Classifications

• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21G—CONVERSION OF CHEMICAL ELEMENTS; RADIOACTIVE SOURCES
  • G21G1/00—Arrangements for converting chemical elements by electromagnetic radiation, corpuscular radiation or particle bombardment, e.g. producing radioactive isotopes
  • G21G1/04—Arrangements for converting chemical elements by electromagnetic radiation, corpuscular radiation or particle bombardment, e.g. producing radioactive isotopes outside nuclear reactors or particle accelerators
  • G21G1/06—Arrangements for converting chemical elements by electromagnetic radiation, corpuscular radiation or particle bombardment, e.g. producing radioactive isotopes outside nuclear reactors or particle accelerators by neutron irradiation

Definitions

• the present invention refers to a method of utilizing the (n, gamma) reaction of thermal neutrons, wherein a target is arranged before a source of thermal neutrons.
• the method of the invention results in possibility of making use of the thermal neutron flux of a nuclear reactor, with disregard to the kind of the reactor, whereby the economy of operating of the different reactors can be highly improved.
• the proposed method can be realised with reactors of diverse kinds, e.g. with experimental reactors, energetic or boiler reactors etc.
• the object of the present invention is to make use of the thermal neutron flux of a reactor for producing non radioactive materials, wherein no special security measures are to be taken.
• the invention is based on the recognition that ytterbium and tungsten can be transformed into a mixture of different elements showing no or very low level radioactivity by means of the thermal neutrons generated in each radioactive reactor.
• the invention proposes a method of utilizing the (n, gamma) reaction of thermal neutrons of a reactor, the method comprising the step of arranging a target directed with its front surface to a source of thermal neutrons, especially a reactor, wherein according to the invention the target is consisted of 70 Yb and/or 74 W. It is especially advantageous to apply before the target a plate shaped body for slowing down the quick and/or the reactor neutrons, consisted of 41 Nb for slowing down the reactorneutrons and/or 59 Pr for slowing down the quick neutrons.
• this moderator of neutrons can be made also of beryllium.
• a beryllium plated can be applied also for covering the rear side of the target - this ensures reflection of the neutrons back to the target.
• about 30 % of the amount of ytterbium can be transformed into lutetion and the same amount of tungsten into rhenium. Above that about 20 % of tungsten transform into osmium.
• the metals received, i.e. lutetium, rhenium and osmium are much more expensive than the input metal of the process and can be separated therefrom by simple thermal processing because of considerable differences in the respective melting points.
• FIG. 1 shows the cross-section of a target applied in realising the present invention.
• the target 2 In the vicinity of a reactor 1 limited by a wall 7 a target 2 is arranged in an appropriate place.
• the target 2 consists of a front layer 3 forming a moderating body, a metal plate 4 including ytterbium and/or tungsten to be transformed and a rear reflecting layer 5.
• the front layer 3 is made of 41 Nb and/or 59 Pr. If necessary, 4 Be can be applied to.
• the mentioned metals slow down the flux of the neutrons leaving the interior of the reactor 2.
• the reflecting layer 5 covering the rear surface of the metal plate 4 reflects the neutrons back to the metal plate 4.
• the target 2 is arranged to be irradiated by a thermal neutron flux 6 and the front layer 3 receives the neutrons before entering the metal plate 4.
• the neutron flux 6 can be directed to the target 2 through the wall 7 of the raactor 1 in a known way, e.g. by the means of a window prepared in the wall 7.
• the metal plate 4 is made of ytterbium and/or tungsten.
• the irradiation of this plate carried out by the thermal neutrons generated by the reactor 1 or produced by the front layer in a (n, 2n) reaction should result in an alloy like mixture consisting of the following metals (the composition is given with approxinate data):
• the metal When taking ytterbium, the metal includes the following isotopes:
• the percentage values means the proportion of the given stable isotope in the metal mentioned.
• the metal When taking tungsten, the metal includes the following isotopes: v
• rhenium Re can be also activated and in decay processes (e-, gamma, K) it can be transformed partly into tungsten, partly into osmium: a dominate part, however, remains unchanged in form of rhenium.
• the gamma radiation coming into being is a low energy, low intensity weak radiation.
• the metallic mixtures prepared by the invention require at least 1/2 year storage before further processing. During this time the radiation level of the mixture falls under a maximum level allowed by the rules.
• the target 2 in the proximity of the active zone of the reactor, but under the condition that the target can not be the object of radiation comprising charged particles and fission products. If these factors are excluded the only disturbing effects follow from the gamma radiation of the reactor and the flux of quick neutrons emitted from the reactor. In both cases the loss of neutrons by the nucleus can follow in (gamma, n) and (n, 2n) reactions, however, these are low probability processes Therefore the only requirement is to moderate the quick neutrons, because the reactions with loss of neutron constitute a part of the reactions which hardly play important rule.
• the reactor neutrons show a wide spectrum with average energy 0.72 MeV (the flux may contain also neutrons with energy 20 MeV), therefore it is advantageous to slow down (moderate) the reactor neutrons and the quick neutrons by the means of (n, 2n) reactions whereby the yield of neutrons can be increased.
• the beryllium moderator is in this case a further element after that applied for slowing down the reactor and quick neutrons.
• the reactions of the reactor neutrons are characterized by small cross-section. Hence, they can be slowed down by means of the reaction 93
• the target 2 includes advantageously a rear reflecting layer 5 for reflecting back the neutrons.
• This layer can be made of beryllium ( 4 Be).
• the plate 4 of the target 2 is arranged preferably so that the neutron flux of the reactor falls under right angle (90°) on its surface.
• the method of the invention should be realised with a target 2 including after the reactor a layer made of ⁇ and/or b, a moderator (of 4 Be), the metal plate 4 made of 74 W and/or 70 Yb and a mirror layer (rear reflecting layer 5, made of 4 Be) .
• the beryllium can be preferred because it is a neutron source under influence of the gamma radiation emitted by the reactor, with the following reactions:
• the process of the invention can be applied for preparing catalyzer substances - this improves the economy of operating a reactor. No specific security means or expenses are necessary.
• the metal mixtures can be separated into components according to the known thermal techniques or applied as alloys.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• High Energy & Nuclear Physics (AREA)
• Particle Accelerators (AREA)

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• 1989
  • 1989-11-20 AU AU45283/89A patent/AU4528389A/en not_active Abandoned
  • 1989-11-20 WO PCT/HU1989/000054 patent/WO1990006583A1/en not_active Application Discontinuation
  • 1989-11-20 EP EP19890912826 patent/EP0400122A1/de not_active Withdrawn
  • 1989-11-23 CA CA 2003671 patent/CA2003671A1/en not_active Abandoned

Non-Patent Citations (1)

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