Factors Affecting Feasibility of Increased Nuclear Generation

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Can the number of power reactors be increased in the foreseeable future so as to significantly decrease greenhouse gas emissions? To answer this question successfully, one needs to look at the world situation. Currently, the U.S. and other countries are considering major new nuclear building programs. There are currently 59 countries with nuclear power. An additional 21 others have indicated an interest in the construction of nuclear power plants. These programs feature a new generation of power reactors that are designed to be safer, cheaper to build, and are also expected to be easier to operate and maintain than the original designs now used. While for the most part these designs are based on the current technologies, they do represent some technological and cost risk since most of the design work has yet to be completed and only one of the new generation reactors has actually been built.

As a result of the TMI and Chernobyl accidents, as well as the significant cost overruns associated with the current generation of nuclear power plants, the nuclear industry worked to develop simpler, safer, and easier to build nuclear reactor designs. These designs are referred to as Generation 3+ and are evolutionary in nature resembling the boiling water and pressurized water reactors currently in operation. Modifications to the U.S. licensing process were also made that provide for a one-step license.

The new designs that are currently being considered for construction are Westinghouse's Advanced Passive 1000 (AP 1000), AREVA's Evolutionary Power Reactor (EPR), General Electric-Hitachi's Economic Simplified Boiling Water Reactor (ESBWR), General Electric's Advanced Boiling Water Reactor (ABWR), and Mitsubishi's Advanced Pressurized-Water reactor (APWR) [23]. Of these, only the ABWR has been built and is in operation; four in Japan, and two in Taiwan. AREVA is in the early stages of construction of two EPR's; one in Finland and the other in France.

Each of these designs includes safety features that are intended to reduce the likelihood of an accident and the probability of a catastrophic release of radioactivity should an accident occur. The EPR, for example, has a double walled containment and four redundant electrically powered safety coolant injection systems. Each of these systems is capable of pumping enough water into the reactor to keep the reactor core from melting in the event of a catastrophic pipe break. The AP 1000, in contrast to the EPR, has a specially designed containment system and water tanks that rely on passive phenomena such as gravity and the tendency of hot water to rise, thus requiring no electrical pumps to provide cooling water to the reactor in the event of such an accident. Similar features are designed into the other vendors' reactor designs to increase safety and reduce the risk of the release of radioactivity.

The designs are also intended to be easier to build and less susceptible to construction delay through the use of modular construction techniques. Here, the approach is to construct many of the piping systems, platforms, and structures that make up the reactor systems in a factory remote from the construction site. Construction at the site is then limited to installing these systems and interconnecting them. Modular construction methods have long been in use in the shipbuilding industry and found to minimize schedule risk and improve quality, since much of the work is done in a factory environment not subject to the vagaries of weather. Using modular construction also enables the subassemblies to be fabricated anywhere in the world, making more facilities available. Such an approach is widely used in the aircraft industry for the construction of airliners such as the Boeing 757 and later aircraft.

Another advantage of the use of standardized design is building nearly identical reactors again and again, reducing cost and construction time. Currently, the U.S. has nearly 104 different reactor designs since each of the reactors built during the current generation are essentially one of a kind. By comparison, the French nuclear program has only three different designs in its 58 nuclear reactors. With this next generation of reactors, it is likely that no more than five designs will dominate the market.

Despite the improvements in the designs of the new reactors and the use of modular construction methods, opinion is mixed on whether these reactors can be built on time and within budget constraints. Both of the EPR's currently under construction are considerably behind their original construction schedules. The causes of the delays are not unlike those experienced during the construction of the current generation of nuclear power plants and include poor workmanship requiring costly rework, poor project management, and a lack of understanding of the regulatory requirements. Although these are the first of the new design pressurized water reactors to be built, the types of construction delays are not expected to be design dependent and, thus, could occur on any of the other reactor designs. Only the ABWR's built in Japan experienced minimal construction delays. The ABWR's were built in a carefully defined manner in close cooperation with the regulators and were finished very close to their original schedule. This success points to the need for good project management, attention to detail, and an understanding of the regulatory environment, all of which can be attained with proper planning and personnel.

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