Euradwaste '08 - EU Bookshop - Europa

the bottom of the heated press-mold the PM film (polyimide film) was placed and above it the mixture
of crushed prepreg and resin. Pressing was conducted at 5 - 250 atm.
Another variant envisaged mixing of crushed carbon with the resin containing the elements under
study; then, molten binder was added on heating and stirring; the resulting mixture was transferred
into the heated press-mold. Pellets were pressed at 300�� for 1 hour.
It was found that among three variants of matrix production the third one is most feasible; in this
case no prepregs should be preliminarily prepared. This method allows to avoid the non-controlled
losses of investigated elements and to obtain sufficiently strong pellets. Besides, one can introduce
nuclides in a carrier (ion-exchange resin, fullerene soot) as well as in any other solid chemical form,
for example oxide.
Table 1. Properties of composites containing VP-1AP
Ratio of ITA-31: VP-1AP
Properties of �-� composite
Compression strength, MPa Modulus of elasticity, GP� Mass loss on carbonization, %
8 : 1 84 90 12
6 : 1 79 82 14
4 : 1 80 81 16
2 : 1 54 57 17
3.3 Leach rates of investigated elements
Alongside the thermal and strength characteristics the leach rates of immobilized radionuclides or
their chemical analogs are of significance in defining the chemical stability of matrices. In this work
the leach rate was determined in accordance with the recommendations of the International standards.
Distilled water was used as liquid phase; open surface area for different samples was 1.2 –
2.0 cm 2 . It is determined that the leach rates of rhenium from sample prepared on the basis of rhenium-saturated
resin VP-1AP are 6.8×10 -5 – 1.7×10 -7 g/cm 2 ×day upon leaching during 1 – 90 days;
of europium from sample prepared on the basis of SF-5 resin saturated with europium are 2.5×10 -5
– 1.6×10 -7 g/cm 2 ×day on leaching within the same time interval; of iodine from sample prepared on
the basis of AB-17 saturated with iodide-ion are 4.8×10 -5 – 2.7×10 -6 g/cm 2 ×day.
3.4 Radiation stability of matrices.
It is shown that irradiation of the matri�es by neutrons and gamma-irradiation in research reactor
VVR-M in PNPI at neutron-flux density ~ 4·10 n/cm 2 ·s and integral flow ~ 10 18 n does not render
the essential influence on their mechanical properties and leach rates of investigated elements. The
values of these parameters for the samples after irradiation practically such, either as for samples
before irradiation.
4. Conclusions
The chemical analogues of such long-lived radionuclides as 99 Tc, 129 I, and 241 Am were immobilized.
Rhenium, stable iodine and europium were used as the corresponding analogs, respectively. It
was shown that the samples carbonized at temperatures up to 600-650°� possess high thermal stability.
The produced samples exhibit high mechanical strength. Their compression strength varies
418