white paper - Copenhagen Atomics

FT
Copenhagen
Atomics
DR
A
Affordable Sustainable Clean Energy
White Paper
November 2014
DR
A
FT
i
Overview
Copenhagen Atomics aims to provide an economically viable solution to the problem
of long lived radioactive waste from the nuclear industry.
DR
A
About this Document
FT
A key feature is chemical reprocessing of spent nuclear fuel, to separate it into 3
groups that can be handled differently.
The most dangerous group, plutonium and other long lived radioactive isotopes, will be
permanently destroyed in the Copenhagen Atomics Wasteburner reactor. The reactor
will supplement the spent nuclear fuel with thorium, as this avoids the breeding of new
plutonium.
Of the remainder, chemically pure uranium constitutes the bulk, and can be resold as
raw materials for fresh reactor fuel, as it is still slightly enriched compared to natural
uranium. This leaves the medium long lived fission products, but once separated from
the long lived actinides, these can be relatively easily stored until they are no longer
significantly radioactive.
This document is the first public draft of the Copenhagen Atomics Whitepaper, presenting our plans and goals. Please note that the information given herein is tentative,
as the designs are still in their early stages.
For more information, please contact Copenhagen Atomics at:
[email protected]
ii
Copenhagen Atomics
Contents
1 Meeting the Worlds Rapidly Expanding Energy Needs
1
2 Reduction of Waste by Copenhagen Atomics
2.1 Chemical Separation of Commercial Light Water Reactor Waste . . . .
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3 Wasteburner Design
3.1 Structural Design . . .
3.2 Reactor Core . . . . .
3.3 Salt Composition . . .
3.4 Onboard Reprocessing
3.5 Cooling . . . . . . . .
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4 Safety & Decommissioning
4.1 Walk-Away Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.2 Decommissioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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5 Cost Analysis
5.1 Cost of construction of the first demonstration Wasteburner . . . . . . .
5.2 Cost not directly related to R&D and construction of the machine . . .
5.3 Cost of Wasteburner in a mass production scenario . . . . . . . . . . . .
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6 Non-proliferation
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7 Summary
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Meeting the Worlds Rapidly Expanding Energy Needs
1
1 Meeting the Worlds Rapidly Expanding Energy Needs
DR
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The Role of Nuclear Power
FT
Rapid economic growth in Asia is lifting millions of people out of poverty each year.
This growth is fueled by an equally rapidly increasing demand for electricity, which is
currently being met with the use of cheap coal power. Unfortunately this has come
at the cost of severe air pollution plaguing the industrial and population centres of
the region[1], and significantly increasing the world’s carbon emissions, threatening
catastrophic climate change. This is driving a demand for cleaner, non-fossil energy
sources from the affected populations.
Solar and wind power are intermittent and thus cannot provide baseload power, and
the cost[2] of a large scale deployment would place an unacceptable damper on economic development. Even with significant public and political pressure to move power
production in this direction, the world has gone from 0.3% of electricity production
from solar and wind in 2001 to only 2.3 % in 2011[3].
Hydro power can be a cheap and dependable power source, but capacity is limited and
there can be significant social and environmental impact in affected areas.
Nuclear power is capable of delivering clean and affordable energy, and can be scaled
rapidly. This is evidenced by France, which prompted by the oil crisis of 1973 went
from having 8% nuclear power in 1973 to 49% in 1983 and 75% in 1990[4]. This
ability to scale rapidly is crucial for the practicality of using nuclear power to meet the
demands of the rapidly growing Asian economies.
The main challenges facing such a large scale deployment of nuclear are:
1. Building the power plants cheaply.
2. Running the power plants safely.
3. Handling the radioactive waste.
The first two challenges are being tackled by a number of companies in the nuclear
industry, by research into advanced reactor designs such as small modular reactors,
low pressure molten salt reactors, as well as the use of passive safety systems.
Copenhagen Atomics aims to solve the third challenge: The issue of nuclear waste.
Tackling the Long Lived Nuclear Waste
The nuclear waste in spent fuel rods from the current and past generation of conventional light water reactors (LWRs) is composed of a large amount of uranium, a small
amount of fission products, and a very small amount of long lived transuranic elements.
Copenhagen Atomics will chemically separate this waste into 3 groups:
• Pure uranium
This is no more dangerous or radioactive than natural uranium, and has approximately the same isotopic composition. This can be disposed of in the same manner as the natural uranium present in the tailings of
rare earth mining operations, or sold as raw materials for re-enrichment for fresh
Copenhagen Atomics
FT
2
DR
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Figure 1: Composition of spent nuclear fuel from a typical commercial LWR[5].
nuclear fuel, as it still contains a slightly higher fraction of
mined uranium. (Blue area in figure 1.)
235 U
than freshly
• Fission products
These are the lighter elements created as a result of the
fission of uranium. Their radioactivity is dominated by a half-life of less than
30 years. This means that if it is stored for 300 years, the radioactivity will be
reduced by a factor of more than 1000, at which point the radioactivity is at
the level of natural uranium dug up from the ground, and can be disposed of
in the same manner[6]. Although 300 years is a long time by human standards,
engineering storage for this length of time is certainly feasible using existing
techniques. (Green and red areas in figure 1.)
• Plutonium and other transuranic elements
These contain very long
lived isotopes that are radioactive for a very long time and that would need to
be stored on geological time scales. Storage for this length of time is extremely
difficult to engineer, and it is impossible to ascertain that it will safely contain
the waste over such a length of time. Storage facilities of this kind have been
constructed, such as the American Yucca Mountain Nuclear Waste Repository,
but at immense cost and it has since been abandoned[7]. (Yellow and pink areas
in figure 1.)
Copenhagen Atomics’ solution to the problem of transuranics is to destroy them
permanently by recycling them as fuel and fissioning them in our Wasteburner reactor.
This process will be far cheaper than building a geological storage facility, and will
produce a net surplus of energy.
Reduction of Waste by Copenhagen Atomics
3
2 Reduction of Waste by Copenhagen Atomics
The Copenhagen Atomics Wasteburner starts with spent nuclear fuel from a LWR,
after the fuel has been stored in cooling pools for at least a decade, making it safer to
handle. The composition of spent fuel varies somewhat between different reactors, but
the typical composition is as shown in figure 1.
FT
After decladding, the fuel will be separated chemically as described below into pure
uranium, fission products, and actinides. The actinides will subsequently be fed into
the reactor to be destroyed.
As the fission products are dominated by a half-life of 30 years, long lived nuclear waste
is virtually eliminated by this method.
2.1 Chemical Separation of Commercial Light Water Reactor Waste
DR
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The Wasteburner will be able to receive spend fuel elements which will be processed
and fed into the thorium based reactor. The main process is based on the FLUOREX[8]
reprocessing method. This method is favoured as it is well documented, and it is based
on a technology that is also suitable for cleaning up molten salt for fission products
during reactor operations.
The process backbone is an improved fluoride volatility, where Pu is never separated.
The spent fuel rods are chopped and processed by a cyclic high temperature oxidation/reduction, where the cladding is removed from the fuel together with volatile
fission products such as Xe, Kr and I[9]. After decladding, the spend fuel consist primarily of triuranium octaoxide together with plutonium oxide, other actinide oxides,
and non-volatile fission products.
The improved fluoride volatisation process is carried out in an aluminum oxide fluid
bed reactor, which is fine tuned by diluting the fluoride with argon or alternatively using inter halogen gases, such as bromine pentafluoride or chloride trifluoride, to remove
uranium and leave plutonium dirty. The decontamination factor (DF) of the plutonium
uranium mixture is 102 (DF = 102 ). After a hydrogen reduction, the dirty plutonium
is entered into the molten salt stream. The plutonium separation from uranium can be
tuned by adjusting the fluorination conditions, so there is between 2% and 10% 238 U
in the dirty plutonium stream which enters the reactor. The uranium hexaflouride is
processed through retrification followed by a sodium fluoride trap, similar to that used
for the molten salt processing, in order to remove more volatile fission products.
The finished uranium has a decontamination factor of DF = 105 , and is therefore
ready to be shipped to re-enrichment or other uses.
4
Copenhagen Atomics
3 Wasteburner Design
FT
The Copenhagen Atomics Wasteburner reactor will be a molten salt reactor fuelled
by plutonium from stockpiled nuclear waste, mixed with thorium, small amounts of
uranium, and various minor actinides. The primary purpose of the reactor will be
to destroy plutonium and minor actinides from nuclear waste through transmutation
and fission. Therefore thorium will be used instead of uranium, to avoid breeding new
transuranic elements. A 232 Th nucleus would need to capture 7 neutrons in succession
without fissioning, in order to be transmuted into 239 Pu. Therefore only very minimal
quantities of plutonium will be produced from thorium.
The reactor design will be very similar to the proven Molten-Salt Reactor Experiment
reactor at the Oak Ridge National Laboratory, and other proposed molten salt reactor
designs, by companies such as Flibe Energy and Transatomic Power.
For the initial version, we envision a reactor output of 50 MWth. Significantly higher
output will be possible in future versions, with some changes to the original design.
3.1 Structural Design
DR
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The Copenhagen Atomics Wasteburner reactor is designed to fit inside a standard
shipping container. This allows it to be constructed in a central factory, rather than
on-site, greatly reduced construction time and cost. The container will be shipped
without nuclear materials, placed inside a prebuilt concrete housing, and fuelled onsite.
The chemical reprocessing unit will also be produced in a central factory and placed
in the shipping container next to the reactor.
Aside from the concrete housing, other on-site facilities will include:
• Secondary coolant loop for transporting heat away from the reactor. This will
be connected to an interface on the container.
• Steam generators and turbines for power production from the reactor heat.
• Emergency coolant pool to remove initial decay heat at reactor shutdown.
All of which can be pre-constructed.
3.2 Reactor Core
The heart of the facility is a compact, graphite moderated, high temperature, density
controlled, single salt, liquid fuel core, which will fulfil the following demands:
1. It will be ”walk away safe” (See chapter 4).
2. It can be run on nuclear waste, without requiring separation of Pu.
3. It will be based on a closed fuel cycle.
The reactor core design, including primary safety barrier, control mechanism and
primary heat exchanger, consumes a total volume of 2 × 2 × 6 m3 . The core itself is
divided into two parts: the critical inner core where neutrons are thermalised in the
Reactor Core
5
DR
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FT
3.2
Figure 2: Layout of the Copenhagen Atomics Wasteburner design. The reactor and
reprocessing is housed in a shipping container, shielded inside a concrete
vault. The reactor is sealed shut during its operating lifetime, with cooling
pipes, power lines, and data connections the only link to the outside world.
6
Copenhagen Atomics
moderator assembly, and the subcritical outer core which acts as a shield for radiation
from the inner core. Although the outer core is subcritical it still produces significant
amounts of energy from cascades of fast and epithermal fissions triggered by leakage
of neutrons from the inner core.
FT
Utilising the fact that the fuel is liquid, it is possible to exploit the temperaturedensity relation in the fuel salt to construct a passive control mechanism with strong
negative temperature coefficient. Simulations show that this can be utilised to make
the energy production, to first order, proportional to the cooling rate. The reactor’s
load following can thus be controlled by the flow speed of the cooling salt. Furthermore,
if cooling is stopped and the reactor is left alone, the core will heat up and saturate at
a temperature related to the operator defined power level, which can be controlled by
a pressure valve.
DR
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By controlling the fuel composition, via the in situ chemical reprocessing plant and
the amount of fuel salt present in the outer core, the reactor burnout can be varied
between high waste burn rate and high Th closed fuel cycle burn rate. When optimised
for waste burnup, the reactor will have a low Th breeding rate, hence it will need a
steady inflow of new nuclear waste. When tuned for high burnup, the inflow of new
nuclear waste will decrease over time. Though calculations show that a thermal Th
reactor of this type can achieve a fully self-sustained closed fuel cycle, this will only be
possible for a reactor of this size when running at reduced power.
3.3 Salt Composition
The molten salt consists of 7 LiFThF4 along with actinides such as 7 LiFThF4 AcF4
where Ac is actinides. The salt is processed by a novel fluorination process invented by
Copenhagen Atomics that fluorinates most of the plutonium which is recycled with uranium and neptunium, and separated from volatile fission products through consecutive
sodium fluoride traps. This is followed by liquid bismuth extraction[10] which removes
and recycles actinides and separates lanthanides. This procedure never separates pure
plutonium and therefore it creates no proliferation concerns.
3.4 Onboard Reprocessing
During operations noble gasses will be removed continously by helium bubbling, and
trapped by cryocooling after the helium is regenerated by distillation.
The molten salt will be reprocessed by a flow of approximately 30 L/day. From the
molten salt system only fission products will leave, and when they are separated from
the salt stream they are treated in a pyrohydrolysis reactor leaving fission products as
oxides. Fission products will be stored in storage tanks in the chemical reprocessing
part of the reactor.
The chemical processing system is designed to be in a 20’ container and will be able
to sustain itself if electric power is supplied during the lifetime of the reactor system.
After shutdown, a cooling period of a decade is used before the fission products are
removed from the chemical processing system.
Cooling
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FT
3.5
Figure 3: Decay heat produced after reactor shutdown. Note that the values given here
are for a 30 MWth reactor.
3.5 Cooling
The primary loop contains the fuel salt where the nuclear fission occurs. The heat is
transferred through heat exchangers to a secondary loop, which transfers the energy
to steam generators at the surface. In this way, no radioactive material leaves the
container.
The container with the reactor is connected to a set of dump tanks constructed
underneath the container. They are connected with the primary loop with a freeze
plug, which will melt in case of overheating. In a Fukushima type emergency where
all control of the reactor is lost and cooling is interrupted, the buildup of heat will
melt the freeze plug, and gravity will force the liquid fuel to drain into the dump tanks
where the nuclear chain reaction will cease.
The dump tanks are submerged in an emergency coolant pool, which is a tank of water
of sufficient size to absorb the initial decay heat before evaporating. After this point
the thermal output from the dump tanks will be reduced to the point that natural air
convection provides sufficient cooling.
In this way the reactor is able to withstand an emergency shutdown with complete
coolant failure with no risk of meltdown, using only basic physical laws such as gravity
and thermal convection, without the need for any moving part, power, or human
intervention.
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Copenhagen Atomics
4 Safety & Decommissioning
Safety is critical, both during operations and decommisioning. In the nuclear industry
the subject of safety is paramount, but this chapter only attempts to make a short introduction to the special safety issues related to the Copenhagen Atomics Wasteburner
design.
FT
4.1 Walk-Away Safety
The term Walk-Away Safety, also known as Inherent Safety, is a term used to describe a
reactor that will remain safe even if all the operators were to walk away and disconnect
the external power, leaving the reactor to itself for an extended period of time[11].
In order to be termed Walk-Away Safe, a reactor must be able to perform the following
automatically without human intervention or any power supply:
DR
A
1. Regulate the nuclear chain reaction to avoid a runaway process. The Copenhagen
Atomics Wasteburner design achieves this by having a negative thermal coefficient of reactivity; i.e. if the nuclear reactivity increases, the reactor enters a
negative feed-back loop where the reactivity decreases due to thermal expansion
and a resulting decrease in reactivity.
2. Automatically shut down the reactor in the event of a complete cooling failure.
The Copenhagen Atomics Wasteburner design achieves this through a combination of the negative thermal coefficient of reactivity mentioned above, and a set
of dump tanks where the fuel will be stored in a non-critical configuration. In
the event of overheating, the valve to the dump tanks is opened automatically by
the melting of a freeze plug, and the liquid fuel is then drained out of the reactor
by gravity, making this feature completely passive.
3. Remove the decay heat of radioactive isotopes left in the fuel after the reactor
has shut down. The Copenhagen Atomics Wasteburner design achieves this by
draining the fuel into dump tanks as mentioned above. The dump tanks are
submerged in an emergency coolant pool, which is a tank of water of sufficient
size to absorb the initial decay heat before evaporating. After this point the
thermal output from the dump tanks will be sufficiently low that cooling can be
managed through natural air convection.
Modern Generation III commercial nuclear reactors fulfil only the first 2 criteria. By
also fulfilling the third one, accident scenarios such as Three Mile Island and Fukushima
can be avoided. As the Copenhagen Atomics Wasteburner fulfils all 3 criteria, it is
completely walk-away safe in any realistic scenario.
Another important safety factor is that the Copenhagen Atomics Wasteburner reactor
will run at below atmospheric pressure, unlike traditional light water reactors. This
means there is no risk of a steam explosion in the reactor, in the case of a structural
failure of the reactor vessel. This is possible due to the very high melting point of the
molten salt at atmospheric pressure. Running the reactor at below ambient pressure
prevents leakage of gaseous radioactive elements such as Tritium and Krypton.
Additionally our design will be built inside a shipping container, which is reinforced and
4.2
Decommissioning
9
made 100% air tight, to further reinforce against unintentional release of radioactive
gasses to the environment.
4.2 Decommissioning
FT
After the reactor has expanded its operating lifetime, the inner parts will have been
activated by the neutron flux, and will therefore remain radioactive, even after the fuel
and fission products have been removed. This is true for any nuclear reactor, be it
fission or fusion, and the reactor must therefore be decommissioned safely.
The specifics of decommissioning is governed by the local regulations, which vary from
country to country; therefore it will not be detailed in this document.
DR
A
However it should be noted that decommissioning will be considerably easier - and
thus cheaper - with the Copenhagen Atomics Wasteburner, than with a traditional
nuclear power reactor. Not only will there be drastically less long lived waste produced
by the reactor, but the small size and portable nature of the reactor means that it can
be transported to a specialised facility for decommissioning, rather than doing it onsite.
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Copenhagen Atomics
5 Cost Analysis
As the Copenhagen Atomics Wasteburner will operate at slightly below atmospheric
pressure, the cost will be drastically reduced compared to a traditional LWR operating
at very high pressure. Operating at ambient pressure means that the need for housing
the reactor in a pressure vessel is eliminated, and the requirements for the shielding
can be significantly relaxed. Additionally the need for specialised parts and labour will
be reduced accordingly.
FT
As Copenhagen Atomics is aiming for an easily mass produced and transported design, it will be possible to achieve a large cost decrease between the demonstration
Wasteburner and the mass produced version.
The following cost analysis will be divided into 3 separate paragraphs, as each one of
them is quite different in nature.
5.1 Cost of construction of the first demonstration Wasteburner
DR
A
The work that has been conducted until now is dominated by simulations and research
into existing papers and technologies. This work will continue for some time and, by
nature, consists primarily of man hours from engineers and scientists. At this stage
there are several critical measurements of the chemical processing loop that need to
be obtained before further dimensioning of the overall system can happen. We believe
that the construction of the first demonstration Wasteburner will require approx. 1
year from the time when the dimensioning of the full system design has been completed.
The first demonstration version of the Wasteburner machine will be the same size as
commercial units. But because it is planned to run less than 12 months, the quality of
some of the special materials can be downgraded slightly, which has a very big influence
on cost and availability of these materials and special components. Currently our best
estimates show that cost of materials and man hours will be approximately 50% / 50%
of the total machine cost. A significant part of this construction cost, in both time and
materials, is related to measurement equipment, some of which is not available off the
shelf, and must be constructed in collaboration with suppliers of such instruments.
Our current focus is on constructing the chemical processing loop, which will allow
us to make the measurements that are needed for further dimensioning of the overall
system. We believe that it may be necessary to construct several versions of such
chemical processing loops. Construction time of each of these may be up to 6 months,
with time and material costs of less than $ 1 million per loop. It will be build inside a
standard shipping container. R&D design cost is not included in the mentioned cost
estimate. The most uncertain element in terms of cost is related to the measurement
equipment. Further analysis is currently in progress.
Because the tests of the chemical processing loops take place with only small amounts
of nuclear material, we believe that the approval processes of such tests are similar to
other research experiments and thus we assume the cost of approval work to be insignificant. The major emphasis will be on the disassembly and handling of radioactive
contaminated components after the test. After the dimensioning of the overall system
has been completed the design of the entire Wasteburner machine will be submitted to
5.2
Cost not directly related to R&D and construction of the machine 11
a more detailed approval process and it is expected that this approval will take several
months to complete. It should be noted that this is a demonstration reactor, designed
to turn on and off for small test runs with time frames of less than one hour, and not
configured for long term operation. At the time of writing we are unsure if it can be
classified as a research reactor. More details about the approval process are needed
before planning and investments in the demonstration reactor can be allocated.
5.2 Cost not directly related to R&D and construction of the machine
DR
A
FT
The proof of concept milestone will be reached when the first demonstration reactor
has been shown to work and to reduce the volume of radioactive material from spent
nuclear fuel in a cost efficient manner. In the next phase, emphasis will be on approval
for long term operation. The next Wasteburners to be built will be designed to run for
many years and to process significant volumes of spent nuclear fuel. At this stage the
project will move from a small research project with relatively few people involved to a
full scale production system, requiring significant approval activity for all components
and materials for long term operation, safety and decommissioning analysis. At this
stage the customer will need to spend significant time to evaluate if the Wasteburner
from Copenhagen Atomics is the right fit for the energy strategy of their country.
The molten salt reactor is significantly safer to operate than traditional light water
reactors, for reasons described in detail in chapters 3.5 and 4. Thus we expect that
the cost of a full license from the nuclear commission to operate the machine will be
significantly less than a license to operate a traditional light water reactor. However,
if the Copenhagen Atomics Wasteburner is the first commercial molten salt reactor to
be licensed in the world, we do expect significant cost to accumulate during this phase.
In fact the cost of these approvals and production of the related documentation is
expected to be much higher than the cost of building the demonstration Wasteburner
described in chapter 5.1. We believe that further estimates of the exact time and cost
of this approval period will be difficult to estimate at this time, both for our team as
well as for the nuclear commission.
The complexity of the project and the requirements and the number of stakeholders
will be much higher at this stage, eventually resulting in increased cost both for the
manufacture and the customer. Indeed, the cost of actual time and material to build
the first long running Wasteburner machine at this stage will probably be less than
10% of the expected system cost.
5.3 Cost of Wasteburner in a mass production scenario
The cost of the Wasteburner in a mass production scenario has 4 major components
that will determine the price.
1. Capital cost. Meaning how much it cost to get to this point and the level or risk of
the investments made previously. Two things drive this cost: If the time it takes from
this white paper to mass production doubles, the capital cost will typically more than
quadruple. The second factor is uncertainty - i.e. if the stakeholders cannot estimate
and agree on the time it will take to get from white paper to mass production. Capital
cost is very high in the first phase, leading to a slowdown and thus further increase
12
Copenhagen Atomics
of the capital cost. Thus in order to create a low whole system cost structure, it is
important that the stakeholders can get to a common understanding of the expected
evolution from white paper to mass production.
FT
2. Cost of monopoly. If someone becomes a gatekeeper with some kind of monopoly
status on some part of the machine, then mass production cost is likely to be dictated
by this monopoly factor rather than the actual cost of time and material. This can
happen via patents or special materials or components that are only available from
one supplier. The monopoly effect is undesirable because it adds additional risk to the
system and thus it drives up cost of all components and suppliers involved. When the
capital cost is high, investors tend to try to protect their investment with some kind
of special rights.
DR
A
3. Cost of time and material. The best way to drive down cost of mass production
is with a component based system design similar to that of the PC industry. Using
this approach, the demonstration Wasteburner is made from components which have
well defined interfaces, allowing each component to be sourced from several suppliers.
When the machine is ready for mass production these interfaces are handed over to a
standards committee made up of all stakeholders. This way stakeholders can ensure
that the cost drops as fast as possible. It should be noted that a Wasteburner is made
up of metal pipes, pumps , valves, measurement equipment and electronics, all of which
can be driven to very low cost when the volume is sufficient. Thus under the optimum
scenario the cost of Wasteburners can potentially reach a cost drop curve similar to
those observed in the PC industry and the mobile phone industry.
4. Cost of public uncertainty. Large sections of the public are afraid of nuclear energy.
There is a small potential risk that the Wasteburner can become subject to negative
public debate. If this happens it would drive additional cost and increase the capital
cost significantly. There will always be people for and against. However we think that
the best way to avoid negative public debate is to invite first movers who are interested
in the technology to be educated about how it works, be open about the pros and cons,
and be honest about risks and costs. When the first movers have sufficient knowledge
they are likely to become involved in the public debate with a positive outcome and
at no additional cost.
We hope this chapter has conveyed a more modern way of developing much needed
technology for the people of this planet. We hope it can inspire you to look at the
whole cost estimation problem with new eyes. We look forward to a more detailed
debate about the subject should you choose to go forward with the suggestions in this
white paper.
Non-proliferation
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6 Non-proliferation
FT
In the chemical reprocessing plant of the Copenhagen Atomics Wasteburner, only one
element of proliferation concern will be separated, namely uranium. The uranium
separated will be spent nuclear fuel quality and will have 1-2% 235 U content and fairly
high 234 U and 236 U contamination, making it unsuitable for weapon production, even
after enrichment. Being a thorium based wasteburner 233 U will be bred in the core.
Doubling times are expected to be above 20 years. Additionally, significant amounts
of 232 U and 234 U will also be bred in the reactor, and significant amounts of 238 U will
be added to the fluid from the processed spent fuel. Even if uranium were separated
from the reactor inventory, the presence of these other isotopes means that it would
not be suitable for weapon production, without enrichment to a much higher extent
than that needed to produce weapon grade material from natural uranium.
DR
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With extensive modification of the chemical loop, separation of protactinium from the
reactor inventory might be possible, and 233 U could be extracted from the protactinium
after a few hundred days. However, the protactinium content in the fluid will be less
than 1 PPM, and the total inventory will never exceed a few grams, thus protactinium
separation would be tremendously difficult, and it would take hundreds of years for
any useful amount to accumulate. Due to the tight neutron economy in the thorium
cycle, removal of protactinium will upset the reactor cycle, and alternative fuel will be
needed. This will make it very easy to detect if protactinium is being separated from
the reactor inventory, and it will not be an economical or viable way of accumulating
weapons grade fissile material.
Plutonium will not be separated from other actinides at any point in the Copenhagen
Atomics Wasteburner operation process, but it must be recognised that the reactor
core will contain significant amounts of 239 Pu, mainly from fed-in spend nuclear fuel.
It should be noted that the fed-in plutonium is not weapon grade, as it originates
from high burnup spent nuclear fuel with a high 240 Pu content. Being a Wasteburner,
the reactor will burn more plutonium than it creates from the small amount of fedin uranium, or from several neutron captures by the thorium. As mainly 239 Pu and
241 Pu are burned, the reactor will increase the fraction of 240 Pu and 242 Pu in the
reactor plutonium inventory, and as a result the Copenhagen Atomics Wasteburner
will reduce not only the amount, but also the weapons quality of fed-in plutonium.
To summarise, no weapons grade material is separated at any stage in the Copenhagen
Atomics Wasteburner design. The fissionable isotopes produced in the reactor will be
burned up rather than accumulated. It will not be practical to covertly modify the
operation to accumulate material for weapons.
14
Copenhagen Atomics
7 Summary
The Copenhagen Atomics Wasteburner is designed to drastically reduce the long term
radioactive waste generated by commercial nuclear power plants, while also producing
electricity for the grid.
The design consists of two main parts: a machine for chemical separation of spent
commercial fuel, and a molten salt nuclear reactor which will burn the long term
radioactive waste, permanently destroying it.
FT
The chemical separation machine has at its heart a novel fluoride volatility process,
which effectively separates the spent nuclear fuel into 3 parts: pure uranium, fission
products, and the transuranic elements such as plutonium. It is the transuranic elements which drive the long term radioactivity of spent nuclear fuel, and it is these that
the Copenhagen Atomics Wasteburner will destroy by loading them into the reactor
fuel salt. No weapons grade material will be produced by this process.
DR
A
The reactor is a compact graphite moderated molten salt reactor, very similar in
design to existing - and successfully tested - molten salt designs. It will be fueled by
plutonium from the spent nuclear fuel, over time supplemented by transmuted thorium.
It will operate at near atmospheric pressure, which allows it to be small enough to fit
inside a standard shipping container, together with the onboard reprocessing system,
which continually removes fission products from the fuel salt and adds new fuel.
The reactor will be fully ’Walk Away Safe’, meaning that it can self-regulate and
automatically shut down if necessary. This relies on simple and infallible physical
laws, such as gravity, thermodynamic expansion, and convection.
In the event of total external cooling and power failure, this system will cause the fuel
to drain into dump tanks submerged in an emergency coolant pool, which will absorb
the initial decay heat before evaporating, after which natural air convection will suffice.
Fitting the Wasteburner into a standard shipping container is an important goal for
Copenhagen Atomics, as it allows the reactor to be produced in a factory, shipped to
the customer, and easily installed. This will allow for a significant reduction in cost.
References
[1] World Health Organization, Fact Sheet N. 313 (2014)
[2] The Royal Academy of Engineering, The Economics of Renewable Energy (2008)
[3] International Energy Agency, Key World Energy Statistics (2011)
[4] Tina Gant, International Directory of Company Histories, p 140 (2001)
[5] U.S. Government Accountability Office, Nuclear Fuel Cycle Options: DOE Needs
to Enhance Planning for Technology Assessment and Collaboration with Industry
and Other Countries (2011)
[6] Charles E. Till and Yoon Il Chang, Plentiful Energy p. 232 (2011)
[7] Mark E. Gaffigan, Commercial Nuclear Waste: Effects of a Termination of the
Yucca Mountain Repository Program and Lessons Learned (2011)
References
15
[8] Hiroaki Kobyashi et al., Fluorex reprocessing system for thermal reactors cycle and
future thermal fast reactors (coexcistence) cycle, Progress in nuclear energy, Vol 47,
No. 1 4, pp. 380-388 (2005)
[9] M. Kamoshida et al., A New comcept for the nuclear fuel recycle system: Application of the fluoride volatility reprocessing, Progress in nuclear energy, Vol 37, No. 1
4, pp. 145 150 (2000)
[10] S. Delpech et al., Reprocessing physic and reprocessing scheme for innovative
molten salt reactor system, Journal of fluorine chemistry, p 130, 11 17 (2009)
DR
A
FT
[11] International Atomic Energy Agency, Safety related terms for advanced nuclear
plants (1991)