To obtain a neutron detector capable of measuring high dose neutrons with high neutron/gamma-ray discrimination ability and high efficiency.

A scintillator 10 has a layered structure in which a phosphor layer 11 and a light transmission layer 12 are alternatelylaminatedin z direction. The phosphor layer 11 is made of a phosphor material emitting fluorescent light by absorbing neutrons, the material being, for example, a scintillator material used in neutron detectors having alreadybeen known. The light transmission layer 12 is made of a material highly transmitting fluorescent light emitted by the phosphor materialand only slightlyabsorbingneutrons. In the scintillator 10, when neutrons and gamma-ray photons enter it, luminescence intensity (pulse height) due to neutrons is significantly different from that due to gamma-ray photons. It makes it easy to discriminate between outputs due to the two kinds of radiations.

To obtain a neutron detector capable of measuring high dose neutrons with high neutron/gamma-ray discrimination ability and high efficiency.

A scintillator 10 has a layered structure in which a phosphor layer 11 and a light transmission layer 12 are alternatelylaminatedin z direction. The phosphor layer 11 is made of a phosphor material emitting fluorescent light by absorbing neutrons, the material being, for example, a scintillator material used in neutron detectors having alreadybeen known. The light transmission layer 12 is made of a material highly transmitting fluorescent light emitted by the phosphor materialand only slightlyabsorbingneutrons. In the scintillator 10, when neutrons and gamma-ray photons enter it, luminescence intensity (pulse height) due to neutrons is significantly different from that due to gamma-ray photons. It makes it easy to discriminate between outputs due to the two kinds of radiations.

A temperature measurement sensor for use in a nuclear reactor is described. The sensor includes a first neutron detector member and a second neutron detector member. The first neutron detector includes an outer shield material with an effective neutron capture cross section that is temperature dependent. The first neutron detector member outputs a first current signal and the second neutron detector member outputs a second current signal. An electrical connection between the first and second neutron detector members produces a net current that is the difference in current between the first and second signals. The difference is proportional to changes in temperature.

A temperature measurement sensor for use in a nuclear reactor is described. The sensor includes a first neutron detector member and a second neutron detector member. The first neutron detector includes an outer shield material with an effective neutron capture cross section that is temperature dependent. The first neutron detector member outputs a first current signal and the second neutron detector member outputs a second current signal. An electrical connection between the first and second neutron detector members produces a net current that is the difference in current between the first and second signals. The difference is proportional to changes in temperature.

The active neutron spectrometer (1) comprises a polyhedral moderator body (2) of hydrogenated material having a first, a second and a third orthogonal main axis (X.sub.1, X.sub.2; Y.sub.1, Y.sub.2; Z.sub.1, Z.sub.2), a first series of thermal neutron detectors (3.sub.a1, 3.sub.a2, 3.sub.a3, 3.sub.a4, 3.sub.a5, 3.sub.a6, 3.sub.b1, 3.sub.b2, 3.sub.b3, 3.sub.b4, 3.sub.b5, 3.sub.b6) arranged along the first main axis (X.sub.1, X.sub.2), a second series of thermal neutron detectors (4.sub.a1, 4.sub.a2, 4.sub.a3, 4.sub.a4, 4.sub.a5, 4.sub.a6, 4.sub.b1, 4.sub.b2, 4.sub.b3, 4.sub.b4, 4.sub.b5, 4.sub.b6) arranged along the second main axis (Y.sub.1, Y.sub.2), and a third series of thermal neutron detectors (5.sub.a1, 5.sub.a2, 5.sub.a3, 5.sub.a4, 5.sub.a5, 5.sub.a6, 5.sub.b1, 5.sub.b2, 5.sub.b3, 5.sub.b4, 5.sub.b5, 5.sub.b6) arranged along the third main axis (Z.sub.1, Z.sub.2).

The active neutron spectrometer (1) comprises a polyhedral moderator body (2) of hydrogenated material having a first, a second and a third orthogonal main axis (X.sub.1, X.sub.2; Y.sub.1, Y.sub.2; Z.sub.1, Z.sub.2), a first series of thermal neutron detectors (3.sub.a1, 3.sub.a2, 3.sub.a3, 3.sub.a4, 3.sub.a5, 3.sub.a6, 3.sub.b1, 3.sub.b2, 3.sub.b3, 3.sub.b4, 3.sub.b5, 3.sub.b6) arranged along the first main axis (X.sub.1, X.sub.2), a second series of thermal neutron detectors (4.sub.a1, 4.sub.a2, 4.sub.a3, 4.sub.a4, 4.sub.a5, 4.sub.a6, 4.sub.b1, 4.sub.b2, 4.sub.b3, 4.sub.b4, 4.sub.b5, 4.sub.b6) arranged along the second main axis (Y.sub.1, Y.sub.2), and a third series of thermal neutron detectors (5.sub.a1, 5.sub.a2, 5.sub.a3, 5.sub.a4, 5.sub.a5, 5.sub.a6, 5.sub.b1, 5.sub.b2, 5.sub.b3, 5.sub.b4, 5.sub.b5, 5.sub.b6) arranged along the third main axis (Z.sub.1, Z.sub.2).

A system includes a tool for measuring properties of a formation. The tool includes a tool body, a neutron source to emit neutrons disposed within the tool body, a neutron detector disposed within the tool body spaced apart from the neutron source, and a neutron shield arranged in operational relationship to the neutron detector, the neutron shield defines an exterior surface and an interior volume, the neutron shield to prevent neutrons having an energy below a first predetermined threshold from traveling from the exterior surface to the interior volume. The neutron shield is movably coupled to the tool body, wherein the neutron shield defines a non-occluded position relative to the neutron detector such that the neutron detector is at least partially outside the interior volume, and the neutron shield defines an occluded position relative to the neutron detector such that the neutron detector is disposed within the interior volume.

A system includes a tool for measuring properties of a formation. The tool includes a tool body, a neutron source to emit neutrons disposed within the tool body, a neutron detector disposed within the tool body spaced apart from the neutron source, and a neutron shield arranged in operational relationship to the neutron detector, the neutron shield defines an exterior surface and an interior volume, the neutron shield to prevent neutrons having an energy below a first predetermined threshold from traveling from the exterior surface to the interior volume. The neutron shield is movably coupled to the tool body, wherein the neutron shield defines a non-occluded position relative to the neutron detector such that the neutron detector is at least partially outside the interior volume, and the neutron shield defines an occluded position relative to the neutron detector such that the neutron detector is disposed within the interior volume.

The active neutron spectrometer (1) comprises a polyhedral moderator body (2) of hydrogenated material having a first, a second and a third orthogonal main axis (X.sub.1, X.sub.2; Y.sub.1, Y.sub.2; Z.sub.1, Z.sub.2), a first series of thermal neutron detectors (3.sub.a1, 3.sub.a2, 3.sub.a3, 3.sub.a4, 3.sub.a5, 3.sub.a6, 3.sub.b1, 3.sub.b2, 3.sub.b3, 3.sub.b4, 3.sub.b5, 3.sub.b6) arranged along the first main axis (X.sub.1, X.sub.2), a second series of thermal neutron detectors (4.sub.a1, 4.sub.a2, 4.sub.a3, 4.sub.a4, 4.sub.a5, 4.sub.a6, 4.sub.b1, 4.sub.b2, 4.sub.b3, 4.sub.b4, 4.sub.b5, 4.sub.b6) arranged along the second main axis (Y.sub.1, Y.sub.2), and a third series of thermal neutron detectors (5.sub.a1, 5.sub.a2, 5.sub.a3, 5.sub.a4, 5.sub.a5, 5.sub.a6, 5.sub.b1, 5.sub.b2, 5.sub.b3, 5.sub.b4, 5.sub.b5, 5.sub.b6) arranged along the third main axis (Z.sub.1, Z.sub.2).

The active neutron spectrometer (1) comprises a polyhedral moderator body (2) of hydrogenated material having a first, a second and a third orthogonal main axis (X.sub.1, X.sub.2; Y.sub.1, Y.sub.2; Z.sub.1, Z.sub.2), a first series of thermal neutron detectors (3.sub.a1, 3.sub.a2, 3.sub.a3, 3.sub.a4, 3.sub.a5, 3.sub.a6, 3.sub.b1, 3.sub.b2, 3.sub.b3, 3.sub.b4, 3.sub.b5, 3.sub.b6) arranged along the first main axis (X.sub.1, X.sub.2), a second series of thermal neutron detectors (4.sub.a1, 4.sub.a2, 4.sub.a3, 4.sub.a4, 4.sub.a5, 4.sub.a6, 4.sub.b1, 4.sub.b2, 4.sub.b3, 4.sub.b4, 4.sub.b5, 4.sub.b6) arranged along the second main axis (Y.sub.1, Y.sub.2), and a third series of thermal neutron detectors (5.sub.a1, 5.sub.a2, 5.sub.a3, 5.sub.a4, 5.sub.a5, 5.sub.a6, 5.sub.b1, 5.sub.b2, 5.sub.b3, 5.sub.b4, 5.sub.b5, 5.sub.b6) arranged along the third main axis (Z.sub.1, Z.sub.2).