Framatome Gmbh

Areva Np Gmbh

Christian Royere

Mathieu Segond

Patrice Mahe

Christophe Lasne

A method is for monitoring a nuclear reactor comprising a core in which fuel assemblies are loaded, each assembly comprising nuclear fuel rods each including nuclear fuel pellets and a cladding surrounding the pellets. The method includes determining () at least one operating time limit (T) for the extended reduced power operation of the reduced power nuclear reactor, so as to avoid a rupture of at least one of the claddings, operating () the nuclear reactor at reduced power for an actual time strictly less than the time limit (T), and relaxing () at least one threshold for protecting the nuclear power plant as a function of a difference between the time limit (T) and the actual time.

Method for monitoring a nuclear core comprising a relaxation of a threshold, and associated programme, support and nuclear reactor

A method for protecting a nuclear reactor includes reconstructing a maximum linear power density released among the fuel rods of the nuclear fuel assemblies of the core; calculating the thermomechanical state and the burnup fraction of the rods; calculating a mechanical stress or deformation energy density in the cladding of one of the rods by using the said reconstructed maximum linear power density, the calculated thermomechanical states and the calculated burnup fractions, by means of a meta-model of a thermomechanical code; comparing the calculated mechanical stress or the calculated deformation energy density with a respective threshold; and stopping the nuclear reactor if the calculated mechanical stress or the calculated deformation energy density exceeds the respective threshold.

Method for protecting a nuclear reactor and corresponding nuclear reactor

The present invention relates to a method for detecting the drop of a cluster in a pressurized-water nuclear reactor, comprising the steps of: detecting a negative time derivative of the neutron flux, and comparing the absolute value of said time derivative to a first threshold value (S); triggering a time delay (&#x394;T) if said absolute value is greater than said threshold value (S); detecting a positive time derivative of said neutron flux, and comparing the absolute value of said time-derivative to a second threshold value (S); and triggering the emergency shutdown of the reactor if the absolute value of said positive time derivative of said flux becomes greater than said second threshold value (S) during said time delay (&#x394;T).

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Clamart, France

Christian Royere