The European nuclear industry believes its prospects are good
With startup of the latest French N4 reactors and progress with development of the EPWR, the potential for nuclear power is brighter now than for many years
By Kevin Dodman
Four of the latest N4 reactors are currently nearing completion. The first is Chooz Unit B1, which is located near the border between France and Belgium. It was connected to the grid for the first time on Aug. 30, 1996, and is currently going through its commissioning phase prior to full power operation, which is scheduled for January 1997.
The other three reactors are Chooz Unit B2 and Civaux Units 1 and 2. Fuel was loaded into Chooz Unit B2 in the first week of September 1996, and connection to the grid is scheduled for January 1997, followed by full power operation in June 1997. Unit 1 at Civaux, near Poitiers, is scheduled for full power operation in September 1997, followed by fuel loading and grid connection at Unit 2 during 1998.
Speaking exclusively to Power Engineering International magazine, Herv? Machenaud, Electricit? de France (EDF) Engineering Department executive vice president, commented that after the four N4 units are operational, no new capacity will be needed in France for 10 to 15 years. This is mainly because the existing nuclear units, of which there were 54 prior to startup of Chooz B1, had achieved much higher availability than had been anticipated.
A 75 percent availability had been assumed for planning purposes, and in 1990 this estimate looked optimistic, as the figure achieved for that year was only 72 percent. However, availability is now running at 82 percent, and EDF expects to achieve 85 percent in the near future. The 10 percentage-point difference is equivalent to 10 generating units, and Machenaud expects EDF to be able to export power equivalent to the output of seven units.
Commenting on the latest N4 units, he said that the new design has many innovative features. In particular, the turbogenerator set used is smaller and less expensive than earlier designs, while having a higher output. However, he said that the main aspect of the N4 is its fully automated process control system, commenting, “This is a major change in the way plants are operated.”
The control system has a set of programmed operating states–which means that for the first time ever operators have detailed, real-time plant diagnostics. It provides computer-aided operation, which marks a major advance in nuclear plant operating aids. The major change with respect to earlier systems is not the level of automation, which remains almost the same, but rather how information is processed. Computers gather the information concerning the operation of the plant from 12,000 sensors, format it to make it easily readable by operating teams, display it on screens and then receive corresponding operating commands from the teams.
Once the command has been carried out, the sensors indicate the new states, which once again are routed by the controllers to the computers and display panels in the control room. The entire sequence is checked in real time. If an order is not carried out as required, the operator calls up the source of the alarm on the same screen and has access to the recommended procedure, according to the Nuclear Safety Directorate`s instructions. On the basis of this information, he can then send the commands needed to rectify the situation.
Latest German reactor
Nuclear reactor development is also continuing in Germany, where Siemens recently announced the SWR 1000 project, based on proven boiling water reactor (BWR) technology. The project will enable German nuclear plant operators and Siemens to investigate whether a medium-capacity 1000 MW reactor can generate electricity at competitive cost. The distinguishing features of the SWR 1000 design are its passive systems for cooling the reactor in the event of a failure of the steam turbine cycle or the feedwater system. The decay heat produced after a trip would be removed via a system of four emergency condensers arranged in an elevated core flooding pool. The system would be self-actuating as soon as the water in the reactor pressure vessel dropped below a certain level. In addition to classical reactor protection, the SWR 1000 would also have passive pressure pulse transmitters for the actuation of safety functions such as reactor trip and pressure relief from the reactor pressure vessel.
With the combination of active and passive safety features, Siemens claims that a core melt accident initiated by in-plant events would be even more improbable with the SWR 1000 than with existing reactors. The reactor`s design and the cooling of the pressure vessel would mean that a core melt would be retained within the reactor pressure vessel and permanently cooled. Work on the SWR 1000 began in early 1992, and the four-year basic design phase has been under way since mid-1995. Because of the long-term schedule for the basic design and the time that will be required for the test program, it is anticipated that the SWR 1000 will be ready for construction considerably later than the European Pressurized Water Reactor described below. An adequate assessment of technical feasibility and cost-effectiveness will not be possible until around the turn of the century. Only then will it be possible to decide whether to continue with detailed planning and the instigation of a licensing procedure. Therefore construction of an SWR 1000 could not start until the middle of the next decade at the earliest.
Reactor of the future
While representing the latest in nuclear technology, both the French N4 reactor and the SWR 1000 are also steps toward the development of a future common reactor within the framework of the EPWR project. Work on EPWR started in 1989, when Framatome of France and Siemens of Germany commenced conceptual design work on a Franco-German pressurized water reactor (PWR). Their goal was to create a reactor that would be used initially by EDF and by nine leading German utilities and would subsequently be exported worldwide. The EPR development schedule is shown in Table 1. Since 1992, development has been supported by the French and German utilities, and the conceptual design was completed early in 1995. A contract was then awarded to NPI, Framatome and Siemens/KWU for the second phase of the project, the basic design phase, covering design of the nuclear island. NPI is a 50/50 joint venture between Framatome of France and Siemens of Germany. The EPWR organization structure is shown in Figure 1.
According to Framatome, the main objective of the EPWR project is to assure the replacement of the existing nuclear power plants, while further improving safety and enabling nuclear power to compete with fossil fuels. The company comments, “Even if expectations for additional baseload capacity are low, EPWR would also meet such needs a few years from now. Once proven on the domestic markets, EPR will play a key role on the international market.”
In France, EDF is supporting the EPWR project both financially and by carrying out part of the design work. There are now 55 PWRs operating in France, and EPWR would be a natural successor to the oldest of these units when they need to be replaced during the early part of the next century. In Germany, the 19 nuclear units built by Siemens/KWU cover about 30 percent of the country`s electricity demand. Given the slow increase in demand, there will be no need to build new power plants within the next 10 years. However, German operating companies are said to regard it as essential to retain the option to build new nuclear capacity, and to maintain the country`s leading position with regard to nuclear technology.
German nuclear operators have therefore decided to help finance the development of the EPWR and to build EPWR units if the political climate allows them to be licensed. The EPWR will have an electric power output of 1,450 MW per unit, which is regarded as a level well suited to European grids. A particular feature of the design is that for countries where nuclear power is a significant part of total generating capacity, it will be possible to regulate the power delivered by the reactor to suit grid requirements. Several features of the design will also help reduce operating and maintenance costs. These include:
– The design of the core and its surrounding structures (with the thick core barrel serving as a neutron reflector) lowers the fuel enrichment required.
– The discharge fuel burnup will be increased to 60 GWd/t which, together with an increased core fuel inventory, will enable refueling cycles to be increased to between 18 and 24 months.
– The core is designed to accept mixed oxide fuel (MOX) as well as conventional uranium fuel, making it possible to recycle plutonium in the EPWR.
– The duration of the outages required for refueling, in-service inspection and maintenance operations will be reduced
The main components of the reactor incorporate a number of improvements over previous designs. These include a reactor vessel with a usable life of 60 years, achieved by providing a massive core barrel and a greater water gap between the core barrel and the inner wall of the reactor vessel. Thus increasing protection against neutron bombardment. In addition, the reactor core will be larger, with 241 17 by 17 array fuel assemblies, compared to 205 in the N4 reactor and 193 18 by 18 array fuel assemblies in the Konvoi units.
Machenaud commented that the major driving force for the EPWR was to reach a common concept that would meet utilities` requirements across Europe. The basic design should be completed by the end of 1997, after which it will be necessary to decide how to proceed. One option would be to construct the first unit at the beginning of the next century, enabling feedback data to be gathered prior to commencement of full production in around 2015. He concluded, “What happens to the N4 reactor depends on the success of EPWR, which is a natural evolution of the N4.”
Energy demand growth
The latest World Energy Council estimates indicate that global energy demand will be 50 percent higher in 2020 than it was in 1990–13.4 billion tons of oil equivalent (TOE) compared to 8.8 billion TOE. The expected evolution of energy demand for each region from 1990 to 2020 is shown in Table 2. Nuclear power could play a key part in meeting this increased demand, given favorable public opinion and a corresponding political climate. This would then clearly be a significant opportunity for reactor designs such as the EPWR.
The proportion of electricity derived from nuclear power has increased by a factor of 20 over the last 20 years, even though the annual rate of increase slowed from the 18 percent achieved between 1973 and 1985, to 3.5 percent between 1989 and 1991. The steep rise in demand for electricity in countries where there is rapid economic growth has led some of them–including China, Korea and Japan–to look increasingly at the nuclear option. For Korea and Japan it is a logical choice because, like France, they have almost no domestic fossil fuel resources.
China has large quantities of coal, but its coal mines are a long way from the areas of greatest economic growth. It is therefore planning an ambitious program of nuclear energy development, so that by 2020, nuclear units in operation or under construction are scheduled to represent a total installed capacity of 50,000 MWe. The role and prospects for nuclear energy have changed little in the Organization for Cooperation and Development countries in recent years.
According to data from the Nuclear Energy Agency, nuclear power plants supplied 24.4 percent of the electricity produced at the end of 1994, and the share contributed by nuclear power in these countries is expected to remain at around this level until 2005, then decline slightly. Nevertheless, the quantity of nuclear-generated electric power is forecast to rise from 1828 TWh to 2173 TWh by 2010, to meet the growing demand. With such significant growth anticipated in electricity demand, and the development of ever-safer reactors, prospects for nuclear power look encouraging. However, the most important, and least predictable, factors remain public opinion and the political climate.
EDF`s Chooz B power plant. Photo courtesy of Studio 17.
The Arabelle turbine used at Chooz B1 is 5 m shorter and 13 percent lighter than earlier units. Photo courtesy of Photothéque EDF.
The SWR 1000 is an advanced BWR being developed by Siemens, in cooperation with German nuclear power plant operators. Photo courtesy of Siemens.