The systematic procedure developed b y Brosens e t al. to derive the interatomic pair potential from the experimental phonon spectra is modified and generalized to cover a variety of metals.A set of metals (Na, K, Al, Cu, Fe) is investigated as prototypes for the general class of simple, noble, and transition metals. Comparisons are made between this potential and other potentials including those obtained from liquid metal structure factor data and pseudopotential theory. Reliability of the potentials is argued on the basis of comparison with experimental data, reliable theoretical potentials (where available). and internal consistency. The potentials are not recommended in modeling defects (vacancies, cracks) which introduce large inhomogeneities in the electron density.
The service-dependent degradation (aging) of light water reactor (LWR) pressure vessels due to irradiation embrittlement is discussed in this paper. The major variables which influence the irradiation embrittlement of LWR vessels are the copper and nickel content of the vessel materials and the fluence. The vessel beltline region is subjected to the largest fluences. A surveillance program, which consists of tension and Charpy-V-notch (CVN) testing of irradiated specimens of base, heat-affected-zone, and weld materials, is required to monitor changes in their embrittlement. Three main unresolved technical issues are: (1) the limited range and accuracy of the current correlations for calculating shifts in the reference temperature for nil-ductility transition (RTNDT) and changes in the Charpy upper shelf energy; (2) the need to demonstrate the conservatism of using CVN-based RTNDTshifts for certain sensitive reactor pressure vessel materials; and (3) the type of surveillance program required for any renewed operating license period. The damage caused by irradiation embrittlement can impact plant operating procedures, including heat up/cool down and hydrostatic test procedures, as well as the acceptability of various plant transients.
The use of the Wedepohl potential or the use of the vacancy format,ion energy as auxiliary conditions for a n empirical potential derived from phonon data are examined. 9 pair potential for aluminum, derived from a non-local pseudopotential model, is used as a benchmark. These auxiliary conditions are found to be unreliable. Reasons for this are discussed within a more general framework.Es wird die Benutzung des Wedepohl-Potentials oder der Leerstellenbildungsenergie als Hilfsbedingungen fur ein aus den Phononendaten abgeleitetee empirisches Potential iiberpruft. Zur Eichung wird ein von einem nichtlokalen Pseudopotentialmodell abgeleitetes Paarpotential fur Aluminium benutzt. Es wird gefunden, daB diese Hilfsbedingungen unzuverlassig sind. Grunde dafiir werden in einem allgemeineren Rahmen diskutiert.
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