On the Isothermal Hydrogen Diffusion in Zircaloy‐Yttrium‐Combinations

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...

Diffusivity of hydrogen isotopes in liquid lithium and in solid yttrium

“…Close agreement is found among experiments where no surface resistance was possible: Carlson et al (1966), Fresius et al (1972), and Fresius et al (1976). Using a least-squares fit for the data in these references, the diffusivity of protium in yttrium is calculated to be log (D ± 20%) = -2.425 -2402 /T (8)…”

Diffusion of deuterium in Zr–2.5Nb alloy under neutron irradiation

“…The results obtained from two similar specimens showed about 25% difference and they attributed this difference to a possible variation in the crystallographic texture of the two specimens. They compared these results with those of Kearns [12] and their own [13] earlier measurements of the diffusion coefficients for Zircaloy-4 without irradiation. This comparison showed an enhancement of about a factor of two, which they attributed to the fast neutron irradiation.…”

Numerical investigation of hydrogen isotope retention by an yttrium pebble-bed from flowing liquid lithium

“…Table 2 presents a list of determined values for K s,0 and E s that could be found in literature describing the solubility of Table 2. Pre-exponential factors K s,0 and activation energies Es of the Sieverts' constant (15) for hydrogen isotopes in yttrium found in the literature. Error margins have not been reported in the literature.…”

“…Table 3. Pre-exponential factors K s,0 and activation energies Es of the Sieverts' constant (15) for hydrogen isotopes in lithium found in the literature. The temperature dependent density of lithium ρ Li (T) [kg m −3 ] arises from the conversion of the literature values of K s,0 to SI units.…”