Energia Hidrogenului - Nuclear Hydrogen Production - Course 4

5/26/2018 Energia Hidrogenului - Nuclear Hydrogen Production - Course 4

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NUCLEAR HYDROGENPRODUCTION

Course 4 - 2014


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Agenda

Application of nuclear energy for environmentallyfriendly hydrogen generation

Safety aspects of nuclear hydrogenproduction

High-temperature electrolysisHigh-temperature steam electrolysis for hydrogen production

Thermochemical sulphur processAssessment of the sulphur-iodine cycle for hydrogen

production

Item 1

Item 2

Item 5

Item 3

Item 4

Thermochemical copper chloride and calciumbromide processes


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Changing the world with hydrogen and

nuclear

Hydrogen and nuclear reactions have been at the origin of the universe.

Hydrogen is the simplest atom (made of only one proton and one electron). It was

synthetised first and it is by far the most abundant in the universe. It is at the origin of

the energy of stars that are both energy sources of the universe and factories of

heavier atoms released into the space by supernovae.

Since the beginning of life on Earth, our comfort here stems from hydrogen and nuclear

and our ancestors have been enjoying them for long before they understood why. This

is an example of what the French mathematician, physicist and philosopher Blaise

Pascal summarised in the 17th century in saying,

We always understand more than we know.

Uranium is the heaviest element, so that together with hydrogen, the

lightest, we may think they both surround all elements of the universe,

including those that constitute the Earth, ourselves and the items of our

daily life. Hydrogen and uranium are this sort of alpha and omega thatMother Nature invented to energize our universe and to support the


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Four major endeavours gathering hydrogen and

nuclear

Over the 20th century, hydrogen and nuclear

not only experienced an active development

of their applications separately, but they also

led together to at least four major technology

breakthroughs that revolutionized the sectors

of energy and transportation and will shape

the future in these domains.

Light water reactors

First, the rec

ognition that

hydrogen is the most efficient

moderator to slow down fast

neutrons gave birth in the late

1950s to light water reactors that

afford a greater compactness

and power density than graphite-moderated cores. This

advantage that stems from the

lowest atomic mass of hydrogen

was first used to power military

ships and submarines, and it

was then applied to develop

more economically competitivepower reactors that still

constitute more than 80% of the

Nuclear rocketsSecondly, the nuclear rocket programme

ROVER/NERVA that was developed from the1960s up to 1973 for defence applications

and exploration of space combined a core

designed for an extreme power density and

the use of hydrogen as coolant and

propellant. The advantage of hydrogen here

was its low molecular weight that assured

maximum specific impulse at a given outlet

temperature and its storability as a liquid at

cryogenic temperature.


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Hydrogen and nuclear

Controlled fusionThirdly, the understanding of fusion reactions in the sun by Hans Bethe triggered the interest in

controlled thermonuclear fusion through both the magnetic and the inertial approaches. Two

isotopes of hydrogen, deuterium and tritium, are rapidly identified as being the less demanding

in terms of temperature and confinement requirements to achieve fusion, due to the low electric

charge of their nucleus that minimises the energy needed to overcome their electrostatic

repulsion. First tests of fusion reactions with D-T plasmas occurred in the Joint European Torus

(JET) in the 1990s, and this is the goal of ITER to demonstrate the controllability of a D-T

plasma in a close to ignition sustained operating mode.These three forms of nuclear systems make respective use of hydrogen as neutron moderator,

coolant and nuclear fuel.

The PNP-500 projectThe fourth breakthrough with hydrogen and nuclear that was well on track in the 1980s consisted

in the Power Nuclear Project (500 MWth) in Germany that aimed at using nuclear heat to produce

hydrogen with the process of steam methane reforming. This project led to develop and test large

modules of heat exchangers and steam reformer in the facilities EVA on the research centre of

Jlich and KVK at Interatom in Bensberg. The whole programme stopped in the late 1980s shortly

after the decision to shutdown prototypes of high temperature reactors both in Germany and the

United States.

Over the 20th century, hydrogen and nuclear had been instrumental as alternative energy sources

to fossil fuels and as enabling technologies for specific and strategic applications such as space

missions and propulsion of surface ships and submarines. New concerns that emerged in the 21st

century about the growth potential and the sustainability of all energy production means call for a

stronger role of hydrogen and nuclear energy in the future energy system.


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Renaissance of nuclear energy

This context revived the interest in nuclear power that had been

banned in Western countries in the 1990s. In addition to short- and

medium-term plans to facilitate new orders of light water nuclear

plants, several international initiatives were launched to specify and

develop in co-operation nuclear systems that would supplement LWR

in the 21st century and achieve the various types of nuclearproduction needed in the longer term. The Generation IV International

Forum that was launched by the US DOE in 2000 has certainly been

the most active so far. A European initiative of the same inspiration

was launched in Europe in late 2007 after a strategic planning of

energy technologies had emphasized the strategic nature of nuclear

energy to meet goals of the European Commission and Council

regarding reductions of greenhouse gas emissions (-20% by 2020and evolution towards a carbon-free energy system by 2050).

Future nuclear energy systems are basically of two kinds:

Fast neutron reactors with a closed fuel cycle to achieve a durable

production of electricity while minimising needs of uranium and the

burden of long-lived radioactive waste.

High temperature reactors to possibly extend the nuclear production

to the supply of process heat to the industry, especially for the


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Technologies for nuclear hydrogen

production

general considerationsClean and sustainable ways of producing hydrogen rely on water splitting with electricity and heat generated by CO2-freeenergy sources (renewable energies and nuclear).As demonstrated, hydrogen production technologies are an area of significant international activity and co-operation. Majorresearch frameworks include the International Partnership for the Hydrogen Economy (IPHE), the Generation IV InternationalForum, Joint Technology Initiatives in Europe and leading research or industrial organisations such as DOE-INL and ANL (USA),JAEA (Japan), BARC (India), European Framework Programmes, CEA (France).Different methods for hydrogen production have different characteristics. For nuclear-generated hydrogen those characteristicsinclude (1) economics that favors large-scale centralized production of hydrogen, (2) the co-production of oxygen as a by-product and (3) the availability of low-cost heat.

Hydrogen can be produced by thermochemical,

electrochemical and hybrid (electro-thermochemical)

processes using nuclear energy as the primary

thermal energy source. The hydrogen production

processes properties determine the types of reactors

that can appropiatelly be coupled to the relevant

hydrogen production technologies. The first important

design requirement for both thermochemical and

electrochemical hydrogen production is the relatively

high temperature needed for achieving high thermal-

to-hydrogen energy efficiency. This is the most

important factor in the economics of the technologies

, though the relative magnitude of importance can

differ from process to process.


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Nuclear hydrogen technologies

Each hydrogen production process, and the nuclear system

supporting it, has technological features that can significantly

influence the economic compatibility of the system in the hydrogen

markets. It is important to understand such technical features of the

nuclear hydrogen production technologies for determining the

thresholds of their cost and performance to be viable.

Alkaline electrolysis is a mature technology. It features a good efficiency(~66% LHV), an excellent lifetime of cell (above 20 years currently), and a

production of 99.8% pure hydrogen at 30 bars. This leads to a global efficiency

of ~24% (based on a heat/electricity conversion efficiency of ~35%). The

main issue is the large fraction of the production cost (~80%) tied to the consumption of electricity.

Besides, progress is sought to reduce the investment cost.

The steam electrolysis at high temperature (600-800C) features a potential efficiency of ~100% LHV with extra heat

available. Its technology benefits from current developments made of solid oxide fuel cells. However, many uncertainties and

issues remain to achieve a commercial viability. Prominent issues include improving the reliability and the lifetime of electrolytic

cells and stack of cells and decreasing the investment and operating costs with a view to decreasing the currently estimatedproduction cost from 4 to about EUR 2/kg H2 .

The thermochemical cycles (S-I > 850C) or hybrid cycles (S-electrolysis > 850C) still feature many uncertainties in terms of

feasibility and performances. Uncertainties still exist in parts of the flow sheet and technologies needed to provide high

temperature heat whether from solar or nuclear nature. Potential assets of thermochemical cycles lie in a theoretical potential for

a global efficiency above 35% and a scaling law of the hydrogen plant after the volume of reactants instead of the total surface

of electrolytic cells. In return, their practical feasibility and economic viability have to be entirely demonstrated. Especially, a

global efficiency above 30% is to be demonstrated to compete with alkaline electrolysis. Moreover, the safety of co-located

nuclear and chemical plants has to be demonstrated.

All these processes will have to compete with steam methane reforming associated with carbon capture and storage that is

currently developed with prospects of commercialisation around 2015.


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Relationship of Nuclear

Power to Energy Currencies

and ServicesHydrogen has an additional use,

aside from its role as an energy

carrier. As a chemical product,

hydrogen can be used to

manufacture other chemical and

products, icnludign other energy

currencies. This opens a new

opportunity for nuclear-generated

hydrogen: it can transform other

primary energy sources into a newset of energy currencies in an

environmentally sustainable way.

In the schematics, nuclear hydrogen

and heat can transform coal and tar

sands into liquid fuels for

transportation, making coal and tar

snads more environmentally

acceptable and providing a means

for nuclear energy to contribute to

the transp[ortation sector.

The infrastrurcture developed

through these markets may

eventually serve as stepping stones

to the direct use of hydrogen as a

transportation fuel, as long asneeded modifications to the physical


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Nuclear Hydrogen as support for

other renewable energy resourcesThe development of nuclear hydrogen

technologies may contribute to the

adoption of other primary energy

sources, as well. Plant configurations

that allow switching between electricity

and hydrogen production could

provide the backup power needed to

make intermittent renewable energysources such as sunlight and wind

viable.

A major limitation of these renewable

energy sources is their inconsistency

in power production depending on light

levels in the one case and wind speed

in the other. With a dual-purposenuclear power plant, makeup

electricity can be provided during

times of low output from the renewable

sources. This arrangement would alter

the market attractiveness of the

renewable options. However, relatively

higher investment requirements for

either of the components may limit theapplication of the backup


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Candidate Nuclear Reactor Technologies

and Power Conversion Systems

For processes that require electricity input in addition

to thermal energy, or for plant configurations that co-

generate hydrogen and electricity, an efficient and

economical power conversion system has to support

the nuclear reactor. The following technologies show

potential for the near- and long-term applications:

Steam turbine power conversion systems;

Helium gas turbine power conversion system;

Supercritical CO2 (S-CO2) gas turbine powerconversion system.


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Hydrogen Production Technologies Using Nuclear

Energy

Nuclear energy can be used in hydrogen production mainly in three ways:

By using the electricity from the nuclear plant for conventional liquid water electrolysis.

By using both the high-temperature heat and electricity from the nuclear plant for steam electrolysis

or hybrid processes.

By using the heat from the nuclear plant for

pure thermochemical processes.

The technology options for the production of

hydrogen using nuclear energy are presentedfurther. Up to now, no consensus has been

reached on the efficiency and cost of these

technologies. All candidate technologies, the

leading ones being high-temperature steam

electrolysis and the high-temperature

thermochemical water-splitting cycles, have

margins for improvement in their efficiency and

cost. Nevertheless, efficiency improvements may

come at the price of higher complexity and

capital cost.

Table presents an overview of nuclear

hydrogen production technologies. Water

electrolysis coupled to an LWR is the least

energy efficient, but it is a well commercialized

and non-GHG emitting technology and canyield high efficiencies.


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Thermochemical Processes

Thermochemical processes for hydrogen production

involve thermally assisted chemical reactions that

release the hydrogen from hydrocarbons or water. The

most widespread thermochemical process for hydrogen

production is steam methane reforming (SMR).

Although this technology is the most economic today, it

yields considerable carbon dioxide emissions. The

currently commercial steam methane reformingtechnology can be coupled to a nuclear source for near-

term applications to reduce the overall production of

carbon dioxide. This technology poses a higher near-

term implementation potential owing

to the proven

operation of the

method, but withthe disadvantage

of CO2 emissions.

Alternative thermochemical processes are

those that do not have hydrocarbon

feedstock, but that split water into hydrogen

and oxygen through a series of thermally

driven chemical reactions.

The purpose is to generate hydrogen at lower

temperatures than that for pyrolysis of water,which takes place at temperatures greater

than 2500oC. A screening study identified two

thermochemical water splitting cycles as with

the highest commercialization potential and

with practical applicability to nuclear heat

sources. These were the sulfur-iodine (SI) and

calcium-bromine-iron (UT-3) cycles. SI cycledevelopment is being investigated in the U.S.,

France, and Japan. The UT-3 cycle, which

was named in recognition of its origins at the

University of Tokyo, has been investigated by

JAERI. A lower-temperature version of this

cycle that eliminates the use of iron is being

developed at Argonne National Laboratory

(ANL). ANL is also working on achievingthermochemical water splitting processes at


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Thermochemical processes (2)

In the following sections, alternative thermochemical processes that can use nuclear energy as

the primary heat source, their potential economics and related uncertainties, and technological

barriers are discussed.


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Steam methane reforming

(SMR)


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Sulfur-Iodine (SI) Cycle


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Bunsen section

The Bunsen section is central to the cycle, not only

because it objectively is the section which produces the

two acids that are independently processed in the other

two sections, but also because its optimisation is key

for the whole cycle efficiency. Indeed, the Bunsen

reaction does not actually proceed as written above,

but requires large amounts of excess water and excessiodine:

9 I2+ SO2+ 16 H2O (2 HI + 10 H2O + 8 I2) + (H2SO4

+ 4 H2O)

Excess water makes the reaction spontaneous, and

excess iodine leads to spontaneous separation of the

two acid phases, which is a major breakthrough in

terms of feasibility. However, these excess products

weigh on the energy consumption of the other two

sections, and the reduction of over-stoichiometries

appears as an important factor for the improvement of

the overall cycle efficiency. At the same time, it must berecognised that, beyond phase separation, excess


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SI process

Sulphur section

It is anticipated that sulphuric

acid enters the sulphur

Section along with four

Water molecules. In order

to avoid heating these

water molecules up to

the very high

temperatures (around 850C)

required to decompose SO3and

release oxygen, the section is split into

several subsections:

a concentration section, which uses

temperature- and pressure-staged flashes to

concentrate sulphuric acid up to a roughlyequimolar H2SO4/H2O composition;

a decomposition section where this mixture is

brought to around 850C in the presence of a

catalyst, leading to SO2 regeneration and O2

release;

a coupling component which recovers

undecomposed SO3

to form H2

SO4

and send it

back to the decomposition section.

Iodine section

It was selected reactive distillation as the

reference process for the iodine sectionbecause of its simplicity and potential

efficiency. In reactive distillation, iodine

stripping from the HI/I2/H2O mixture produced

by the Bunsen section is performed in the

same column as HI gas

phase decomposition, taking advantage of

iodine condensation into the liquid phase to

displace the thermodynamically limited

decomposition equilibrium.


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SI Major Challenges

The most important technical issues and uncertainties that influence the performance and economics of this

process are reported as:

- Materials durability at high temperature high acidity environment;

- HI inventory recovery in the system;

- Separations between reactants and products in solutions.

If better heat recuperation can be achieved or heat losses can further be eliminated by using highly effective

compact heat exchangers, the energy efficiency of the process can be enhanced, contributing to better

economics. Decomposition of sulfuric acid and hydrogen iodide involve aggressive chemical environments.Hence, the materials for the SI cycle hydrogen plant should be chosen to accommodate corrosion and


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Ca-Fe-Br (UT-3) cycle


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Cu-Cl cycle

An electrochemical

process is required,either separately from

the hydrogen reaction

(separate Steps 1

and 2 in Table),

or combining

electrochemical and

thermochemical processes together to produce hydrogen directly via electrolysis. Past studies demonstrate the scientific

feasibility of the latter process of cuprous chloride/HCl electrolysis. Oxidation of cuprous chloride (CuCl) during an

electrochemical reaction occurs in the presence of hydrochloric acid (HCl) to generate hydrogen. The cuprous ion is

oxidised to cupric chloride at the anode, and the hydrogen ion is reduced at the cathode.


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Four step Cu-Cl cycleelectrochemical

processes


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Electrochemical Processes

High temperature electrolysis


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HTSE - basics


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HTSEsystem definition


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HTSE efficiency -performance

The electrical energy demand decreases with increasing

temperature for electrolysis. The decrease in electrical

energy demand drives the thermal-to-hydrogen energy

conversion efficiency to higher values. The HTSE process

can be particularly advantageous when coupled to high-

efficiency power cycles and can consequently promise

high overall thermal-to-hydrogen efficiency. The highertemperature also favors electrode activity and helps lower

the cathodic and anodic over-potentials. Therefore, it is

possible to increase the electric current density at higher

temperatures and consequently lower the polarization

losses, which yields an increase in the process efficiency.

Thus, the HTSE is advantageous from both

thermodynamic and kinetic standpoints over lower-temperature electrolysis.

The steam electrolysis concept can be coupled to a range

of nuclear technologies, such as gas cooled reactors,

lead-bismuth cooled reactors, and molten salt cooled

reactors, all of which can deliver relatively high

temperatures and relatively high net power cycle

efficiencies. Different configurations reported for producing

hydrogen using HTSE with SOECs supported with hightemperature reactors indicate a range of efficiencies for


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HTE plant process

The overall process includes a very high-temperature helium-cooled reactor (VHTR) coupled to the direct helium recuperated

Brayton power cycle and an HTE plant with air sweep. For the base case, the primary helium coolant exits the reactor at

900C. This helium flow is split, with more than 90% of the flow directed toward the power cycle and the remainder directed to

the intermediate heat exchanger to provide process heat to the HTE loop. Within the power-cycle loop, helium flows through

the power turbine where the gas is expanded to produce electric power. The helium, at a reduced pressure and temperature,

then passes through a recuperator and pre-cooler where it is further cooled before entering the low-pressure compressor. To

improve compression efficiencies, the helium is again cooled in an intercooler heat exchanger before entering the high-

pressure compressor. The helium exits the high-pressure compressor at a pressure that is slightly higher than the reactor

operating pressure of 7 MPa. The coolant then circulates back through the recuperator where the recovered heat raises itstemperature to the reactor inlet temperature of 647C, completing the cycle.


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Water splitting by solar heat

The most benign and renewable method for obtaining hydrogen is by using sunlight to split water. Splitting

water directly with solar-thermal energy is not practical since the temperature required in order to obtain high

conversion is above 4,000 K. Another huge challenge is the requirement to separate gaseous hydrogen from

oxygen at these temperatures. Multi-step thermochemical cycles which split water through a series of two or

more chemical reactions provide an opportunity for carrying out the high temperature step in the process at

more modest temperatures of less than 2,000 K. In addition, with thermochemical cycles, oxygen and

hydrogen are removed in separate steps, thus avoiding the recombination issues. The Mn 2O3/MnO andferrite cycles allow lower operating temperatures compared to other thermochemical metal oxide cycles and


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HTSEmajor Challenges


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Safety aspects of nuclear hydrogen

production

The existing nuclear power plants are used exclusively to generate electricity. As large and relatively complex facilities, there are

a number of upsets and accidents that can challenge the operation of the plants and the barriers in place to prevent the release

of radioactive materials.

As shown in Fig., the NGNP prototype or subsequent high temperature gas-cooled reactors will be coupled to a hydrogen

production facility and possibly other chemical or petroleum facilities. There is also a possibility that the NGNP could serve

multiple purposes such as producing energy for electricity generation and process heat applications. The close coupling of a

nuclear power plant to a hydrogen production facility or other co-generation facility will introduce additional concerns that will

need analysis and possible design features such as control systems, barriers between nuclear and process systems, detection

systems and mitigation systems to protect the nuclear fuel and prevent the release of radioactive materials.

f


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Events or releases from the

chemical plantA chemical release from a hydrogen production facility coupled to a nuclear power plant could introducehazards for both nuclear plant systems, structures and components (SSC) and to plant operators. This includes

the possible routine or accidental release of oxygen from the hydrogen production facility. Hazards to SSC

could include blast effects from explosions, fires, degradation from chemical exposure and possibly rendering

equipment inoperable (e.g. starvation of oxygen from diesel generators). The operators of the nuclear power

plant could likewise face hazards from explosions, fires or toxic chemicals. The applicant for the NGNP

prototype reactor or other nuclear plant coupled to a hydrogen production facility will need to analyse such

hazards and demonstrate that nuclear power plant safety is provided by measures such as separation, existingdesign features (e.g. Building structures, control room isolation) or special design features (e.g. berms, blast

walls). A summary of issues from the NRCshydrogen production PIRT is provided in the following table:


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Energia Hidrogenului - Nuclear Hydrogen Production - Course 4