ArticleName 
Integral code GeRa for radioactive waste disposal safety validation 
ArticleAuthorData 
Author 1: Name & Surname: Kapyrin I. V. Company: Institute of Problems of Safe Nuclear Power Development, Russian Academy of Sciences Work Position: Head of Laboratory Scientific Degree: Candidate of PhysicoMathematical Sciences Contacts: kapyrin@ibrae.ac.ru
Author 2: Name & Surname: Ivanov V. A. Company: Institute of Problems of Safe Nuclear Power Development, Russian Academy of Sciences Work Position: Junior Researcher
Author 3: Name & Surname: Kopytov G. V. Company: Immanuel Kant Baltic Federal University (Kaliningrad, Russia) Work Position: Head of Department Scientific Degree: Candidate of PhysicoMathematical Sciences
Author 4: Name & Surname: Utkin S. S. Company: Institute of Problems of Safe Nuclear Power Development, Russian Academy of Sciences Work Position: Head of Department Scientific Degree: Candidate of PhysicoMathematical Sciences

Abstract 
The paper addresses the topical issue related with total longterm safety of underground disposal of radioactive waste (RAW and highlevel waste (HLW). The authors present the new computation code GeRa, developed at the Institute of Problems of Safe Nuclear Power Development RAS jointly with other institutions engaged in the given research area, for modeling geopercolation and geomigration of radionuclides in rock masses planed for RAW disposal and isolation. Code GeRA is an integral code allowing overall estimation of RAW disposal safety—starting from the models of percolation, transmission, chemical interaction, convection, sorption, radioactive decay etc. and finishing with the calculation of radiation exposure of people when using water from underground sources that occur on migration ways of radionuclides. The code includes options for modeling: intense percolation in pressure and no pressure formulations, intense–not intense percolation, advective–diffusion–dispersion transport considering radioactive decay; equilibrium sorption by isotherm, including variable distribution factor Kd; transport with detail calculation of chemical interactions in water–rock system using module PHREEQC; convection. The structure and capacity of computation code GeRa are illustrated using the model of a regional RAW disposal project in the Northwestern region of Russia. Furthermore, the authors present MSPP software platform, designed in the framework of GeRa architecture, for concurrent operation with grids, data and systems of linear equations. By the authors’ estimates, GeRa code and its infrastructural support are equal to its foreign analogs of the present day and in some aspects even exceed them. The current studies aim at expansion of modeling range, and verification and crossverification of the code. GeRa code is placed under use test at the National Operator for Radioactive Waste Management and has passed testing at Lomonosov Moscow State University. It is planned to obtain the state certification of the code. 
keywords 
RAW disposal, longterm safety, geomigration of radionuclides, groundwater, computational code GeRa, software support, regional repository, visualization, verification 
References 
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