In accordance with a number of state contracts the Russian Federation constructs several dozens of NPP units abroad and produces nuclear fuel for them. Besides, the Russian Federation implements spent nuclear fuel (SNF) reprocessing services for some of these NPP units. It is supposed that this service will be enhanced for several new NPP units. In order to maintain the ecological balance and to reduce the negative impact from the activities on reprocessing of SNF generated during the operation of NPPs built abroad, the Russian Federation legislation provides for the priority of the right to return the reprocessing products of the SNF to the supplier. 

Determination of the volume and type of returned reprocessed products is carried out according to the methods of activity equivalence determination agreed by both parties. However, the legislation does not provide the specific procedure, according to which the volumes of reprocessed products should be determined. Taking this into account, in 2013 a safety guide “Recommendations on Safety Justification in Returning of Spent Fuel Assemblies Reprocessing Products to the Supplier State” (RB-092-13) was developed, which established a unified approach to determination of the activity equivalence of SNF and reprocessing products. Nevertheless, despite the wide approbation of RB-092-13, the approaches used in it do not fully take into account the current level of development of science, technology and production. For instance, this safety guide does not consider the possibility of extraction of nuclear materials from foreign SNF (for production of MOX-fuel) and the possibility of fractioning of radioactive waste. 

In order to update the methodology of activity equivalence determination, the SEC NRS carried out a revision of RB-092-13 and developed a new version of this safety guide (RB-092-21), that was approved by the Federal Environmental, Industrial and Nuclear Supervision Service. Before the approval of RB-092-21 an analytical work had been carried out. This analysis included a comparison of various methods of activity equivalence determination and an assessment of these methods applicability to different reprocessing products. The Russian and international experience has been also taken into account. 

The RB-092-21 contains renewed recommendations for determination of activity equivalence, provides analytical equations that should be used for this purpose, and takes into account a possibility of MOX-fuel or fractionated radioactive waste return. This safety guide can be used as a basis for development of agreements between the Russian organizations and international contractors.