阅读说明：本技术 用于表面缺陷检测和分析的产生脉冲中子的瞬时伽马发射测量系统 (Transient gamma emission measurement system for generating pulsed neutrons for surface defect detection and analysis ) 是由 M·D·海尔贝尔 于 2017-04-13 设计创作，主要内容包括：本发明公开一种确定部件中的结构缺陷的方法,该方法利用具有通过毛细吸收渗透到材料表面上的小裂缝的能力的溶液的中子激活,当暴露于中子脉冲时,所述溶液产生限定能量的可分辨的瞬时伽马释放。在表面上的用户受控位置以期望能量产生的伽马射线的强度被用于确定裂缝位置、长度和深度。(A method of determining structural defects in a component is disclosed that utilizes neutron activation of a solution having the ability to penetrate small cracks on the surface of the material by capillary absorption, which solution produces a resolvable transient gamma release of defined energy when exposed to a neutron pulse. The intensity of gamma rays at a user controlled location on the surface at a desired energy generation is used to determine fracture location, length and depth.)

1. A method of non-destructive inspection of a structural defect (22) in a surface (20) of an irradiated material, comprising the steps of:

applying to a surface (20) of a material to be inspected a mixture of non-corrosive fracture penetrants (30) comprising chemicals of larger cross-section for fast neutron-induced transient gamma-emission reactions of defined energy, such as chemicals comprising nitrogen, scandium, titanium, manganese, or vanadium;

irradiating the surface of the material with a neutron pulse generator (12);

positioning a plurality of beta radiation detectors (24) in a regular pattern on a surface of a material to which the mixture is applied, the beta radiation detectors (24) being tuned to the defined energy of photo-generated electrons produced by an electron generation window (36) located between an active region (42) of the detectors and the surface being inspected, the plurality of beta radiation detectors each providing an output indicative of receipt of an instantaneous gamma release (38) of the defined energy in a surface region viewed by a corresponding one of the plurality of beta radiation detectors; and

-determining a characteristic of the defect (22) using the receiving.

2. The method of claim 1, wherein the feature is at least one of a location, a length, and a depth of the defect (22) on the surface (20).

3. The method of claim 2, wherein the depth of the defect (22) is determined from the received intensity.

4. The method according to claim 1, wherein the mixture (3) is absorbed into the surface (20) by capillary absorption.

5. The method of claim 1, wherein the neutron pulse generator (12) is a neuston-type neutron pulse generator.

6. The method of claim 1 wherein tuning of the beta radiation detector (24) is accomplished by disposing a high atomic number sacrificial material (36) between the inspected surface (20) and an active portion (42) of the beta radiation detector as an electron radiator.

7. The method of claim 6 wherein the beta radiation detector (24) is a silicon carbide (SiC) detector, the type of material used in the sacrificial layer (36) of the beta radiation detector (24), the distance from the active detector region (42), and the thickness being selected to ensure that a majority of electrons generated by photoelectric absorption of the desired emitted instantaneous gamma radiation energy (38) come to a complete stop inside the active region of the SiC detector.

8. The method of claim 6, wherein the sacrificial material (36) is platinum or tungsten.

9. An apparatus for non-destructively detecting and characterizing defects (22) in a surface (20) of an irradiated material, comprising:

a spraying system (18) configured to spray a mixture of non-corrosive fracture infiltrants (30) having a high nitrogen content, or mixed with a chemical substance having a large number of isotopes having a photo-electric defined energy, large fast neutron transient capture gamma emission cross-section, such as nitrogen, scandium, vanadium, manganese, or titanium, onto the surface of the material to be inspected;

a neutron pulse generator (12) configured to irradiate a surface (20) of a material;

a plurality of beta radiation detectors (24) tuned to the defined energy of photogenerated electron energy produced by an electron generation window (36) located between an active region (42) of the beta radiation detectors (24) and a surface (20) being inspected, the beta radiation detectors being positioned in a predetermined pattern on the surface of the material to which the mixture is applied, the plurality of beta radiation detectors each providing an output indicative of receipt of an instantaneous gamma release (38) of the defined energy in a surface region viewed by a corresponding one of the plurality of beta radiation detectors; and

-a beta radiation detector output, from which said reception is used to determine a characteristic of said defect (22).

10. The apparatus of claim 9, wherein the characteristic is at least one of a location, a length, and a depth of the defect (22) on the surface (20).

11. The apparatus of claim 10, wherein the depth of the defect (22) is determined from the received intensity.

12. The apparatus of claim 9, wherein the neutron pulse generator (12) is a neuston-type neutron pulse generator.

13. The apparatus of claim 9 wherein the beta radiation detector (24) includes a high atomic number sacrificial material (36) as an electron radiator located between the surface (20) being inspected and the active portion (42) of the beta radiation detector.

14. The apparatus of claim 13 wherein the beta radiation detector is a silicon carbide (SiC) detector, the type of material used in the sacrificial layer (36) of the beta radiation detector (24), the distance from the active detector region (42), and the thickness being selected to ensure that a majority of electrons generated by photoelectric absorption of the desired emitted instantaneous gamma radiation energy (38) come to a complete stop inside the active region of the SiC detector.

15. The apparatus of claim 13, wherein the sacrificial material (36) is platinum or tungsten.

Technical Field

The present invention relates generally to the detection of cracks in irradiated surfaces, and more particularly to the non-destructive inspection of irradiated components to determine structural flaws.

Background

When handling of highly radioactive components or containers of radioactive material is required, it is important to ensure that the structural integrity of the component or material container is assessed to reduce the likelihood of the radioactive material running away or losing containment. Due to the impact of the radiation field on equipment evaluation and operability, it is difficult to assess the structural integrity of radioactive components or containers of radioactive materials located in high radiation fields using standard visual and ultrasonic non-destructive inspection (NDE) techniques. There is a need to provide an apparatus for assessing the structural integrity of radioactive components and containers of radioactive materials using a method and apparatus suitable for high radiation environments.

Disclosure of Invention

A method for non-destructively detecting structural defects in the surface of an irradiated material includes the step of applying to the surface of the material a liquid fracture penetrating agent that emits a transient gamma-release of defined energy, preferably having a high nitrogen content, or mixed with a chemical species having a large amount of isotopes having a large fast neutron transient capture gamma-emission cross-section, such as scandium, vanadium, manganese, or titanium. Then irradiating the surface with a neutron pulse generator and positioning beta radiation detectors tuned to the defined energy in a regular pattern on the surface of the material to which the mixture is applied; the plurality of beta radiation detectors each provide an output indicative of receipt of the instantaneous gamma release of the defined energy in a surface region viewed by a corresponding one of the plurality of beta radiation detectors. The receiving is used to determine the characteristics of the defect. In one embodiment, the characteristic is the location and length of the defect on the surface. In another embodiment, the feature is a depth of a defect on the surface. Preferably, the depth of the defect is determined from the received intensity.

In one such embodiment, the mixture is absorbed into the surface by capillary absorption. Desirably, the neutron pulse generator is a neutron pulse generator of the neutered (neutron) type. Preferably, the electron radiator is formed by disposing a high atomic number sacrificial material between the surface and the active portion of the beta radiation detector. Desirably, the beta radiation detector is a silicon carbide (SiC) detector, the type of material used in the sacrificial layer of the beta radiation detector, the distance from the active detector region, and the thickness being selected so as to ensure that a majority of electrons generated by photoelectric absorption of the desired emitted transient gamma radiation energy are completely stopped in the active region of the SiC detector. In one such embodiment, the sacrificial material is platinum or tungsten.

Drawings

A further understanding of the present invention can be obtained from the following preferred embodiments when read in conjunction with the appended drawings. Wherein

FIG. 1 is a schematic representation of the layout of the apparatus of the present invention; and

FIG. 2 is a schematic layout of SiC detectors and preamplifiers used in the SiC detector array of FIG. 1.

Detailed Description

The operation of the present invention is based on a novel combination of dye penetrant crack detection, transient neutron-gamma (γ) radiation detection, and planar Computed Tomography (CT) techniques. The system also uses a novel SiC tuned gamma intensity detection method and a preamplifier for very small SiC signal outputs based on solid state vacuum tube technology. The preferred embodiment is as follows: non-corrosive fracture penetrants, preferably of high nitrogen content, or such as those available from the Dynaflux Quality Products Company of Cartersville, georgia, mixed with a chemical species containing a large proportion of large fast neutron transient capture gamma emission cross-sections (e.g., scandium, vanadium, manganese, titanium), are applied as appropriate under controlled temperature and pressure to ensure that the penetrants are in a liquid state when they reach the surface being inspected. The system described in this disclosure has the ability to spray the mixture at high pressure onto the surface to be inspected to allow the substance to be applied without the system hardware actually touching the surface. A Neutron Pulse Generator (NPG) module of the "neuston" type developed by Sandia National Laboratory ("Innovation markplace", 2014 9, vol 1, No. 3) contained in the measurement assembly was placed by the operator at a radial position within one inch of the surface, which is known to be within 0.1mm of a fixed surface reference point on the surface. Specially configured SiC radiation detector arrays (e.g., 1 mm) for NPG modules²A 100 x 100 square of detectors, such as that described in patent application No. 13/769,401 filed on 2013, 2, 18, entitled "Solid State Radiation Detector With Enhanced Gamma Radiation sensing", whose location is known to be within 0.05mm of a reference point on the NPG assembly, are tuned to measure primarily the intensity of electrons generated by absorption of photoelectrons generated in the material between the Gamma Radiation emitted from the transient Gamma emitting isotope in the fracture penetrant mixture and the active region of the SiC Detector, as shown in fig. 1.

The nondestructive inspection system 10 of the present invention has a spray system 18 that is movable over the surface 20 of the material to be inspected to crack the penetrant solution 30 on the surface. The neutron pulse generator 12 emits a pulse stream that reacts with isotopes in the fracture penetrant solution 30 to emit transient gamma radiation that is detected by the SiC radiation detector 24. The output of the SiC radiation detector is fed to a preamplifier 26, the output of which is sent to processing electronics, which interprets the intensity and variation of the received signal to determine the presence and location, length and depth of the crack. Tuning of the SiC beta (β) radiation capability sensitivity is achieved by placing a sacrificial material of a prime atomic number, such as platinum or tungsten, as an electron radiator between the active portion and the surface of the SiC detector. The type of material used in the sacrificial layer of the detector, the distance from the active detector area, and the thickness are selected to ensure that the majority of electrons generated by photoelectron absorption in the sacrificial layer of the desired emitted transient gamma radiation energy are stopped entirely within the active area of the SiC detector. This can be achieved by the person skilled in the art by: the distance between the surface of the electron radiator and the front surface of the aluminum of the SiC overlying the schottky interface region is suitably adjusted so that electrons having less than full gamma energy are less likely to reach and stop in the active volume of the SiC detector. This will ensure that the measured detector output is proportional to the amount of penetrant material in the fracture, and thus the dimensional properties of the fracture, seen by each detector. Fig. 2 provides a schematic diagram of a SiC detector and associated array geometry.

The SiC detector 24 receives the transient gamma radiation 38 through the sacrificial material 36, the sacrificial material 36 converts the transient gamma radiation to generate electrons by photoelectron absorption, wherein the distance of the sacrificial material 36 from the schottky contact is variable to ensure that all electrons are captured. In this embodiment, the electrons travel through the approximately 10 μm thick N-doped SiC 40 to the substrate 42 where they are collected by the gold-backed ohmic contact 44, and the output current 28 is transmitted through the preamplifier 26 to the processing electronics 46. The relative measured intensity data obtained by each very small and precisely positioned SiC detector in the detector array after one or more triggering of the neutron pulse generator will be used to determine the dimensional characteristics of the defect. The Detector signal outputs will be input into separate preamplifiers that are integrated into a neutron pulse generator structure utilizing a miniaturized design, such as that described In U.S. patent application No.14/996,667 entitled "In-Containment Ex-Core Detector System," filed 1/15/2016. The amplified measurement detector current signal is then sent to a measurement and analysis system located at a convenient location outside the high radiation area. Using a planar CT algorithm, an application-specific correlation between desired measured crack size attributes (e.g., depth, width, length) is determined from the SiC detector array geometry and the relative measurements of each detector in the array.

While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular embodiments disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the appended claims and any and all equivalents thereof.