Kinetics Parameters and Reactivity Measurement Experiments

Abstract

Introduction To analyze reactor kinetics, we need to know the kinetics parameters of the reactor. Also, we build the reactor, operate it in the critical state, and determine the reactivity of each control rod. This chapter explains the primary steps of these operations.

An erratum to this chapter can be found at http://dx.doi.org/10.1007/978-4-431-54195-0_12

Chapter 4 Exercises

• 1. The reactor has control rods at approximately 50 % position and is being maintained at the low-output critical state. When we have pulled the control rods out by 15 cm, the output has increased with period T = 30 s. In this case, how much reactivity is there per 1 cm of control rods? Here, we assume that the reactor kinetics is affected by a group of delayed neutrons. Use the following equations and constants.

  Reactivity	δk = l/T + β/(1 + λT)
  Neutron average lifetime	l = 10−3 s
  Ratio of delayed neutrons	β = 0.0064
  Decay constant of delayed neutron	λ = 0.077 s−1

  (The 4th test for license of chief reactor engineers of Japan, question 3-3)

• 2. After the reactor has reached the critical state, we inserted the control rods from the 100 % pullout position into the 80 % position in order to calibrate the control rods. When we measured the neutrons using the neutron counter, it was 38,728 cpm. The equivalent reactivity for insertion of control rods was −0.38 %.

  After that, when we inserted the control rods into the 60 %, 40 %, 20 %, and 0 % position, the respective counting values were 7,889, 3,602, 2,240, and 1,848 cpm. Determine the equivalent reactivity of control rods at each position.

  (The 4th test for license of chief reactor engineers of Japan, question 3-4)