Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
  • G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
  • G01T1/16—Measuring radiation intensity
  • G01T1/20—Measuring radiation intensity with scintillation detectors
• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21C—NUCLEAR REACTORS
  • G21C17/00—Monitoring; Testing ; Maintaining
  • G21C17/06—Devices or arrangements for monitoring or testing fuel or fuel elements outside the reactor core, e.g. for burn-up, for contamination
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E30/00—Energy generation of nuclear origin
  • Y02E30/30—Nuclear fission reactors

Definitions

• the present invention relates to a method for simulating the response of a radiation detector emitted by radioactive objects as well as to a method for monitoring nuclear fuel elements using this simulation.
• nuclear fuel rods which comprise stacks of pellets of this fuel, these pellets emitting ⁇ radiation.
• the detector of this chain is for example that which is described in the documents FR-A-2437002, EP-A-0009450 and JP-A-1527161 and which comprises an annular scintillator, this the latter preferably being sodium iodide activated with thallium Nal (Tl).
• This calibration also consists in constructing particular pencils and passing them past the detector to obtain what is called in statistics regression lines which here give the detector's response to the mixtures of powders making up the pellets, according to the content of their components (uranium and plutonium for example), for homogeneous portions of pencils or for pellets of one category isolated from a group of pellets of another category.
• the object of the present invention is to remedy the above drawbacks by proposing a method making it possible to economically control nuclear fuel rods or, more generally, nuclear fuel elements.
• this method the preliminary calibration of the measuring chain is eliminated and replaced by a simulation of the response of the detector of the measuring chain, that is to say of the counting carried out by this measuring chain.
• the present invention firstly relates to a method of simulating the response of a radiation detector emitted by radioactive objects, these objects containing radioelements or mixtures thereof, this process being characterized in that:
• the operating characteristics of the radiation received are determined, - radioelements or mixtures of these are chosen from among those whose spectra have been stored, and
• the detection characteristics and the operating characteristics are processed so as to reproduce step by step the radiations emitted for selected radioelements or mixtures of radioelements, to obtain the simulated response of the detector.
• the detection characteristics include data representative of the thicknesses crossed by the radiations before their detection.
• the operating characteristics include the opening angle of the detector, the energy bands detected and the electronic amplification characteristics of the detector.
• regression lines are also constructed from the simulated response.
• the detector is for example a ⁇ radiation detector and the invention applies all particularly in the case where said objects are nuclear fuel elements.
• the invention also relates to a method for controlling a set of nuclear fuel elements implementing the simulation method.
• the corrected response is corrected using the response of the detector obtained during the calibration, and
• the elements are for example nuclear fuel rods, these rods comprising stacks of pellets of this nuclear fuel.
• the detector comprises for example an annular scintillator and it is for example possible to use a sodium iodide scintillator.
• FIG. 1 is a schematic view of a detector for which the response is to be simulated, along a plane perpendicular to the axis of this detector and •
• Figure 2 is a schematic view of the detector shown in its shielded enclosure, along a plane parallel to its axis.
• each pencil is a stack of pellets containing for example uranium oxide and / or plutonium oxide. These pencils are checked by pellets.
• the detector described in the documents mentioned above is used for example. The structure of this detector is recalled in what follows with reference to FIGS. 1 and 2.
• ⁇ radiation detector which includes a scintillator 1 of annular shape, associated with three photomultipliers 2, 3 and 4.
• the detector also comprises a diaphragm or collimator 6. This diaphragm limits the flux of ⁇ radiation emitted by this patch towards the scintillator to approximately the length of each patch.
• the three photomultipliers are regularly distributed around the periphery of the scintillator. The outputs of these photomultipliers are connected to electronic measuring means forming a counting chain 7 to which we will return later.
• the scintillator is divided into identical sectors 10, 11 and 12 optically isolated from one another and respectively associated with photomultipliers 2, 3 and 4.
• This scintillator is of preferably sodium iodide type, activated with thallium.
• a shielded enclosure E protecting the detector against external ⁇ radiation that could disturb the measurements.
• the pellets 5 of the pencil 16 are contained in a sheath 17. This pencil is moved by means not shown in a direction 18.
• two annular parts 19 and 20 which constitute the diaphragm 6 and are opaque to radiation ⁇ . These parts have a spacing e which can be adjusted by means not shown. The displacement of the pencil to be checked takes place in the axis 21 of the detector.
• the counting chain 7 comprises amplifier-stabilizers 22 respectively associated with the photomultipliers, a summator 23, the inputs of which are connected to these amplifiers, and single-channel analyzers 24 (four in the example of FIG. 2) whose inputs are connected at the output of the summator 23.
• a computer 25 is provided for processing the signals supplied by these single-channel analyzers 24. This computer is associated with a memory 26 and with display means 27 and also provided for implementing the software used for simulating the detector response.
• the simulation of the response of detector D is purely digital and is based on the software which is stored in memory 26 and into which we introduce: (a) radioactive emission spectra representative of certain radioelements or their mixtures and which are also stored in memory 26, (b) detection characteristics, in the form of coefficients and data modeling in particular the thicknesses crossed by ⁇ rays and therefore representing the attenuation, (c) radiation exploitation characteristics ⁇ received, representing in particular the opening angle of the detector, the energy bands detected and the amplification of the electronics and (d) a mathematical engine to reproduce step by step the ⁇ radiation emitted for the selected radioelements or the mixtures of selected radioelements.
• the mathematical engine makes it possible to make a Gaussian distribution of energy according to the resolution.
• the parameters relating to the pellet thus checked are introduced into the computer.
• the computer calculates a spectrum for a region of interest (i.e. one or more energy bands of interest). If the count obtained by simulation is too strong or on the contrary not strong enough we correct the fictitious mass until obtaining the same count as with the really controlled pellet (the fictitious mass being the mass of pellet for which one wants to simulate a response on the part of the detector and involving not the shape of the spectrum but the amplitude of that -this). When we obtain an equivalent count, that is to say the correct fictitious mass, we save this value which allows the calculation of all the other points of the regression lines. Many other detectors can be used in place of the sodium iodide annular scintillator detector.
• the invention makes it possible to simulate and control other fuel elements than the aforementioned rods, the pellets of which are generally cylindrical.
• the present invention is not limited to the simulation and control of nuclear fuel elements. It makes it possible to simulate and control many other radioactive objects such as, for example, mass-produced containers containing radioactive material.
• Z ( k) atomic number of the attenuating element (k)
• p (k) density of the attenuating element (k)
• a (k ) atomic mass of the attenuating element (k)
• N 1200 vn values are calculated by drawing random numbers according to a Gaussian distribution centered on a mean value equal to Energy (j ') and having a standard deviation equal to
• Front diffusion (-, ' ⁇ ) ⁇ f (NaI) xZ (hbI) x final flux (1 , - ,, w x P (Nai,, Ni) r A (NaI)
• N 1200 vn values are calculated by drawing random numbers according to a Gaussian distribution centered on a mean value equal to Energy, ⁇ -) and having a standard deviation equal to
• N 1200 vn values are calculated by drawing random numbers, following a Gaussian distribution centered on an average value equal to Energy, -, '" , and having a standard deviation equal to
• a region of interest or energy band of interest for example from 75 keV to

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• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• High Energy & Nuclear Physics (AREA)
• Plasma & Fusion (AREA)
• General Engineering & Computer Science (AREA)
• Health & Medical Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• General Physics & Mathematics (AREA)
• Molecular Biology (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Measurement Of Radiation (AREA)
• Monitoring And Testing Of Nuclear Reactors (AREA)

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Citations (6)

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• 1998
  • 1998-08-18 FR FR9810513A patent/FR2782562B1/fr not_active Expired - Fee Related
• 1999
  • 1999-08-17 DE DE69938455T patent/DE69938455T2/de not_active Expired - Lifetime
  • 1999-08-17 RU RU2001107118/28A patent/RU2219565C2/ru not_active IP Right Cessation
  • 1999-08-17 JP JP2000566697A patent/JP4731688B2/ja not_active Expired - Fee Related
  • 1999-08-17 US US09/763,217 patent/US6704385B1/en not_active Expired - Fee Related
  • 1999-08-17 WO PCT/FR1999/002000 patent/WO2000011496A1/fr not_active Ceased
  • 1999-08-17 ES ES99936745T patent/ES2306520T3/es not_active Expired - Lifetime
  • 1999-08-17 EP EP99936745A patent/EP1105751B8/fr not_active Expired - Lifetime
• 2003
  • 2003-12-11 US US10/734,416 patent/US20040136486A1/en not_active Abandoned

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