Patent Description:
The primary aim of neutron detectors is reducing energy of neutrons received by the detector with the effect of scatterings. The reason for such a case is the need for slowing down the neutrons to the low energies named thermal energy level to allow them to be captured. Otherwise, a neutron that is not reduced to this level would leave a detector without being captured and hence a user cannot measure these neutrons in the medium. To this end, the materials named moderators are used on the outer layer of the neutron detectors. The neutron in the medium firstly passes through this material and, after losing its energy, reaches the main detector tube.

The interaction amount required for a neutron to be reduced to the thermal energy level, which is a measurable level, varies depending on the amount of it's incoming energy. As a neutron that has high energy performs more scatterings and hence can be reduced to the thermal energy level in comparison to a neutron having lower amount of energy. It is required for the high-energy neutrons to be slowed by means of a thicker moderator layer.

In various applications, such as particle accelerators that are being gradually used more frequently and in nuclear power plants, secondary neutron radiation is produced over a wide energy range. In this context, it is known that measurements carried out by use of detectors having the thickness of single and fixed moderators fail to count most of these neutrons.

In most of the neutron detectors that have now been commercially used, the fixed size moderator or set of moderators with various thicknesses are preferred. In these cases, the neutrons that do not have enough energy to pass through the moderator layer are not capable of reaching the main detector tube in which measurement would be performed. Even though they can pass through the moderator layer, the neutrons that have high energy and are not reduced to a measurable energy level leave the detector tube without being captured.

In the prior art, the FHT <NUM> Wendi-<NUM> model neutron detector obtained from the company Thermofisher is used. In said detector, a solid material having a wall thickness of <NUM> is used as a moderator. With this design approach and when the aforementioned description is considered, the detector has low sensitivity.

Another neutron detector that has been used in the prior art is the Microspec Neutron Probe of the company Bubble Technology Industries. In this design, two detectors having different moderator thicknesses have been used in order to increase the energy range of measurement. This case improves the measurement sensitivity of the detector to an extent; however, it still does not allow measurement within wide energy range.

Other designs that are commercially used to meet the need for the detectors having various moderator thicknesses are the detectors in which the moderator thickness can be changed by the use of a many detectors encircled with moderators having different thicknesses or that can be changed manually by users.

The other spectrometers used in the prior art are the Bonner Sphere Spectrometer of the company Else Nuclear and the Nested Neutron Spectrometer of the company Detec. When considering the area they cover, their weights and difficulty in handling, it is obvious that it won't be practical to perform a neutron measurement by using these detectors. In the Nested Neutron Spectrometer, it is required for the user to enter an irradiation room and to change the moderator after every measurement. This case causes the duration of measurement to be extended in measurements carried out in wide energy range. Furthermore, since the radiation level in the irradiation room is not suddenly reduced to zero once the process of irradiation is completed, entrance into the irradiation room would not be appropriate in terms of radiation safety.

Another spectrometer used in the prior art is the Rotating Neutron Spectrometer that has been manufactured by the company Bubble Technology Industries. This design has been achieved by disposing of seven individual detectors with different moderator thicknesses on a rotating system. When compared to other designs, while this design is more successful as it can perform measurement in the energy range of thermal to <NUM> MeV energy, such an energy range is even insufficient for most of the applications wherein secondary neutrons are produced. Moreover, the product fails to provide variety in accordance with the need of users. During the rotation process, the resolution of measurements will be lowered depending on the detectors being exposed to different irradiation fields out of the primary irradiation field.

Another invention known from the prior art is the patent document numbered <CIT>. When said patent document is reviewed, it can be seen that it has been aimed to provide a moderator layer at different thicknesses by using a liquid moderator. This embodiment is achieved by filling in pools located in the detector that are shown in globular shape by injection from a liquid reservoir. When the description of the present invention is reviewed, it can be evidently seen that the design does not have the required structure for preventing the gamma radiation in the medium. In most of the embodiments wherein a neutron production occurs, a large number of gamma radiations are also involved. To allow the detector to carry out a neutron measurement efficiently, the gamma radiation must be rejected. According to the patent document, it is understood that the detector container has a spherical geometry. As it wouldn't be possible to move with such a spherical geometry, the chambers in which the liquid moderator is filled are designed from a material such as aluminum or lead and in a fixed position to the detector. In this regard, even if the liquid moderator is drained, as there will be a lot of adhered layers left around the detector tube, it can be understood that the design is not applicable for measuring low-energy neutrons.

<CIT> discloses a multi-layer spherical slowing body container and a real-time measuring device for neutron energy spectrum. A multi-layer spherical body container is composed of a plurality of concentric hollow spherical shell layers having different inner diameters from the inside to the outside and hollow spherical shell is connected to the external liquid moderator loop through the corresponding pipeline.

<CIT> discloses a fully automatic Bonner sphere neutron spectrometer with water inlet and water outlet, which comprises a detector system a 3He spherical neutron detector for neutron detection, a water inlet and water outlet system and an evaluation and processing system.

<CIT> discloses that a neutron detection system comprises a neutron detector including a plurality of neutron detection devices, a control system configured to generate a detector response library, wherein the detector response library includes one or more sets of data indicative of a response of the detector to a known neutron source, receive one or more measured neutron response signals from each of the neutron devices, the one or more measured response signals response to a detected neutron event, and determine one or more characteristics of neutrons emanating from a measured neutron source by comparing the one or more measured neutron response signals to the detector response library.

The most important trait of our design is that time-dependent changes such as locations of the solid moderators and the step of filling of the liquid chambers can be controlled by the user. In different mediums of neutron radiation, as different parameters are needed, the design requires controllability.

The aim of the invention is to develop a neutron detector that is capable of measuring at high sensitivities in a wide range of energies, with a novel design logic that is completely different from the neutron monitoring instruments currently used commercially.

It has been conceived to provide that the solid and liquid moderators that are changeable in thickness are used in the same design instead of the single solid moderator that is not applicable to be changed in thickness. Due to its changeable moderator structure, the detector would allow the user to perform a measurement at different thicknesses of moderator in single irradiation by being programmed before or remotely controlled during the measurement.

Therefore, a neutron detector that is capable of performing precise measurements, that eliminates the limitation of measuring at low ranges of energy, and that enables the user to carry out measurements at the energy levels determined by the detector is provided. Another important significant feature of the detector is to allow the use of different solid and liquid moderators in the detector at research and development studies.

In the neutron detector with the solid-liquid moderator, the time dependent changes including the location of the solid moderators, and the step of filling the liquid chambers, can be controlled by the user. In different neutron radiation fields, as different parameters are needed, the design requires controllability.

The drawings and the related description used in an attempt to better disclose the neutron detector with the solid-liquid moderator that has been developed with the present invention are as follows:.

The elements and parts presented in the figures to better disclose the neutron detector with the solid-liquid moderator that has been developed with the present invention are numbered, each number thereof having the corresponding definitions below:.

The invention is a neutron detector that is capable of measuring neutrons at different energy ranges, according to claim <NUM>.

The solid moderators (<NUM>) are formed of polyethylene or a high-density polyethylene material, which are interconnected cylinders having a wall thickness of <NUM> and are connected to the solid moderator motion lever (<NUM>). The solid moderators (<NUM>) move in the solid moderator slide gaps (<NUM>) as a result of a movement of the solid moderator motion lever (<NUM>) in the vertical axis. After the solid moderator (<NUM>) is placed in the detector measurement chamber (<NUM>), the solid moderator motion lever (<NUM>) releases the solid moderator (<NUM>) defined by the user by rotating at a determined angle in the horizontal axis. After the process is completed, the solid moderator motion lever (<NUM>) turns back to the solid moderator movement chamber (<NUM>).

The detector (<NUM>) with BF<NUM> or He<NUM> gas is fixed to the center of the detector measurement chamber (<NUM>). The data cable (<NUM>) connected to the detector (<NUM>) is connected to the signal processing unit (<NUM>) by extending out of the gap in the solid moderator motion lever (<NUM>). The detector (<NUM>) is covered with the hollow cylindrical sheath (<NUM>) made of tungsten material having <NUM> wall thickness to protect the detector (<NUM>) from gamma radiation in the medium. In the cases where a measurement is not carried out, the portion remaining out of the detector measurement chamber (<NUM>) outside the detector (<NUM>) and the tungsten sheath (<NUM>) is called the gap.

The liquid moderator storage chamber (<NUM>) is the volume in which the liquid to be used as a moderator is stored. The liquid movement path (<NUM>) is fixed to the liquid storage chamber and the liquid is charged and discharged through this path. When needed, the liquid movement path (<NUM>) is moved in the vertical axis and thus the liquid can be provided to fill in the related gaps in the detector measurement chamber (<NUM>). The liquid moderator transfer openings (<NUM>) are provided at the ceiling of the liquid moderator storage chamber (<NUM>). The liquid moderator transfer openings (<NUM>) have the function of allowing the liquid contained in the liquid moderator storage chamber (<NUM>) to pass into the detector measurement chamber (<NUM>). All of these openings are controlled by the user via the electronic control unit and the passage of the liquid moderator is allowed from the holes that are desired to be filled with the liquid moderator according to the area between the solid moderators (<NUM>) that are desired to be filled.

Different configurations of detectors can be obtained in research and development studies as the liquids to be used as moderator in the detector can be charged and discharged utilizing the liquid movement path (<NUM>) and the solid moderators (<NUM>) can be mounted and dismounted from the solid moderator motion lever (<NUM>). Therefore, the opportunity to develop the detector is given to the user.

The neutron detector consists of several component and many different electronic units that have been standardized on nuclear instrumentation. These are; a signal processing unit (<NUM>), an external processing unit (<NUM>), an actuator unit (<NUM>), a sensor unit (<NUM>), a liquid reservoir control unit (<NUM>), a power circuit control unit (<NUM>), a memory unit (<NUM>), a warning unit (<NUM>) and a status data reading unit (<NUM>). <FIG> shows a block diagram of the electronic control unit of the neutron detector. The electronic control unit consists of the components disclosed in detail below.

The signal processing unit (<NUM>) of the neutron detector functions as the brain of the system. The signal processing unit (<NUM>) performs all of the actions that must be conducted by the system and also provides communication between other units in the electronic control unit.

Controlling of movements of the moderator layers in the neutron detector is carried out by means of a DC motor.

As the neutron detector operates in a radiation field, the status data such as temperature, humidity, pressure are required to be obtained. The reading of these data is carried out in the sensor unit.

The liquid moderator storage chamber (<NUM>) is provided at the lower portion of the neutron detector. Said chamber must be controlled to protect the detector from any damage likely to occur as a result of leaking of liquids. The liquid contained in the liquid moderator storage chamber (<NUM>) is constantly controlled through the liquid reservoir control unit (<NUM>).

The power circuit control unit allows providing energy to the electronic components and controls the amount of the current that the electronic units draw.

The memory unit (<NUM>) of the neutron detector saves the data received and processed. Thus, the data is enabled to be backed up.

The warning unit (<NUM>) enables an alarm of the detector to be activated once the received neutron data or dose rate of the medium reaches higher values than a determined level.

Receiving and interpreting the data obtained from the sensor unit is carried out in the status data reading unit. Said unit controls if the detector operates smoothly by evaluating the status data.

Once the entire system is collectively operated, the user can control the entire data from a single unit using the external processing unit (<NUM>).

The neutron detector subject to the present invention enables the moderator thickness to be changed by the user by being programmed before irradiation or being controlled remotely during irradiation, which helps the present neutron detector be distinguished from the neutron detectors already known from the prior art. Variable thicknesses of the moderator can be obtained by filling the constant-volume ducts to be disposed of in the moderator chamber with the liquid moderator. Therefore, it would be possible to measure the neutrons at wide ranges of energy, which is different from the neutron detectors known from the prior art.

The use of a neutron detector having all of the aforementioned characteristics in critical fields of study wherein the energy range of neutrons should be known in detail would help an important need in the industry, to be met. Moreover, the present neutron detector does not need large area and is very portable.

Claim 1:
A neutron detector allowing measurement of neutrons at different energy ranges, comprising
• a detector (<NUM>) configured to measure neutrons,
• a detector measuring chamber (<NUM>) in which the detector (<NUM>) is located,
• a liquid moderator storage chamber (<NUM>) in which liquid moderator is stored,
• liquid moderator transfer openings (<NUM>) that are located on the ceiling of the liquid moderator storage chamber (<NUM>) and configured to allow the liquid contained in the liquid moderator storage chamber (<NUM>) to pass into the detector measurement chamber (<NUM>)
• and an electronic control unit,
characterized by comprising
• a solid moderator movement chamber (<NUM>) comprising solid moderators (<NUM>) wherein the solid moderators (<NUM>) can move in the vertical axis,
• a solid moderator motion lever (<NUM>) configured to enable the solid moderators (<NUM>) to move in the vertical axis in the solid moderator movement chamber (<NUM>),
• a liquid moderator movement path (<NUM>) that is connected to the liquid moderator storage chamber (<NUM>), and is movable in vertical axis and configured to enable the liquid moderator to pass through the transfer openings (<NUM>) to the detector measuring chamber (<NUM>),
• a sheath (<NUM>) configured to Prevent gamma radiation by surrounding the detector (<NUM>),
• slide gaps (<NUM>) configured to allow the solid moderators (<NUM>) to move in as a result of a movement of the solid moderator motion lever (<NUM>) in the vertical axis.