Nuclear reaction protection system

A safety grade protection system for (i) monitoring parameters indicative of the status of a core of a nuclear reactor including nuclear fuel and control rods and having radial and axial dimensions, the parameters including a measure of neutron output at a plurality of axial and radial points within the core, and (ii) reducing the criticality of the nuclear reaction within the fuel when the onset of an unsafe condition is detected, the protection system comprising:

• an in-core power monitoring system having a plurality of radially spaced detectors, each of said detectors extending substantially over the axial length of the core and responsive in real time to provide a neutron sensitive output, that is apportioned among a plurality of axial segments of the core, without consideration of a delayed gamma or control rod emitted gamma response, said monitoring system providing a real time, three-dimensional direct measurement of the plurality of axial and radial points within the core at least normal operating power levels and having an output representative of the actual power measured at those points;
• a plurality of sensors for monitoring parameters characteristic of the heat removed from the core in real time and respectively providing an output characteristic of each of those parameters;
• and
• a processor having an input from the power monitoring system and the plurality of sensors and from those inputs and without a determination of control rod position, directly calculates, in real time, values representative of the actual condition of the fuel, the heat transfer condition at the fuel boundary and the rate of power change within the core compares those values against corresponding set points representative of the limits of acceptable operation for each of those conditions, and sends a signal to reduce the nuclear reaction within the core below critically if any of those set points are exceeded.