Neutron generation source, and neutron generation device
|Posted date||Aug 26, 2019|
|Date of filing||Mar 6, 2013|
|Gazette Date||Jan 14, 2015|
|Gazette Date||May 6, 2020|
|International application number||JP2013056188|
|International publication number||WO2013133342|
|Date of international filing||Mar 6, 2013|
|Date of international publication||Sep 12, 2013|
|Title||Neutron generation source, and neutron generation device|
|Abstract||The present invention provides a novel neutron source. A neutron source (1) of the present invention includes a neutron producing material layer (3) and a metal layer (2), and the metal layer (2) contains a metal element which has a high hydrogen diffusivity and generates radionuclides having a short half-life upon receipt of irradiation of neutron beams.|
|Outline of related art and contending technology||
In recent years, instead of a method of producing neutron beams with high energy efficiency as used in a large facility, there has been tried to be developed a method of producing neutron beams with use of low energy beams. In such a method, neutron beams are produced by, for example, irradiating a target (e.g., Be, Li, or the like) with proton beams to thereby cause a nuclear reaction. This method can produce neutron beams with use of extremely low energy proton beams.
According to the above method, for example, there is no need to provide a gigantic radiation blocking structure which can be accepted only in a large facility. It is therefore considered that a neutron source employing the above method is extremely suitable for use in a small facility. In particular, in a case where proton beams having an energy of not more than 13 MeV are used, the neutron source can be easily handled because an amount of a resultant radioactivated material is extremely low.
However, low energy proton beams penetrate a target extremely shallowly. Therefore, a proton, with which a material is irradiated becomes hydrogen and the hydrogen is easily accumulated in the target locally. In view of this, it is known that a target is broken mainly by a mechanism of hydrogen embrittlement for an extremely short time. This phenomenon is called blistering. From a practical standpoint, the blistering is a fatal problem in a low energy neutron generator employing the above method.
In view of this problem, various researches have been conducted. There is reported a neutron source for producing neutron with use of a Li (p, n) reaction in which Li is used (Non-patent Literatures 1-4).
In Non-patent Literatures 1 through 3, blistering of a Li target was verified. Specifically, Non-patent Literatures 1 through 3 report that, in a case where a Li target is irradiated with proton beams of 2.5 MeV or 1.9 MeV, blistering occurs due to a beam current having 10 mA after 3.5 hours from this irradiation. Those literatures conclude that the blistering is not problematic from a practical standpoint, because a single irradiation time period in a BNCT therapy (Boron Neutron Capture Therapy) is shorter than the above time period.
Non-patent Literature 4 reports a structure for preventing hydrogen embrittlement of a target. According to the report, protons (hydrogen atoms) which have passed through Li are absorbed and diffused by the structure in which a thin film made from Pd having high hydrogen transparency is formed under Li.
Non-patent Literature 5 shows a result of simulation for preventing hydrogen embrittlement with use of a target other than Li. From the simulation, such a result was obtained that, when a neutron source is formed by joining thin Be and Nb, hydrogen embrittlement is preventable because almost all irradiated proton beams penetrate Be and are remained in Nb. Therefore, there is a possibility that the structure stably prevents hydrogen embrittlement of a neutron source for a long time.
Non-patent Literature 6 reports results of tests regarding conditions for causing blistering in various metals when the various metals are irradiated with proton beams. The test is carried out by observing the metals which have been irradiated with proton beams of 200 keV with use of, for example, an electron microscope by an optical method. As the result of this, it is reported that blistering does not occur in V and Ta under the tested conditions.
Patent Literature 1 discloses a neutron source wherein neutrons of 14 MeV are produced by irradiating Tritium or Deuterium with a Deuterium beam. The Tritium and the Deuterium used for the neutron production are comprised in a target assembly, wherein the target comprises Be, Ti and Ni.
Non-patent Literature 1
B. Bayanov et. al., Neutron producing target for acceleratorbased neutron capture therapy, Journal of Physics Conference Series 41 pp. 460-465, 2006 Institute of Physics Publishing
Non-patent Literature 2
B. Bayanov et. al., A neutron producing target for BINP accelerator-based neutron source, Applied Radiation and Isotopes, Volume 67, Issues 7-8, Supplement, Pages S282-S284, 2009
Non-patent Literature 3
V. Aleynik et. al., BINPacceleratorbasedepithermalneutronsource, Applied Radiation and Isotopes vol. 69, pp. 1635-1638, 2011
Non-patent Literature 4
C. Willis et. al., High-power lithium target for accelerator-based BNCT, Proceedings of the XXIV Linear Accelerator Conference, pp. 223-225, 2008
Non-patent Literature 5
J. Ju et. al., Simulation and design of beryllium target combined with hydrogen diffusible metal for compact neutron source in RIKEN, PS2-074, p. 359, Abstract of 1st Asia-Oceania Conference on Neutron Scattering, 2011
Non-patent Literature 6
S. V. Polosatkin et. al., Experimental Studies of Blisteringof Targets Irradiated by Intense 200 keV Proton Beam, Proceedings of the 9th Conference on Modification of Materials with Particle Beams and Plasma Flows, Sep. 21-26, pp. 131-134, 2008.
Patent Literature 1: DE 1564582.
|Scope of claims||
1. A neutron source (1), comprising:
a neutron producing material layer (3) configured to produce neutron beams upon receipt of irradiation of proton beams or deuteron beams;
wherein said neutron producing material layer (3) contains a neutron producing material which is selected from the group consisting of Be, a Be compound, Li, and a Li compound;
a metal layer (2) joined with the neutron producing material layer,
wherein the metal layer (2) contains a number of moles of a metal element which is greater than 50 % of the total numbers of moles of the molecules constituting said metal layer,
wherein said metal element has a hydrogen diffusion coefficient of not less than 10-11 (m2/sec.) at 60° C,
wherein said metal element is selected from the group consisting of V, Ni, and alloys of any combination of V, Ni and Ti,
wherein said metal element is arranged in said neutron source (1) so as to be irradiated from said neutron beams characterised in that
said metal is further configured,upon said irradiation from said neutron beams, to produce radionuclides including ones having a half-life not longer than 12 hours which are the radionuclides with the largest total radiation dose among the radionuclides generated from the metal element.
2. The neutron source (1) according to claim 1, wherein the neutron producing material layer (3) has a thickness of 50 µm to 1.2 mm.
3. The neutron source (1) according to claim 1 or claim 2, wherein the neutron producing material layer (3) and the metal layer (2) are joined by diffusion bonding or brazing.
4. A neutron generator (10) characterised by a neutron source (1) according to any one of claims 1 to 3.
|IPC(International Patent Classification)||
|Specified countries||Contracting States: AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR|
Contact Information for " Neutron generation source, and neutron generation device "
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