Reactivity Summary

Reactor Theory (Nuclear Parameters) DOE-HDBK-1019/2-93 REACTIVITY COEFFICIENTS REACTIVITY COEFFICIENTS Changes in the physical properties of the materials in the reactor will result in changes in the reactivity. Reactivity coefficients are useful in quantifying the reactivity change that will occur due to the change in a physical property such as the temperature of the moderator or fuel. EO 2.1 EXPLAIN the conditions of over moderation and under moderation. EO 2.2 EXPLAIN why many reactors are designed to be operated in an under moderated condition. EO 2.3 STATE the effect that a change in moderator temperature will have on the moderator to fuel ratio. EO 2.4 DEFINE the temperature coefficient of reactivity. EO 2.5 EXPLAIN why a negative temperature coefficient of reactivity is desirable. EO 2.6 EXPLAIN why the fuel temperature coefficient is more effective than the moderator temperature coefficient in terminating a rapid power rise. EO 2.7 EXPLAIN the concept of Doppler broadening of resonance absorption peaks. EO 2.8 LIST two nuclides that are present in some types of reactor fuel assemblies that have significant resonance absorption peaks. EO 2.9 DEFINE the pressure coefficient of reactivity. EO 2.10 EXPLAIN why the pressure coefficient of reactivity is usually negligible in a reactor cooled and moderated by a subcooled liquid. EO 2.11 DEFINE the void coefficient of reactivity. EO 2.12 IDENTIFY the moderator conditions under which the void coefficient of reactivity becomes significant. Rev. 0 NP-03 Page 23