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The response of neutron flux and reactor power to changes in reactivity is much different in a critical reactor than in a subcritical reactor. The reliance of the chain reaction on delayed neutrons makes the rate of change of reactor power controllable. EO 2.1DEFINE the following terms: a. Reactor period b. Doubling time c. Reactor startup rate EO 2.2DESCRIBE the relationship between the delayed neutron fraction, average delayed neutron fraction, and effective delayed neutron fraction. EO 2.3WRITE the period equation and IDENTIFY each symbol. EO 2.4Given the reactivity of the core and values for the effective average delayed neutron fraction and decay constant, CALCULATE the reactor period and the startup rate. EO 2.5Given the initial power level and either the doubling or halving time, CALCULATE the power at any later time. EO 2.6Given the initial power level and the reactor period, CALCULATE the power at any later time. EO 2.7EXPLAIN what is meant by the terms prompt drop and prompt jump. EO 2.8DEFINE the term prompt critical. EO 2.9DESCRIBE reactor behavior during the prompt critical condition. EO 2.10 EXPLAIN the use of measuring reactivity in units of dollars. Reactor Period ( The reactor period is defined as the time required for reactor power to change by a factor of "e," where "e" is the base of the natural logarithm and is equal to about 2.718. The reactor period is usually expressed in units of seconds. From the definition of reactor period, it is possible to develop the relationship between reactor power and reactor period that is expressed by Equation (4-6).
where:
The smaller the value of There are numerous equations used to express reactor period, but Equation (4-7) shown below, or portions of it, will be useful in most situations. The first term in Equation (4-7) is the prompt term and the second term is the delayed term. where:
where:
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