No abstract

Trends in the properties of defects, reflecting the role of Ni and P in the enhanced precipitation of copper during irradiation, have been studied by small angle neutron scattering (SANS) in a set of 8 model RPV steels. The alloys in the set contain different, selected amounts of Cu, Ni and P, while the composition of all the 8 samples concerning the rest of the alloying elements, the ‘RPV steel background’, was invariant throughout the series. The irradiation was done in a test reactor at 290C, at controlled radiation conditions, for two neutron fluences of 5∙1018 and 5∙1019 n/cm2. The SANS data show an approximately quadratic relationship between the precipitated volume fraction fm of damage particles and the nickel content cNi of the sample for the medium-copper cCu = 0.16% alloys, with a nearly zero initial slope of fm; the coefficients in the equation vary substantially with the fluence. A nearly perfect correlation of fm with the increase of microhardness was found for all alloys. The size distribution, as deduced from magnetic scattering, differs systematically from that found by analysis of the nuclear scattering; this difference correlates with both cCu and cNi. For the two low-copper alloys, phosphorus is seen to enhance production of radiation damage centers, whereas for the medium-copper alloys a refinement of the precipitated phase occurs.

Small angle neutron scattering (SANS) techniques have been employed to study the nature of the radiation damage and its dependence on phosphorus concentration at two different copper levels (0.002 and 0.3%) in a set of laboratory melts of A533-B steel irradiated to ˜2.5 × 1019 n/cm2 at 288°C under test reactor conditions. In all materials, distributions of clusters were found with number densities ˜ 1017 to 1018 cm-3 and diameters ˜ 1 to 2 nm. Cluster volume fractions were approximately an order of magnitude higher in the 0.3% Cu steels, which were associated with greater radiation strengthening and embrittle-ment. Magnetic and nuclear scattering data are best interpreted in terms of mixed clusters containing Cu, Mn, and Ni; increasing P content leads to some refinement of the cluster distributions. In the low-Cu steels embrittlement is also associated with radiation hardening via cluster formation promoted by increasing phosphorus content.

No abstract

The hydrogen content at O"C, 1 atm, is n = 0.73 [Ill; the ratio of the diffusion coefficients can be obtained from the measurements in Fig. 3 as: DDO,/D, = 0.85. Equation (4a) then yields: pD = 0.15.The order of magnitude: about 10% of the diffusion jumps in P-phase PdD, are displacement jumps, seems not unreasonable.In the second case, tracer diffusion of tritium in PdH,, we get instead of Equation (4):The ratios of the probabilities p can be related to the difference of the activation energies EH -E, = d E and to the ratio of the frequency factors w i and w: in the same way as before.But now, contrary to the case before, A E < 0 and wi/w: < 1.Since values from the pure P-phase PdT, are not available we will, for purpose of estimation, make use of the a-phase values ConclusionThe numerical values obtained here can not be taken for more than first approximations. For a better base of numerical data the experimental techniques and the precision of their results have to be improved markedly. The foregoing considerations may have shown that it would be worth while to develop such improvements. They would open a new approach to investigating correlation problems which could hardly be studied in so clear and distinct way with other diffusion systems of more complicated nature. AcknowledgementWe gratefully acknowledge the financial support of the experimental investigations by the Deutsche Forschungsgemeinschaft providing for stipends and for equipment. The diffusion of dissolved hydrogen in two metals welded together and with different affinities to hydrogen is investigated experimentally and theoretically. The hydrogen distribution is measured nondestructively by a collimated Cadmium-filtered neutron beam of the FRG-1. For theoretical analysis the methods of expanding the solution into eigenfunctions of the problem must be generalized towards piecewise continuous eigenfunctions because of the concentration jump at the boundary between the two metals. The diffusion constants and the Nernst distribution coefficient are determined by a special method from the experimental curves. ReferencesDie Diffusion von gelostem Wasserstoff in zwei aneinandergeschweiBten Metallen mit unterschiedlicher Affinitat gegenuber Wasserstoff wird experimentell und theoretisch untersucht. Mit Hilfe eines mit Cadmium gefilterten Neutronenstrahls des FRG-1 werden die Konzentrationskurven des Wasserstoffs zerstorungsfrei gemessen. Eine Verallgemeinerung der Eigenfunktionsmethode auf stuckweise stetige Eigenfunktion erkdubt die geschlossene Losung bei Berucksichtigung des Konzentrationssprungs an der Grenze zwischen beiden Metallen, der nach dem Nernstschen Verteilungssatz auftritt. Nach einem speziellen Verfahren werden die Diffusionskonstanten und der Nernstsche Verteilungskoeffizient aus den gemessenen K u m n bestimmt.operation, because the consequent precipitation of zirconium hydride in the metal is detrimental to the mechanical behaviour of the fuel cans. On account of its technical importance much work has been devoted to the solubility...