NUCLEAR REACTORS FOR INDUSTRIAL APPLICATIONS

ELECTRIC APPLICATIONS

Reporting on the three generations of nuclear power plants, IAEA finds that:

“Like any other established technology, nuclear power has passed through different levels of development….The first generation of nuclear reactors from the 1950s and 1960s was characterized by a relatively simple and cheap technology for a rapid realization of electricity generation”.

“The second generation is formed by the plants constructed from the 1970s to the early 1990s. The deployment of nuclear reactors was advancing rapidly in that period. Like for the reactors of the first generation, operation was basically in an open fuel cycle with the uranium burnt once and then disposed. But activities were intensified on the reprocessing of nuclear fuel by extraction of the fissile material, the generated Pu and still unburnt U, using a mixture of Pu and U oxides to form MOX fuel for nuclear plants, a way towards closure of the fuel cycle….

“Up to today, most of the nuclear power plants are of LWR-type, either pressurized water reactors or boiling water reactors. Light Water Reactors will most certainly continue to dominate for the next decades. New nuclear reactors which are ready for today’s market are counted to the third generation. They are characterized by a simpler design with a higher level of passive (inherent) safety systems based on the physical principles of gravitation, natural circulation, evaporation, condensation rather than active components…. Design improvements are given in the fuel technology allowing higher burnups to reduce the amounts of fuel and waste.”

NON-ELECTRIC APPLICATIONS

IAEA finds that less than 1% of the heat generated in nuclear reactors is used for non-electric

applications:

“Direct use of heat energy is more desirable from an energy efficiency point of view and nuclear energy is an enormous source of greenhouse-gas-free energy. However, nuclear power has remained primarily a source for electricity generation. Presently about 30% of the world’s primary energy is used for electricity production, and approximately 2/3 of this energy is thrown away as waste heat. Yet despite past and current use models, it is possible to optimise the use of nuclear heat for both electric and non-electric applications, thereby making more efficient use of nuclear energy. Experience in co-generation of nuclear electricity and heat has been gained in Bulgaria, Canada, China, Hungary, Kazakhstan, Russia, Slovakia and Ukraine”.

The utilization of nuclear non-electric process heat has potential in four areas: desalination of sea water and waste water; district heating of residence and commercial buildings; industrial process heat supply; and fuel synthesis.

ROLE OF REACTOR SIZE

Industrial and commercial sectors consume large quantities of energy in boiler systems which are used for heating with hot water or steam in industrial process applications. The demand for industrial heat is highly variable, and combined heat and power (CHP) system sizes are typically in the range of 1–500 MW(e). In terms of thermal power, the needs of the vast majority of industrial users are less than 300 MW(th), which accounts for about 80% of the total energy consumed, and half of industrial users require less than 10 MW(th).

Size requirements of a nuclear unit for industrial applications can lead to designs that are larger and smaller than the current norm. For example, nuclear hydrogen production for petroleum refining, which might be a near term opportunity, and other industrial processes may need smaller units in the range of 50–500 MW(th). As a customer can operate more than one boiler, its size is most pertinent when deciding on the application of a (single use) nuclear boiler.

For the most part, Generation IV reactors are not specifically designed for the smaller power levels. Centrally generated hydrogen, for example, would call for quite large nuclear plants as well. Hydrogen plants currently under design using non-nuclear sources would require a reactor (assuming 50% production efficiency) of 1600 MW(th).

This is well within current parameters, but depending on how the hydrogen market evolves over the next few decades, reactors conceivably two or three times this output might be needed to meet market requirements. Small Generation IV concepts are aimed at 200 MW(th) and greater, although some concepts might be adaptable to the lower power range. Further evaluation is needed for the adaptability of current Generation IV designs for smaller applications.

AVAILABILITY AND RELIABILITY REQUIREMENTS

Most industries need to rely on a secure and economic supply of energy to guarantee continuous and reliable operation of their process units. Ensuring supply security by diversification of the primary energy carriers and, at the same time, limiting the effects of energy consumption on the environment will become more important goals in future.

The industrial requirement of full availability and reliability on energy supply needs additional backup systems, since any interruption of industrial processes can lead to disturbances, with potentially severe technical and financial consequences.

A final requirement is the need to ensure that under no circumstances can radioactive material find its way to industrial circuits and contaminate the end products delivered to the consumers. This will definitely have impacts on the nuclear design and the coupling system by defining a sufficient safety distance between the reactor and industrial applications. Potential contamination refers in particular to the highly mobile tritium and the possibility of permeation from its origin in the primary system through heat exchanging systems or the gas purification plant toward the outside environment. In practice, however, the risk of tritium contamination is considered very low, since isolation devices and physical separations between primary fluid and heat transfer fluid will be employed.

Requirements and acceptance criteria to deal with the risk of contamination of end user products will be subject to discussions with safety authorities.

COGENERATION APPLICATIONS

An IAEA publication in 2017 on the opportunities of cogeneration finds that:

“The CHP operation mode has long been used as a means to optimize energy flows and to minimize losses, thereby improving energy (and fuel) efficiency and security, and reducing industrial CO2 emissions”.

 “Industries with a high and constant demand for steam and power and the need to handle considerable amounts of byproducts or waste fuels are ideally suited for cogeneration. The chemical and petrochemical sectors (and also iron and steel) are the most energy intensive, accounting for approximately 50% of the total final industrial energy use. Together with food, pulp and paper sectors, they represent more than 80% of the total electric capacities at existing CHP installations.”

The International Energy Agency (IAE) reports that:

“Moreover, the share of industrial CHP within the total CHP capacity varies, due to differences in a country’s economic structure, e.g. energy intensive sectors, climate, role of district heating, and the history of barriers and policies to promote CHP”.

“Only a few countries have a CHP contribution to power generation larger than 20%. China, the EU countries, Japan, Korea, Russia and the United States show the highest estimated fuel savings from CHP.”

Industrial CHP systems include components such as steam turbines, gas turbines, combined cycle systems, reciprocating engines, or fuel cells to deal with all kinds of fuel (primary and waste) fuel. The IEA reports that widely spread combustion turbines are most typically fuelled with natural gas; however, coal, wood and process by-products are also extensively consumed, especially in large CHP systems, in industrial processes such as heating, cooling, drying and torrefying, or in indirect applications such as the generation of steam, hot water or hot air.

Cogeneration plants (both nuclear and fossil fuel) that operate under the low temperature conditions of existing LWRs derive their principal revenues from electricity. This poses challenges to the nuclear heat option:

(a) Two thirds of the nuclear energy produced in existing reactor types is heat, which is usually lost to the environment. To provide this heat at a high quality (higher temperatures and pressures), some of the electricity production needs to be sacrificed, further increasing the share of heat.

(b) While the economy of scale principle is applicable to the generation of electricity, this does not hold for process heat, since heat cannot be as easily distributed as electricity.

For HTGRs, revenues are likely to depend more on the value of the process heat. What is definitely different from LWRs is the much smaller size of process heat HTGRs. It is anticipated that a first of a kind HTGR is unlikely to be competitive with alternative fossil fuel options.

With regard to economical and thermal efficiency, the coupling of the nuclear plant to process heat applications as topping or bottoming cycles for power conversion promises a significant improvement in efficiency. Since all types of nuclear reactor can be principally operated in the CHP mode, with any heat to electricity ratio possible, CHP nuclear plants can be readily integrated into an electrical grid system supplying any surplus electricity or serving as backup system for electricity generation.

MAPPING REACTORS AND APPLICATIONS

In today’s concepts for nuclear process heat applications, intermediate circuits will be employed for the transfer of process heat from the nuclear plant to the chemical plant. At the same time, it represents a clear separation between the two islands preventing a direct access of fluids and products from one island to the other. It has the advantage that both plants can be treated independently, and particularly the chemical plant be operated and maintained as a conventional plant (i.e. under non-nuclear conditions).

Whether or not a nuclear system is appropriate for being coupled to a certain industrial application is determined by the level of the reactor coolant outlet temperature. All of the Generation IV nuclear reactor concepts promise an average coolant temperature at the exit of at least 550°C, which already meets the demand of quite a number of applications in various industries. Lead cooled fast reactors (LFRs), molten salt reactors (MSRs), gas cooled fast reactors (GFRs) and VHTRs would enable steam reforming and hydrogen production processes.

In an HTGR, the typical helium temperature drop expected when transferring heat via the intermediate heat exchanger (IHX) to the secondary circuit is around 50°C . In the first high temperature experiment in 2004 at the High Temperature Engineering Test Reactor (HTTR), the coolant temperatures measured in the IHX were 941°C on the primary side and 859°C on the secondary side, the still somewhat larger difference being due to the requirement to stay below the actual licencing limit.

Industrial heat demands are characterized by a wide diversity with respect to countries, branches and energy supply.

The EU project EUROPAIRS, with the target to establish a roadmap for the design of an HTR for cogeneration of heat and electricity to be coupled with an industrial heat consuming plant, a categorization of chemical processes in three classes according to temperature and the technology used was made:

“The first family corresponds to the ‘steam class' of processes, i.e. processes using steam as heat transport and heating media. The steam class extends from 150°C to approximately 600°C.”

“The second class of processes is called 'the chemical class' because heat is the driver of chemical reactions and is consumed as reaction enthalpy at constant temperature. The process temperature lies between 600°C and 900°C. Heat is mainly supplied by combustion and sometimes also by electrical heating.”

“The third class is called ‘the mineral class' because heat is used to melt solid or to drive reactions between solids. For this class of processes, the temperatures required are usually above 1000°C.”

7. Read and translate the text:

Generation IV systems for non-electrical energy missions

In 2000, the Generation IV International Forum (GIF) was created to promote and provide “a framework for international cooperation in research for a future generation of nuclear energy systems”. The GIF charter was signed in 2001 by nine founding members (Argentina, Brazil, Canada, France, Japan, Republic of Korea, South Africa, United Kingdom and United States of America); Switzerland, the European Atomic Energy Community (Euratom), China and the Russian Federation joined later, between 2002 and 2006. Working groups and committees were formed by interested members to elaborate a technology roadmap for Generation IV nuclear systems.

The four pillars of Generation IV development are sustainability, economics, safety and proliferation resistance:

1.    Sustainability: Generation IV nuclear energy systems will provide sustainable energy generation that meets clean air objectives and promotes long-term availability of systems and effective fuel. They will minimize and manage their nuclear waste and notably reduce the long-term stewardship burden in the future, thereby improving protection for the public health and the environment.

2.    Economics: Generation IV nuclear energy systems will have a clear lifecycle cost advantage over other energy sources. They will have a level of financial risk comparable to other energy projects.

3.    Safety and Reliability: Generation IV nuclear energy systems operations will excel in safety and reliability. Generation IV nuclear energy systems will have a very low likelihood and degree of reactor core damage, and they will eliminate the need for offsite emergency response.

4.    Proliferation Resistance and Physical Protection: Generation IV nuclear energy systems will increase the assurance that they are a very unattractive and the least desirable route for diversion or theft of weapons-usable materials, and provide increased physical protection against acts of terrorism.”

The new reactor generation will further enhance the role of nuclear energy in the reduction of GHG emissions by expanding its product spectrum beyond electricity. The generation of high quality process heat and steam will allow serving in numerous energy intensive industrial applications to substitute for conventional fossil fuels. Reduction of long term radiotoxicity will simplify the requirements for safe performance of repositories.