Method and apparatus for measuring the concentration of a component, for instance iron, in a material

• US 4,028,267 A
• Filed: 03/27/1975
• Issued: 06/07/1977
• Est. Priority Date: 04/09/1974
• Status: Expired due to Term

• Current Assignee: Stiftelsen Isotoptekniska Laboratoriet
• Original Assignee: Stiftelsen Isotoptekniska Laboratoriet
• Inventors: Koski, Kaijo Aatto Matias, Ljunggren, Knut Lennart, Christell, Adolf Ragnar Roland Umberto Einarsson
• Primary Examiner(s): Borchelt, Archie R.
• Application Number:
  US05/562,460
• Time in Patent Office: 803 Days
• Field of Search: 250/308, 250/359, 250/360, 250/390, 250/391, 250/392
• US Class Current: 250/359.1
• CPC Class Codes: G01N 2223/0745 neutron-gamma activation analysis
• CPC Class Codes: G01N 2223/302 comparative arrangements
• CPC Class Codes: G01N 2223/643 object on conveyor
• CPC Class Codes: G01N 23/222 using neutron activation analysis [NAA]

Abstract

Method and apparatus for measuring the concentration of various components, such as the iron component in iron ore, by exposing the material to irradiation between a neutron source and a gamma ray detector. The emitted gamma rays are captured by the detector and transformed into a signal which is transmitted to a recording device for measuring the gamma ray radiation.

Claims

1. In the method of measuring the concentration of a component in a material sample, which at the measuring location is at rest or moves as a stream of material, that improvement which includes

irradiating said sample with thermally-moderated neutrons and detecting resultant gamma ray emission from said sample to provide a base line measurement;

irradiating said sample with unmoderated neutrons to provide a gamma ray emission from said sample and measuring same; and

determining said concentration by comparison of known gamma ray emissions relative to concentration

whereby the concentration of said component in said material sample may be determined.

2. The method according to claim 1 including shielding the unmoderated neutron source to prevent gamma rays from said source reaching the measuring means.

3. The method according to claim 1 including substituting at least one reference plate containing known quantities of the component to be measured for said material sample and thereby calibrating said measuring means.

4. Apparatus for measuring the concentration of a component in a material sample comprising a radioactive neutron source and a gamma ray detector, said apparatus being characterized by the provision of a first neutron moderator surrounding said neutron source, shielding means for protecting the detector from direct gamma radiation from the neutron source, a second neutron moderator surrounding the detector, shielding means for protecting the detector for neutrons emitted from the neutron source, and means for transforming the gamma rays captured by the detector to a signal and for transmitting the signal to a recording device.

5. Apparatus according to claim 4, in which the neutron source is disposed in hydrogenous material, which together with the neutron source is formed as a unit adapted to be inserted and fixed in a first neutron moderator in a first container, and in which the detector is surrounded by a second neutron moderator and is disposed in a second container, said containers being carried by a frame at a distance from one another so that a measuring location for the material is formed between the containers, means for shielding the detector from gamma rays radiated directed from the neutron source, means for shielding the detector from neutron radiation from the neutron source, means for supplying electric power to the detector, and means for transforming the gamma rays captured by the detector to a signal and for transmitting said signal to the recording device.

6. Apparatus according to claim 5, in which the unit consists substantially of hydrogenous material of the group including paraffin and polythene in which the neutron source is fixed in the first moderator in a location so selected that the unit together with the neutron source may be rapidly moved to or from said location with consequent minimized risk of exposure to the personnel.

7. Apparatus according to claim 5, in which shielding means of lead are provided in the unit on the side of the neutron source facing the detector, so that the detector is protected against direct gamma radiation from the neutron source.

8. Apparatus according to claim 6, in which the first neutron moderator consists of water in a container in which the unit is fixed in the selected location.

9. Apparatus according to claim 5, in which the second neutron moderator consists of water in a container in which the detector is fixed in a location, in which it is protected against direct gamma and neutron radiation from the neutron source.

10. Apparatus according to claim 9, in which the detector is surrounded by shielding means comprising hydrocarbon polymer material containing boron.

11. Apparatus according to claim 5, in which the second neutron moderator consists of polythene.

12. Apparatus according to claim 5, in which the frame and the containers define a gap open on three sides, so that the frame and the containers from one side of a conveyor belt may be brought into a position with the first container below and the second container above the conveyor belt, on which the material is transported.

13. Apparatus according to claim 12, in which at least one reference plate is inserted between the first and the second container and the conveyor.

14. Apparatus according to claim 5, in which a spectrum stabilizer is connected in series with the detector and utilizes the gamma radiation with energe 2.23 MeV which during the neutron capture is emitted by the hydrogen of the moderators for stabilizing the measuring system and counteracting drift of the electronic equipment.

15. Apparatus according to claim 4 in which the neutron source is ²⁴¹ Am-Be.

16. Apparatus according to claim 4 in which the neutron source is ²⁵² Cf.