US3892969A - Neutron detector with gamma compensated cable - Google Patents

Neutron detector with gamma compensated cable Download PDF

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Publication number
US3892969A
US3892969A US458152A US45815274A US3892969A US 3892969 A US3892969 A US 3892969A US 458152 A US458152 A US 458152A US 45815274 A US45815274 A US 45815274A US 3892969 A US3892969 A US 3892969A
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US
United States
Prior art keywords
leadwire
sheath
cable
neutron
diameter
Prior art date
Legal status (The legal status 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 status listed.)
Expired - Lifetime
Application number
US458152A
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English (en)
Inventor
Holland D Warren
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Babcock and Wilcox Co
Original Assignee
Babcock and Wilcox Co
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 Babcock and Wilcox Co filed Critical Babcock and Wilcox Co
Priority to US458152A priority Critical patent/US3892969A/en
Priority to CA218,134A priority patent/CA1022634A/en
Priority to GB3683/75A priority patent/GB1487271A/en
Priority to AU77745/75A priority patent/AU492097B2/en
Priority to BE153107A priority patent/BE825244A/xx
Priority to IT20034/75A priority patent/IT1031532B/it
Priority to AT110575A priority patent/AT334994B/de
Priority to FR7506828A priority patent/FR2266942B1/fr
Priority to SE7503832A priority patent/SE429072B/xx
Priority to JP50040478A priority patent/JPS5853443B2/ja
Application granted granted Critical
Publication of US3892969A publication Critical patent/US3892969A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B7/00—Insulated conductors or cables characterised by their form
    • H01B7/16—Rigid-tube cables
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T3/00—Measuring neutron radiation
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21C—NUCLEAR REACTORS
    • G21C17/00—Monitoring; Testing ; Maintaining
    • G21C17/10—Structural combination of fuel element, control rod, reactor core, or moderator structure with sensitive instruments, e.g. for measuring radioactivity, strain
    • G21C17/116—Passages or insulators, e.g. for electric cables
    • 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

  • An illustrative embodiment of the invention describes a technique for essentially eliminating the radiation induced background currents that are generated in the cable that connects an in-core neutron detector to an electrical terminal that is outside of the reactors radiation field. This undesirable radiation-induced cable current is suppressed through an appropriate selection of conductor and cable sheath materials and sizes that generally satisfy the equation:
  • a typical cable that does meet this criterion at low temperatures has a centrally disposed Zircaloy-2 inner conductor of 0.011 inch diameter, an annular insulation of magnesium oxide powder compacted to 100% density, and an Inconel sheath with an outside diameter of 0.062 inch and 0.011 inch wall thickness.
  • a self-powered detector of this sort has a centrally disposed emitter that responds to neutron radiation by emitting relatively high energy electrons (beta particles").
  • the energy of these electrons is sufficient to traverse a sleeve or annulus of insulating material that encloses the centrally disposed emitter to enable these electrons to impact on an electrically conductive outer sheath or collector.
  • the intensity of incident neutrons is related to beta particle production. Consequently, the electrical current, which is a way of expressing electron flow through a conductor per unit time, provides a measure of the neutron population at the place of measurement within the reactor.
  • the detector is coupled to instruments in a control panel by means of a coaxial cable.
  • these cables have a centrally disposed leadwire that is electrically isolated, or insulated, from an encircling electrically conducting sheath.
  • the cable materials are chosen from a group of materials that do not exhibit neutron sensitivity and exhibit a low probability for neutron-electron reactions. Substantiallengths of this connecting coaxial cable are nevertheless exposed to the gamma radiation that is generated within the core..
  • the array of detectors that is lodged in a reactor core is provided with at least one cable that is not connected to a neutron detector.
  • This unconnected cable produces a current that is subtracted from the other incore detector signals.
  • This cable response subtracted either manually or through automatic computation from each of the observed detector. signals, approximately eliminates that portion of the uncorrected detector signal that is attributable to gamma ray induced electrical currents in the detectors cable.
  • Another technique to compensate for these induced cable currents makes use of a single cable that has two insulated leadwires which are twisted about each other.
  • One of the leadwires is connected to a neutron detector to provide a combined neutron detector and cable" signal.
  • the other leadwire is not connected to a detector and thus generates only a background cable signal. Algebraic subtraction of these two signals should provide a result that is essentially an indication of the neutron population at the place of measurement within the reactor core. All of these correction systems require at least one extra leadwire and a provision for an algebraic subtraction, or its equivalent.
  • the signal from a neutron detector coupled: to a cable built in accordance with these principles generally reflects the reactor core neutron population at the place of measurement to the exclusion of any straycurrents induced in the cable through gamma ray interactions with the leadwireand sheath materials. More specifically, the electrons that are released from the sheath and pass through the interposed insulator to the leadwire produce a net negative current. Those electrons that flow in an opposite direction from the leadwire to the sheath produce inturn, a net positive current when measured at the sheath and leadwire terminals. ln accordance with a feature of the invention, it has been noted that this gamma radiation induced electron emission is almost proportional to the area of the emitting surface.
  • a relatively low Z material is chosen for the larger surface area sheath and a higher Z material for the smaller surface leadwire.
  • the oppositely directed gamma ray induced electrical currents are brought into an essentially matching balance or mutual cancellation that approaches a zero net background current.
  • a number of cables that specifically embody these principles of the invention can be made from an lnco nel 600 sheath that has an outside diameter of 0.062 inch and an inside diameter of 0.040 inch.
  • the number of electrons leaving the cable sheath also are proportional to:
  • the're isa further need to select materials that are metallurgically and mechanically compatible.
  • the properties of the sheath and leadwire materials may be so different that it could be extremely difficult to anneal drawn or swaged cable.
  • a number of cables were built in which a sheath formed of Inconel 600 having a 0.062 inch outside diameter and a 0.040 inch inside diameter was used in conjunction with a leadwire 11 formed from zirconium (Zircaloy-2) and having diameters in the range of 0.0085 inches up to 0.025.
  • An insulator 12 of magnesium oxide was compacted in the annular space between the leadwire 11 and the enclosing sheath l0.
  • neutron reactions with the insulation mate-. rial are also to be avoided 'as much as possible.
  • lnconel 600 has, a typical, composition, by weight, of 76.5 parts nickel; 14.5 parts chromium; 8.2 parts iron; .19 parts copper; .26 parts silicon; .007 parts sulfur; .25 parts manganese; and .03 parts carbon;
  • the manganese concentration should be reduced to,.l part byweight or less and cobalt, although not shown in the foregoing illustrative, composition, also should be avoided in order to reduce to a minimum the major source of undesired neutron, induced electron emissions.
  • trace amounts of otherelements also can be present. 4
  • Zircaloy-2 typically comprises Zirconium with a balance of 1.5% tin; .12% iron; .ll% chromium; 06% nickel, and as many as ten other elements present in trace concentrations, of which aluminium, boron, carbon, copper, and hafnium are illustrative.
  • each of the cables were tested in the neutron and gamma ray environment established within a one megawatt pool-type reactor'at less than 300 "F.
  • the background currents produced in each of the tested cables as a result of this'ne utron and gamma ray exposure was observed during a period of about minutes. It was found that the 0.01 1 inch diameter leadwire cable, exposed to an average neutron flux of about 1.6 X 10 nvwithin the reactor environment generated not more than 7 X 10 amps/nv-inch. This induced current is a factor of about less than the background current generated in a conventional cable containing an 0.009 inch diameter Inconel leadwire.
  • An electrical conductor comprising a sheath havtions of all of the constituents of the composition under ing a material that has a low probability for neutronelectron reactions, a leadwire within said sheath, said leadwire being formed from another material that also has a low probability for neutron-electron reactions, said leadwire material also having anatomic number that is larger than the atomic number of the sheath material, in order to generally satisfy the equation in which I identifies said leadwire, s identifies said sheath, d is a size characteristic, Z is the atomic num- 5
  • said leadwire further comprises a diameter in the range between 0.01 l and 0.013 inches.

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  • Physics & Mathematics (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Engineering & Computer Science (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Molecular Biology (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Plasma & Fusion (AREA)
  • General Engineering & Computer Science (AREA)
  • Measurement Of Radiation (AREA)
  • Communication Cables (AREA)
US458152A 1974-04-05 1974-04-05 Neutron detector with gamma compensated cable Expired - Lifetime US3892969A (en)

Priority Applications (10)

Application Number Priority Date Filing Date Title
US458152A US3892969A (en) 1974-04-05 1974-04-05 Neutron detector with gamma compensated cable
CA218,134A CA1022634A (en) 1974-04-05 1975-01-14 Mineral insulated coaxial cable for neutron detectors
GB3683/75A GB1487271A (en) 1974-04-05 1975-01-28 Electrical conductors
AU77745/75A AU492097B2 (en) 1975-01-30 Gamma compensated conductor
BE153107A BE825244A (fr) 1974-04-05 1975-02-06 Cable pour le genie nucleaire
IT20034/75A IT1031532B (it) 1974-04-05 1975-02-07 Conduttore elettrico specialmente per reattdri nucleari e simili
AT110575A AT334994B (de) 1974-04-05 1975-02-14 Koaxiales verbindungskabel zu neutronendetektoren
FR7506828A FR2266942B1 (de) 1974-04-05 1975-03-05
SE7503832A SE429072B (sv) 1974-04-05 1975-04-03 Elektrisk signalkabel for anvendning i kernreaktorer
JP50040478A JPS5853443B2 (ja) 1974-04-05 1975-04-04 デンドウタイ

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US458152A US3892969A (en) 1974-04-05 1974-04-05 Neutron detector with gamma compensated cable

Publications (1)

Publication Number Publication Date
US3892969A true US3892969A (en) 1975-07-01

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Family Applications (1)

Application Number Title Priority Date Filing Date
US458152A Expired - Lifetime US3892969A (en) 1974-04-05 1974-04-05 Neutron detector with gamma compensated cable

Country Status (9)

Country Link
US (1) US3892969A (de)
JP (1) JPS5853443B2 (de)
AT (1) AT334994B (de)
BE (1) BE825244A (de)
CA (1) CA1022634A (de)
FR (1) FR2266942B1 (de)
GB (1) GB1487271A (de)
IT (1) IT1031532B (de)
SE (1) SE429072B (de)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2737470A1 (de) * 1976-08-26 1978-03-02 Westinghouse Electric Corp Elektrisches signalkabel
US5078956A (en) * 1990-07-31 1992-01-07 Westinghouse Electric Corp. Neutron flux detector distribution system with improved drivability
US5305357A (en) * 1992-06-24 1994-04-19 Westinghouse Electric Corp. Low activated incore instrument
EP1146523A2 (de) * 2000-03-31 2001-10-17 Whittaker Corporation Koaxialkabel mit schwarzem Oxid und zugehöriges Herstellungsverfahren
FR2836246A1 (fr) * 2002-02-15 2003-08-22 Incore Services Dispositif et procede de deplacement d'un element mobile fixe a une extremite d'un cable de deplacement et de commande, a l'interieur d'un conduit tubulaire

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112992418A (zh) * 2020-12-30 2021-06-18 安徽华菱电缆集团有限公司 一种柔性防断裂光电复合电缆

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2976418A (en) * 1957-11-22 1961-03-21 Leslie E Johnson Gamma-compensated ionization chamber
US3375370A (en) * 1965-12-28 1968-03-26 Ca Atomic Energy Ltd Self-powered neutron detector
US3787697A (en) * 1971-01-19 1974-01-22 Ca Atomic Energy Ltd Neutron and gamma flux detector

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2976418A (en) * 1957-11-22 1961-03-21 Leslie E Johnson Gamma-compensated ionization chamber
US3375370A (en) * 1965-12-28 1968-03-26 Ca Atomic Energy Ltd Self-powered neutron detector
US3787697A (en) * 1971-01-19 1974-01-22 Ca Atomic Energy Ltd Neutron and gamma flux detector

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2737470A1 (de) * 1976-08-26 1978-03-02 Westinghouse Electric Corp Elektrisches signalkabel
US5078956A (en) * 1990-07-31 1992-01-07 Westinghouse Electric Corp. Neutron flux detector distribution system with improved drivability
US5305357A (en) * 1992-06-24 1994-04-19 Westinghouse Electric Corp. Low activated incore instrument
EP1146523A2 (de) * 2000-03-31 2001-10-17 Whittaker Corporation Koaxialkabel mit schwarzem Oxid und zugehöriges Herstellungsverfahren
EP1146523A3 (de) * 2000-03-31 2002-02-13 Whittaker Corporation Koaxialkabel mit schwarzem Oxid und zugehöriges Herstellungsverfahren
FR2836246A1 (fr) * 2002-02-15 2003-08-22 Incore Services Dispositif et procede de deplacement d'un element mobile fixe a une extremite d'un cable de deplacement et de commande, a l'interieur d'un conduit tubulaire

Also Published As

Publication number Publication date
CA1022634A (en) 1977-12-13
JPS50136678A (de) 1975-10-30
IT1031532B (it) 1979-05-10
GB1487271A (en) 1977-09-28
AT334994B (de) 1977-02-10
BE825244A (fr) 1975-05-29
JPS5853443B2 (ja) 1983-11-29
FR2266942A1 (de) 1975-10-31
ATA110575A (de) 1976-06-15
SE7503832L (sv) 1975-10-06
SE429072B (sv) 1983-08-08
FR2266942B1 (de) 1981-06-19
AU7774575A (en) 1976-08-05

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