QUIZ 1 - TERMINOLOGY - EXPLANATION SHEET
last update April 2, 1996
- The effective multiplication factor, keff, can be expressed as the ratio of neutrons in successive prompt neutron lifetime intervals. ... FALSE "in successive generations"
- Delta-k defines the reactor's nuclear status in terms of its "deviation from criticality". ... TRUE "delta-k = k - 1, where k = 1 at criticality"
- The time required for reactor power to change by a factor-of-ten is called the reactor period. ... FALSE "by a factor-of-e"
- The time required following precursor decay for a delayed neutron to slow down to thermal energy and cause fission is called the neutron generation time. ... FALSE "neutron generation time is a weighted average of the prompt and delayed neutron lifetimes"
- The two conditions required for a reactor to be supercritical are: keff must be greater than 1.0 and power must be increasing with time. ... FALSE "a single condition defines supercriticality, namely that keff is greater than one ... power may be increasing or decreasing ... the direction of power change is irrelevant, stay tuned for more on this"
- Source multiplication is a unique process that occurs only when the reactor is subcritical. ... FALSE "source multiplication is a manifestation of many ongoing chain reactions and occurs in all modes of reactor operation, from shutdown to full power ... see NUKEFACT #3 " .
- The fraction of the neutron population that consists of delayed neutrons is represented by the Greek letter beta. ... FALSE "beta is the precursor yield fraction ... see NUKEFACT #1 ."
- The weakest neutron source in the core is always the non-fission source. ... FALSE "delayed neutrons act as source neutrons and at reactor shutdown their strength is less than that of the non-fission neutrons ... see NUKEFACT #2 "
- Prompt jump is used to describe reactor rate behavior during a step change in reactivity. ... FALSE "prompt jump describes power behavior"
- The rule-of-thumb value for the single precursor group effective decay constant (lambda- effective) at criticality is zero. ... FALSE "lambda-effective at criticality is 0.08 seconds-1".
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