US 4,588,547 A · Method and apparatus for determining the nearness to criticality of a nuclear reactor

Abstract

The approach to criticality of a nuclear reactor provided with an artificial neutron source is monitored by two neutron detectors, one which measures the neutron flux in a localized region around the artificial neutron source, and the other located simlarly with respect to the core geometry but removed from the localized region. When the reactor is subcritical, the artificial source dominates and the outputs of the two detectors are noticeably different. As the reactor approaches criticality, the critical mode distribution of neutrons, which is symmetrical with respect to the two detectors, becomes dominant and the detector outputs approach each other in magnitude. The ratio of the output signals therefore, provides an indication of the reactor reactivity state. Either linear or logarithmic ratio signals can be generated, and if desired, either can be compared with an appropriately scaled reference signal representative of a selected reactivity state, such as a multiplication factor of 0.99, with the result of the comparison used to control a "near-criticality/not near-criticality" logic output.

Claims15

Dependent claims

A method of determining the reactivity of the reactor fuel in the core of a nuclear reactor having an artificial neutron source within the reactor core which generates a source neutron flux in a localized region around said source which is substantially greater than the neutron flux of the reactor fuel when the core is subcritical but is negligible compared to the neutron flux of the reactor fuel when the core is critical, said method comprising:

generating a first electrical signal representative of the neutron flux in said localized region of the core;
generating a second electrical signal representative of the neutron flux in another region of the core similarly located with respect to the configuration of the reactor fuel in the core as the localized region but removed from said localized region;
generating from said first and second electrical signals a signal representative of the ratio between the neutron flux in said other region and the neutron flux in said localized region;
and
generating an output signal representative of the criticality of the reactor fuel as a function of the ratio signal.

2 more elements

Apparatus for determining the reactivity of reactor fuel in the core of a nuclear reactor, comprising:

an artificial source of neutrons implanted in the reactor fuel which generates a neutron flux only in a localized region;
a first neutron detector positioned to detect neutrons in the localized region from the artificial source and from the reactor fuel and to generate a first electrical signal representative of the neutron flux in said localized region;
a second neutron detector positioned in a similar relationship to reactor fuel in the reactor core as the first neutron detector but removed from said localized region to generate a second electrical signal representative of the neutron flux generated by the natural neutron sources in the reactor fuel but not the neutron flux generated by the artificial neutron source;
means for generating a ratio signal representative of the ratio of the second electrical signal to the first electrical signal;
and
means for generating an output signal from the ratio signal representative of the reactivity of the reactor fuel in the reactor core as a function of the ratio signal.

3 more elements

Dependencies are inferred from the claim text.

Method and apparatus for determining the nearness to criticality of a nuclear reactor

Life of this patent

Method and apparatus for determining the nearness to criticality of a nuclear reactor

Life of this patent

Abstract

Claims15