Prsentation PowerPoint

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Advantages of a safe nuclear energy Nuclear
energy is a concentrated energy source (adapted
to mega-cities), not very dependent of weather or
climate (if nuclear reactors are sited on the
sea) A well proved technology, which can be still
largely improved (life of reactor up to 60 years,
load ratio up to 90, BU up to 60
GWjt-1) Important and diversified sources of
natural and man-made fissile nuclides (Pu
isotopes). U ores are widespread and abundant
without competing uses and it is easy to store.
More than 50 years of production at the present
level of production can be achieved A low cost of
kWhe (full life cycle cost analysis).
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A very low radiological impact for the
environment and no release of CO2 (but 6 of the
world energy consumption). A worldwide system of
protection for workers Extension of the present
technology to produce electricity (with reactors
of 300 MWe) and high temperature heat
(metallurgical processes, H2 production). New
technology using all U isotopes (and Th) could
provide fission energy over a very long time (see
later).
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Disadvantages (drawbacks) of safe nuclear
energy A high investment costs with a long
payback of money (10 years for construction of a
reactor and a large amount of money in case of
accident) A difficulty to follow variable
electricity demand (base load generation
only) An accumulation of civil Pu. In average
the world-wide production is 75 tons a year. The
status of Pu is peculiar according of its use as
a fuel or its management as waste. As Pu239 has
a lower ? of delayed neutron than U235 the
quantity to be introduced in reactor is limited
to 12 (30 of MOX sub-assemblies in a 900 MWe
PWR initially loaded with UOX). The isotopic
composition Pu MOX SF does not allow a second
recycle in PWR (too much even-even nuclides which
decrease the quantity of fissile nuclides by
thermal neutrons).  
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Attached to the accumulation and separation of Pu
from SF is the question of dissemination of
fissile material (nuclear weapons
proliferation) A production of nuclear wastes
difficult to manage in the long term whatever
they are, SF or packages of wastes from
reprocessing. LL-SLW packages (PF and AP), are
disposed of in ground or underground
repositories. The HL-LLW and MLL-LW packages,
which contain LL radionuclides, are put in
interim storage waiting for a final destination,
which is the matter of hard discussions A
controversial appreciation by citizen
(anti-nuclear people against nuclear technocrats,
very low risk can have tremendous consequences,
effects of radioactivity difficult to
understand). Real efforts, but too recent, have
been done to give an objective information on
nuclear problems, but in general the dialogue is
difficult to be established (except in some
countries)
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Nuclear energy, environment and society. Is this
energy compatible with sustainable
development? Releases The radioactivity of the
gas or the aqueous solutions (called ultimate
effluents) which are released in atmosphere and
hydrosphere during operating reactors or
facilities of the fuel cycle are controlled
according to the safety rules for radiation
protection. The authorisations of releases are
calculated on the basis of the dose for the most
exposed people at the limit of the site according
to scenarios (and others regulations). The true
releases are only several per cent of the
authorisations (T, volatile FP, ? emitters). The
case of accidents is special The release of heat
and chemicals by reactors and facilities of the
fuel cycle have no special status versus
industrial rules.
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Society The links between nuclear energy and
society are complex. The concerns are all linked
to the concept of radiological dose and
associated risk. In short the hazard of nuclear
energy comes from an exposure to ionising
radiations, appreciated by the calculated dose
The dose depend on scenarios of exposure. The
risks depend on the dose. A reference point is
the natural dose. The low doses (less than
immediate lethal doses) are given in Sievert
(Sv). Natural dose is around 2.5 mSv/year. The
radiological risk, RR, associated to a dose is RR
(t-1) p (Sv-1) ?i Pi (t-1) Ei (Sv-1) where p is
the probability of occurrence of the effects, Pi
is the probability of the occurrence of an event
i, and Ei is the calculated dose given by the
event i. For low dose the unit of time is the
year.
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The basic hypothesis supporting the RR for low
doses is called the LNT (linear no threshold).
The value of p 0.073 Sv-1 (0.06 for a cancer
leading to death and 0. 013 for hereditary effect
according to IRCP 60) means that 6 cancers per
year can appear in a population of 100 000
inhabitants, each having got 1mSv. The value
0.073 is on debate. There are also debates on LNT
and the mechanisms of induced cancer by ionising
radiations IRCP considers that an acceptable
risk correspond to a dose added to the natural
dose of 1 mSv/year for any individual of the
public. This dose is considered to have any
effect on the expected life IRCP considers that
a trivial added dose is 1 microSievert (1/100
of the natural dose).
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For a given amount of radioactive matter (1 ton
of SF for instance or quantity of SF to produce 1
TWhe) the inventory of radiotoxicity, in short
the radiotoxicity, is defined as ?i RRi
calculated supposing that all radionuclides, i,
are incorporated. It represents a potential risk.
The residual risk is ?i RRi calculated for a
given case of exposure . It takes into account
the management of the radioactive matter (like in
geological disposal for instance). Doses due to
the use of nuclear energy are low compared to the
natural doses and those given by medical
diagnostic (1.5 mSv/year in average per person)
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Sustainable development Sustainable development
requires to meet technical and societal criteria.
Here they are essentially discussed in the
context of the pursuit of the present technology
of reactors according to a moderate increase of
the use of nuclear energy. Up to 2050 nuclear
energy will lie on U/Pu fissile nuclides
(impossibility to launch many fast neutron
reactor to use U238, lack of Pu and reprocessing
SF facilities). Phase out of nuclear energy is
not considered (but is not a simple problem)
Forecasts are difficult (visibility on the
demands of the open market, safety rules) due to
the complexity of the economy and the changing
feeling of the society on the nuclear energy.
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Technological criteria At least 4 technical
criteria have to be fulfilled by nuclear energy
(and any source of energy) providing adapted
power to the energy needs, safe technology,
durability of resources (Unat), no collateral
damage (proliferation of nuclear material).
Management of nuclear wastes for the coming years
rise some technical problems but the main
problems are of societal type (see later). As
discussed the 3 first criteria are fulfilled (30
to 80 of electricity depending countries,
Generation III reactors will have improved
systems to reinforce safety, Unat resources are
secure for the next decades at known prices, Pu
can be recycled once in PWR without difficulty).
The proliferation is a question of technical and
political means controls. It is more easy to have
fissile nuclides with high level enriched Unat in
U235 (ultra-centrifugation) than to produce
Pu239. Both techniques are very heavy.
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Social criteria There are 2 important criteria
cost and wastes management, the radiological
impact being low (except in the case of
accidents) Price is around 3 to 4 cents of Euro
per kWhe (including provisions for waste
management and decommissioning) whatever would be
the interest of money (5 to 10 ) on the next 40
years Waste management of LLW is a major concern
(U ores mining, ML-LLW and HL-LLW). High
isolation and confinement or radioactivity over
long periods of time is necessary (105 time
compared to toxic industrial wastes). Actually
10 000 tons of SF are yearly unloaded in the
world. Nobody knows exactly if it will be
possible to transmute on an industrial scale the
LL radionuclides, indefinite storage raise the
problem of the stability of society, sitting of
deep geologic disposal is difficult.
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• A geologic repository could be designed to
  dispose of around 80 000 tons of SF (or
  equivalent reprocessing packages). In 2020, 200
  000 tons of SF will have to be managed. If
  geological disposal is chosen, that will need 3
  disposal sites (an increase of the use of nuclear
  energy must be considered with respect to the
  need of more repositories)
• There are 4 characteristic periods of time in LL
  nuclear wastes
• 5 (to 10 ?) decades during which SF or HL-LLW
  must be cooled (heat released by FP and SL
  actinides, Pu241, Cm244, Cm243 for UOX and
  additionally Pu238 for MOX). During this time
  either the way to change the type of wastes or to
  dispose of the wastes is decided.
• several decades to implement the choice (no need
  of cooling)
• The problems during these two periods are of
  national relevance and solved by man-made
  technique (for geological disposal heat released
  by Am241 and Pu238 lay down the size)a

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• - the third period extends to 100 000 years
  during which radionuclides must be
  isolated/confined, for instance in canisters and
  engineered barriers of high performances (Pu239,
  Pu240, Pu242, Am241 and Np237). Concentration of
  ? emitters must be less than 10-10 M in
  environment, much less than chemical pollutants
  (linked to 1mSv/year got by drinking water).
• over 100 000 years the radionuclides (U
  isotopes, Np237 and Pu242 and also long-lived
  FP) must be confined by natural rocks
• During these two last periods the problems can
  only be solved by geology

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Is nuclear energy renewable? The question is a
matter for the next half of this century and
later The present yield for the utilisation of
the energy of fission contained in Unat is less
than 1. But when U238 is used as fissile and
fertile nuclide (fast neutrons) the period of
time during which energy can be produced is
measured, as least in theory, in thousands of
years (renewable energy?) In the case of lack of
U, or in parallel for technical or social
reasons, the use of Th (thermal neutrons) can
also be considered on the same scale. But the
massive use of new reactors and new nuclear
systems is mandatory.
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Resources in U The stockpile of Udep is enormous
(230 000 tons in France) and will increase using
Uenr as nuclear fuel. Udep is easy to manipulate.
The quantities of Urep are less (20 000 tons in
France) but will increase using MOX fuel.
Declassified military high enriched U (up to 90
in U235) or fissile Pu239 could be
used. According to some forecasts the need of
Unat could be important. For instance a power of
250 GWe in 2020 would require 100 kt per year of
Unat. So extraction of Unat both from pure U ores
and as by-product (industry of Cu, Au or P)
should be boosted
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Reactors for the future (2050), valorisation of
resources, optimisation of waste management. The
nuclear energy for the future will be developed
in the direction of mixing this source of energy
with other sources in an energetic mix whatever
the other objectives are. The future nuclear
systems energy including Generation IV reactors
and associated cycle facilities should have the
objective to valorise the resources in fissile
nuclides and to optimise the management of
wastes. Along the long way to launch these
systems the most advanced new reactors are HTR
and FNR Two international projects of HTR of low
power (100 and 300 MWe) are developed (derived
from experimental reactors operated in USA and
Germany in the sixties-seventies). Two HTR are
presently operated in China-10 MWth- and Japan
-30 MWth)
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The coming HTR will be fuelled with Uenr (8 to 10
) or with MOX made with military Pu239,
moderated with C, cooled with He and operated
following an open cycle (75 of loaded Pu could
be burnt). With He at 600C directly associated
with a gas turbine a yield of 50 is expected
(Brayton cycle). Their fuel will be based on
micro-spheres of ceramic oxides (or carbides)
coated by several layers of C and by SiC and
embedded in C. This is a new fuel. The layers
will isolate FP and actinides from He (like
cladding of pins in PWR) up to 1600 C. SF at
high BU (100 to 150 GWjt-1) will be a waste
because its reprocessing will be very difficult
(but not impossible).
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FNR. Fast neutrons allow the use of all
isotopes of U, Pu and heavier actinides (?f/?c of
fast neutrons gt ?f/?c of thermal neutrons). The
resource of fissile nuclides is practically
increased by a factor of 50 (twice in theory).
The technology of FNR cooled by Na is known. They
are fuelled with MOX of high content in Pu (up to
20 ) and need to be launched 10 to 15 tons of
Pu/GWe (in fact with 9.6 tons of fissile Pu
isotopes) They can be operated giving as much Pu
as they burn (regeneration) or more
(over-generation or breeding). But it takes 2 to
3 decades to have sufficient Pu to launch a new
FNR (50 years for a PWR!). Worldwide Pu
production is around 75 tons (and 7.5 tons of
other actinides) which could allow to launch 5 to
7 GWe/year. In 2030 the stockpile of Pu in SF
will be around 3000 tons.
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Transmutation of actinides (FNR and ADS) FNR can
burn actinides (Np, Pu, Am, Cm) if they are
included in U based fuel but in limited
quantities (due to safety problems raised by the
decrease of available delayed neutrons). Special
fuel (metallic alloys, oxides, other compounds)
must be used of which preparation and
certification have to be implemented.
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ADS (Accelerator driven system). ADS are based,
like FNR, on fission induced by fast neutrons.
But the core (U) is sub-critical (keff around
0.98 for instance) and the fast neutrons needed
to have ? 0 are given by a spallation source.
In this device (cooled molten Pb-Bi alloy,
diameter 0.5 m, height 1 m) a beam of high
energetic and high flux of proton (1 GeV, 20 mA
at the limits of present accelerators) is
transformed in fast neutrons (1 to 2 MeV) by
nuclear spallation reactions The power of the
reactor, Pr, is controlled by the power of the
accelerator, Pa (Pr/Pa 6 ?/? (keff/1-keff)).
The use of ADS is foreseen to transmute Am
(and/or Pu) embedded in inert target (without U).
Transmutation with ADS allows a load in actinide
higher than in critical FNR because operating the
reactor does not need delayed neutrons.
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Other reserves of fertile nuclides It is possible
to launch thermal neutrons based reactors using
the fertile monoisotopic Th232 and fissile
nuclides (U235 or Pu isotopes) as a match.
Fissile U233 is formed, which can be recycled.
U233 has very attractive nuclear properties. U233
can be, or could be, produced in PWR by
irradiation of Th232 A molten salts reactor (MSR)
in USA (7.5 MWth, U235 and U233 fuelled) has
shown, in the sixties, the possibility of
breeding. A modern version is under evaluation.
MSR are high temperature reactors (600 to 700 C)
where molten salts (Li and Be fluorides) are both
fuel and coolant and the moderator is C. It needs
1.2 tons of fissile nuclide per GWe, around 1/10
of a FNR-Na load. It does not produce heavy
actinides (U238 is not present) Such reactor can
transmute actinide in line.
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Conclusion Technology and economy make fission
nuclear energy a sustainable energy Unat
resources for decades (and possible use of
made-man fertile nuclides), safe technology and
possible improvement, low price of kWhe compared
to other sources (without considering CO2
emission tax), environment friendless and no
health impact by additional low dose of
radiation. A renew of nuclear energy could be
possible. But problems remain public antipathy
(difficult to change), waste management (problems
identified, but not solved), policy for
international licensing (visibility for
development), ethical (intergeneration
relationships). It is reasonable to forecast that
during the next 15-20 years (say up to 2025) no
drastic change will occur in nuclear energy
production.
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This period will be for each country a period of
thinking on the use of nuclear energy,
confirmation of phase out, maintaining present
level or increasing it in the energetic
mix. This period will be also a test period for
the implementation of programmes set up to renew
world-wide nuclear energy as for instance the
GNEP (Global Nuclear Energy Partnerships) leaded
by USA. Finally this period will be devoted to
test the will of countries in developing
international research to prepare possible
launching of reactors of Generation IV, and
associated nuclear fuel cycles, in the second
half of the century according to the objectives
of GIF.
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GIF (Generation IV International Forum, 11
partners) was initiated in 2002. Several
organisational steps have been implemented up to
2005. It is aimed at developing 6 new types of
reactors based on fast and thermal neutrons for
optimising the use of fertile nuclides, producing
less waste and opening new uses of nuclear energy
(high temperature heat production). The GNEP
organisational programme, launched in 2005 by
USA, proposes to complete the objectives of GIF
as follows. In the short term encourage
launching of new reactors particularly for
developing countries (low power reactor), in the
long term develop new technologies proliferation
resistant, for recycling Pu and other actinides
and develop advanced burners of Pu and actinides.
For both actions it is proposed to set up an
international system of nuclear services
(enrichment, reprocessing) under international
control
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What will happen after 2025 for nuclear energy is
relevant to prospective because choices on energy
are subject to too many parameters In the
countries where nuclear option will remain open
one can think that coexistence of Generation II
and III of reactors will exist. Indeed the
Generation III reactors are designed for a 60
years lifetime. These reactors, and associated
fuel cycle facilities, could finally dominate the
nuclear landscape up to the end of the century.
This will not lead to a great change in nuclear
industry In the case of positive tests for a
possible development of nuclear energy, which
will mean that a drastic increase in nuclear
energy will have been accepted, research for
nuclear energy for the future will be boosted
to prepare the use of fertile nuclides (U238 and
Th232) and to implement the objectives of GIF.