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WO1998057194A1 - Modulation/activation neutroniques pour mesurer le contenu fissile et la vitesse d'ecoulement d'une matiere fissile - Google Patents

Modulation/activation neutroniques pour mesurer le contenu fissile et la vitesse d'ecoulement d'une matiere fissile Download PDF

Info

Publication number
WO1998057194A1
WO1998057194A1 PCT/US1998/011613 US9811613W WO9857194A1 WO 1998057194 A1 WO1998057194 A1 WO 1998057194A1 US 9811613 W US9811613 W US 9811613W WO 9857194 A1 WO9857194 A1 WO 9857194A1
Authority
WO
WIPO (PCT)
Prior art keywords
conduit
neutron
source
detector
gamma ray
Prior art date
Application number
PCT/US1998/011613
Other languages
English (en)
Inventor
John T. Mihalczo
James A. Mullens
Jose A. March-Leuba
Original Assignee
Lockheed Martin Energy Research Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Lockheed Martin Energy Research Corporation filed Critical Lockheed Martin Energy Research Corporation
Priority to AU78186/98A priority Critical patent/AU7818698A/en
Publication of WO1998057194A1 publication Critical patent/WO1998057194A1/fr

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/704—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow using marked regions or existing inhomogeneities within the fluid stream, e.g. statistically occurring variations in a fluid parameter
    • G01F1/708—Measuring the time taken to traverse a fixed distance
    • G01F1/712—Measuring the time taken to traverse a fixed distance using auto-correlation or cross-correlation detection means
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/704—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow using marked regions or existing inhomogeneities within the fluid stream, e.g. statistically occurring variations in a fluid parameter
    • G01F1/7042—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow using marked regions or existing inhomogeneities within the fluid stream, e.g. statistically occurring variations in a fluid parameter using radioactive tracers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/76—Devices for measuring mass flow of a fluid or a fluent solid material
    • G01F1/86—Indirect mass flowmeters, e.g. measuring volume flow and density, temperature or pressure
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T3/00—Measuring neutron radiation
    • G01T3/06—Measuring neutron radiation with scintillation detectors

Definitions

  • the present invention relates generally to the field of flow measurement within a conduit, such as, for example, a pipe. More particularly, the present invention relates to flow measurement in a conduit that does not require penetration of the conduit perimeter. Specifically, a preferred implementation of the present invention relates to neutron modulation/activation of the material that is being conducted within the conduit. The activity of the material is subsequently measured. The present invention thus relates to a flow measurement system of the type that can be termed nonintrusive. 2. Discussion of the Related Art Historically, it was known in the field of materials handling to measure flow rates within conduits. (1 2) However, all the prior art flow measurement methods, including the ultrasonic approach, are intrusive. (3) All the prior art flow measurement methods are intrusive in that they require penetration of the conduit perimeter.
  • Flow measurements of uranium hexafluoride (UF 6 ) gas within a pipe are performed by installing flow monitoring hardware inside the pipe.
  • pressure differential measurement hardware typically includes an orifice that passes through a sidewall of the conduit with pressure measured on each side of the orifice.
  • this approach requires penetration of the wall.
  • ultrasonic measurement the acoustic energy must be coupled into the gas. This is usually done by installing an ultrasonic transducer inside the conduit. This approach also requires penetration of the wall.
  • the invention uses a modulated thermal neutron source that is arranged in an external configuration, relative to the conduit.
  • the thermal neutrons activate the material within the conduit (e.g., UF 6 gas).
  • a detector of emitted radiation which is also arranged in an external configuration, detects the residual activation of the material at a downstream location.
  • Gamma ray detectors are used in this invention but detectors of of other emitted radiation can be used. For example, neutron detectors for counting delayed neutrons downstream could be used although the delayed neutron yield is lower than the delayed gamma yield.
  • the invention provides an important advantage versus the prior art approaches because both the mass flow rate and the fissile content (e.g., 235 U) of difficult to handle materials (e.g., UF 6 ) can be determined without penetrating the conduit.
  • the fully external nature of the apparatus makes maintenance easier.
  • Another advantage of the invention is that it can be attached and detached in a portable manner. Activation of the fluid in the pipe by external modulated radiation sources and correlating the signal downstream with the modulation also results in much shorter measurement times than are achievable by relying on the inherent radioactivity of a fluid and using two detectors on a pipe and correlating fluctuation produced by density or turbulence in the pipe.
  • FIG. 1 illustrates a schematic view of a system, representing an embodiment of the present invention
  • FIG. 2 illustrates a plot of correlated component of a gamma ray detector resonse and a modulation of a source, representing an embodiment of the present invention
  • FIG. 3 illustrates a block diagram of an exemplary system, representing an embodiment of the present invention.
  • the invention can measure both the flow velocity of a material (e.g.,
  • the invention can determine the mass flow rate of that fissile isotope in the conduit.
  • the invention activates the material in the conduit with a modulated thermal neutron source and detects the residual activation downstream with a gamma ray sensitive detector.
  • the gamma detector response is a function of delayed gamma rays resulting from fission induced upstream near the modulated thermal neutron source.
  • the detector response is correlated to the modulation of the source.
  • FIG. 1 shows a high level schematic view of an embodiment of the invention.
  • a thermal neutron source 110 is located near a conduit 120.
  • the material flowing through the conduit 120 includes UF 6 .
  • conduit is recited generically for a variety of materials handling structures whose species include, for example, ducts, hoses, tubes, pipes, and the like.
  • the source 110 includes sufficient 252 Cf to produce a flux of, for example, approximately 1 x 10 7 n/sec.
  • Other sources of neutrons, or other particles can be used to activate the material moving in the conduit 120.
  • Pu and Li e.g., more than one
  • a plurality of sources could be provided near the conduit 120.
  • Coupling the activation energy from the source 110 to the UF 6 gas in the conduit 120 is not a problem.
  • Neutrons pass through most structural materials.
  • the thermal neutrons that reach the interior of the conduit 120 induce fission in the UF 6 containing material flowing through the conduit 120.
  • the source 110 can be enclosed in a neutron moderator block 115 which is used to optimize the efficiency of the source neutrons to induce fission in the 235 U of the UF 6 .
  • the neutron moderator block 115 slows down the neutrons and reflects some of those moving away from the pipe back towards the pipe where they can induce fission in the UF 6 gas.
  • the neutron moderator block 115 includes polyethylene. Other neutron moderators materials and moderator blocks of alternative construction may be used.
  • the source 110 is modulated by moving a mechanism 130 that is located between the source 110 and the conduit 120. Although two such mechanisms 130 are shown in FIG. 1 , they are substantially the same and only one will be described in detail.
  • the mechanism 130 includes a neutron absorbing material 140 (e.g., cadmium) that is located between the source of thermal neutrons 110 and the conduit 120.
  • the mechanism 130 can be moved between i) a closed position (shown in FIG. 1) between the moderator block 115 and the conduit 120 and ii) an open position (not shown in FIG. 1) away from the moderator block 115.
  • This movement can be effected by an electric motor that is controlled by a processor that is part of a data acquisition computer. (The electric motor, the processor, and the data acquisition computer are not shown in FIG. 1.)
  • the mechanism 130, the electric motor and the computer compose a shutter that provides the source modulation.
  • the shutter can switch between i) a material that is opaque to thermal neutrons (e.g., cadmium) and ii) a material that is transparent to thermal neutrons.
  • the source modulation is a binary sequence that results in an input frequency spectrum associated with the source modulation frequency up to about 1 Hz.
  • the source modulation can be checked by independently detecting the position of the mechanism 130 which includes the neutron absorbing material 140.
  • the source modulation can be checked by one or more neutron detectors (not shown in FIG. 1) that measure the transmission of thermal neutrons from the source 110 to the conduit 120. In either event, the source modulation is a first signal that is input to the processor.
  • Delayed gamma rays from the fission in the material within the conduit 120 are detected downstream with a gamma ray detector 150 that is located near the conduit 120. Detecting gamma rays from the downstream UF 6 gas is not made problematic by the presence of the conduit 120. The gamma rays of interest pass through most structural materials.
  • the detector 150 can mounted directly on the conduit 120.
  • the detector 150 can be a commercially available detector (e.g, Nal or BGO) set to count gamma rays with energies above 0.3 MeV. In this way, the proliferation of 186 KeV gamma rays from the alpha decay of 235 U are not counted.
  • the output from the detector 150 is a second signal that is input to the processor. In fact, there can be a collection of detectors spaced around the conduit
  • the resulting plurality of output signals are summed and input to the processor as the second signal.
  • Gamma ray shielding 160 (e.g., lead) is advantageously provided between the source 110 and the detector 150.
  • the shielding 160 reduces the background noise from source 110 that is detected by detector 150.
  • the source modulation produces a modulation of a delayed gamma ray signal from the material in the conduit 120 which is correlated to the source modulation.
  • Cross correlation measurements between the detector 150 and the modulation of the thermal neutrons from the source 110 are measured.
  • the time lag of the cross correlation function gives the flow velocity and the amplitude of the signal yields the active species (e.g., 235 U) content of the material.
  • the product of the 235 U content and the flow velocity gives the 235 U mass flow rate.
  • This activation of the fissile material by a modulated source of thermal neutrons can also be used to obtain flow velocity and mass flow from any gases or liquids, or slurries, which emit delayed gamma rays from neutron absorption.
  • a device in accordance with the invention be mounted on (i.e., directly, or closely, adjacent) the outside of a conduit, the device does not necessarily need to be in contact with the conduit.
  • Such a device can be installed on existing pipes without modification of the pipes.
  • FIG. 2 is a plot of the correlated component of the gamma ray detector response and the modulation of the source, assuming that there is no detection background.
  • the lag of the correlated component of the detector response is related to the time it takes the gas flow from the source to the detector. For turbulent flow there will be a single time lag and the ratio between the separation distance and this time lag gives the velocity. For laminar flow, there will be a dispersion of time lags and the average flow velocity can be obtained using a model of laminar flow in the pipe.
  • the amplitude of the correlated signal is directly proportional to the fissile content and to other known parameters such as pipe diameter, source strength, detector efficiency, and fission fragments decay constants. Thus both the flow velocity and the fissile content can be obtained from these measurements.
  • this example application of the invention uses the correlated component of the detector response, a similar data analysis yielding the same results can be performed using the cross correlation function or the cross power spectral density between the radiation detector and the source modulation signal.
  • FIG. 3 shows an electronic interface suitable for use with the invention.
  • a position detector 310 for independently determining the neutron absorber (shutter) position inputs a first signal to a processor 320.
  • the first signal is the source modulation signal.
  • the processor 320 can be a personal computer (PC) based processor and is the controller of the neutron absorber (shutter) position.
  • the processor 320 outputs a control of shutter position signal to a motor 330 that adjusts the neutron absorber (shutter) position.
  • An inorganic scintillator 340 (e.g., Nal or BGO with lead shield) is connected to a photomultiplier tube 345.
  • the scintillator 340 detects delayed gamma rays from the activated material.
  • the photomultiplier tube 345 is connected to a base 350.
  • the base 350 is connected to a power supply 355.
  • scintillator 340, photomultiplier tube 345, base 350 and supply 355 compose a gamma ray detector 360.
  • the gamma ray detector 360 is connected to a preamplifier 365. In fact, a plurality of detectors can be arranged around a single conduit and the summation of their signals sent to the preamplifier 365.
  • the preamplifier 365 is connected to an amplifier 370.
  • the amplifier 370 is connected to a discriminator 375.
  • the discriminator 375 is connected to a pulse counter 380 that is part of the processor 320.
  • the gamma ray detector 360, the preamplifier 365, the amplifier 370, and the discriminator 375 compose a gamma ray detection channel.
  • the gamma ray detection channel can be a standard commercially available detection-system electronics from ORTEC or TENNELEC.
  • the gamma ray detection channel outputs a second signal to the processor 320.
  • a flow measurement system representing an embodiment of the invention is cost effective and advantageous for at least the following reasons.
  • the invention is nonintrusive (i.e., no penetration of the pipe required).
  • the invention is easily installed and can be embodied in a portable package so as to be readily attachable-detachable without modification of the conduit to which it is attached.
  • These external devices make maintenance easy, since all components are outside the pipe which contains the radioactive materials.
  • the individual components need not be formed in the disclosed shapes, or assembled in the disclosed configuration, but could be provided in virtually any shape, and assembled in virtually any configuration. Further, the individual components need not be fabricated from the disclosed materials, but could be fabricated from virtually any suitable materials. Further, although the apparatus described herein is a physically separate module, it will be manifest that the apparatus may be integrated into the apparatus with which it is associated. Furthermore, all the disclosed elements and features of each disclosed embodiment can be combined with, or substituted for, the disclosed elements and features of every other disclosed embodiment except where such elements or features are mutually exclusive.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Molecular Biology (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Measurement Of Radiation (AREA)

Abstract

Cette invention se rapporte à des systèmes et à des procédés servant à réaliser des mesures du contenu fissile et de la vitesse d'écoulement d'une matière fissile par modulation/activation neutroniques. On utilise à cet effet un appareil comprenant une source (110) de neutrons placée à l'extérieur d'un conduit (120): un matériau (130) absorbant les neutrons placé de façon déplaçable entre la source de neutrons et le conduit; un détecteur (150) de rayons gamma placé à proximité adjacente du conduit et un écran (160) à rayons gamma placé entre le détecteur de rayons gamma et la source de neutrons. Ces systèmes et ces procédés présentent des avantages étant donné qu'aucune pénétration du conduit n'est nécessaire, que l'appareil peut être facilement monté et démonté sans modification du conduit sur lequel il est monté et que la durée des mesures est beaucoup plus courte que dans les techniques avec pénétration.
PCT/US1998/011613 1997-06-13 1998-06-11 Modulation/activation neutroniques pour mesurer le contenu fissile et la vitesse d'ecoulement d'une matiere fissile WO1998057194A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU78186/98A AU7818698A (en) 1997-06-13 1998-06-11 Neutron modulation-activation for fissile material flow velocity and fissile content measurement

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US87423097A 1997-06-13 1997-06-13
US08/874,230 1997-06-13

Publications (1)

Publication Number Publication Date
WO1998057194A1 true WO1998057194A1 (fr) 1998-12-17

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WO (1) WO1998057194A1 (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8080808B2 (en) 2006-07-18 2011-12-20 BOSS Physical Sciences, LLC Remote detection of explosive substances
US8357910B2 (en) 2008-11-24 2013-01-22 Boss Physical Sciences Llc Background signal reduction in neutron fluorescence applications using agile neutron beam flux
US8410451B2 (en) 2009-04-09 2013-04-02 Boss Physical Sciences Llc Neutron fluorescence with synchronized gamma detector
US8785864B2 (en) 2009-09-22 2014-07-22 Boss Physical Sciences Llc Organic-scintillator compton gamma ray telescope
CN108086970A (zh) * 2017-12-27 2018-05-29 中国石油天然气股份有限公司 一种脉冲氧活化测井自相关解释方法和装置

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2640936A (en) * 1950-02-07 1953-06-02 Pajes Wolf Szmul Method and apparatus for indicating the movement of material
US3577158A (en) * 1969-01-07 1971-05-04 Industrial Nucleonics Corp Mass flow rate measuring utilizing the scattering cross section of a material for fast neutrons
US4200789A (en) * 1978-06-29 1980-04-29 Texaco Inc. Measuring oil and water cuts in a multiphase flowstream with elimination of the effects of gas in determining the liquid cuts

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2640936A (en) * 1950-02-07 1953-06-02 Pajes Wolf Szmul Method and apparatus for indicating the movement of material
US3577158A (en) * 1969-01-07 1971-05-04 Industrial Nucleonics Corp Mass flow rate measuring utilizing the scattering cross section of a material for fast neutrons
US4200789A (en) * 1978-06-29 1980-04-29 Texaco Inc. Measuring oil and water cuts in a multiphase flowstream with elimination of the effects of gas in determining the liquid cuts

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8080808B2 (en) 2006-07-18 2011-12-20 BOSS Physical Sciences, LLC Remote detection of explosive substances
US8288734B2 (en) 2006-07-18 2012-10-16 Boss Physical Sciences Llc Remote detection of explosive substances
US8357910B2 (en) 2008-11-24 2013-01-22 Boss Physical Sciences Llc Background signal reduction in neutron fluorescence applications using agile neutron beam flux
US8410451B2 (en) 2009-04-09 2013-04-02 Boss Physical Sciences Llc Neutron fluorescence with synchronized gamma detector
US8785864B2 (en) 2009-09-22 2014-07-22 Boss Physical Sciences Llc Organic-scintillator compton gamma ray telescope
CN108086970A (zh) * 2017-12-27 2018-05-29 中国石油天然气股份有限公司 一种脉冲氧活化测井自相关解释方法和装置
CN108086970B (zh) * 2017-12-27 2021-04-27 中国石油天然气股份有限公司 一种脉冲氧活化测井自相关解释方法和装置

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