Canada’s program on nuclear hydrogen production and the thermochemical Cu–Cl cycle

Abstract

This paper presents an overview of the status of Canada’s program on nuclear hydrogen production and the thermochemical copper–chlorine (Cu–Cl) cycle. Enabling technologies for the Cu–Cl cycle are being developed by a Canadian consortium, as part of the Generation IV International Forum (GIF) for hydrogen production with the next generation of nuclear reactors. Particular emphasis in this paper is given to hydrogen production with Canada’s Super-Critical Water Reactor, SCWR. Recent advances towards an integrated lab-scale Cu–Cl cycle are discussed, including experimentation, modeling, simulation, advanced materials, thermochemistry, safety, reliability and economics. In addition, electrolysis during off-peak hours, and the processes of integrating hydrogen plants with Canada’s nuclear plants are presented.

Introduction

Climate change and urban air quality continue to be significant issues today with well documented environmental and health impacts. Hydrogen is a potentially major solution to the problem of climate change, as well as addressing urban air pollution issues. But a key future challenge for hydrogen as a clean energy carrier is a sustainable, low-cost method of producing it in large capacities. Most of the world’s hydrogen (about 97%) is currently derived from fossil fuels through some type of reforming process (such as steam–methane reforming; SMR). Nuclear hydrogen production is an emerging and promising alternative to SMR for carbon-free hydrogen production in the future. This paper presents an overview of Canada’s program on nuclear hydrogen production and the thermochemical Cu–Cl cycle, specifically with recent advances in Canada since the time of an earlier review paper by Naterer et al. [1].

Hydrogen is used widely by petrochemical, agricultural (e.g., ammonia for fertilizers), manufacturing, food processing, electronics, plastics, metallurgical, aerospace and other industries. For example, in Alberta, Canada, the oil sands sector needs vast amounts of hydrogen to upgrade bitumen to synthetic crude oil and remove impurities. Hydrogen has recently made significant commercial penetration with fuel cells in the lift-truck market, as well as back-up power systems for cell phone communication towers. In the transportation sector, major auto-makers are investing significantly in fuel cell vehicles, and there are a number of demonstration projects ongoing. Hydrogen is becoming an increasingly important energy carrier. It can be stored and used to generate electricity, either onboard vehicles or stationary power systems [2].

The transportation sector contributes significantly to GHG emissions in Canada. A fuel cell vehicle (FCV) and battery electric vehicle (BEV) are the two main transportation technologies that can achieve a major reduction in GHG emissions. Despite the promising capabilities of hybrid, plug-in hybrid, and electric vehicles, some ongoing challenges associated with battery powered vehicles include: long battery recharge times, limited storage capacity, cold weather performance, and durability in real-world conditions, among others. As a result, hydrogen will continue to have an important role in light duty vehicle powertrains as a “range extender” fuel in plug-in hybrid vehicles, or eventually as standalone hydrogen fuel cell vehicles. The envisioned future hydrogen economy in the transportation sector will require significant increases to the world’s current capacity to generate hydrogen, particularly in a clean, sustainable manner without relying on fossil fuels.

Thermochemical water decomposition is an emerging technology for large-scale production of hydrogen. Typically using two or more intermediate compounds, a sequence of chemical and physical processes split water into hydrogen and oxygen, without releasing any pollutants externally to the atmosphere. These intermediate compounds are recycled internally within a closed loop. Previous studies have identified over 200 possible thermochemical cycles [3], [4]. However, very few have progressed beyond theoretical calculations to working experimental demonstrations that establish scientific and practical feasibility of the thermochemical processes.

The sulfur–iodine (S–I) and hybrid sulfur cycles are prominent cycles that have been developed extensively by several countries. These include the USA (General Atomics, Savannah River National Laboratory, among others), Japan (Japan Atomic Energy Agency, JAEA), France (Commissariat à l’Energie Atomique, CEA), Italy and others [5], [6]. About 30 l/h of hydrogen production has been demonstrated by an S–I pilot facility at JAEA [5]. Canada, Korea (KAERI), China and South Africa also have active programs in nuclear hydrogen production. The following seven cycles (in addition to the S–I and hybrid sulfur cycles) were identified in a Nuclear Hydrogen Initiative [4] as the most promising cycles: copper–chlorine (Cu–Cl) [7], cerium–chlorine (Ce–Cl) [8], iron–chlorine (Fe–Cl) [8], vanadium–chlorine (V–Cl) [8], copper-sulfate (Cu-SO₄) [8] and hybrid chlorine [8]. Experimental work has been conducted for processes in these cycles to demonstrate their scientific feasibility. However, most of these cycles require heat at temperatures over 800 °C from very high temperature (Generation IV) reactors, which are not currently available and entail major design and material challenges. The Cu–Cl cycle has a significant advantage over these other cycles, due to lower temperature requirements around 530 °C and lower. As a result, it can be eventually linked with the Generation IV SCWR (Super-Critical Water Reactor) or ultra-super-critical thermal stations.

Advantages of the Cu–Cl cycle over others include lower operating temperatures, ability to utilize low-grade waste heat to improve energy efficiency, and potentially lower cost materials. Another significant advantage is a relatively low voltage required for the electrochemical step (thus low electricity input), which will be further explained in this paper. Other advantages include common chemical agents and reactions going to completion without side reactions, and lower demands on materials of construction. Solids handling between processes and corrosive working fluids present unique challenges, however this paper will outline recent advances made towards the development of corrosion resistant materials for these working fluids.

The University of Ontario Institute of Technology (UOIT), Atomic Energy of Canada Limited (AECL), Argonne National Laboratory (ANL) and other partner institutions are currently collaborating on the development of enabling technologies for the Cu–Cl cycle, through the Generation IV International Forum (GIF; [7]). This paper describes the status of these enabling technologies for the Cu–Cl cycle, as well as other nuclear hydrogen research and development programs in Canada, including electrolysis during off-peak hours for hydrogen usage by the transportation sector. Experimental work on the Cu–Cl cycle, modeling and simulation, thermochemistry, corrosion resistant materials, safety, reliability and linkage between nuclear and hydrogen plants, will be presented and discussed in this paper.