Keywords: thermal simulation, spent nuclear fuel, prototype repository, finite element method.

Even with the rapid development of new technologies amount of highly radioactive waste remains from nuclear power plants or from different industries. Thos wasteshould be isolated from the biosphere for thousands years. A mixture of technological and natural barriers is required for the safe deposition of this radioactive waste. The most promising natural barrier in the Czech Republic is shown to be the massive rock of granite which fulfils the requirements for the long term stability, homogenity, minumum flow of groundwater, having suitable physical and chemical characteristics of the rock [1].

The mathematical models of the thermal dimensioning must be evaluated with the physical experiments. One of the most complex experiments relating to the deep geological spent nuclear fuel repository was realised in Sweden, in the SKB Aspo Hard Rock Laboratory (HRL) [2]. The so called prototype repository simulates a part of a KBS-3 nuclear waste repository. The aim of the prototype repository is to demonstrate the integrated function of the repository components and to provide a full-scale reference for comparison with models and assumptions.

The simple model representing the prototype repository for comparison the model results and the experiment is presented here. The model represents a structure of boreholes in the tunnel of the prototype repository. It is a good model for local temperature analysis in the vicinity of the canisters [3]. Material properties are based on the data from [4,5].

The model represents the tunnel with deposition holes (prototype repository) with the surrounding granite massiff. The dimensions of the granite "box" surrounding the prototype repository are approximately 170x120x60 m. We solved the problem with the ANSYS software package. All tasks are performed in the ANSYS Workbench. The more sofisticated procedures for the ANSYS usage were shown in [6]. The most important result of this short case study is, that we have a good qualitative model for the thermal dimensioning of the deep geological spent nuclear fuel repository. The next step of the work is a sensitivity analysis of the model, we can study the influence of the material properties on the maximal temperatures achieved in the repository, the influence of the geometric parameters of the repository etc.

1

SURAO, "Why Deep Geological Repository?", 2009. http://www.proe.cz/surao2/index.php?c=300

2

SKB, "Aspo Hard Rock Laboratory", 2011. http://www.skb.se/Templates/Standard____25506.aspx

3

M. Hokr, J. Novak, "Thermal simulations of high-level waste repository", in "Proceedings of 8th ECMS 2007", Liberec, Czech Republic, 2007.

4

O. Kristensson, L.E. Johannesson, "Description of the Prototype Repository Test compiled for EBS Task-Force - DRAFT", Clay Technology AB, 2010.

5

Sprava ulozist radioaktivnichch odpadu, "Zadavaci bezpecnostni zprava, Priloha c. 1, Referencni projekt hlubinneho uloziste v hostitelskem prostredi granitovych hornin", SURAO - EGP Invest, Uh. Brod 1999.

6

J. Novak, M. Hokr, "Finite Element Simulations of the Thermal Conditions in a High-Level Waste Repository", in B.H.V. Topping, L.F. Costa Neves, R.C. Barros, (Editors), "Proceedings of the Twelfth International Conference on Civil, Structural and Environmental Engineering Computing", Civil-Comp Press, Stirlingshire, United Kingdom, paper 130, 2009. doi:10.4203/ccp.91.130

purchase the full-text of this paper (price £20)

go to the previous paper
go to the next paper
return to the table of contents
return to the book description
purchase this book (price £130 +P&P)