Page 189 - Dynamics and Control of Nuclear Reactors

186 CHAPTER 13 Boiling water reactors

2
DECAY RATIO,DR = 0.024
DAMPING COEFFICIENT,
x = 0.51
IMPULSE RESPONSE 0
1

–1
0 2 4 6
TIME (S)
4
DECAY RATIO,DR = 0.37
DAMPING COEFFICIENT,
IMPULSE RESPONSE 2 0
x = 0.16

–2
0 2 4 6
TIME (S)
FIG. 13.11
Impulse response to reactivity perturbation of two BWR-4 systems at different power-to-flow
operations. The estimated decay ratios are: 0.024 (top), 0.37 (bottom).

• Turbine power "
• Steam pressure #
• Moderator/coolant boiling "
• In-core voids "
• Reactivity #
• Reactor power #
This scenario shows that the inherent initial response in a BWR is a reduction in reac-
tor power in response to an increase in steam flow. The control engineer’s job is to
overcome this behavior through appropriate control action.