Nuclear evaluation

In preparation of ENDF/B-V, a great deal of testing has been done with ENDF/B-IV as well as preliminary versions of ENDF/B-V. This data testmg, covering the major fissile and fratile materials, highlighted a number of discrepancies and contributed to a number of data improvements by the nuclear evaluators that have signifi tly... 

Eddy-current non-destructive evaluation is widely used in the aerospace and nuclear power industries for the detection and characterisation of defects in metal components. The ability to predict the probe response to various types of defect is highly valuable since it enables the influence of particular parameters to be studied without recourse to costly and time consuming experiments. The solution of forward problems is also essential in the process of inverting experimental data. 

The case of thin-skin regime appears in various industrial sectors such as aerospace (with aluminium parts) and also nuclear in tubes (with ferromagnetic parts or mild steel components). The detection of deeper defects depends of course on the choice of the frequency and the dimension of the probe. Modelling can evaluate different solutions for a type of testing in order to help to choose the best NDT system. 

In service inspections of French nuclear Pressure Water Reactor (PWR) vessels are carried out automatically in complete immersion from the inside by means of ultrasonic focused probes working in the pulse echo mode. Concern has been expressed about the capabilities of performing non destructive evaluation of the Outer Surface Defects (OSD), i.e. defects located in the vicinity of the outer surface of the inspected components. OSD are insonified by both a "direct" field that passes through the inner surface (water/steel) of the component containing the defect and a "secondary" field reflected from the outer surface. Consequently, the Bscan images, containing the signatures of such defects, are complicated and their interpretation is a difficult task. 

MAPPscan is a manual ultrasonic testing system connected to an acoustic positioning system.. The system is developed as a consequence of the increased radiation doses in nuclear plants The system has the same flexibility as manual scanning with the same accuracy and the possibilties to collect, store and evaluate the UT data as with mechanised Ultrasonic systems The positioning system is based on spatial acoustic triangulation and have an accuracy of better than 1.0 mm within its recommended range. 

FI4344 Reconstitution techniques qualification and evaluation to study ageing Dhenomena of nuclear oressure vessel materials Dr Eric Van Walle Studiecentrum voor kernenergie... 

Comcidence experiments have been connnon in nuclear physics since the 1930s.The widely used coincidence circuit of Rossi [9] allowed experimenters to detennine, within tire resolution time of the electronics of the day, whether two events were coincident in time. The early circuits were capable of submicrosecond resolution, but lacked the flexibility of today s equipment. The most important distinction between modem comcidence methods and those of the earlier days is the availability of semiconductor memories that allow one to now record precisely the time relations between all particles detected in an experiment. We shall see the importance of tliis in the evaluation of the statistical uncertainty of the results. 

The data were extracted from M. Lederer and V. S. Shirley, Table of Isotopes, 7th ed., Wiley-Interscience, New York, 1978 A. H. Wapstra and G. Audi, The 1983 Atomic Mass Evaluation, Nucl. Phys. A432 l-54 (1985) V. S. Shirley, ed.. Table of Radioactive Isotopes, 8th ed., Wiley-Interscience, New York, 1986 and P. Raghavan, Table of Nuclear Moments, At. Data Nucl. Data Tables, 42 189 (1989). 

Miscellaneous. NIST has a reference database of criticaUy evaluated x-ray photoelectron and Auger spectral data, which is designed to mn on PCs. It is searchable by spectral lines as weU as by element, line energy, and chemical data (82). The Nuclear Quadrapole Resonance Spectra Database at Osaka University of over 10,000 records is avaUable in an MS-DOS version (83). The NCLl system, SDBS, has esr and Raman spectra, along with nmr, ir, and ms data, as described. 

Fuel and Heavy Water Hvailahility, Report of Working Group 1, International Nuclear Fuel Cycle Evaluation, Vieima, Austria, International Atomic Energy Agency STl/PUB/534, UNIPUB, Inc., New York, 1980, pp. 174-175. 

AGNS Staff, Engineering Evaluations of alternativesfor Processing Uranium-Based Fuels, Studies and Research Concerning the Barnwell Nuclear Fuels Plant (BNFP), AGNS-1040-3.1-32, National Technical Information Service (NTlS), Springfield, Va., 1978. 

Several of the reactor physics parameters are both measurable and calculable from more fundamental properties such as the energy-dependent neutron cross sections and atom number densities. An extensive database. Evaluated Nuclear Data Files (ENDF), has been maintained over several decades. There is an interplay between theory and experiment to guide design of a reactor, as in other engineering systems. 

The NRC safety goal can be evaluated by comparison to the risks from accidents incurred from other human activities (Eig. 2) (29). The safety goal and the safety record of the nuclear power industry indicate much lower societal risks from commercial nuclear power than from a wide range of other common human activities. 

Analysis and Evaluation of Operational Data—1993 Annual Report Reactors, NUREG-1272, Vol. 8, No. 1, U.S. Nuclear Regulatory Commission, Washington, D.C., Nov. 1994. 

Summag Report Screening and Evaluation of Ricense Event Reports for 1979, Nuclear Safety Analysis Center Report, NSAC-2, Palo Alto, Calif., 1980. 

Criticality Precautions. The presence of a critical mass of Pu ia a container can result ia a fission chain reaction. Lethal amounts of gamma and neutron radiation are emitted, and a large amount of heat is produced. The assembly can simmer near critical or can make repeated critical excursions. The generation of heat results eventually ia an explosion which destroys the assembly. The quantity of Pu required for a critical mass depends on several factors the form and concentration of the Pu, the geometry of the system, the presence of moderators (water, hydrogen-rich compounds such as polyethylene, cadmium, etc), the proximity of neutron reflectors, the presence of nuclear poisons, and the potential iateraction with neighboring fissile systems (188). As Httle as 509 g of Pu(N02)4 solution at a concentration Pu of 33 g/L ia a spherical container, reflected by an infinite amount of water, is a critical mass (189,190). Evaluation of criticaUty controls is available (32,190). 

There are single-volume sources available that contain the half-Hves and y-ray intensities for all radionucHdes (15,17—19). These data can also be obtained electronically from the NUDAT (8) or Evaluated Nuclear Stmcture Data File (ENSDF) (17) databases (see Databases). 

Nuclear Data Sheets, Academic Press, San Diego, Calif., TvaluatedNuclear Structure Data File (ENSDF), a computer database of nuclear stmcture data evaluated by an international network of evaluators, is maintained at the National Nuclear Data Center, Brookhaven National Laboratory. NUDNTis a computer database of decay data extracted from the ENSDF. 

The NRC also imposes special security requirements for spent fuel shipments and transport of highly enriched uranium or plutonium materials that can be used in the manufacture of nuclear weapons. These security measures include route evaluation, escort personnel and vehicles, communications capabiHties, and emergency plans. State governments are notified in advance of any planned shipment within their state of spent fuel, or any other radioactive materials requiring shipment in accident-proof. Type B containers. 

In addition, uranium and lead transport mechanisms ia radioactive minerals have been studied ia order to evaluate the suitabiUty of mineral phases as hosts for radioactive wastes. Zircon is one of the most commonly used geochronometers, as well as a proposed nuclear waste matrix material, and there are many mechanisms by which uranium and lead can migrate through its stmcture (19). 

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