=20
production. It is diluted about 25:1 with depleted uranium <BR>> =
before being=20
used as reactor fuel.<BR>> <BR>> Depleted Uranium<BR>> <BR>> =
Every=20
tonne of natural uranium produced and enriched for use in a nuclear =
<BR>>=20
reactor gives about 130 kg of enriched fuel (3.5% or more U-235). The =
<BR>>=20
balance is depleted uranium (U-238, with 0.25-0.30% U-235). This major =
<BR>>=20
portion has been depleted in its fissile U-235 isotope by the enrichment =
<BR>> process. It is commonly known as DU.<BR>> <BR>> DU is =
stored=20
either as UF6 or it is de-converted back to U3O8, which is more <BR>> =
benign=20
chemically and thus more suited for long-term storage. It is also =
<BR>> less=20
toxic. Every year over 50,000 tonnes of depleted uranium joins already =
<BR>>=20
substantial stockpiles in USA, Europe and Russia. World stock is about =
1.2=20
<BR>> million tonnes.<BR>> <BR>> Some DU is drawn from these =
stockpiles=20
to dilute high-enriched (>90%) <BR>> uranium released from weapons =
programs, particularly in Russia, and destined <BR>> for use in civil =
reactors. This weapons-grade material is diluted about 25:1 <BR>> =
with=20
depleted uranium, or 29:1 with depleted uranium that has been enriched =
<BR>>=20
slightly (to 1.5% U-235) to minimise levels of (natural) U-234 in the =
<BR>>=20
product.<BR>> <BR>> Other uses are more mundane, and depend on the =
metal's=20
very high density <BR>> (1.7 times that of lead). Hence, where =
maximum mass=20
must fit in minimum <BR>> space, such as aircraft control surface and =
helicopter counterweights, yacht <BR>> keels, etc, it is often well =
suited.=20
Until the mid 1970s it was used in <BR>> dental porcelains. In =
addition it is=20
used for radiation shielding, being <BR>> some five times more =
effective than=20
lead in this role.<BR>> <BR>> Also because of its density, it is =
used as=20
solid slugs or penetrators in <BR>> armour-piercing projectiles, =
alloyed with=20
abut 0.75% titanium. DU is <BR>> pyrophoric, so that upon impact =
about 30% of=20
the projectile atomises and <BR>> burns to uranium oxide dust. It was =
widely=20
used in the Kuwait war (300 <BR>> tonnes) and less so in Kosovo (11=20
tonnes).<BR>> <BR>> Health aspects of DU<BR>> <BR>> Depleted =
uranium=20
is not classified as a dangerous substance radiologically, <BR>> =
though it is=20
a potential hazard in large quantities, beyond what could <BR>> =
conceivably=20
be breathed. Its emissions are very low, since the half-life of <BR>> =
U-238=20
is the same as the age of the earth (4.5 billion years). There are no =
<BR>>=20
reputable reports of cancer or other negative health effects from =
radiation=20
<BR>> exposure to ingested or inhaled natural or depleted uranium, =
despite=20
much <BR>> study.<BR>> <BR>> However, uranium does have a =
chemical=20
toxicity about the same as that of <BR>> lead, so inhaled fume or =
ingested=20
oxide is considered a health hazard. Most <BR>> uranium actually =
absorbed=20
into the body is excreted within days, the balance <BR>> being laid =
down in=20
bone and kidneys. Its biological effect is principally <BR>> kidney =
damage.=20
WHO has set a Tolerable Daily Intake level for U of 0.6 <BR>> =
microgram/kg=20
body weight, orally. (This is about eight times our normal <BR>> =
background=20
intake from natural sources.) Standards for drinking water and <BR>>=20
concentrations in air are set accordingly.<BR>> <BR>> Like most=20
radionuclides, it is not known as a carcinogen, or to cause birth =
<BR>>=20
defects (from effects in utero) or to cause genetic mutations. Radiation =
<BR>> from DU munitions depends on how long the uranium has been =
separated=20
<BR>> chemically from its decay products. If thorium-234 and =
protactinium-234=20
has <BR>> built up through decay of U-238, these will give rise to =
some beta=20
<BR>> emissions. On this basis, DU is "weakly radioactive" with an =
activity=20
of 39 <BR>> Bq/mg quoted (15 Bq/mg if pure).<BR>> <BR>> In 2001 =
the UN=20
Environment Program examined the effects of nine tonnes of DU <BR>> =
munitions=20
having been used in Kosovo, checking the sites targeted by it. <BR>> =
UNEP=20
found no widespread contamination, no sign of contamination in water of =
<BR>>=20
the food chain and no correlation with reported ill-health in NATO =
<BR>>=20
peacekeepers.<BR>> <BR>> Thus DU is clearly dangerous for people =
in=20
vehicles which are military <BR>> targets, but for anyone else - even =
in a=20
war zone - there is little hazard. <BR>> Ingestion or inhalation of =
uranium=20
oxide dust resulting from the impact of <BR>> DU munitions on their =
targets=20
is the main possible exposure route. See also <BR>> Appendix and WHO =
briefing=20
on DU and WHO fact sheet on DU.<BR>> <BR>> <BR>> <BR>>=20
-------------------------------------------------------------------------=
-------<BR>>=20
<BR>> Sources:<BR>> BNFL, Cogema, JNFL, SKB and ANSTO publications =
and=20
papers.<BR>> Bulletin of Atomic Scientists, Nov-Dec 1999.<BR>> New =
Scientist 5 & 26/6/99, AFP 29/10/01.<BR>> UNEP/UNCHS, 1999, =
Balkans Task=20
Force report, Appendix 4.<BR>> OECD NEA 2001, Management of Depleted=20
Uranium.<BR>> Burchall & Clark, Depleted Uranium, NRPB Bulletin =
#229,=20
March 2001.<BR>> <BR>> <BR>> <BR>>=20
-------------------------------------------------------------------------=
-------<BR>>=20
Appendix:<BR>> Statement by Australasian Radiation Protection =
Society<BR>>=20
Potential Health Effects of Depleted Uranium in Munitions<BR>> =
February=20
2001.<BR>> Some military personnel involved in the 1991 Gulf War have =
complained of <BR>> continuing stress-like symptoms for which no =
obvious=20
cause has been found. <BR>> These symptoms have at times been =
attributed to=20
the use of depleted uranium <BR>> in shells and other missiles, which =
are=20
said to have caused toxic effects. <BR>> Similar complaints have =
arisen from=20
the more recent fighting in the Balkans, <BR>> particularly the =
Kosovo=20
conflict about a year ago.<BR>> <BR>> Depleted uranium (DU) is =
natural=20
uranium which is depleted in the rarer <BR>> U-235 isotope (see =
below). It is=20
a heavy metal and, in common with other <BR>> heavy metals, it is =
chemically=20
toxic. It is also slightly radioactive and <BR>> there is therefore =
said to=20
be a hypothetical possibility that it could give <BR>> rise to a =
radiological=20
hazard under some circumstances, e.g. if dispersed in <BR>> finely =
divided=20
form so that it is inhaled.<BR>> <BR>> However, because of the =
latency=20
period for the induction of cancer by <BR>> radiation, it is not =
credible=20
that any cases of radiation-induced cancer <BR>> could yet be =
attributed to=20
the Kosovo conflict. Furthermore, extensive <BR>> studies have =
concluded that=20
no radiological health hazard should be expected <BR>> from exposure =
to=20
depleted uranium.<BR>> <BR>> The risk from external exposure is=20
essentially zero, even when pure metal is <BR>> handled. No =
detectable=20
increases of cancer, leukaemia, birth defects or <BR>> other negative =
health=20
effects have ever been observed from radiation <BR>> exposure to =
inhaled or=20
ingested natural uranium concentrates, at levels far <BR>> exceeding =
those=20
likely in areas where DU munitions have been used. This is <BR>> =
mainly=20
because the low radioactivity per unit mass of uranium means that the =
<BR>>=20
mass needed for significant internal exposure would be virtually =
impossible=20
<BR>> to accumulate in the body - and DU is less than half as =
radioactive as=20
<BR>> natural uranium.<BR>> <BR>> (see full statement on ARPS =
web=20
site)<BR>> <BR>> <BR>> From National Radiation Protection Board =
(UK)=20
Bulletin Editorial<BR>> March 2001:<BR>> <BR>> Uses and Risks =
of=20
DU<BR>> DU is radioactive and doses from inhalation of dust or from =
handling=20
bare <BR>> spent rounds need to be assessed properly. However, the =
scientific=20
consensus <BR>> at present is that the risks are likely to be small =
and=20
easily avoidable, <BR>> especially compared with the other risks the =
armed=20
forces have to take in <BR>> war.<BR>> (see full statement pdf on =
NRPB web=20
site)<BR>> <BR>> <BR>> --<BR>> Hold the door for the =
stranger behind=20
you. When the driver a <BR>> half-car-length in front of you =
signals to=20
get over, slow down. Smile and <BR>> say "hi" to the folks you =
pass on=20
the sidewalk. Give blood. Volunteer.<BR>> <BR>> =
<BR>>=20
<BR>> <BR>> <BR>> <BR>>=20
_________________________________________________________________<BR>>=
Chat=20
with friends online, try MSN Messenger: <A=20
href=3D"http://messenger.msn.com">http://messenger.msn.com</A><BR>> =
<BR>>=20
<BR>> To subscribe to the Abolition Global Caucus, send an email from =
the=20
account you wish to be subscribed to: "<A=20
href=3D"mailto:abolition-caucus-subscribe@egroups.com">abolition-caucus-s=
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