Category Archives: NUCLEAR REACTOR ENGINEERING

RELIABILITY AND RISK ASSESSMENT [26, 27]. Introduction

12.206. We may define reliability as the probability that a system or component will perform a specified function (or not fail) for a prescribed time. Now, if in addition, we consider the consequences of failure, i. e., a financial loss or injury to people, we have the concept of risk. Mathematical reliability models as design tools evolved from statistical sampling […]

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PLANT OPERATIONAL STRATEGY. Generation Dispatching

14.4. A commercial nuclear power plant station usually consists of one or more generating units connected to the utility’s electrical distribution grid, which is also supplied by other units at various locations. Intercon­nections with grids of neighboring utilities are also provided to meet emer­gency requirements as well as to provide a means to purchase or sell energy. In dispatching load […]

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Gas-Turbine Option

15.45. A design option is to utilize the helium heated in the reactor as the working fluid in a closed-cycle gas turbine power conversion system. The resulting elimination of the steam generator and associated compo­nents leads to system simplification and potential cost savings. However, somewhat more development is required than would be necessary for the steam-generating approach.

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State-Level Regulation [34]

12.248. Investor-owned electric utilities are regulated by state public utility commissions, which have the responsibility for approving rate struc­tures that will provide a fair rate of return on investment (§10.107). In most states, they also are required by statute to judge whether or not new generating facilities are indeed necessary. If approval is obtained, the is­suance of a Certificate of […]

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PLANT MAINTENANCE. Introduction

14.38. Equipment maintenance is a very important plant operations activity, but is generally given little attention in engineering texts. In fact, accommodation of maintenance requirements is a vital plant design re­quirement. Components, piping, wiring, and auxiliary equipment must be arranged in such a manner that routine maintenance and component re­placement can be carried out efficiently. The presence of a radiation […]

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The Size Issue

15.74. Compared with present large reactors having electrical gener­ating capacities in the 1000-MW range, we have seen that smaller passive reactors in the 600-MW(el) range have a number of attractive features. The new designs are simpler since the passive features eliminate the need for some active safety systems. They generally are more forgiving to op­erator and system failures and are […]

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Coolant Recirculation System

13.39. An important feature of BWR operation is the coolant recir­culation system, shown schematically in Fig. 13.10. This system provides the forced convection flow through the core necessary to achieve the re­quired power density in a BWR. About 14 weight percent of the water passing through the core is vaporized and the remainder must be recir­culated. A portion of the […]

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Other Innovations

15.20. Probabilistic risk analysis was used extensively in the design proc­ess to select the design options that would minimize the predicted core melt frequency. This approach contrasts with PR A studies of already built plants for which remedial options are limited. Defense in depth is provided by various redundant safety systems which would be effective before the passive features are […]

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Deterministic and Probabilistic Analysis

12.209. Before we introduce some PRA principles, it is desirable to clarify the difference between deterministic and probabilistic safety anal­ysis. The term deterministic has a philosophical basis which refers to the mechanical correspondence between causes and effects. For example, we could consider a small-break LOCA in a PWR as a “cause,” and by suitable analytical modeling determine the maximum fuel […]

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Operating Cycle Length and Outage Management

14.6. The operating cycle length is the planned operating time before shutdown for refueling is required. It is an important fuel reload design parameter and sometimes is expressed in units of fuel burnup. For many years, operating cycles of 12 months were common. However, in recent years, longer cycles became economical as the cost of uranium and en­richment remained relatively […]

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