VERY HIGH TEMPERATURE REACTOR

Lehrstuhl für Nukleartechnik - Technische Universität München

Boltzmannstr. 15 85747 Garching

www.ntech.mw.tum.de

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1 VERY HIGH TEMPERATURE REACTOR

1.1 CONCEPT DEVELOPMENT

The Generation IV Roadmap selected the Very High Temperature Reactor (VHTR)

concept as one of the six technologies for further development under Generation IV.

The VHTR System Arrangement was signed in November 2006 by Canada, Euratom,

France, Japan, the Republic of Korea, Switzerland and the United States. The

Republic of South Africa is expected to join. The Fuel and Fuel Cycle Project

Arrangement was signed early in 2008 by Euratom, France, Japan, the Republic of

Korea and the United States. The Hydrogen Production Project Arrangement is

expected to be signed later by the same Members. The Materials (MAT) Project

Arrangement, which addresses graphite, metals, ceramics and composites, has

been finalized and is expected to be signed. The Computational Methods Validation

and Benchmarking (CMVB) Project Arrangement will be finalized and ready for

signature. Two other projects on components and high-performance turbo-

machinery, and on design, safety and integration, are being discussed by the VHTR

Steering Committee.

Dr. Regis A. Matzie, Senior Vice President and Chief Technology officer of

Westinghouse Electric Company LLC describes in his numerous presentations

worldwide what a High Temperature Reactor (HTR) is. It will be a small thermal

graphite moderated reactor with a thermal power range between the 400 and 600

MW. It will be cooled using gaseous helium which will reach at the coolant outlet

region of the core a temperature from 850 °C up to 950 °C.

It is not a completely innovative concept since several research, demonstrative and

commercial gas cooled reactors have been operated or are still under operation (i.e.

the Magnox Reactor in the UK). Germany was a pioneer in this technology but at the

end of the ‘80s the federal government in agreement with the Nordrhein-Westfalen

government decided the closure of the HTR-300 power plant. The superion german

know-how in the production of the specific fuel for the HTR reactors is confirmed by

several publications that will be taken into account in the Technical Problems

section. Two reactors were operated: one was the AVR a 15 MWe developmental

reactor and the second-one was a commercial demonstration reactor: the THTR-300

a 300 MWe reactor.

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In the United States during the ‘70s and the ‘80s two reactors were operated: the

Peach Bottom 1 and the Fort St Vrain reactor.

Nowadays experimental reactor are being operated in China, the HTR-10 (10 MWth)

at the Tsinghua University and in Japan, the HTTR (30 MWth).

In South Africa the Pebble Bed Modular Reactor (Pty) Limited (PBMR) was

established in 1999 with the intention to develop and market small-scale, high-

temperature reactors both locally and internationally. The 800-members PBMR

project team is based in Centurion near Pretoria, South Africa. The PBMR is a High

Temperature Reactor (HTR) with a closed-cycle gas turbine power conversion

system. It is considered by the local Government a national strategic project.

Efforts are done also in Europe (ANTARES project, Areva and RAPHAEL project,

integrated research project), in the Russian Federation, in the United States and in

South Korea.

The work is addressed to develop an innovative approach to produce the energy

industry needs to meet the demands of a modern lifestyle. The use of nuclear heat to

produce electricity could change the way energy is produced to meet commercial

and consumer needs. The high temperature gas-cooled reactor is well-suited for

electricity production. The high temperature gas-cooled reactor is expected to be

more efficient than current light water reactor nuclear power plants. The high

temperature gas-cooled reactor could present significant advantages in places

where the electric system infrastructure is not as well developed, smaller population

centers are widely dispersed, or load growth is slower. The modular nature of the

reactor would allow for power production in areas currently unsupported by an

electrical grid, but doesn't have the same high economy of production as light water

reactors.

The efforts will develop the technology for the commercialization of a new generation

of nuclear plants. This systems have a very huge commercial potential since can

supply competitive, emission-free, high temperature process heat, electricity and/or

hydrogen.

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1.2 TECHNICAL ASPECTS

Different concepts for the design of a VHTR are under study and essentially what will

influence the design of the reactor is the type of fuel and the presence or not of an

Intermediate Heat Exchanger (IHX). A resume of the different fuel form options has

been done by Matzie.

1.2.1 Prismatic versus Pebble Fuel design

Fixed vs Dynamic Core

Periodic vs On-line Refueling

Heterogeneous vs Homogeneous Core

Burnable Poison Control vs Fuel Inventory Control of Excess Reactivity

In order to better understand the differences between the different fuel options a

brief general description of the operation of the two technologies follows.

Pebble Bed Reactor

A pebble bed reactor (Figure 1.1) consists of a core filled up by graphite pebbles

(Figure 1.2), each containing in their inner part several hundreds of multicoated fuel

particles.

Figure 1.1: General scheme of a Pebble Bed Reactor with fuel elements

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Figure 1.2: Fuel element - Pebble Design

After a residence time in the core that is very variable for the different fuel pebbles (in

the AVR the first german pebble bed research reactor the residence time was of 4 to

40 - average 68 - months), the fuel elements reach the defueling tube at the core

bottom and are re-fed to the core top. This is repeated until the final burn-up is met

and then the fuel element is replaced by a fresh one. In order to achieve a rather flat

radial temperature profile, low power fuel elements are fed into the core centre and

fresh ones into the outer regions (Figure 1.3).

Figure 1.3: Disposition of the fueling tubes at the top of the core

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Pebble flow velocities are higher in the inner than in the outer core region. Helium

cools the core in up flow direction. A steam generator could be arranged in the top of

the pressure vessel in case of indirect cycle.

Prismatic Fuel Design Reactor

The operating principle is the same of the pebble bed reactor but in this case the fuel

is disposed in a fixed structure. This reactor applies the block-type (prismatic) core

design, in which the coated particle fuel, a common feature of all HTRs, is contained

within a graphite block, the so called ‚fuel compact‛. These blocks are arranged

inside hexagonal fuel assemblies (Figure 1.4) to form the core geometry (Figure 1.5).

Figure 1.4: Fuel element - Prismatic Design

Figure 1.5: Disposition of the hexagonal fuel assemblies inside the core

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1.2.2 Direct versus Indirect Cycles

Concerning the plant layouts Matzie presents the following classification:

Direct versus Indirect Cycles

Gas Turbine vs Steam Generator or Intermediate Heat Exchanger

Brayton vs Rankine Cycle

Single vs Combined Cycle

The indirect cycle involves the presence of the intermediate heat exchanger (IHX).

The thermal power produced in the core is transferred to a secondary loop via an

IHX, where it is used to drive the application of interest. It is possible, in fact, at the

same time to provide a flexible heat source for heat supply or cogeneration without

any modification of the nuclear loop.

Gauthier et al. (FRAMATOME ANP) report that the indirect cycle layout offers several

advantages. First and foremost, it allows a common heat source to be used for both

electricity generation and hydrogen production and minimizes the complexity and

risk associated with the nuclear part of the cycle. It is important that in a first

development stage of the project by the use of this configuration, initial deployment

for electricity generation will provide experience and technology necessary to

support very high temperature process heat applications, such as thermo-chemical

hydrogen production. The indirect cycle design also eliminates the potential for

contamination of the electricity generation and/or hydrogen production equipment by

radionuclide carried within the primary helium coolant.

In addition, separating the nuclear heat generation systems, structures and

components from the industrial application processes simplifies reactor licensing,

startup, operating procedures and maintenance. The second major advantage

offered by the indirect cycle design is the freedom to select a secondary coolant

other than helium. It will be possible then the use of special mixtures with properties

similar to air as the secondary heat transport vector. It will then allow the use of

modified gas turbine technology, including the same design techniques, materials

and testing facilities used for conventional air-breathing gas turbines, to be used for

the VHTR electricity production application.

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Hittner et al. report that there is no experience of coupling a HTR with a large scale

industrial process heat application, even at lower temperature than those that will be

reached in a VHTR. For such an application, a large heat exchanger with a capacity

of heat transfer of several hundreds of megawatt, operating at high or very high

temperature, is necessary. It is far beyond the present industrial experience.

1.2.3 VHTR Projects

Matzie in his work reports a very detailed review of the active or ongoing projects all

around the world. There are seven on-going HTR programs of note today, all backed

by government funding. The activities are carried on in China, France, Japan,

Russian Federation, South Africa, South Korea, and the United States.

CHINA: In China, Tsinghua University has taken the lead for the development of HTR

technology. It spearheaded the design and construction of the small HTR-10 test

reactor and is now moving into the demonstration phase in partnership with China

Nuclear Engineering and Construction Company. See Figure 1.6 for a picture of the

HTR-10.

Figure 1.6: HTR-10 Design

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The HTR-10 started construction in 1995 and achieved criticality in 2000. It is a 10

MWth reactor that utilizes UO2 pebble fuel and a steam generator for heat rejection.

Numerous safety tests have been completed confirming the inherent features of the

design. Further development will be couple this test reactor directly to a gas turbine,

and thereby also demonstrate the Brayton cycle. A commercial project (HTR-PM)

has already been established in cooperation with the China Huaneng Group, a large

Chinese electric utility company. The plant will be sized at 450 MWth with a 750 °C

coolant outlet temperature and a helical steam generator providing steam to a

Rankine cycle.

FRANCE: AREVA NP has established a development project, called ANTARES, with

significant collaboration with CEA and the European Union on basic HTR technology.

The pre-conceptual design of the ANTARES HTR has been completed for a 600

MWth reactor based on a prismatic fuel design and a coolant outlet temperature of

850°C. The ANTARES reactor is coupled through an IHX to combined Brayton and

Rankine cycles. No demonstration plant project has so far been defined in France.

See Figure 1.7 for a diagram of the ANTARES design.

Figure 1.7: ANTARES design

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EUROATOM: An aligned European Union development effort is the RAPHAEL

Project. This is an integrated research project to develop technologies for the Very

High Temperature Reactor (VHTR), the Generation IV high temperature thermal gas-

cooled reactor system. There are 33 organizations from 10 countries attending the

project which is a part of the European Union 6th Framework program. The current

main emphasis of the RAPHAEL Project is fuel technology development, materials

development and testing, component development, and computer modeling and

simulation.

JAPAN: Under the direction and sponsorship of the Japan Atomic Energy Agency

(JAEA), an industry collaborative program on HTRs has been in place for nearly 2

decades. The centerpiece of this program is the High Temperature Test Reactor

(HTTR), which is a 30 MWth reactor utilizing prismatic fuel and a coolant outlet

temperature of up to 950°C. Construction on the HTTR started in 1991 and criticality

was achieved in 2000. The purpose of the project is to establish an HTR technology

basis, to develop process heat application technology, and to provide a heat source

for a hydrogen production plant based on the thermo chemical Sulfur-Iodide (SI)

water splitting process. See Figure 1.8 for a picture of the HTTR. Although no

commercial demonstration project has as yet been defined, the conceptual design of

a commercial co-generation plant, called the GTHTR300C, has been conducted.

Figure 1.8: HTTR design

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RUSSIA: In cooperation with the US DOE and General Atomics, the Russian

Federation, with a team of five Russian organizations lead by OKBM, has been

developing the Gas Turbine - Modular Helium Reactor (GT-MHR). This is a 600

MWth design with prismatic fuel and a coolant outlet temperature of 850°C. The

project is being sponsored by the US National Nuclear Security Administration

(NNSA) as a potential alternative or supplemental way (to the current MOX program)

to disposition of the Russian weapons plutonium. As such, an integral part of the

program is the development of a fabrication process for PuO2 bearing fuel. To this

end, a Bench Scale Facility to fabricate plutonium fuel for irradiation testing is being

constructed in Russia. See Figure 1.9 for a diagram of the GT-MHR design.

Figure 1.9: GT-MHR Design

SOUTH AFRICA: Pebble Bed Modular Reactor (Pty) Ltd is developing the PBMR

design as a national strategic project in South Africa. The design of the

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Demonstration Power Plant is 400 MWth with pebble fuel and a coolant outlet

temperature of 900 °C. See Figure 1.10 for a diagram of the PBMR design.

Figure 1.10: PBMR Design

The PBMR team is currently preparing to build of a commercial scale power reactor

at Koeberg near Cape Town, where Africa’s only nuclear power station is based, and

a fuel plant at Pelindaba near Pretoria, where the pebble fuel will be manufactured.

The PBMR essentially comprises a steel pressure vessel which holds about 450000

fuel spheres. The fuel consists of low enriched uranium triple-coated isotropic

particles contained in a molded graphite sphere. A coated particle consists of a

kernel of uranium dioxide surrounded by four coating layers. The PBMR system is

cooled with helium. The heat that is transferred by the helium to the power

conversion system, is converted into electricity through a turbine.

SOUTH KOREA: South Korea has relatively recently started a HTR program led by

the Korea Atomic Energy Research Institute (KAERI). KAERI is working with an

industrial partner (Doosan). The main interest is in the production of bulk hydrogen

for a future hydrogen economy. There are several research institutes and universities

in Korea that are performing basic research into hydrogen production processes. At

this time, the main focus of this research is on the S-I (Sulfur-Iodine) thermochemical

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water splitting process. A reactor technology choice has not been made as yet, but

this is planned in the future.

UNITED STATES: The US Department of Energy with the Idaho National Laboratory

(INL) has initiated the Next Generation Nuclear Plant (NGNP) program. The intent of

this program is to proceed through a multi-phase design development and

construction project for a full scale co-generation (of electricity and hydrogen)

demonstration plant at the INL site. The NGNP design is envisioned to be a 400-600

MWth. reactor with a coolant outlet temperature in the range of 850-950°C; the fuel

form has not been selected. This project has been authorized by the US Energy

Policy Act of 2005. The initial pre-conceptual engineering design phase has recently

been awarded to multiple design teams. If the full development proceeds,

construction of the NGNP could start in the 2013-2015 timeframe with initial

criticality in 2017-2018 (source INL).

While the NGNP has been launched, a significant R&D program has progressed

under the banner of Generation IV (VHTR) development. The emphasis of this R&D

program is fuels development and testing, materials development and testing, and

the development of the intermediate heat exchanger. In addition, computer code and

analytical tools development is progressing.

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1.3 TECHNICAL PROBLEMS

The European Commission is supporting partnership work on the development of

HTR, that resulted in confirming HTR high potential in terms of safety (inherent safety

features), environmental impact (robust fuel without significant radioactive release),

sustainability (potential suitability for various fuel cycles), and economics (high

efficiency, simplifications arising from safety features). In April 2005, a new 4-year

Integrated Project on HTR/VHTR (RAPHAEL – ReActor for Process Heat And

ELectricity) was started

The main priorities of the project are:

the increase of performances (temperature 800-1000°C, and burn-up up to

200 GWd/tHM)

the adaptation of technologies to the needs of heat supply for industrial

processes,

and in line with the conclusions of the Generation IV roadmap, the main research

topics are

advanced materials,

fuel for higher operating temperatures,

development of components required for heat applications

(Intermediate heat exchanger and high power helium circulator),

examination of the specific issues raised by higher performances and

industrial process heat applications

1.3.1 Advanced Materials

There is an incentive for use of a material with improved temperature performance

compared to PWR vessel steel in order to improve HTR thermal efficiency and to

obtain margins toward reactor vessel failure in accident conditions.

Hittner et al. report that different materials have been examined and the modified

9Cr1Mo steel has been identified as the best candidate. An irradiation of a thick

welded joint of this material has been completed up to a fast fluence equivalent to 60

years of operation and PIE (Post-Irradiation Examination) have shown no significant

change in the mechanical properties both for the base material and for the welded

zone.

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In the FY2005 Report, the US Idaho National Laboratory, reports that for the very-

high-temperature components (>760 °C), the most likely material candidates include

variants or restricted chemistry versions of Alloys 617, X, XR, 230, 602CA, and

variants of Alloy 800H. The upper limit of these materials, however, is judged to be

1000°C. Any component that could experience excursions above 1000 °C would

need greater very-high-temperature strength and corrosion resistance capabilities.

Cf/C or SiCf/SiC composites are the leading choices for materials available in the

near future for service that might experience temperature excursions up to 1200 °C.

Very important is the fact that compatibility tests of the metals with the helium

coolant and irradiation resistance of the potential candidate materials need to be

addressed.

1.3.1.1 Nuclear Fuel

The fuel for the VHTR is based on the TRISO-coated particle fuel design

demonstrated in high-temperature gas-cooled reactors in the United Kingdom,

United States, Germany, and elsewhere. The TRISO-coated particle is a spherical-

layered composite about 1 mm in diameter. It consists of a kernel of uranium dioxide

(UO2) or uranium oxycarbide (UCO) surrounded by a porous graphite buffer layer that

absorbs radiation damage, allows space for fission gases produced during

irradiation, and resists kernel migration at high temperatures. Surrounding the buffer

layer are a layer of dense pyrolytic carbon called the IPyC, a silicon carbide (SiC)

layer, and a dense outer pyrolytic carbon layer (the OPyC). The pyrolytic carbon

layers shrink under irradiation and create compressive forces that act to protect the

SiC layer, which is the primary pressure boundary for the microsphere. The inner

pyrolytic carbon layer also protects the kernel from corrosive gases present during

deposition of the SiC layer. The SiC layer is also the primary containment of fission

products generated during irradiation and under accident conditions. Each

microsphere acts as a mini pressure vessel.

For the pebble bed version of the fuel, the coated particles are over-coated with a

graphitic powder and binders. These over-coated particles are then mixed with

additional graphitic powder and binders and then molded into a 50 mm diameter

sphere. An additional 5 mm fuel free zone layer is added to the sphere before

isostatic pressing, machining, carbonization, and heat-treating.

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Similarly, the prismatic version of the fuel uses over-coated particles mixed with

graphitic powder and binders to form a cylindrical compact about 50 mm long and

12.5 mm in diameter. After final heat treatment, these compacts are inserted into

specified holes in the graphite blocks.

Petti et al. in their publication for the HTR2002 Conference report that fuel for HTR

was produced in Europe and in the US. In Europe it was produced in Germany in

industrial scale to supply the AVR and THTR reactors in Germany and only ~100

defects were found in 3.3 million particles produced. In the US was a mixture of lab

scale and larger scale fabrication. Historically, U.S. high-temperature gas reactor fuel

has experienced failures under irradiation while high quality German fuel did not. The

differences in the U.S. and German fuel performance have been traced to technical

variations in the fabrication processes used in Germany and the United States. Three

specific technical differences in the TRISO fuel coating layers produced by the

respective fabrication processes have important impacts in terms of performance

under irradiation and accident conditions:

pyrocarbon anisotropy and density,

IPyC/SiC interface structure,

SiC microstructure.

To know more in detail about these three processes and their impact on the fuel

fabrication the reading of Petti et al. is advised.

In Europe in order to regain the knowledge on the fuel fabrication efforts are done in

the framework of the French V/HTR fuel development and qualification program. The

Commissariat à l’Energie Atomique (CEA) and AREVA are conducting R&D projects

covering the mastering of UO2 coated particle and fuel compact fabrication

technology. Two French facilities constitute the CAPRI line (CEA and AREVA

PRoduction Integrated line).

The major objectives of the CAPRI line are:

• to recover and validate past knowledge,

• to produce representative HTR TRISO fuel meeting industrial standards,

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• to permit the optimization of reference fabrication processes for kernels and

coatings defined previously at a laboratory-scale and the investigation of

alternative and innovative fuel design (UCO kernel, ZrC coating),

• to test alternative compact process options and

• to fabricate and characterize fuel required for irradiation and qualification

purpose

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1.4 ECONOMIC ASPECTS

The right way to look at VHTR technology is to think that the energy market is

composed not only by the electricity but also by the process heat produced for

industrial scope. VHTR in fact is not a technology to produce electricity, but also a

very bride spectrum of products. The International Energy Agency reports on its

website that in year 2006 (world level) the fraction of the energy submitted to the

industry under the form of process heat was about the 17% of the total. This value

increases if we look at the EU-27 reaching a level of 19.6%. Today, industry depends

on burning fossil fuels to provide the majority of its processing heat.

There are four energy challenges facing the manufacturers competing in a global

economy: the rising costs for premium fuels such as oil and natural gas, dependence

on foreign sources for these premium fuels, concerns about carbon dioxide

emissions, and the use of fossil fuels for hydrogen production.

Companies with commercial interest in this type of nuclear process heat application

include: major oil companies, refineries, existing bulk hydrogen producers and

distributors, processing facilities, gas companies, electric utilities, and the hydrogen

transportation industry (fuel cell).

The research and development plans on VHTR should be considered like a way to

produce efficient clear, sustainable, economic process heat for the industry.

Several considerations on the advantages connected with the VHTR relates to the

economics/environment sphere. Matzie in a conference in 2006 makes a list of

aspects and advantages related to heat production using nuclear energy by the

mean of VHTR technology:

Developing High Temperature Gas Reactors can extend nuclear energy to

other energy market segments

Will help slow the rapid increase in fossil energy prices which hurt our quality

of life and economic health

Carbon emissions from other energy market segments must also be reduced

to address global warming

Energy security and diversity, important for long term industrial growth, are

enhanced by replacing imported fuels

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It will be possible then to apply the HTR technology to fields in which nowadays the

fossil fuels are dominating the scene:

the petroleum industry,

the plastic industry,

the fertilizers industry.

1.4.1 The petroleum industry

There are two incentives for nuclear heat in the refinery: lower energy costs and

reductions in carbon dioxide emissions. There are three potential applications of the

high temperature gas-cooled reactor in the refining segments of the petroleum

industry.

Tertiary recovery in existing oil fields

In-situ recovery of petroleum from tar sands

Eventual in-situ exploitation of oil shale deposits

Like the NGNP Website reports, in the Western United States natural gas is currently

used as the primary heat source for all three processes. With the proper heat transfer

and transport systems, a nuclear reactor can provide the required heat without

burning natural gas and producing significant amounts of carbon dioxide. The high

temperature gas-cooled reactor can also support future refinery operations by

providing process heat and the hydrogen required for the various oil refining

processes.

1.4.2 The plastic industry

The heat to refine the materials is created by burning fossil fuels and can significantly

contribute to carbon dioxide emissions. Replacing the fossil fuel energy with the heat

from a high temperature gas-cooled reactor eliminates carbon dioxide emissions

from the refining and production processes that create plastics.

1.4.3 The fertilizers industry

Fertilizer is often manufactured using the Haber-Bosch process, which produces

ammonia. This ammonia can be applied directly to the soil or used in chemical

combinations. The Haber-Bosch process is important because ammonia is difficult

to produce on an industrial scale. The volatile and upward trend in natural gas prices

leads to increasing prices in ammonia production. The rise of natural gas prices

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could cause less production of ammonia and a greater dependence on ammonia

imports.

Although natural gas is most often used for the production of ammonia, a high

temperature gas-cooled reactor can be used for the production of ammonia suitable

for fertilizers. The increased cost of fertilizer can be traced in part to the increased

demand and rising cost of natural gas. Natural gas makes up nearly 85 percent of

the cost of producing ammonia. Ammonia-based fertilizers are most commonly used

to treat fields for growing corn, followed by barley, sorghum, rapeseed and

sunflower.

1.4.4 Carbon Tax

Various fossil fuel-based technologies dominate the world's electricity production

and have carbon emissions associated with that energy production. An economic

advantage of the production of process heat by the mean of a nuclear reactor is that

the carbon emission associated is zero. Restriction on the emission of greenhouse

gases, particularly carbon dioxide emissions have increased. Many governments —

from counties to countries — are looking at placing a cost, or tax, for each metric ton

of carbon dioxide emitted by industry. The responsible company could pay upwards

of $30 per ton. Because of potential carbon taxes, commercial facilities emitting

carbon dioxide will likely see the costs associated with the production continue to

rise. However, a facility using nuclear process heat will not have the carbon dioxide

emission or those costs associated with production.

The application of a carbon cost could make nuclear electricity and heat even more

economical in the long run.

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1.5 ENVIRONMENTAL AND SOCIAL ASPECTS

In Germany the HTR technology was developed and operated at research and quasi-

commercial scale. Although this pioneer role at the end of the 80s it was decided to

close the commercial reactor THTR-300.

Germany at that moment had a sort of technical worldwide supremacy in the

operation of such a reactor and also in the production of the fuel. The superiority of

the fuel produced in the country is still acknowledged, since actual studies to start a

new production line for the TRISO particles take into account the German process,

and that some industrial partners for actual VHTR projects (South Africa) are German

companies:

EHR - High pressure piping

Uhde - Pilot Fuel Plant design and construction

Nukem - Fuel technology

SGL Carbon - Graphite structures

GEA - Cooler and inter-cooler

The concept of develop a very high temperature reactor take more sense if we think

that in the process industry of for future large scale application a large amount of

energy will be supplied in form of high temperature/pressure steam. Nowadays it is

possible to furnish this energy by the means of fossil fuel that in future will be

replaced by other sources. It should be clear that the ‚renewable energy sources‛

will not for sure be able to satisfy the demand because of their low power density

and non regularity in the production.

Oil and gas have greatest value as feedstock for chemicals and for premium fuel

applications (transportation, peaking) and should not be used for the production of

heat but for much more valuable products. Further the broader use of nuclear energy

can increase carbon efficiencies, because carbon will be used only for electricity

generation in high efficiency power plants.

This will result in extend these valuable resources since their use will be reduce at a

narrow spectrum of applications.

Another advantage that will results in terms of environmental protection and social

acceptance of this technology is considering that energy delivery systems are highly

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integrated (production, distribution, storage, and end use) and are not easy to be

replaced in the short run. If the nuclear energy will be integrated with fossil fuels, this

will results in an extended use of current infrastructure as a bridge to future hydrogen

use. Nuclear process heat applications based on this emerging reactor technology

could provide the vehicle for this change.

Matzie lists several advantages of the fuel cycle for a modern HTR and they are:

Low power density

Good neutron spectrum with minimal neutron self shielding

Minimal neutron parasitic absorption from core structures

On-line refueling (pebble) that minimizes core fission product burden

Particle fuel capable of high burnup (>> LWRs)

Flexible fuel cycle (UO2, ThO2, PuO2, UCO, etc.)

It is also previewed an improved waste disposal since the particle fuel is self-

encapsulating. It means that the fission products are retained inside particle coating.

Other advantages of this fuel form concerning the disposal are that the very stable

ceramic fuel form provides long term stability in waste repository and that the fuel

presents a low decay heat power density that allows air cooling immediately after the

discharge from the reactor.

The High burnup that is possible to reach by this fuel means less waste per volume

of heavy metal and the separation of the coating graphite from the inner particle

(structural graphite decontamination is possible) will then even more reduce the

disposal burden.

The fuel type presents also a high level of proliferation resistance:

High fuel burnup leaves small quantities of plutonium at discharge with poor

isotopics

Low loading of fuel material in graphite matrix requires diversion of large

physical quantities to be a significant material risk

Coated particle barriers are difficult to remove

Totally closed fuel handling and storage system (pebble) makes diversion

easy to detect

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1.6 BIBLIOGRAPHY

2007 Annual Report, GEN IV International Forum

Overview of HTR Technology, Dr. Regis A. Matzie, Senior Vice President & Chief

Technology Officer, Westinghouse Electric Company LLC, October 2, 2006,

HTR2006 Conference

NGPG project website, Copyright © 2009 Idaho National Laboratory

http://www.nextgenerationnuclearplant.com/

A safety re-evaluation of the AVR pebble bed reactor operation and its consequences

for future HTR concepts, Rainer Moormann, Jül - 4275, Forschungszentrum Jülich,

Internal Report

ANTARES: The HTR/VHTR project at Framatome ANP, Jean-Claude Gauthier, Gerd

Brinkmann, Bernie Copsey, Michel Lecomte, Nuclear Engineering and Design 236

(2006) 526–533

RAPHAEL, a European Project for the development of HTR/VHTR technology for

industrial process heat supply and cogeneration,D. Hittner – AREVA NP, E. Bogusch

– AREVA NP, D. Besson – AREVA NP, D. Buckthorpe – AMEC NNC, V. Chauvet –

STEP, M.A. Fütterer – JRC/IE, A. van Heek – NRG, W. von Lensa – FZJ, M. Phélip –

CEA, J. Pirson – Suez Tractebel, W. Scheuermann – IKE /University of Suttgart, D.

Verrier – AREVA NP, Proceedings HTR2006: 3rd International Topical Meeting on

High Temperature Reactor Technology, October 1-4, 2006, Johannesburg, South

Africa

INL FY2005 Report, Appendix1.0 Next Generation Power Plant, Idaho National

Laboratory,, USA, 2005

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