Abstract: An Actinium-225 generator is provided. The generator includes a neutron source; a neutron target arranged to receive neutrons emitted from the neutron source, wherein the neutron target comprises nickel; and a proton target arranged to receive protons emitted from the neutron target, wherein the proton target comprises radium-226. Methods for producing Actinium-225 are also provided.

Abstract: A target device for a neutron generating device, an accelerator-excited neutron generating device, and a beam coupling method thereof are disclosed. The target device comprises a plurality of solid particles serving as a target body; and a target body reaction chamber for accommodating the solid particles. With the accelerator-excited neutron generating device and the beam coupling method according to the present invention, the solid particles which are being circulated and situated outside the target body reaction chamber are processed, thereby overcoming defects in the prior art such as low-efficiency heat exchange, a short life time, a bad stability and a narrow application range, and achieving the advantages of high-efficiency heat exchange, a long life time, a good stability and a wide application range.

Abstract: A nuclear reactor adapted for generating energy and/or decontaminating nuclear fuel using a plurality of energy beam generating accelerator devices configured for inducing a photo-fission reaction in the nuclear fuel.

Abstract: A method is provided for operating a nuclear reactor. The method includes operating the nuclear reactor for at least one plutonium equilibrium cycle during which the core contains plutonium-equilibrium nuclear fuel assemblies; subsequently, operating the reactor for transition cycles, at least some of the plutonium-equilibrium nuclear fuel assemblies being progressively replaced with transition nuclear fuel assemblies and then with uranium-equilibrium nuclear fuel assemblies; and then operating the nuclear reactor for at least one uranium equilibrium cycle.

Abstract: Embodiments of the present invention disclose a nuclide identification method, a nuclide identification system, and a photoneutron emitter. The photoneutron emitter comprises: a pulsed electron accelerator configured for emitting electrons; and a photoneutron converting target configured to receive the electrons emitted by the pulsed electron accelerator and convert the electrons into photoneutrons. The photoneutron converting target has a volume of about 100 to about 8000 cm3, of about 100 to about 2500 cm3, or of about 785 cm3. These embodiments of the present invention can improve an accuracy of identification of a nuclide, and provide a practical photoneutron emitter, method and system for identifying a nuclide. Especially, these embodiments of the present invention can improve an accuracy of identification of a fissile nuclide such as 233U, 235U, and 239Pu, and provide a practical photoneutron emitter, method and system for identifying a fissile nuclide such as 233U, 235U, and 239Pu.

Abstract: Systems and methods permit discriminate access to nuclear reactors. Systems provide penetration pathways to irradiation target loading and offloading systems, instrumentation systems, and other external systems at desired times, while limiting such access during undesired times. Systems use selection mechanisms that can be strategically positioned for space sharing to connect only desired systems to a reactor. Selection mechanisms include distinct paths, forks, diverters, turntables, and other types of selectors. Management methods with such systems permits use of the nuclear reactor and penetration pathways between different systems and functions, simultaneously and at only distinct desired times. Existing TIP drives and other known instrumentation and plant systems are useable with access management systems and methods, which can be used in any nuclear plant with access restrictions.

Abstract: In an embodiment, a hybrid molten salt reactor includes a source of energetic neutrons, the energetic neutrons having a typical energy per neutron of 14 MeV or greater, a critical molten salt reactor, and a molten salt comprising a dissolved mixture of fissile actinides and fertile actinides. The molten salt circulates in a loop through the reactor vessel and around the source of energetic neutrons. The fissile actinides and fertile actinides sustain an exothermic nuclear reaction in which the actinides are irradiated by the energetic neutrons, the energetic neutrons inducing subcritical nuclear fission, and undergo critical nuclear fission when circulating through the critical molten salt reactor. A portion of the daughter neutrons generated by nuclear reactions are captured by the fertile actinides in the molten salt and induce transmutation of the fertile actinides into fissile actinides and sustain critical fission chain reactions in the molten salt reactor.

Abstract: A lightly hydrided/deuterated metallic plutonium-thorium fuel for use in a fast fission pool-type nuclear reactor cooled with liquid metal coolants, including lithium-7 lead eutectic, lead bismuth eutectic or lead. When so used, plutonium-239 is consumed, and merchantable heat is produced along with fissile uranium-233, which can be denatured with uranium-238 and used in light water reactors as fuel.

Abstract: An actinium-227 production device having a plurality of metallic or ceramic caplets, each enclosing a radium-226 compound in redundantly nested sealed cylinders. The radium-226 compound is compacted into a disk and diluted with heat transporting ceramic materials. A thermal neutron shield including spectrum shaping materials to protect actinium-227 produced from exposure to thermal neutrons is included along with a strong neutron absorber to shape the neutron spectrum such that radium-226 nuclei are exposed to neutrons in the higher epithermal energy groups upon entry into the target with an energy of between 20 eV and 1 KeV.

Abstract: Nuclear reactor systems and methods are described having many unique features tailored to address the special conditions and needs of emerging markets. The fast neutron spectrum nuclear reactor system may include a reactor having a reactor tank. A reactor core may be located within the reactor tank. The reactor core may include a fuel column of metal or cermet fuel using liquid sodium as a heat transfer medium. A pump may circulate the liquid sodium through a heat exchanger. The system may include a balance of plant with no nuclear safety function. The reactor may be modular, and may produce approximately 100 MWe.

Abstract: The invention provides methods for the production of radioisotopes or for the treatment of nuclear waste. In methods of the invention, a solution of heavy water and target material including fissile material present in subcritical amounts is provided in a shielded irradiation vessel. Bremsstrahlung photons are introduced into the solution, and have an energy sufficient to generate photoneutrons by interacting with the nucleus of the deuterons present in the heavy water and the resulting photoneutrons in turn cause fission of the fissile material. The bremsstrahlung photons can be generated with an electron beam and an x-ray converter. Devices of the invention can be small and generate radioisotopes on site, such as at medical facilities and industrial facilities. Solution can be recycled for continued use after recovery of products.

Abstract: A first pulsed beam of charged particles from a particle accelerator is accelerated toward a first target that is configured to emit a fast neutron beam in response to being struck by an accelerated particle such that the fast neutron beam is directed toward a physical region. The last neutron beam includes a neutron having an energy sufficient to cause fission in a fissionable material. Data from a sensor configured to detect radiation of a fission product is accessed, and before accelerating a second pulsed beam of charged particles, whether the physical region includes a fissionable material based on the data from the sensor is determined.

Abstract: Disclosed are a method and apparatus for making a radioisotope and a composition of matter including the radioisotope. The radioisotope is made by exposing a material to neutrons from a portable neutron source.

Abstract: Various embodiments of a nuclear fuel assembly and related methods for processing and managing spent nuclear fuel are disclosed. According to one exemplary embodiment, a nuclear fuel may include a plurality of first fuel rods having a plurality of first fuel elements and a plurality of second fuel rods having a plurality of second fuel elements. Each of the first fuel elements may include uranium dioxide fuel, and each of the second fuel elements may include a plurality of tristructural isotropic fuel particles embedded in a silicon carbide matrix. The plurality of first fuel rods and the plurality of second fuel rods are arranged in a fuel assembly.

Abstract: A system for radioisotope production uses fast-neutron-caused fission of depleted or naturally occurring uranium targets in an irradiation chamber. Fast fission can be enhanced by having neutrons encountering the target undergo scattering or reflection to increase each neutron's probability of causing fission (n, f) reactions in U-238. The U-238 can be deployed as one or more layers sandwiched between layers of neutron-reflecting material, or as rods surrounded by neutron-reflecting material. The gaseous fission products can be withdrawn from the irradiation chamber on a continuous basis, and the radioactive iodine isotopes (including I-131) extracted.

Abstract: Example embodiments are directed to apparatuses and methods for producing radioisotopes in instrumentation tubes of operating commercial nuclear reactors. Irradiation targets may be inserted and removed from instrumentation tubes during operation and converted to radioisotopes otherwise unavailable from nuclear reactors. Example apparatuses may continuously insert, remove, and store irradiation targets to be converted to useable radioisotopes.

Abstract: Methods and systems for non-intrusively detecting the existence of fissile materials in a container via the measurement of energetic prompt neutrons are disclosed. The methods and systems use the unique nature of the prompt neutron energy spectrum from neutron-induced fission arising from the emission of neutrons from almost fully accelerated fragments to unambiguously identify fissile material. These signals from neutron-induced fission are unique and allow the detection of any material in the actinide region of the nuclear periodic table.

Abstract: A method and a system for detecting the presence of special nuclear materials in a suspect container. The system and its method include irradiating the suspect container with a beam of neutrons, so as to induce a thermal fission in a portion of the special nuclear materials, detecting the gamma rays that are emitted from the fission products formed by the thermal fission, to produce a detector signal, comparing the detector signal with a threshold value to form a comparison, and detecting the presence of the special nuclear materials using the comparison.

Abstract: Methods and systems for non-intrusively detecting the existence of fissile materials in a container via the measurement of energetic prompt neutrons are disclosed. The methods and systems use the unique nature of the prompt neutron energy spectrum from photo-fission arising from the emission of neutrons from almost fully accelerated fragments to unambiguously identify fissile material. The angular distribution of the prompt neutrons from photo-fission and the energy distribution correlated to neutron angle relative to the photon beam are used to distinguish odd-even from even-even nuclei undergoing photo-fission. The independence of the neutron yield curve (yield as a function of electron beam energy or photon energy) on neutron energy also is also used to distinguish photo-fission from other processes such as (?, n). Different beam geometries are used to detect localized samples of fissile material and also fissile materials dispersed as small fragments or thin sheets over broad regions.

Abstract: A method and a system for detecting the presence of special nuclear materials in a suspect container. The system and its method include irradiating the suspect container with a beam of neutrons, so as to induce a thermal fission in a portion of the special nuclear materials, detecting the gamma rays that are emitted from the fission products formed by the thermal fission, to produce a detector signal, comparing the detector signal with a threshold value to form a comparison, and detecting the presence of the special nuclear materials using the comparison.

Abstract: A method and a system for detecting the presence of special nuclear materials in a suspect container. The system and its method include irradiating the suspect container with a beam of neutrons, so as to induce a thermal fission in a portion of the special nuclear materials, detecting the gamma rays that are emitted from the fission products formed by the thermal fission, to produce a detector signal, comparing the detector signal with a threshold value to form a comparison, and detecting the presence of the special nuclear materials using the comparison.

Abstract: A method and a system for detecting the presence of special nuclear materials in a container. The system and its method include irradiating the container with an energetic beam, so as to induce a fission in the special nuclear materials, detecting the gamma rays that are emitted from the fission products formed by the fission, to produce a detector signal, comparing the detector signal with a threshold value to form a comparison, and detecting the presence of the special nuclear materials using the comparison.

Abstract: A method and associated apparatus for detecting concealed fissile, fissionable or special nuclear material in an article, such as a shipping container, is provided. The article is irradiated with a source of fast neutrons, and fast neutrons released by the fissile or fissionable material, if present, are detected between source neutron pulses. The method uses a neutron detector that can detect and discriminate fast neutrons in the presence of thermal neutrons and gamma radiation. The detector is able to process high count rates and is resistant to radiation damage, and is preferably a solid state neutron detector comprised of silicon carbide.

Abstract: A method for producing ultra-pure Pu-238 is provided. The method comprises the steps of short-term irradiating Am-241 targets with a high, thermal neutron flux greater than 6.5×1014 neutrons cm?2 s?1 and more preferably greater than 1×1015 neutrons cm?2 s?1 for a predetermined period of time preferably from 20 days to 30 days and more preferably approximately 25 days to convert a substantial fraction of the Am-241 to Cm-242, e.g., approximately 0.555 g of Cm-242 per g of Am-241 charged, thereafter promptly chemically separating the produced Cm-242, preferably within 10 days to 20 days of the irradiation cycle of the Am-241 targets and more preferably within about 15 days of the irradiation cycle of the Am-241 targets, and recovering the ultra-pure Pu-238 decay product of the separated Cm-242.

Abstract: A method for transmuting spent fuel from a nuclear reactor includes the step of separating the waste into components including a driver fuel component and a transmutation fuel component. The driver fuel, which includes fissile materials such as Plutonium239, is used to initiate a critical, fission reaction in a reactor. The transmutation fuel, which includes non-fissile transuranic isotopes, is transmuted by thermal neutrons generated during fission of the driver fuel. The system is designed to promote fission of the driver fuel and reduce neutron capture by the driver fuel. Reacted driver fuel is separated into transuranics and fission products using a dry cleanup process and the resulting transuranics are mixed with transmutation fuel and re-introduced into the reactor. Transmutation fuel from the reactor is introduced into a second reactor for further transmutation by neutrons generated using a proton beam and spallation target.

Abstract: A method and apparatus for optimizing the production of Pu-238 in a nuclear reactor during normal reactor operation is disclosed wherein the production of Pu-238 is confined to one or more selectively replaced fuel cells with target cells located in the inside of the active volume of the reactor core to maximize the neutron flux for target irradiation. The target cells are modified existing nuclear fuel assembly cells having some fuel rods replaced with target rods of Np-237 forming a cluster array and having rings of water filled rods surrounding the target cluster to produce the desired optimal Pu-238 production.

Abstract: The invention relates a device for measuring the relative proportions of uranium and plutonium in a radioactive package (16), having: a source of photons (10) for irradiating the package, at least one delayed neutron detector (18) able to deliver counting signals for neutrons emitted by the package, means (22, 30) of acquiring counting signals, able to establish a decrease over time in the neutrons emitted, characteristic of the radioactive package, calculation means (32) for comparing the decay characteristic of the radioactive package with the respective characteristic decays of uranium and plutonium and for establishing relative proportions of uranium and plutonium in the package.

Abstract: An apparatus and method is described for transmuting higher actinides, plutonium and selected fission products in a liquid-fuel subcritical assembly. Uranium may also be enriched, thereby providing new fuel for use in conventional nuclear power plants. An accelerator provides the additional neutrons required to perform the processes. The size of the accelerator needed to complete fuel cycle closure depends on the neutron efficiency of the supported reactors and on the neutron spectrum of the actinide transmutation apparatus. Treatment of spent fuel from light water reactors (LWRs) using uranium-based fuel will require the largest accelerator power, whereas neutron-efficient high temperature gas reactors (HTGRs) or CANDU reactors will require the smallest accelerator power, especially if thorium is introduced into the newly generated fuel according to the teachings of the present invention.

Abstract: In order to use up a stockpile of weapons-grade plutonium, the plutonium is converted into a mixed oxide (MOX) fuel form wherein it can be disposed in a plurality of different fuel assembly types. Depending on the equilibrium cycle that is required, a predetermined number of one or more of the fuel assembly types are selected and arranged in the core of the reactor in accordance with a selected loading schedule. Each of the fuel assemblies is designed to produce different combustion characteristics whereby the appropriate selection and disposition in the core enables the resulting equilibrium cycle to closely resemble that which is produced using urania fuel. The arrangement of the MOX rods and burnable absorber rods within each of the fuel assemblies, in combination with a selective control of the amount of plutonium which is contained in each of the MOX rods, is used to tailor the combustion characteristics of the assembly.

Abstract: A new transmutation assembly permits an efficient transmutation of a long-lived radioactive material (long-lived FP nuclides such as technetium-99 or iodine-129) which was produced in the nuclear reactor. Wire-type members of a long-lived radioactive material comprised of metals, alloys or compounds including long-lived FP nuclides are surrounded by a moderator material and installed in cladding tubes to form FP pins. The FP pins, and nothing else, are housed in a wrapper tube to form a transmutation assembly. The wire-type members can be replaced by thin ring-type members. The transmutation assemblies can be selectively and at least partly loaded into a core region, a blanket region or a shield region of a reactor core in a fast reactor. From a viewpoint of reducing the influence on the reactor core characteristics, it is optimal to load the transmutation assemblies into the blanket region.

Abstract: In order to use up a stockpile of weapons-grade plutonium, the plutonium is converted into a mixed oxide (MOX) fuel form wherein it can be disposed in a plurality of different fuel assembly types. Depending on the equilibrium cycle that is required, a predetermined number of one or more of the fuel assembly types are selected and arranged in the core of the reactor in accordance with a selected loading schedule. Each of the fuel assemblies is designed to produce different combustion characteristics whereby the appropriate selection and disposition in the core enables the resulting equilibrium cycle to closely resemble that which is produced using urania fuel. The arrangement of the MOX rods and burnable absorber rods within each of the fuel assemblies, in combination with a selective control of the amount of plutonium which is contained in each of the MOX rods, is used to tailor the combustion. characteristics of the assembly.

Abstract: A radioisotope production target and a method for fabricating a radioisotope production target is provided, wherein the target comprises an inner cylinder, a foil of fissionable material circumferentially contacting the outer surface of the inner cylinder, and an outer hollow cylinder adapted to receive the substantially foil-covered inner cylinder and compress tightly against the foil to provide good mechanical contact therewith.

Abstract: This invention relates to a method for the destruction of plutonium (Pu) by irradiation in a light water reactor (LWR). According to the invention Pu is mixed with highly enriched uranium (U) in roughly equal weight proportion rates. This mixture is embedded in an inert matrix of a material whose components have an atomic number significantly lower than 92. LWR fuel pins are then produced therefrom and these pins are inserted in a LWR in place of certain normal LWR fuel pins. The irradiation time of the fuel pins containing Pu is significantly longer than that of said normal pins. The irradiation is preferably repeated after about 200 years without any reprocessing of the spent fuel.

Abstract: In order to use up a stockpile of weapons-grade plutonium, the plutonium is converted into a mixed oxide (MOX) fuel form wherein it can be disposed in a plurality of different fuel assembly types. Depending on the equilibrium cycle that is required, a predetermined number of one or more of the fuel assembly types are selected and arranged in the core of the reactor in accordance with a selected loading schedule. Each of the fuel assemblies is designed to produce different combustion characteristics whereby the appropriate selection and disposition in the core enables the resulting equilibrium cycle to closely resemble that which is produced using urania fuel. The arrangement of the MOX rods and burnable absorber rods within each of the fuel assemblies, in combination with a selective control of the amount of plutonium which is contained in each of the MOX rods, is used to tailor the combustion characteristics of the assembly.

Abstract: A heavy ion generator is used with a plasma desorption mass spectrometer to provide an appropriate neutron flux in the direction of a fissionable material in order to desorb and ionize large molecules from the material for mass analysis.The heavy ion generator comprises a fissionable material having a high n,f reaction cross section. The heavy ion generator also comprises a pulsed neutron generator that is used to bombard the fissionable material with pulses of neutrons, thereby causing heavy ions to be emitted from the fissionable material. These heavy ions impinge on a material, thereby causing ions to desorb off that material. The ions desorbed off the material pass through a time-of-flight mass analyzer, wherein ions can be measured with masses greater than 25,000 amu.

Abstract: A radioisotope production target and a method for fabricating a radioisotope production target is provided, wherein the target comprises an inner cylinder, a foil of fissionable material circumferentially contacting the outer surface of the inner cylinder, and an outer hollow cylinder adapted to receive the substantially foil-covered inner cylinder and compress tightly against the foil to provide good mechanical contact therewith.

Abstract: Plutonium is effectively and economically rendered unsuitable for employment in a device for creating a nuclear detonation. Weapons-grade plutonium is made into ceramic fuel in the form of spheroids of submillimeter size, coated with multi-layer fission-product-retentive coatings and disposed in sealed fuel chambers in graphite block fuel elements. These elements are used to form a core for a modular helium-cooled high temperature nuclear reactor which is operated to efficiently generate power by causing the hot high pressure helium coolant to drive a gas turbine directly connected to an electrical generator, which nuclear fuel core has about a 3-year lifetime. Spent nuclear fuel elements are removed at the end of 3 years and shifted to form the core for an accelerator-driven helium-cooled reactor wherein a subcritical core of spent fuel elements is safely caused to effectively continuously fission by a neutron flux created by a Linac which bombards a lead target with a beam of high energy protons.

Abstract: Neptunium of minor actinide nuclides separated from spent fuel is added to fuel of reactor cores (inner reactor cores and/or outer reactor cores) of a fast reactor and americium of the separated minor actinide nuclides and rare earth elements are added to either or both of radial and axial blankets of the fast reactor for burning. Thus, the minor actinide nuclides with long half-lives can be burnt with the fast reactor core with the minimized effects of the rare earth elements. For a burner reactor, americium and rare earth elements may be added to shields for burning. Curium may be added together with americium and rare earth elements. Neptunium is added in amount of 2% to 5% by weight based on the weight of the fuel and the rare earth elements are added in an amount of 50% by weight or less based on the weight of the fuel. A Purex process is used to separate neptunium and a Truex process is used to separate americium and curium.

Abstract: The invention provides a heterogeneously loaded type of fast reactor core in which a reduced number of target fuel assemblies containing minor actinide nuclides are heterogeneously dispersed and loaded. A wrapper tube for each of the target fuel assemblies is of the same shape and size as a hexagonal wrapper tube for an ordinary core fuel assembly. Each of target fuel rods within the wrapper tube contains 20 to 50% of minor actinide nuclides, and has a diameter more reduced than that of an ordinary core fuel rod. The number of the ordinary core fuel rods loaded in the ordinary core fuel assembly is 271 while the number of the target fuel rods loaded in the target fuel assembly is 331 or 397. Thirty to 50 such target fuel assemblies are heterogeneously dispersed and loaded in the fast reactor core.

Abstract: There is provided a fuel assembly for a thermal neutron type reactor in which fuel rods utilizing U-235 enriched uranium-oxide are bundled in a lattice arrangement, and a portion of the fuel rods in the lattice arrangement is substituted with MOX fuel rods provided with no U-235 enriched uranium-oxide fuel portion and no natural or depleted uranium-oxide blanket portion.

Abstract: In a transuranium elements transmuting reactor core in which a reactor is charged with a plurality of fuel assemblies at a core and an amount of a transuranium element to be added is controlled so as to prevent a fuel element contained in the fuel assemblies from melting, the amount of the transuranium elements to be added to the fuel element is controlled so as to keep an excess reactivity of the reactor substantially zero through an operation of the reactor. A charging density of minor actinides is set to lessen outwards of a core central portion in a core area where a plutonium content is made even. The charging density of minor actinides is set high accordingly in an area where a plutonium is enriched high at the core of a plutonium enriched area where a plutonium content varies.

Abstract: The invention relates to a method for producing actinium-225 and bismuth-213. According to the invention, radium-226 is irradiated in the thermal neutron flux of a nuclear reactor, the thorium fraction of the irradiation product is then chemically isolated and therefrom the actinium and radium mixture growing continuously by decay therein is chemically separated, this mixture serving as "cow" for the desired radionuclides which are growing continuously.

Abstract: In a transuranium elements transmuting reactor core in which a reactor is charged with a plurality of fuel assemblies at a core and an amount of a transuranium element to be added is controlled so as to prevent a fuel element contained in the fuel assemblies from melting, the amount of the transuranium elements to be added to the fuel element is controlled so as to keep an excess reactivity of the reactor substantially zero through an operation of the reactor. A charging density of minor actinides is set to lessen outwards of a core central portion in a core area where a plutonium content is made even. The charging density of minor actinides is set high accordingly in an area where a plutonium is enriched high at the core of a plutonium enriched area where a plutonium content varies.

Abstract: Apparatus for nuclear transmutation and power production using an intense accelerator-generated thermal neutron flux. High thermal neutron fluxes generated from the action of a high power proton accelerator on a spallation target allows the efficient burn-up of higher actinide nuclear waste by a two-step process. Additionally, rapid burn-up of fission product waste for nuclides having small thermal neutron cross sections, and the practicality of small material inventories while achieving significant throughput derive from employment of such high fluxes. Several nuclear technology problems are addressed including 1. nuclear energy production without a waste stream requiring storage on a geological timescale, 2. the burn-up of defense and commercial nuclear waste, and 3. the production of defense nuclear material. The apparatus includes an accelerator, a target for neutron production surrounded by a blanket region for transmutation, a turbine for electric power production, and a chemical processing facility.

Abstract: A method for decreasing the amount of hazardous radioactive reactor waste materials by separation from the waste of materials having long-term risk potential and exposing these materials to a thermal neutron flux. The utilization of thermal neutrons enhances the natural decay rates of the hazardous materials while the separation for recycling of the hazardous materials prevents further transmutation of stable and short-lived nuclides.

Abstract: A combination of passive and active neutron measurements which yields quantitative information about the isotopic composition of transuranic wastes from nuclear power or weapons material manufacture reactors is described. From the measurement of prompt and delayed neutron emission and the incidence of two coincidentally emitted neutrons from induced fission of fissile material in the sample, one can quantify .sup.233 U, .sup.235 U and .sup.239 Pu isotopes in waste samples. Passive coincidence counting, including neutron multiplicity measurement and determination of the overall passive neutron flux additionally enables the separate quantitative evaluation of spontaneous fission isotopes such as .sup.240 Pu, .sup.244 Cm and .sup.252 Cf, and the spontaneous alpha particle emitter .sup.241 Am.