According to one embodiment, a neutron position detector includes a gas including a .sup.3He gas and an additive gas. The gas has a gas composition being set so that a total of ranges of a proton and a tritium in the gas is 2.0 to 2.7 mm. The partial pressures are in an extent surrounded by a first gas composition point of the .sup.3He gas of 5 atm and the additive gas of 1.6 atm, a second gas composition point of the .sup.3He gas of 5 atm and the additive gas of 2.3 atm, a third gas composition point of the .sup.3He gas of 20 atm and the additive gas of 0.6 atm, and a fourth gas composition point of the .sup.3He gas of 20 atm and the additive gas of 1.3 atm.

According to one embodiment, a neutron position detector includes a gas including a .sup.3He gas and an additive gas. The gas has a gas composition being set so that a total of ranges of a proton and a tritium in the gas is 2.0 to 2.7 mm. The partial pressures are in an extent surrounded by a first gas composition point of the .sup.3He gas of 5 atm and the additive gas of 1.6 atm, a second gas composition point of the .sup.3He gas of 5 atm and the additive gas of 2.3 atm, a third gas composition point of the .sup.3He gas of 20 atm and the additive gas of 0.6 atm, and a fourth gas composition point of the .sup.3He gas of 20 atm and the additive gas of 1.3 atm.

An in-core nuclear detector for detecting the neutron population surrounding the detector. The detector is an ion chamber having a cylindrical outer electrode that is insulated from a central electrode and capped to contain an Argon gas. An electron radiator that produces prompt neutron capture gamma radiation that is substantially, directly proportional to the local neutron population is disposed between the outer tubular electrode and the central electrode.

A narrow thermal neutron detector includes a slidably receivable ionization thermal neutron detector module within an overall housing body. An active sheet layer of the ionization thermal neutron detector module can be tensioned across its width. The ionization thermal neutron detector module can include module upper major surface extents and module lower surface extents such that, when installed within the housing body, the module upper major surface extents are in a first spaced apart confronting relationship with housing upper major surface extents to define a first clearance and module lower major surface extents are in a second spaced apart confronting relationship with housing lower major surface extents to define a second clearance to accommodate housing flexing due to ambient pressure change. The housing body can be formed with a single opening for receiving the ionization thermal neutron detection module or with opposing first and second opposing end openings.

A narrow thermal neutron detector includes a slidably receivable ionization thermal neutron detector module within an overall housing body. An active sheet layer of the ionization thermal neutron detector module can be tensioned across its width. The ionization thermal neutron detector module can include module upper major surface extents and module lower surface extents such that, when installed within the housing body, the module upper major surface extents are in a first spaced apart confronting relationship with housing upper major surface extents to define a first clearance and module lower major surface extents are in a second spaced apart confronting relationship with housing lower major surface extents to define a second clearance to accommodate housing flexing due to ambient pressure change. The housing body can be formed with a single opening for receiving the ionization thermal neutron detection module or with opposing first and second opposing end openings.

An isotropic neutron detector includes a spherical secondary particle radiator component and a plurality of stacked semiconductor detectors. A first semiconductor detector is coupled to at least a portion of the spherical secondary particle radiator component, forming a portion of a first concentric shell thereover. A second semiconductor detector coupled to at least a portion of the first semiconductor detector, forming a portion of a second concentric shell thereover.

The invention relates to a neutron detector unit for neutrons, in particular thermal and cold neutrons, comprising a detector housing (7, 17, 27), cathode elements and a plurality of anode elements (5, 15, 25), wherein in order to form a volume detector unit the anode elements (5, 15, 25) and the cathode elements enable a three-dimensional spatial resolution for conversion events, characterized by a converter gas in the detector housing (7, 17, 27). According to the invention, in a neutron detector arrangement which includes at least one neutron detector unit the neutron detector unit (3, 13, 23) or at least one of the neutron detector units (3, 13, 23) is oriented in such a way that at least some of the anode elements (5, 15, 25) of the at least one neutron detector unit (3, 13, 23) extend at least predominantly in a longitudinal orientation parallel or almost parallel to the direction of travel of the neutrons (4) to be detected.

A radiation detector to monitor the neutron flux of a nuclear reactor or other high-radiation environment, that can withstand the high temperatures and radiation fields of such environment, is provided. A small dielectric substrate with a low neutron-activation cross section is provided. The substrate is coated with a neutron conversion material, such as uranium oxide or thorium oxide. One or more substrates form a micro-sized detection cavity that is filled with a detection gas. A voltage is provided across anode and cathode wires in the detection cavity. A neutron absorbed in the conversion material may release reaction products into the gas, causing ionization of the gas which then produces a current or voltage signal. The small detector volume minimizes energy deposition into the detection gas by competing particles such as gamma rays, fast electrons, and beta particles, and therefore minimizes false counts while retaining large signals from neutron interactions.

A boron coated straw detector for use in a neutron detection system is disclosed comprising a boron coated straw having at least one boron-coated septum radially oriented and extending a pre-determined distance towards the center of the straw. Preferably, the straw comprises a plurality of septa comprising a rigid surface, coated on both sides with a boron composition. Preferably, the septa run the length of the straw detector from one end of the straw to the other. The area coated on the septa adds to the area coated on the arc segments offering a significant benefit in sensitivity of the neutron detector.

A slow neutron detection device is disclosed, comprising: a first slow neutron converter and a second slow neutron converter, and a readout electrode wire set and cathode wire sets arranged between the first slow neutron converter and the second slow neutron converter. By arranging a readout circuit between the two slow neutron converters, an electron drift distance is reduced by half without changing a dimension of the detection device, and an average over-threshold probability of a signal is increased.