Power Coefficients of Reactivity

• Published in: Nuclear Reactor pp. 1 - 2
• Main Author: Lee, John C
• Format: Book Chapter
• Language: English
• Published: United States John Wiley & Sons 2020; John Wiley & Sons, Incorporated; John Wiley & Sons, Inc
• Subjects: core reactivity; Electrical & Power Engineering; Electrical Safety; nuclear reactors; physical mechanisms; physics parameters; power coefficient of reactivity; quasi‐static reactivity feedback model; sodium‐cooled fast spectrum reactors; two‐group reactivity model
• ISBN: 9781119582328; 1119582326
• DOI: 10.1002/9781119582342.ch14

One of the key parameters affecting passive safety and inherent stability of nuclear reactors is the amount of reactivity change due to a power level variation, which is referred to as the power coefficient of reactivity (PCR). This chapter begins with a general discussion of physical mechanisms affecting the effective multiplication factor of a reactor. To delineate various effects of a power level change on reactivity, definitions for several reactivity coefficients are introduced. The chapter reviews the two‐group model of reactivity, which forms the basis for the physical representation of the temperature feedback on reactivity. It examines how reactivity coefficients are influenced by key reactor physics parameters, e.g. fissile enrichment, soluble boron concentration, lumped neutron poison, and fuel burnup. The chapter discusses the reactivity coefficients of particular interest to sodium‐cooled fast spectrum reactors (SFRs) and a quasi‐static reactivity feedback model for SFR transient events, respectively.