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ID:
164684
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| Summary/Abstract |
This article offers a new analysis of radionuclide and hydroacoustic data to support a low-yield nuclear weapon test as a plausible explanation for the still contentious 22 September 1979 Vela Incident, in which U.S. satellite Vela 6911 detected an optical signal characteristic of an atmospheric nuclear explosion over the Southern Indian or Atlantic Ocean. Based on documents not previously widely available, as well as recently declassified papers and letters, this article concludes that iodine-131 found in the thyroids of some Australian sheep would be consistent with them having grazed in the path of a potential radioactive fallout plume from a 22 September low-yield nuclear test in the Southern Indian Ocean. Further, several declassified letters and reports which describe aspects of still classified hydroacoustic reports and data favor the test scenario. The radionuclide and hydroacoustic data taken together with the analysis of the double-flash optical signal picked up by Vela 6911 that was described in a companion 2017 article (“The 22 September 1979 Vela Incident: The Detected Double-Flash”) can be traced back to sources with similar spatial and temporal origins and serve as a strong indicator for a nuclear explosion being responsible for the 22 September 1979 Vela Incident.
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| 2 |
ID:
164682
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| Summary/Abstract |
Remote monitoring of krypton-85 from undeclared reprocessing of spent nuclear fuel could be part of a fissile material cut-off treaty, could serve as an additional measure for the IAEA safeguards system to monitor compliance with the Non-Proliferation of Nuclear Weapons Treaty, and could be an important verification tool of a reprocessing moratorium or Nuclear Weapon Free Zone in the Middle East or East Asia. Atmospheric transport modelling is applied to determine the area over which krypton-85 emissions from undeclared reprocessing activities at various levels in the Middle East would still be detectable against the high krypton-85 background from reprocessing in historical weapon programs in the United States and USSR as well as more recent and ongoing commercial reprocessing in France and the U.K. Analysis of annual wind flow over Israel's Dimona facility, the only operating reprocessing site in the region, suggests that a known reprocessing plant could be monitored with one or a few fixed monitoring stations. Random air sampling for krypton-85 analysis, perhaps using drones, may be feasible for reliable and timely detection of clandestine reprocessing plants against the krypton-85 background but would require on the order of 50–100 air samples per day. Ending reprocessing at La Hague in France and at Sellafield in the UK and the resulting decline of the krypton-85 background over time would reduce to about 10 the number of daily samples required to monitor the Middle East.
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| 3 |
ID:
164686
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Several nuclear archaeology techniques have been proposed to determine historic plutonium production in dedicated nuclear reactors. These methods rely on sampling materials from the reactor core, or specially designed monitor tags, to examine suited isotopic ratios and deduce the amount of plutonium produced. However, some production reactors are capable of producing isotopes other than plutonium, such as tritium. If a reactor was declared to produce tritium, it would be crucial to confirm that it was in fact producing tritium, and not plutonium. In this paper, we describe how isotopic ratios discrepancies could be used to distinguish between plutonium and tritium production modes. We present results obtained from the simulation of reactor lattices inspired by Savannah River Site heavy-water production reactors and show that elements such as hafnium and tungsten can detect undeclared production of plutonium.
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| 4 |
ID:
164685
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| Summary/Abstract |
Before a nuclear warhead is dismantled, the special nuclear material and explosives must be identified and authenticated. This paper proposes a passive method to detect and identify weapons-grade plutonium cores and explosives in nuclear warheads based on neutron analyses techniques. This paper first describes the principles of a passive detection method that calculates the element number ratio (namely the ratio between the nucleus numbers of two different elements) of the element of interest to identify a source and how this method could be applied to the detection of warhead explosives. Second, a simulation of weapons-grade plutonium using JMCT software is described. The simulation assumes the elemental components of the explosives are activated by the production and transport of neutrons from the weapons-grade plutonium core and counted the gamma ray emissions of from the resultant hydrogen, carbon, and nitrogen nuclides with a high-purity germanium detector (HPGe) array. After an hour of counting, the element number ratios of these elements in the simulation were reconstructed and accurately matched the values for the explosives in the warhead. These results suggest that the passive method can be used to identify the presence of weapons-grade plutonium in the warhead. In addition, the simulation showed that the passive method can also discriminate between the various types of explosives in warheads, providing important physical information for the verification process during dismantlement.
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| 5 |
ID:
164688
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| Summary/Abstract |
Over the last 2 decades there has been renewed interest in developing advanced nuclear reactors and fuel cycles. Many of these advanced design concepts require or can use fuel elements that contain actinides recycled from light water reactor spent fuel. Irradiation of these elements in fast nuclear reactors is supposed to transmute them into less toxic isotopes and reduce their mass. Since transmutation is not efficient, recycling into new advanced reactor fuel must occur repeatedly to achieve a substantial reduction in mass. The introduction of this technology will create long-term proliferation risks and require safeguarding not only of plutonium, but also of the other target actinides: neptunium, americium, and curium. These elements will be present in isotopic mixtures for which information on their critical masses is unavailable. This paper provides data on critical masses and spontaneous fission neutron background for the isotopic compositions of the actinides of interest and their evolution in light water reactor fuel of various burnups and during spent fuel storage. These data are complemented by generic estimates of total inventories of these elements present in full-scale partitioning and transmutation fuel cycles being considered for commercial scale and of the time periods required for significantly reducing their proliferation potential.
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