Method And Apparatus For Probing Nuclear Material By Photofission

• US 20090065693A1
• Filed: 06/14/2005
• Published: 03/12/2009
• Est. Priority Date: 06/21/2004
• Status: Active Grant

• Current Assignee: Commissariat a L'Energie Atomique (French Alternative Energies and Atomic Energy Commission)
• Original Assignee: Commissariat a L'Energie Atomique (French Alternative Energies and Atomic Energy Commission)
• Inventors: Safa, Henri
• Granted Patent: US 9,297,908 B2
• Time in Patent Office: Days
• US Class Current: 250/310
• CPC Class Codes: G01T 1/167 Measuring radioactive content of objects, e.g. contamination whole body counters G01T1/163
• CPC Class Codes: G01T 3/00 Measuring neutron radiation G01T5/00 takes precedence

Abstract

The invention relates to a method and a system for using photofission to probe an article containing potentially radiation-emitting elements. The article is bombarded by a beam of electrons of sufficient energy, and they are converted into photons by bremsstrahlung directly within the article to be probed, which article is likely to contain photofissile material. No target is added to the package to perform this conversion. Preferably, the article to be probed is a package of radioactive waste, in which the container is made of thick absorbent concrete.

Claims

1. A method of probing an article containing potentially radiation-emitting elements, in which said article is irradiated by means of a beam of particles having sufficient energy to cause photofission of radiation-emitting elements of the article, and the neutrons produced by photofission are measured by means of at least one neutron detector, wherein said particles are electrons irradiating the article directly, and wherein the conversion of electrons into photons suitable for generating photofission is performed directly by the article to be probed.

2. A method according to claim 1, wherein the article to be probed is a package of radioactive waste containing nuclear material.

3. A method according to claim 1, wherein the article to be probed comprises a container made of concrete and content including nuclear material.

4. A method according to claim 1, wherein the electron beam that irradiates the package is pulsed, and wherein the at least one neutron detector detects delayed neutrons generated by photofission after the flash that results from the electron beam pulse.

5. A method according to claim 4, wherein the at least one neutron detector also detects prompt neutrons emitted during the electron beam pulse.

6. A method according to claim 5, wherein the isotopic composition of actinides present in the radiation-emitting elements is determined from the ratio of measured prompt neutrons to delayed neutrons.

7. A method according to claim 5, wherein the total quantity of actinides present in the radiation-emitting elements is determined from the measured prompt neutrons and delayed neutrons.

8. A method according to claim 1, wherein the article to be probed is irradiated by transporting the electron beam up to the article in a vacuum line.

9. A method according to claim 1, wherein the electron beam scans all or part of the article to be probed.

10. A method according to claim 1, wherein the article to be probed is caused to move relative to the electron beam in such a manner that the electron beam irradiates all or part of the article to be probed.

11. A method according to claim 1, wherein the size of the electron beam is caused to vary in such a manner as to cause the precision of the irradiation to vary.

12. A method according to claim 3, wherein, by scanning the article by means of the electron beam, particles emitted by the scanned portions are detected simultaneously so as to locate the radiation-emitting elements within the article.

13. Apparatus for probing an article containing radiation-emitting elements, the apparatus comprising means for irradiating said article by means of a beam of particles of energy that is sufficient to cause photofission of the radiation-emitting elements of the article, and at least one neutron detector for measuring the neutrons produced by photofission, wherein said particles are electrons directly irradiating the nuclear material, the conversion of electrons into photons suitable for generating photofission being performed directly by the article to be probed.

14. Apparatus according to claim 13, including means for emitting the electron beam in the form of at least one pulse, and means for detecting and measuring the prompt neutrons emitted during the pulse.

15. Apparatus according to claim 14, wherein the detection means are disposed behind the article when the electron beam reaches the article from the front.

16. Apparatus according to claim 13, including means for detecting and measuring delayed neutrons.

17. Apparatus according to claim 13, including:

means for emitting the electron beam in the form of at least one pulse, and means for detecting and measuring the prompt neutrons emitted during the pulse;

means for detecting and measuring delayed neutrons; and

a processor unit for determining the isotopic composition and the total quantity of actinides present in the radiation-emitting elements from the measured prompt neutrons and delay neutrons.

18. Apparatus according to claim 13, including a vacuum line for transporting the electron beam.

19. A method according to claim 18, wherein the end of the vacuum line includes an outlet window that is put into contact with the article.

20. Apparatus according to claim 13, including scanner means suitable for directing the electron beam.

21. Apparatus according to claim 13, including means for setting the article into movement relative to the electron beam.

22. Apparatus according to claim 13, including focusing means for focusing the electron beam on a portion of the nuclear material.