Operational and safety characteristics of reactors with materials having remarkable indeterminateness in data

High Pu isotopes and minor actinides occur in contemporary reactors only in the very small amount and that is why we have not needed their data with high precise and it was also practically excluded to test them on the standard reactors measurements. On the contrary in the trans mutational technologies reactors consist of only such fissionable materials. Taking into account how hard was in the past to have good uranium libraries we can hardly rely that there will be such in our disposal before the start up the first experimental reactor for transmutation. (Authors)