9. Inherently Safe Reactor Designs - INHERENTLY SAFE...

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INHERENTLY SAFE REACTORS DESIGNS © M. Ragheb 3/11/2009 1. INTRODUCTION The electrical power production industry worldwide is faced with a need for new generating capacity. In the USA, the need is for an increase of 1/3 of the existing capacity. The utilities in the USA are currently building gas turbine and combined cycle plants to meet peaking and intermediate needs. Of a forecast need of 150 GWe, 65 Gwe are for peaking and intermediate capacity, and 85 Gwe are needed for uncommitted baseload capacity. A new generation of nuclear power plants possessing passive inherently safe safety features is replacing the older designs, and are being constructed or in the conceptual design stage. The inherent safety features are a response to the understanding that human factors significantly contributed to the Three Mile Island and the Chernobyl reactor accidents. These plants would contribute to the reduction of the environmental costs of emitting nitrogen oxides (NO x ), sulphur dioxide (SO 2 ), and carbon dioxide (CO 2 ) from fossil fuels. As these emissions become economically monetized, nuclear electricity is expected to offer both an environmental and a cost advantages. The safety improvements in the new generation of plants are quantified by the Core Damage Frequency (CDF), resulting from Probabilistic Risk Assessment analyses (PRAs). The design goals for CDFs for the new generation of nuclear power plants are set at 10 -7 per reactor.year. This is compared to the value of 10 -4 for existing power plants. For existing plants the frequency of 1/10,000 translates into one severe core accident per 200 years for a world with 500 reactors (500 x 200 = 10,000). For the new generation of reactors, even with a world with more than double the number of reactors as today (434 plants as of the year 2001) at 1,000 plants, the frequency of 1/10,000,000 translates into one severe core accident in 10,000 years (1,000 x 10,000 = 10,000,000). The new design also satisfy the Nuclear Regulatory Commission's (NRC) Severe Accident criteria, which require that these new plant possess the capability to protect the public from radiation releases, even in the improbable situation of a severe accident. 2. ADVANCED LIGHT WATER REACTOR (ALWR) The USA Department of Energy (DOE) has launched cost share programs with the USA electric utilities, and vendors to develop advanced LWR reactor designs. On the basis that reactor safety is a global concern, government agencies and companies from about 20 other countries participate in the program. The development of a new generation of reactors has moved in two directions: 1. Evolutionary plant designs. 2. Passive plant designs EVOLUTIONARY PLANT DESIGNS
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