81 results about "Epithermal neutron" patented technology

A set of alloy formulations is disclosed to use with thorium based nuclear fuels in a fast spectrum reactor; with thorium based nuclear fuels in existing thermal spectrum power reactors; for medical isotope production in the epithermal, the fast, the fission spectrum and the thermal spectra; and to use as fuel in test and experimental reactors that are non proliferative. The alloys form inert metal matrixes to hold fine particles of dispersed thorium containing fuel. The formulations also are useful for the production of medical and commercial isotopes in the high energy, fast and epithermal neutron spectra.

The invention provides a beam shaper for neutron-capture therapy in order to improve flux and quality of a neutron source. The beam shaper comprises a target, a slowing body adjacent to the target, a reflector wrapping the slowing body, a thermal neutron absorber adjacent to the slow body, a radiation shield arranged in the beam shaper and a beam outlet. The target generates nuclear reaction with a proton beam incident from a beam inlet so as to generate neutrons, the neutrons form a neutron beam which defines a main axis, the slowing body slows down the neutrons generated from the target to an epithermal neutron energy region, the reflector guides the neutrons deviating from the main axis to the main axis so as to improve intensity of the epithermal neutron beam, a gap passage is arranged between the slowing body and the reflector so as to improve epithermal neutron flux, the thermal neutron absorber is used for absorbing the thermal neutron so as to avoid causing overmuch dosed with shallow normal tissue during therapy, and the radiation shield is used for shielding leaked neutrons and photon so as to reduce normal tissue dose in a non-radiation region.

A method for producing ²²⁹Th includes the steps of providing ²²⁶Ra as a target material, and bombarding the target material with alpha particles, helium-3, or neutrons to form ²²⁹Th. When neutrons are used, the neutrons preferably include an epithermal neutron flux of at least 1×10¹³ n s⁻¹·cm⁻². ²²⁸Ra can also be bombarded with thermal and/or energetic neutrons to result in a neutron capture reaction to form ²²⁹Th. Using ²³⁰Th as a target material, ²²⁹Th can be formed using neutron, gamma ray, proton or deuteron bombardment.

In order to improve the flux and the quality of a neutron source, the invention provides a beam shaping body for neutron capture therapy. The beam shaping body comprises a beam inlet, a target, a retarding body adjacent to the target, a reflecting body surrounding the external of the retarding body, a thermal neutron absorber adjacent to the retarding body, and a radiation shield and a beam outlet formed in the beam shaping body, wherein the target has nuclear reaction with proton beam entering from the beam inlet, so as to produce a neutron; the neutron forms a neutron beam; the neutron beam defines a main axis; the retarding body slows down the neutron produced by the target to an epithermal neutron energy region; the retarding body is designed to a shape containing at least one cone; the reflecting body guides the neutron deviated from the main axis back to the main axis, so as to improve the strength of an epithermal neutron beam; the thermal neutron absorber is used for absorbing a thermal neutron, so as to prevent the thermal neutron from causing excessive dosage with a superficial normal tissue during therapy; the radiation shield is used for shielding leaked neutron and photon, so as to reduce the normal tissue dosage of a non-irradiated region.

A neutron logging tool includes a neutron source and at least one position sensitive thermal or epithermal neutron detector. The logging tool further includes an electronic controller configured to estimate the axial location of detected neutrons. Measurement of the axial neutron flux distribution enables other formation and borehole parameters such as formation porosity and sensor standoff to be computed. In logging while drilling embodiments, a borehole caliper may also be computed form the axial neutron flux distribution.

An apparatus for producing thermal or epithermal neutrons in a sample has a plurality of fast neutron sources positioned around a cylindrical or spherical moderator to maximize the neutron flux at a sample placed in a void at the center of the moderator.

Apparatus and methods for determining borehole diameter and standoff for neutron porosity logging systems. The apparatus comprises an isotopic neutron source, a single epithermal neutron detector and two thermal neutron detectors, where all detectors are at different axial spacings from the neutron source. Thermal neutron porosity is determined from the combined response of the thermal neutron detectors. Epithermal neutron porosity is determined from the response of the single epithermal neutron detector. Embodied as a wireline system, a difference between thermal neutron porosity and epithermal neutron porosity is used to compute a tool standoff, which in turn is used to correct the thermal neutron porosity for effects of standoff. Borehole size measurements are made independently and preferably with a mechanical caliper of a density tool subsection. Embodied as a LWD system, the difference between thermal neutron porosity and epithermal neutron porosity is used to correct the thermal neutron porosity measurement for both borehole diameter and radial position (standoff) of the tool within the borehole.

A method for determining at least one formation property calculated from neutron measurements acquired with a downhole tool includes emitting neutrons from a source in the tool into the formation, detecting neutrons with at least one detector in the downhole tool, calculating a first slowing-down length (L₁) based on the detected neutrons, and deriving a second slowing-down length (L₂) based on the first slowing-down length (L₁). Further steps include deriving a correlation function for relating slowing-down lengths from a first tool to slowing-down lengths associated with a different source, wherein the correlation function depends on formation properties such as bulk density; and applying the correlation function to the slowing-down length of the first tool to derive the slowing-down length of the second tool. A method for determining a thermal neutron formation porosity based on a slowing-down length from epithermal neutron measurements from an electronic neutron source includes converting the slowing-down length into a computed neutron slowing-down length from thermal neutron measurements from a chemical neutron source, wherein the converting uses a correlation function that depends on formation bulk density; deriving a thermal neutron countrate ratio based on the computed neutron slowing-down length, wherein the deriving uses a function that depends on the formation bulk density and formation sigma; and computing the thermal neutron formation porosity from the thermal neutron countrate ratio.

A device for online measurement of a flow of fast and epithermal neutrons. The device has a fast and epithermal neutron detector (DNR) able to detect principally fast and epithermal neutrons; a thermal neutron detector (DNT) able to detect principally thermal neutrons; a first circuit (C1) for processing the signal delivered by the fast neutron detector; a second circuit (C2) for processing the signal delivered by the thermal neutron detector; a means (CE, PMM) suitable for determining the progressive sensitivity to the fast neutrons and to the thermal neutrons of each of the neutron detectors, and a computer (CALC) which computes the flow of fast and epithermal neutrons on the basis of the said progressive sensitivities and of the signals delivered by the first and second processing circuits.

The invention discloses a neutron filter material and a preparation method thereof. The preparation method comprises 1, orderly carrying out primary compacting molding, sintering and hot isostatic pressure molding on an epithermal neutron filter material, or 2, putting the epithermal neutron filter material into a jacket and carrying out hot isostatic pressure molding, wherein the epithermal neutron filter material comprises at least one of tungsten powder, aluminum powder, titanium powder, boron carbide, titanium oxide, lithium fluoride, aluminum fluoride, gadolinium oxide, gadolinium fluoride, boron nitride, boron oxide, zirconium boride, titanium boride and lithium oxide powder. The neutron filter material has the advantages that 1, the neutron filter material has outstanding filterability and provides a specific energy section and especially provides a neutron beam of an epithermal neutron energy section, 2, the preparation method is reliable, product performances are outstanding, and in boron neutron capture therapy device use, the epithermal neutron filtration satisfies apparatus design indexes, and 3, the large-scale thick neutron filter material can be prepared and machining can be realized.

Described is a method of using gadolinium-containing compounds as agents for neutron capture therapy to treat neoplastic cell growth. The subject is exposed to a gadolinium-containing compound for a time sufficient to allow the compound to accumulate in neoplastic cells. The subject is then exposed to a thermal and/or epithermal neutron flux, thereby initiating a neutron capture reaction in the gadolinium atoms that results in specific death of neoplastic cells.

The invention provides a radiation shielding glass, which is represented by mass percentage and whose chemical composition is SiO ₂ : 10~30%, PbO: 25~60%, Al ₂ o ₃ : 0~20%, B ₂ o ₃ : 0~20%, Li ₂ O: 0~20%, Re ₂ o ₃ (Re=Gd, Eu, Dy): 0~15%, In ₂ o ₃ : 0~15%, CeO ₂ : 0~1.5%, and provide a preparation method of shielding glass with the same composition, the gamma ray absorption coefficient of the shielding glass is 0.5cm ^‑1 (0.511MeV) and 0.3cm ^‑1 (1.25MeV), the visible light transmittance is greater than 80% when the thickness is 6mm, and the shielding rates of slow, medium energy and fast neutrons are above 97%, 40% and 20% respectively, which can be used for gamma rays and medium neutrons in the nuclear industry. Shielding windows (plates) for neutron radiation, epithermal neutron radiation fields for medical use or gamma rays for PET inspection.

A beam shaping assembly for neutron capture therapy includes a beam inlet, a target having nuclear reaction with an incident proton beam from the beam inlet to produce neutrons forming a neutron beam defining a main axis, a moderator adjoining to the target, a reflector surrounding the moderator, a thermal neutron absorber adjoining to the moderator, a radiation shield arranged inside the beam shaping assembly and a beam outlet. The neutrons are moderated to epithermal neutron energies. The reflector leads the neutrons deviated from the main axis back, and a gap channel is arranged between the moderator and the reflector. The thermal neutron absorber is used for absorbing thermal neutrons so as to avoid overdosing in superficial normal tissue during therapy. The radiation shield is used for shielding leaking neutrons and photons so as to reduce dose of the normal tissue not exposed to irradiation.

The invention relates to a fission neutron well logging correction method, which comprises the following steps that: 1, a correction counting rate of a neutron monitor of a tested wellhole is obtained; 2, a water correction factor is obtained; 3, the neutron counting rates near a well wall and along a well axis after the water correction in a tested well are obtained; and 4, the neutron counting rates near the well wall and along the well axis after the epithermal neutron service life correction in the tested well are obtained. The method provided by the invention can be used for directly measuring the uranium content. Compared with drill hole rock core sampling chemical analysis results, the method has the advantages that the deviation does not exceed 10 percent. The uranium ore grade is more objectively reflected; particularly in sections with damaged uranium-radium balance, conventional gamma well logging is combined, and a uranium-radium balance factor of a drill hole ore block can be determined in site; and the rock core sampling quantity is reduced, and the uranium resource investigation cost is reduced. The method can be used for accurately measuring the uranium leaching rate in mining using the leaching technology, avoids the environment pollution and the cost waste due to unquestioning excessive liquid injection in the process of the mining using the leaching technology, and has important practical significance on improving the efficiency of the mining using the leaching technology, reducing the cost and protecting the environment.

The invention discloses a prompt uranium fission neutron logging technique based on the epithermal neutron and thermal neutron ratio. The technique is specifically characterized in that in boreholes, fast neutrons, also called virgin neutrons, are transmitted to formation rock by means of pulsing; the virgin neutrons are successively moderated by in-well medium into epithermal neutrons and thermal neutrons; the thermal neutrons induce 235U fission to radiate prompt uranium fission neutrons, also called secondary neutrons; the secondary neutrons are successively moderated into epithermal neutrons and thermal neutrons, inducing 235U fission again; from any moment t after the virgin neutrons are moderated into the thermal neutrons, the total nE(t) of existing epithermal neutrons in the formation rock is in direct proportion to the total nT(t) of existing thermal neutrons and uranium content qu, namely nE(t)<nT(t) qu. By using a bi-neutron detector and a dual-time detector disposed in the invention to measure time spectra of the epithermal and thermal neutrons and defining an attenuation ratio of the epithermal neutrons to the thermal neutrons as 'E/T', from a moment, when the virgin neutrons are moderated into the thermal neutrons, to any moment, a uranium quantitative real-time algorithm based on saturated seams is constructed.

A neutron moderation material for use in a BNCT beam shaping assembly. The neutron moderation material comprises three elements, i.e., Mg, Al, and F, wherein the mass fraction of the Mg element is 3.5%-37.1%, the mass fraction of the Al element is 5%-90.4%, and the mass fraction of the F element is 5.8%-67.2%; the sum of the weights of the Mg, Al, and F elements is 100% of the total weight of the neutron moderation material. The neutron moderation material may be doped with a small amount of ⁶Li-containing substances, and the addition of the ⁶Li-containing substances effectively decreases the content of γ-rays in epithermal neutron beams.

The embodiment of the invention provides a neutron beam current device. The neutron beam current device is used for carrying out neutron energy spectrum adjustment on a neutron beam entering the neutron beam current device, wherein particles of the neutron beam comprise fast neutrons, epithermal neutrons, thermal neutrons and gamma photons. The neutron beam current device comprises a filtering part, an adjusting part and a collimator, wherein the filtering part is used for filtering fast neutrons in the neutron beam; the adjusting part is used for adjusting the neutron energy spectrum of the neutron beam so as to obtain an epithermal neutron beam or a thermal neutron beam; and the collimator is used for carrying out collimated emission on the adjusted neutron beam, wherein the filtering part, the adjusting part and the collimator are sequentially arranged in the neutron beam current device in a direction from a position that the neutron beam enters the neutron beam current device to aposition that the neutron beam is emitted out of the neutron beam current device. According to the neutron beam current device provided by the embodiment of the invention, two neutron beams, namely the thermal neutron or the epithermal neutron, can be provided through one beam current channel, so that two beam current channels do not need to be separately arranged, a larger space occupied by a plurality of beam current channels is avoided, and increase of construction cost is avoided.