US3784823A - Method and device for the detection of fission products - Google Patents

Method and device for the detection of fission products Download PDF

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Publication number
US3784823A
US3784823A US00218861A US3784823DA US3784823A US 3784823 A US3784823 A US 3784823A US 00218861 A US00218861 A US 00218861A US 3784823D A US3784823D A US 3784823DA US 3784823 A US3784823 A US 3784823A
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United States
Prior art keywords
discs
disc
magazine
transfer plate
collection chamber
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Expired - Lifetime
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US00218861A
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English (en)
Inventor
S Kostic
Meur R Le
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Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
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Commissariat a lEnergie Atomique CEA
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    • 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
    • G21C17/07—Leak testing
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21C—NUCLEAR REACTORS
    • G21C17/00—Monitoring; Testing ; Maintaining
    • G21C17/02—Devices or arrangements for monitoring coolant or moderator
    • G21C17/04—Detecting burst slugs
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21C—NUCLEAR REACTORS
    • G21C17/00—Monitoring; Testing ; Maintaining
    • G21C17/02—Devices or arrangements for monitoring coolant or moderator
    • G21C17/04—Detecting burst slugs
    • G21C17/044—Detectors and metering devices for the detection of fission products
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21C—NUCLEAR REACTORS
    • G21C17/00—Monitoring; Testing ; Maintaining
    • G21C17/02—Devices or arrangements for monitoring coolant or moderator
    • G21C17/04—Detecting burst slugs
    • G21C17/044—Detectors and metering devices for the detection of fission products
    • G21C17/045—Precipitation chambers
    • 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

  • ABSTRACT The method consists in carrying out the electrical collection of fission products on both sides of very thin metallized discs of polyester insulating material which are placed at the center of a spherical chamber and in measuring the radioactivity with a set of two electron detectors mounted to detect activity of the discs in all directions.
  • the device for carrying out the method comprises a magazine constituted by a rotary circular ring provided with spaced openings each intended to accommodate a disc, a spherical ion-collection chamber, two parallel semiconductor detectors and a unit for conveying each disc from the magazine into an opening formed in a transfer plate.
  • the disc is transferred by the plate to an ion-collection chamber, then passed between the two detectors in order to measure the activity and energy spectrum of the beta radiation of the collected ions then returned to the magazine.
  • This device finds an advantageous application in the detection of fuel-can failures in nuclear reactors as a result of detection of fission products either in the coolant gas or in the gases extracted from the coolant fluid or in the blanket gas.
  • the fraction of gas which is employed for the detection is held within a suitable reservoir for a sufficient period of time to ensure the formation of radioactive ions derived from the fission products which are present in the gas these ions are then collected by precipitation by means of an electric field in selected zones on the surface of a conveying unit which may be either a drum or disc. After collection in a predetermined zone, this zone is brought by rotation of the conveying unit in front of a measuring apparatus consisting as a rule of a scintillator and a photomultiplier followed by an electronic counting device.
  • the movement of the conveying unit is such that a further collection in a predetermined zone is possible only after a time interval which is sufficient to ensure that this zone is relatively decontaminated as a result of natural decay of the collected products. While a measurement is in progress, a sweeping neutral-gas stream can be injected between the detection unit and the conveying unit in order to reduce the undesirable influence of the active gases which may be present between these two units.
  • devices of this type do not permit fine ,B-ray spectrometry by reason of the lack of resolution of the scintillators and especially the magnitude of the backscattering phenomenon arising from thethickness of the conveying unit which is necessary to obtain good mechanical strength and which has the result of deforming the energy spectrum.
  • the device in accordance with the invention which makes it possible in particular to carry out burst-can detection operations of the kind referred-to above is primarily intended for the study of short-lived fission products by fine fi-ray spectrometry.
  • the present invention utilizes beta spectrometry of fission products with electrical collection and makes it possible to obtain good resolution and a reduction of the backscattering efiect.
  • the invention is directed to a method of detection of fission products which consists in carrying out the electrical collection of fission products on both sides of very thin metallized discs of polyester insulating material which are placed at the center of a spherical chamber known as a 4n chamber and in measuring the radioactivity with a set of two electron detectors mounted to detect activity of the discs in all directions.
  • the invention also relates to a device for carrying out said method, wherein said device essentially comprises a magazine constituted by a rotary circular ring pierced by equal and uniformly spaced openings each intended to contain a very thin disc of polyester insulating material matallized on both faces, a spherical collection chamber, two identical electron detectors or semiconductors having a surface area at least equal to that of a disc and mounted in parallel relation at a very short distance from each other, a transfer plate provided with an opening which is capable of receiving each of said discs in succession, and a conveying unit in which is formed a chamber having the thickness of said discs and capable of coming to the level of said circular ring and to the level of said transfer plate, the arrangement being such that, by virtue of suitable coordination of the displacements of the transfer plate and the conveying unit, said unit causes one disc to pass from said magazine into the opening of the transfer plate, that said transfer plate displaces said disc to the center of the collection chamber in order to permit collection of the ions and then between the two detectors
  • FIG. 1 illustrates the complete device in accordance with the invention, looking at the level ofits disc magazine
  • FIG. 2 illustrates the same device to a different scale, looking at right angles to FIG. 1
  • FIG. 3 illustrates the conveying unit alone, to a larger scale than in FIG. 2
  • FIG. 4 illustrates, to a larger scale than in FIG. 2 and in greater detail, the portion of the device according to the invention which comprises the two semiconductors.
  • the detection device as shown in these figures comprises essentially a magazine 1 constituted by a circular ring pierced by uniformly spaced openings 2 (which may be twenty in number, for example), said openings being each intended to contain a disc in accordance with the invention, a spherical collection chamber 3 (referred-to as a 41'r chamber), two parallel silicon semiconductors 4, a transfer plate 5 provided with an opening 6 which is capable of receiving each disc in turn and of bringing them in accordance with a predetermined cycle into the collection chamber 3 and into the measuring chamber and a unit 7 for conveying the discs between the magazine -1 and the transfer plate 5,
  • Each disc (shown in FIG. 4) is constituted by a very thin leaf 9 of polyester insulating material (for example the product known by the name of Mylar) which is metallized on both faces in order that the ions may be collected by both sides of the discs, said leaf being held in position by means of a retaining ring 10.
  • the thickness of the leaf 9 is 13 microns, for example.
  • the detectors 4 which are known as semiconductors have the shape of parallel circular plates. These detec' tors by reason of the fact that they each have a surface area at least equal to that of the discs, are capable of detecting the activity of these discs in all directions of the space.
  • the operation of the detection device according to the invention is as follows:
  • the operator When actuating a crank-handle 11, the operator causes the magazine 1 to rotate in such a manner as to bring one of the discs (9, 10) of this magazine ll into position 12, that is to say opposite to the transfer plate 5 which is then in the position of passage, that is to say in a position such that the opening 6 of said plate is located opposite to said position 12.
  • the conveying unit 7 then takes up a position which, for the sake of convenience ofterminology, will be referred-to hereinafter as the bottom position, assuming that FIG. 2 is oriented in such manner that the magazine 1 is located beneath the transfer plate 5. In this bottom position, the disc is maintained by the conveying unit 7 within the magazine 1 and imprisoned in the chamber 8.
  • the operator Since the transfer plate 5 remains stationary, the operator then causes the conveying unit 7 to move upwards to the central position in which the chamber 8 coincides with the opening 6 of the transfer plate.
  • the disc (9, 10) is then located within this opening 6.
  • the conveying unit 7 is so designed that its arm 13 prevents the magazine 1 from rotating when the transfer plate 5 carries out a movement of displacement.
  • the operator then moves the transfer plate 5 forward in such manner that its opening 6 (and therefore the disc 9, 10) is located at the center of the spherical collection chamber 3.
  • the disc is then brought to a negative potential with respect to said chamber 3.
  • radioactive ions of the gas under study which penetrates through the openings 14, 15 of the chamber 3 are then collected on both faces of the disc, this collection being an electrical connection in 41r geometry (that is to say in all the directions of the space).
  • the operater After this collection, the operater returns the disc between the semiconductors 4 where a measurement of the activity of collected ions is carried out, whereupon the transfer plate 5 is returned to the position of passage in such manner that the disc which has just been subjected to this measurement of activity is located opposite to the magazine 1. Finally, by actuating the conveying unit 7 and restoring this latter to the bottom position, the operator replaces the disc in the magazine 1 in position 12.
  • Metallizing on both faces of the disc has the advantage of producing the same attenuation of the radiation which reaches each of the detectors, with the result that these latter measure the same energy.
  • the device according to the invention is designed for beta spectrometry, the influence of gamma radiations, for example, is eliminated firstly by taking a measurement of the beta gamma activity of the disc followed by a second measurement after having placed on each side of the disc two retractable screens 17 ac tuated by two arms 18 which stop the beta radiations.
  • the apparatus according to the invention is intended for the study of short-lived fission products by fine beta spectrometry.
  • the electronic pulse-processing circuitry is not included in the figures which only show preamplifiers 19 at the level of the semiconductors 4.
  • the detector according to the invention has the advantage of practically eliminating backscattering by reason of the size and spacing of the two semiconductor detectors and by virtue of the fact that the discs are of extremely small thickness.
  • replacement of the disc may then be carried out either by returning the studied disc into the magazine 1 as explained earlier and by rotating said magazine in order to cause the following disc to come into position 12, or by extracting the studied disc by moving the conveying unit 7 upwards to the top position in which its chamber 8 and the disc contained therein are located outside the apparatus, then by inserting a fresh disc.
  • This possibility ofintroducing discs into the apparatus makes it possible to calibrate the semiconductors by means of source discs (standard activity, standard energy) which can be placed directly beneath the semiconductors.
  • the possibility of extraction of discs permits measurement of their activity in other devices such as a gamma spectrometer, for example.
  • a device for the detection of fission products comprising: a magazine established by a rotary circular ring having equal and uniformly spaced openings each adapted to contain a very thin disc of insulating material metallized on both faces, a spherical collection chamber, two identical semiconductor electron detectors having a surface area at least equal to that of a disc and mounted in parallel relation at a very short distance from each other, a transfer plate provided with an opening capable of receiving each of said discs in succession, and a conveying unit defining a chamber having a thickness of said discs and movable between said circular ring and said transfer plate, whereby through suitable coordination of transfer plate and conveying unit displacement, one disc is caused to pass from said magazine into the opening of the transfer plate and displaced by said transfer plate to the center of the collection chamber so as to permit collection of the ions, then located between the two detectors in order to permit measurement of the activity and of the energy spectrum of the collected ions and is then returned to said conveying unit and to the magazine.
  • discs are each constituted by a polyester film such as Mylar" which is metallized on both faces.
  • a device according to claim 1, wherein said device comprises retractable screens which stop beta radiations and can be interposed between the semiconductors and the faces of the disc under study.
  • a device comprising a conveying unit which permits the discharge of contaminated discs and the introduction of fresh discs or of source discs for either activity or energy calibration.
  • a detector of fission products for use with a collection chamber containing a gas having radioactive ions derived from fission products present in the gas, the improvement comprising:
  • magazine means for holding said discs and for serially positioning said discs in a first position for movement from said magazine
  • detector means at said measuring station for measuring the activity of said collected radioactive ions in all directions.
  • each of said discs comprises: a very thin leaf of insulating material which is metallized on opposite sides.
  • said insulating material is a polyester such as Mylar.
  • said magazine means comprises: means defining a plurality of uniformly spaced openings each capable of holding one of said discs and indexing means for serially positioning each of said discs in said first position.
  • said means defining a plurality of openings is a rotatable ring and said indexing means is a crank mechanically coupled to said ring.
  • said moving means comprises: conveying means for moving said individual disc from said first position to a transfer position, and transfer means for moving said individual disc from said transfer position to said collection chamber and then to said measuring station, from where said conveying means returns said individual disc to said magazine.
  • said detector means comprises: two identical circular semiconductors each having a surface area at least equal to that of one of said discs.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • General Engineering & Computer Science (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Measurement Of Radiation (AREA)
  • Other Investigation Or Analysis Of Materials By Electrical Means (AREA)
US00218861A 1971-01-22 1972-01-19 Method and device for the detection of fission products Expired - Lifetime US3784823A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR7102218A FR2122365B1 (enrdf_load_stackoverflow) 1971-01-22 1971-01-22

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US3784823A true US3784823A (en) 1974-01-08

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US00218861A Expired - Lifetime US3784823A (en) 1971-01-22 1972-01-19 Method and device for the detection of fission products

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US (1) US3784823A (enrdf_load_stackoverflow)
FR (1) FR2122365B1 (enrdf_load_stackoverflow)
GB (1) GB1350554A (enrdf_load_stackoverflow)
IT (1) IT948910B (enrdf_load_stackoverflow)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4032395A (en) * 1974-10-07 1977-06-28 General Atomic Company Fuel leak detection apparatus for gas cooled nuclear reactors
US4464331A (en) * 1980-07-10 1984-08-07 Commissariat A L'energie Atomique Transfer and positioning apparatus for the irradiation of targets
US5164149A (en) * 1990-08-28 1992-11-17 Japan Atomic Energy Research Institute Nuclide separation type of precipitator system

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2576616A (en) * 1949-09-20 1951-11-27 Livingston Ralph Monitor for fission gases
US2985785A (en) * 1958-04-18 1961-05-23 Tracerlab Inc Low background counter
US3084252A (en) * 1958-06-23 1963-04-02 Commissariat Energie Atomique Monitoring of fission products in a gaseous stream, particularly for detecting burst slugs in nuclear reactors

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE628411A (enrdf_load_stackoverflow) *

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2576616A (en) * 1949-09-20 1951-11-27 Livingston Ralph Monitor for fission gases
US2985785A (en) * 1958-04-18 1961-05-23 Tracerlab Inc Low background counter
US3084252A (en) * 1958-06-23 1963-04-02 Commissariat Energie Atomique Monitoring of fission products in a gaseous stream, particularly for detecting burst slugs in nuclear reactors
US3136891A (en) * 1958-06-23 1964-06-09 Commissariat Energie Atomique Monitoring devices for detecting fission products in a gaseous stream

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4032395A (en) * 1974-10-07 1977-06-28 General Atomic Company Fuel leak detection apparatus for gas cooled nuclear reactors
US4464331A (en) * 1980-07-10 1984-08-07 Commissariat A L'energie Atomique Transfer and positioning apparatus for the irradiation of targets
US5164149A (en) * 1990-08-28 1992-11-17 Japan Atomic Energy Research Institute Nuclide separation type of precipitator system

Also Published As

Publication number Publication date
FR2122365B1 (enrdf_load_stackoverflow) 1973-11-30
IT948910B (it) 1973-06-11
DE2202943B2 (de) 1975-09-11
DE2202943A1 (de) 1972-08-03
GB1350554A (en) 1974-04-18
FR2122365A1 (enrdf_load_stackoverflow) 1972-09-01

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