Druck-Materie 20b.qxd - JUWEL - Forschungszentrum Jülich

Due to insufficient number of irradiation runs with hydrates, it is impossible to restore data on
saturation time. One only may conclude that it is somewhere around 10-15 hours at irradiation
temperature 25-30 K, that is, close to that of pure water ice.
Q, J/g
140
120
100
80
60
40
20
0
0 5 10 15 20 25
Time, hours
145
THF
methane hydrate
ice in Ar
Q(t)=115*(1-exp(-t/13))
Figure 10. Stored energy versus irradiation time for hydrates and beads of ice
8.2. Condition for spontaneous and thermally stimulated burps
From four experiments with THF hydrates (see in Tables 2 and 5) it can be deduced that
this substance behaves similar to pure ice. Duration of burps in THF appeared to be longer
than in pure water ice due to slow leading front, see in relevant figures in Appendix. One
spontaneous burp occurred in THF hydrate after irradiation for 13 h at temperature 20÷27 K
with Q=100 J/g (experiment # 44). Another, longer irradiation at the same temperature (experiment
#40) displayed but induced burp with Q=115 J/g.
Similar behavior is displayed by methane hydrate. One spontaneous burp occurred at irradiation
temperature 20÷25 K after 13 h with Q ∼ 80÷90 J/g (experiment #50). At irradiation
temperature >25 K no spontaneous burp was registered even for longer time of irradiation
(experiments #51, 53), see in Table 2a and 5 and plots of burps.
As distinct from pure water ice when both spontaneous and induced burps were equally
fast (or no burp occurred), induced burps in hydrates had a long leading front.
Finally, one may conclude that spontaneous burps occur in hydrates of THF and methane
at irradiation temperature around 20 K and stored energy ≥ 80-100 J/g, absorbed dose >
5.1 MGy, accordingly. Temperature limit of spontaneous burping is near to 25K. Total
combination of experimental data on ice and hydrates samples points to an existence of effect
of «amorphous» state of ice (hydrates can be considered also as pure ice with defects) on both
production of stabilized radicals and their critical concentration.