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Submitted on 1 Jan 1980
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Reactor-induced bubble formation in potassium iodide single crystals
F. Felix, W. Montserrat Benavent, M. Müller
To cite this version:
F. Felix, W. Montserrat Benavent, M. Müller. Reactor-induced bubble formation in potas- sium iodide single crystals. Journal de Physique Colloques, 1980, 41 (C6), pp.C6-352-C6-352.
�10.1051/jphyscol:1980690�. �jpa-00220128�
JOURNAL DE PHYSIQUE
Colloyur C6, suppliment au no 7 , Tome 41, Juillet 1980, page C6-352
Reactor-induced bubble formation in potassium iodide single crystals
F. W. Felix, W. E. Montserrat Benavent and M . Miiller
HAhn-Meitncr-Institut fur Kernforschung GmbH Berlin Glienickerstrasse 100, D-100 Berlin 39, Germany
RbsumC. - D e nouveaw resultats sont prksentes sur la formation des bulles de gaz dans des cristaux de K I
[I].
Ces bulles de gaz d'une forme parallirlepiptdique (dimension moyenne de 2
ii
3 pm) se developpent en chaufant des cristaux, irradies par neutronsi
des doses entre 4 x1016
et 2 x1019
cm-*,a
des temperatures a u plus de 400 OC. On Ctudie I'influence de la dose des neutrons et des conditions du recuit. Le volume specifique des bulles de gaz augmente proportionnellernent ii (@t)'.'. Une fois formees, les bulles sont stables, mCme pres de la tempe- rature de fusion.I1 est raisonnable de supposer que les bulles sont stabilisees des leur formation par le xenon a une pression proche de la pression atmosphkrique, lequel est forme par la reaction 1-127(n, y) 1-128 Xe-128.
Abstract.
-
Further experimental results are presentedon
the formation of bubbles in KIcrystals[I].
Bubbles of parallelepipedic form (medium edge length of 2-3 prn) are formed when heating neutron-irradiated crystals above 400 OC after irradiation doses o f 4 x1016
to 2 x1019
~ m - ~ . The dependence of bubble formation on neutron dose and on annealing conditions is reported. The specific bubble volume is found to increase propor- tionally to (@I)'.'. The once formed bubbles are extremely stable, even in the vicinity of the melting point.It is assumed that the bubbles are initially stabilized by xenon a t about atmospheric pressure which is produced by the neutron reaction I- 127(n, y ) 1-1 28
5
Xe-128.DISCUSSION
Question. - M . IKEYA.
The pressure in the voids in LiH is more than hundreds atmospheric pressure. If one takes a certain number of lattice points and puts the same number of gaseous molecules, the pressure is 7 000 atm. for LiH. Is there no possibility that the voids involve iodine molecules with very high pressure
?N o absorption due to the iodine molecule will occur due to the scattering of the light by the surface.
Reply.
-F . W . FELIX.
Such a high pressure would not allow the cubic form of our high temperature defects to be stable.
The gas pressure in the defects is in the order of 1 atm.
Above 400 OC any molecular iodine would dissolve in the crystal and diffuse to the surface.
Comment.
-L. W. HOBB~.
Large cavities have been observed as well under heavy electron irradiation at elevated temperature in the electron microscope. We have speculated that the source of the vacancies required is substitutional
halogen (neutral halogen molecules in vacancy pairs), formed during interstitial stabilization a t dislocation loops. Diffusion of halogen out of the crystal or recombination of these centres with F centres lead to high concentrations of Schottky pairs which may aggregate to form cavities. Substitutional halogen may initially stabilize such cavities at moderate tern- peratures, but at higher temperatures another source of insoluble gas, such as your transmutation products, would be required.
Comment. - A. E . HUGHES.
I would like to mention an observation which supports Dr. Felix's suggestion that the bubbles are stabilized by transmutation gases. If one takes KI crystals which have been gamma-irradiated to very high doses (> 1000 M (mega not milli) R A D ) ; and subjects them to the same heat treatment as used for Dr. Felix's neutron irradiated crystals, large bubbles are not produced. The crystals become trans- parent with no sign of the opacity produced in neutron irradiated crystals.
Reference
[ I ] FELIX, F. W., MO~TSERRAT BENAVENT, W. E., Reactivity in Solids, J . Wood, 0. Lindqvist, C. Holgesson, N.-G.
Vannerberg (Plenum Press) 1977, p. 105.
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1980690
