# US 12,111,432 B2 · System for measuring fast neutron fluence for a nuclear reactor, associated installation, measurement method and computer program product > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,111,432 B2 - Document ID: US12111432B2 - Status: Granted - Kind: B2 - Application number: 17/789,545 - Filed: 2020-12-29 - Published: 2023-01-19 - Granted: 2024-10-08 - Earliest claimed: 2019-12-30 - Assignees: Commissariat A L'energie Atomique Et Aux Energies Alternatives - Applicants: Commissariat A L'energie Atomique Et Aux Energies Alternatives - Inventors: Jonathan Dumazert; Sylvain Magne; Romain Coulon; Guillaume Laffont - Web page: https://patentgrep.com/patent/US12111432B2 ## CPC - G01T 3/00: Measuring neutron radiation (G01T5/00 takes precedence) - G01T 3/006: {using self-powered detectors (for neutrons as well as for Y- or X-rays), e.g. using Compton-effect (Compton diodes) or photo-emission or a (n,B) nuclear reaction (radioisotopic generators G21H1/00, e.g. G21H1/02, G21H1/04; photo-tubes H01J40/00; thermionic generators H01J45/00)} - G01N 23/222: using neutron activation analysis [NAA] - G21C 17/108: Measuring reactor flux - Y02E 30/30: Nuclear fission reactors - G01T: MEASUREMENT OF NUCLEAR OR X-RADIATION (radiation analysis of materials, mass spectrometry G01N23/00; tubes for determining the presence, intensity, density or energy of radiation or particles H01J47/00) - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) - G21C: NUCLEAR REACTORS (fusion reactors, hybrid fission-fusion reactors G21B; nuclear explosives G21J) - Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION ## Abstract A measuring system includes a detector having an optical waveguide including a primary dopant capable of transmuting, by neutron capture, into a stable secondary dopant that is less neutron-absorbent than the primary dopant, a moderation layer suitable for slowing down fast neutrons, and an analysis device connected to the detector. The analysis device is configured to inject, into the waveguide, an interrogation wave having a wavelength corresponding to an absorption peak of the secondary dopant, detect a response wave emitted by the waveguide, calculate, from the detected response wave, a piece of information relating to a concentration of secondary dopant in the waveguide, and, based on the information relating to the calculated concentration of secondary dopant, determine a fluence of fast neutrons during a predetermined secondary period. ## Claims ### Claim 1 A system for measuring fast neutron fluence for a nuclear reactor, comprising at least one detector and an analysis device connected to each detector, each detector comprising: an optical waveguide including a primary dopant capable of transmuting, by neutron capture, into a secondary dopant, the secondary dopant having an atomic number different from that of the primary dopant, the secondary dopant being stable and being less neutron-absorbent than the primary dopant; and a moderation layer configured to slow down fast neutrons and arranged between the optical waveguide and an external surface of a wall of a reactor vessel; and the analysis device being configured, for each detector, to: inject, into a corresponding optical waveguide, a secondary interrogation wave having a secondary wavelength at which the secondary dopant has an absorption peak, a smallest difference between the secondary wavelength and a wavelength corresponding to an absorption peak of the primary dopant being greater than or equal to a first predetermined minimum difference; detect a secondary response wave emitted by the corresponding optical waveguide from the secondary interrogation wave; calculate, from the detected secondary response wave, a piece of information relating to a concentration of secondary dopant in the corresponding optical waveguide; and based on the calculated piece of information relating to the concentration of the secondary dopant, and conversion data relating to the nuclear reactor, determine a fast neutron fluence experienced by the wall of the vessel for a predetermined secondary period. ### Claim 2 (depends on 1) The measurement system according to claim 1, wherein the primary dopant is thulium and/or europium, the secondary dopant being ytterbium or samarium, respectively. ### Claim 3 (depends on 1) The measurement system according to claim 1, further including a thermal neutron barrier layer configured to be arranged between the moderation layer and the external surface of the wall of the vessel. ### Claim 4 (depends on 3) The measurement system according to claim 3, wherein the thermal neutron barrier layer is made of cadmium. ### Claim 5 (depends on 1) The measurement system according to claim 1, wherein the analysis device is configured, for each detector, to determine, by time-domain reflectometry or by frequency-domain reflectometry, from the detected secondary response wave, an attenuation profile of the corresponding optical waveguide at the secondary wavelength according to a position along the optical waveguide, and the analysis device is configured to calculate the piece of information relating to the concentration of secondary dopant from the determined attenuation profile at the secondary wavelength. ### Claim 6 (depends on 1) The measurement system according to claim 1, wherein the analysis device is also configured, for each detector, to: inject, into the corresponding optical waveguide, one or two optical complementary secondary interrogation waves each having a complementary secondary wavelength corresponding to a respective foot of the absorption peak associated with the secondary wavelength; for each complementary secondary interrogation wave, detect a corresponding complementary secondary response wave emitted by the corresponding optical waveguide; and determine, by time-domain reflectometry or by frequency-domain reflectometry, from each detected complementary secondary response wave, an attenuation profile of the corresponding optical waveguide at the complementary secondary wavelength according to a position along the optical waveguide, the analysis device being configured to calculate the piece of information relating to the concentration of secondary dopant from a result of a correction of the attenuation profile at the secondary wavelength by the attenuation profile associated with each complementary secondary wavelength. ### Claim 7 (depends on 1) The measurement system according to claim 1, wherein the analysis device is configured, for each detector, to determine, from the detected secondary response wave, a secondary total amount of fluorescence light emitted by the corresponding optical waveguide over its entire length in a secondary fluorescence spectral band associated with the secondary dopant, the piece of information relating to the concentration of secondary dopant in the corresponding optical waveguide being calculated from the total secondary amount. ### Claim 8 (depends on 1) The measurement system according to claim 1, wherein for each detector, the primary dopant is also capable of being transformed into a tertiary dopant by irradiation by a photon, the tertiary dopant having a same atomic number as the primary dopant but a different valence; and the analysis device is also configured, for each detector, to: inject, into the corresponding optical waveguide, an optical tertiary interrogation wave having a tertiary wavelength at which the tertiary dopant has an absorption peak, the tertiary wavelength being such that a smallest difference between the tertiary wavelength and a wavelength corresponding to an absorption peak of the primary dopant or of the secondary dopant is greater than or equal to a third predetermined minimum difference; detect a tertiary response wave emitted by the corresponding optical waveguide from the tertiary interrogation wave; calculate, from the detected tertiary response wave, a piece of information relating to a concentration of tertiary dopant; and determine, based on the piece of information relating to the concentration of tertiary dopant and the conversion data, a dose of photon radiation absorbed by the wall of the vessel for a predetermined tertiary period. ### Claim 9 (depends on 8) The measurement system according to claim 8, wherein the tertiary dopant is divalent thulium and/or divalent europium, the primary dopant being trivalent thulium or trivalent europium, respectively. ### Claim 10 (depends on 8) The measurement system according to claim 8, wherein the analysis device is configured, for each detector, so as to determine, by time-domain reflectometry or by frequency-domain reflectometry, from the detected tertiary response wave, an attenuation profile of the corresponding optical waveguide at the tertiary wavelength, according to a position along the optical waveguide; and the analysis device is configured to calculate the piece of information relating to the concentration of tertiary dopant from the attenuation profile at the tertiary wavelength. ### Claim 11 (depends on 8) The measurement system according to claim 8, wherein the analysis device is also configured, for each detector, to: inject, into the corresponding optical waveguide, one or two optical complementary tertiary interrogation waves, each having a complementary tertiary wavelength corresponding to a respective foot of the absorption peak associated with the tertiary wavelength; for each complementary tertiary interrogation wave, detect a corresponding complementary tertiary response wave emitted by the optical waveguide; and determine, by time-domain reflectometry or by frequency-domain reflectometry, from each detected complementary tertiary response wave, an attenuation profile of the corresponding optical waveguide at the complementary tertiary wavelength according to a position along the optical waveguide, the analysis device being configured to calculate the piece of information relating to the concentration of tertiary dopant from a result of a correction of the attenuation profile at the tertiary wavelength by the attenuation profile associated with each complementary tertiary wavelength. ### Claim 12 (depends on 8) The measurement system according to claim 8, wherein the analysis device is configured, for each detector, to determine, from the detected tertiary response wave, a total tertiary amount of fluorescence light emitted by the corresponding optical waveguide over its entire length, in a tertiary fluorescence spectral band associated with the tertiary dopant, the piece of information relating to the concentration of tertiary dopant in the corresponding optical waveguide being calculated from the total tertiary amount. ### Claim 13 (depends on 1) An installation comprising a nuclear reactor and a measurement system according to claim 1, each detector being disposed on an external surface of a wall of a vessel of the nuclear reactor and, for each detector, the moderation layer being arranged between the corresponding optical waveguide and the external surface. ### Claim 14 A method for measuring fast neutron fluence for a nuclear reactor having at least one detector comprising: an optical waveguide including a primary dopant capable of transmuting, by neutron capture, into a secondary dopant, the secondary dopant having an atomic number different from that of the primary dopant, the secondary dopant being stable and being less neutron-absorbent than the primary dopant; and a moderation layer configured to slow down fast neutrons and arranged between the optical waveguide and an external surface of a wall of a reactor vessel, the measurement method comprising, for each detector: injecting, into a corresponding optical waveguide, a secondary interrogation wave having a secondary wavelength at which the secondary dopant has an absorption peak, a smallest difference between the secondary wavelength and a wavelength corresponding to an absorption peak of the primary dopant being greater than or equal to a predetermined minimum difference; detecting a secondary response wave emitted by the corresponding optical waveguide from the secondary interrogation wave; calculating, from the detected secondary response wave, a piece of information relating to a concentration of secondary dopant in the corresponding optical waveguide; and based on the calculated piece of information relating to the concentration of secondary dopant, and conversion data relating to the nuclear reactor, determining a fast neutron fluence experienced by the wall of the vessel for a predetermined secondary period. ### Claim 15 (depends on 14) A non-transitory computer program product comprising program code instructions which, when executed by a computer, implement the calculating and determining of the measurement method according to claim 14.