45 research outputs found
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Status of safeguards instrumentation
The International Atomic Energy Agency is performing safeguards at some nuclear power reactors, 50 bulk processing facilities, and 170 research facilities. Its verification activities require the use of instruments to measure nuclear materials and of surveillance instruments to maintain continuity of knowledge of the locations of nuclear materials. Instruments that are in use and under development to measure weight, volume, concentration, and isotopic composition of nuclear materials, and the major surveillance instruments, are described in connection with their uses at representative nuclear facilities. The current status of safeguards instrumentation and the needs for future development are discussed
Constraints on the Nucleon Strange Form Factors at Q^2 ~ 0.1 GeV^2
We report the most precise measurement to date of a parity-violating
asymmetry in elastic electron-proton scattering. The measurement was carried
out with a beam energy of 3.03 GeV and a scattering angle =6
degrees, with the result A_PV = -1.14 +/- 0.24 (stat) +/- 0.06 (syst) parts per
million. From this we extract, at Q^2 = 0.099 GeV^2, the strange form factor
combination G_E^s + 0.080 G_M^s = 0.030 +/- 0.025 (stat) +/- 0.006 (syst) +/-
0.012 (FF) where the first two errors are experimental and the last error is
due to the uncertainty in the neutron electromagnetic form factor. This result
significantly improves current knowledge of G_E^s and G_M^s at Q^2 ~0.1 GeV^2.
A consistent picture emerges when several measurements at about the same Q^2
value are combined: G_E^s is consistent with zero while G_M^s prefers positive
values though G_E^s=G_M^s=0 is compatible with the data at 95% C.L.Comment: minor wording changes for clarity, updated references, dropped one
figure to improve focu
Measurement of the single-spin asymmetry A y 0 in quasi-elastic 3He↑(e,e′n) scattering at 0.4 < Q 2 < 1.0 GeV/c 2
No abstract available
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Safeguards instrumentation: past, present, future
Instruments are essential for accounting, for surveillance and for protection of nuclear materials. The development and application of such instrumentation is reviewed, with special attention to international safeguards applications. Active and passive nondestructive assay techniques are some 25 years of age. The important advances have been in learning how to use them effectively for specific applications, accompanied by major advances in radiation detectors, electronics, and, more recently, in mini-computers. The progress in seals has been disappointingly slow. Surveillance cameras have been widely used for many applications other than safeguards. The revolution in TV technology will have important implications. More sophisticated containment/surveillance equipment is being developed but has yet to be exploited. On the basis of this history, some expectations for instrumentation in the near future are presented
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Understanding national and international safeguards: an evolutionary process
Domestic and international safeguards have been evolving and will continue to evolve. in the case of the United States, the concern was to protect the classified materials, at first. Then attention focussed on material accounting, then on measures to promptly detect theft by individuals with access, and later on physical protection to ward-off armed terrorists. The objective of the IAEA has always been to provide assurance that nuclear materials are not being diverted from the peaceful facilities that are under safeguards. The evolution has taken place in deciding how to provide this assurance, and in the definition of specific safeguards goals. In both cases the technology needed to meet the goals has improved due to R and D and to experience. A plea is made for more cooperation betwen those who develop and manage the policies, those who develop safeguards techniques, and those who are subject to national and IAEA safeguards. Some illustrations of the evolution of policies, inadequate coordination and general progress are given
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Zone approaches to international safeguards of a nuclear fuel cycle
At present the IAEA designs its safeguards approach with regard to each type of nuclear facility so that the safeguards activities and effort are essentially the same for a given type and size of nuclear facility wherever it may be located. Conclusions regarding a state are derived by combining the results of safeguards verifications for the individual facilities within it. We have examined safeguards approaches for a state nuclear fuel cycle that take into account the existence of all of the nuclear facilities in the state. We have focussed on the fresh-fuel zone of an advanced nuclear fuel cycle, the several facilities of which use or process low-enriched uranium. At one extreme, flows and inventories would be verified at each material balance area. At the other extreme, the flows into and out of the zone and the inventory of the whole zone would be verified. The intention is to develop an approach which will make it possible to compare the technical effectiveness and the inspection effort for the facility-oriented approach, for the zone approach and for some reasonable intermediate safeguards approaches. Technical effectiveness, in these cases, means an estimate of the assurance that all nuclear material has been accounted for
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POSITRON SCANNER FOR LOCATING BRAIN TUMORS
A system is described that makes use of positron emitting isotopes for locating brain tumors. This system inherentiy provides more information about the distribution of radioactivity in the head in less time than existing scanners which use one or two detectors. A stationary circular array of 32 scintillation detectors scans a horizontal layer of the head from many directions simultaneously. The data, consisting of the number of counts in all possible coincidence pnirs, are coded and stored in the memory of a Two-Dimensional Pulse- Height Analyzer. A unique method of displaying and interpreting the data is described that enables rapid approximate analysis of complex source distribution patterns. (auth