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US 8,135,106 B2Granted
Protection of reactor cores from unstable density wave oscillations
AssigneeAreva Np
InventorsYousef M. Farawila, Douglas W. Pruitt
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Abstract
The present invention provides a method of operating a Boiling Water Reactor, having the steps of analyzing LPRM signals for oscilliatory behavior indicative of neutron-flux-coupled density wave oscillations, determining if oscilliatory behavior is present in the signals; initiating a reactor protective corrective action if the oscilliatory behavior is determined, and in addition, initiating corrective actions if neutron uncoupled oscillations are possible. Detecting the later is performed through analytically determined exclusion zone on the power flow map or by on-line stability calculations for several high power channels.
Claims7
A method of operating a Boiling Water Reactor comprising:
- a step of analyzing Local Power Range Monitor signals in the Boiling Water Reactor for oscillatory behavior indicative of neutron-flux-coupled density wave oscillations;
- determining if oscillatory behavior is present in the signals;
- and
- initiating a first reactor protective corrective action if the oscillatory behavior is determined to be present;
- and
- if the Local Power Range Monitor signals analyzed in the step of analyzing Local Power Range Monitor signals are not oscillatory beyond noise levels,
- a step of anticipating and suppressing instability in the Boiling Water Reactor caused by single channel thermal-hydraulic density waves in at least one fuel channel of the Boiling Water Reactor, wherein the single channel thermal-hydraulic density waves are uncoupled from neutron flux variations;
- the step of anticipating and suppressing the instability comprising performing analytical simulations of the Boiling Water Reactor, independent of neutron flux;
- the analytical simulations identifying relationships between output power of the Boiling Water Reactor and coolant flow in the Boiling Water Reactor that result in the single channel thermal-hydraulic density waves in the at least one fuel channel of the Boiling Water Reactor;
- thereby
- defining a boundary of an exclusion zone on a power-coolant flow operating map of the Boiling Water Reactor where neutron-flux-uncoupled density wave oscillations are possible in the at least one fuel channel of the Boiling Water Reactor;
- determining whether operating power and coolant flow in the Boiling Water Reactor are within the exclusion zone of the power-coolant flow operating map of the Boiling Water Reactor while the Local Power Range Monitor signals are not oscillatory beyond noise levels;
- initiating a second reactor protective corrective action if the operating power of the Boiling Water Reactor and coolant flow in the Boiling Water Reactor are within the exclusion zone of the power-coolant flow operating map;
- and
- repeating at least the step of analyzing Local Power Range Monitor signals if the operating power of the Boiling Water Reactor and coolant flow in the Boiling Water Reactor are outside the exclusion zone of the power-coolant flow operating map.
12 more elements
A method of establishing a stable region on a power-coolant flow operating map for a Boiling Water Reactor and operating the Boiling Water Reactor in the stable region, the method comprising:
- providing a power-coolant flow operating map for a Boiling Water Reactor;
- and
- performing analytical simulations of the Boiling Water Reactor, independent of neutron flux, the analytical simulations identifying relationships between output power of the Boiling Water Reactor and coolant flow in the Boiling Water Reactor that result in single channel thermal-hydraulic density waves in at least one fuel channel of the Boiling Water Reactor, wherein the single channel thermal-hydraulic density waves are uncoupled from neutron flux variations, such that neutron flux signals are not oscillatory beyond noise signals, thereby defining an exclusion zone on the power-coolant flow operating map where neutron-flux-uncoupled density wave oscillations are possible in the at least one fuel channel of the Boiling Water Reactor, wherein a stable region on the power-coolant flow operating map of the Boiling Water Reactor is established under the exclusion zone, where signals from Local Power Range Monitors are not oscillatory beyond noise levels, and operating the Boiling Water reactor in the stable region.
A method of operating a Boiling Water Reactor with improved operational flexibility, the method comprising:
- providing a power-coolant flow operating map for a Boiling Water Reactor;
- performing analytical simulations of the Boiling Water Reactor, independent of neutron flux, the analytical simulations identifying relationships between output power of the Boiling Water Reactor and coolant flow in the Boiling Water Reactor that result in single channel thermal-hydraulic density waves in the at least one fuel channel of the Boiling Water Reactor, wherein the single channel thermal-hydraulic density waves are uncoupled from neutron flux variations, such that neutron flux signals are not oscillatory beyond noise signals, thereby defining an exclusion zone on the power-coolant flow operating map where neutron-flux-uncoupled density wave oscillations are possible in the at least one fuel channel of the Boiling Water Reactor, wherein a stable region on the power-coolant flow operating map is established under the exclusion zone;
- and
- operating the Boiling Water Reactor at a power and a coolant flow which are in the stable region on the power-coolant flow operating map, where signals from Local Power Range Monitors are not oscillatory beyond noise levels.
1 more element
Dependencies are inferred from the claim text.