SAFETY ANALYSIS OF THE NUCLEAR LEGACY AND THE RADIOACTIVE WASTE DISPOSAL

In the context of implementation of the FTP "Nuclear and Radiation Safety for 2016 and for the Period till 2030" (hereinafter ‑ the Program) the challenge of ensuring the radio-ecological safety of radioactive waste disposal has become very topical in recent years. In particular, it includes the justification of:

• simple and inexpensive solutions for the disposal of Very Low-Level Waste (VLLW);
• safety of existing waste disposal sites including landfills for Liquid Radioactive Waste (LRW) injection and sites for special radwaste;
• decisions for the construction of ultimate-disposal facilities for Low-Level and Intermediate-Level Waste (LLW and ILW);
• decisions for safety of deep ultimate-disposal facilities for High-Level Waste (HLW).

Adequate solution of these problems is based on the development of an up-to-date methodology for radwaste-management safety justification and on the generation of appropriate computer codes.

IBRAE RAN conducts extensive basic and applied research to assess long-term safety of nuclear-power facilities and industrial complexes, and to justify safety of disposal of radwaste and nuclear-legacy facilities. The key areas of these investigations are as follows:

• development of a general safety-justification methodology for SNF and radwaste management;
• generation of software tools enabling calculated estimates of radwaste disposal safety;
• safety assessment of specific facilities and sites;
• development of non-classical models of radionuclide migration in geological media;
• systematic analysis of environmental risks in regions of location of nuclear power and industry facilities;
• generation of a database for 2500 NRHF.

To simulate the processes of radionuclide migration in ground waters as well as in heterogeneous and porous geological media, software tools of a new generation are being developed that use the capabilities of modern supercomputers to implement most effective numerical methods in terms of performance and reliability (in particular, the method of adaptive computational grids). New computer codes for analysis, calculation and justification of nuclear & radiation safety of nuclear-legacy and radwaste-disposal facilities, 3D modeling of radionuclide transport in all media, calculations of exposure doses, and analysis of radiation risks and environmental threats have been generated.

Arrival of the first special train with SNF from Leningrad NPP to new dry-storage facility at the Mining Chemical Combine. 
Its establishment has become one of the key results of the Program.

The outcomes of IBRAE basic and applied research in the field of safety justification are applied not only at individual facilities (the Techa cascade of reservoirs; commercial uranium-graphite reactors at Siberian Chemical Combine and PA "Mayak"; deep disposal facility "Zheleznogorskiy" for liquid radwaste; Kirov-Chepetsk Chemical Plant; and disposal facilities for LLW and ILW), but also when providing scientific and technical support of the FTP "Nuclear and Radiation Safety for 2016 and for the Period till 2030" and the FTP "New Technology Platform for Nuclear Power".

Development of technology to assess the long-term safety of industrial uranium-graphite reactors using a 3D model of the facility and a computational model of admixture filtering in geological media may be cited as an example of adaptation of physical models developed at IBRAE to specific nuclear-legacy facilities. This technology enables calculations for super-long-lived radionuclides, e.g. ³⁶Cl, 1000 years and even 10 000 years ahead.

Simulation of the processes occurring in the course of decommissioning of industrial uranium-graphite reactor AV-1