Thermo-hydro-mechanical effects in host rock for spent nuclear fuel repositories : master's thesis

Odlukom Vlade Republike Hrvatske (124. sjednica 9.11.2018) o donošenju Nacionalnog programa provedbe Strategije zbrinjavanja radioaktivnog otpada, iskorištenih izvora i istrošenog nuklearnog goriva, problem zbrinjavanja radioaktivnog otpada u Hrvatskoj postaje aktualan. Slovensko-hrvatsko Suvlasništvo nad Nuklearnom elektranom Krško (NEK) znači da polovina pogonskog i dekomisijskog otpada te istrošenog nuklearnog goriva (ING) pripada Hrvatskoj. Hrvatski program zbrinjavanja nisko i srednje radioaktivnog otpada polako napreduje, ali ING se i dalje čuva u bazenu NEK, a predviđeno je i suho skladištenje do trenutka odlaganja. U svijetu jedino Finska ima građevinsku dozvolu za odlaganje ING-a. Republika Slovenija je izradila generički projekt odlagališta ING koji je već prošao drugu reviziju i recenziju. Projektna ideja uključuje traženje lokacije na teritoriju obje države te konceptualno rješenje tipa SKB-3V u kristaliničnoj stijeni. U radu je dana procjena termičko-hidro-mehaničkih efekata (THME) odlagališta ING-a u kristaliničnoj stijeni (granodiorit) SKB-3V koncepta izradom numeričkog modela u programima SIGMA/W, SEEP/W i TEMP/W. Za usporedbu, procijenjeni su i THME u istim programima za Koncept-4 (odlaganje aksijalno u tunelu). Simulacijama je dokazano kako je moguće izraditi odlagalište ING-a u kristaliničnim stijenama Hrvatske ili Slovenije, da je generički projekt odlagališta dobro dizajniran te da se može izraditi model hidro-termomehaničkih efekata istrošenog nuklearnog goriva na stijenu u Hrvatskoj/Sloveniji koji dokazuje podobnost stijenske mase za ovu svrhu. Dokazano je kako je primjena Koncepta-4 također moguća, ako ne i poželjnija. Izrađen je kvalitativni model ponašanja potencijalne stijene i funkcionalnosti odabranog koncepta odlaganja ING-a i time je dokazano kako u Hrvatskoj postoje kapaciteti za izradu projekata i studija funkcionalnosti i sigurnosti budućeg odlagališta ING-a.By the Decision of the Government of the Republic of Croatia (124th Session, November 9th, 2018) on the adoption of the National Program for the Implementation of the Strategy for the Management of Radioactive Waste, Used Resources and Spent Nuclear Fuel, the issue of radioactive waste management in Croatia becomes current. Slovene-Croatian co-ownership over the Krško nuclear powerplant (KNPP) means that half of the operational and decommissioning waste, as well as spent nuclear fuel (SNF) belongs to Croatia. The Croatian low and intermediate radioactive waste management program is slowly advancing, but SNF is kept in the pool at KNPP, and dry storage before disposal is also planned. Only Finland has a building permit for the disposal of SNF. The Republic of Slovenia has developed a generic project of the SNF repository that has already undergone a second revision and review. The project idea involves site selection in both countries and the conceptual solution of the SKB-3V type in the crystalline rock. The paper presents the estimate of the thermalhydro- mechanical effects (THME) of the SNF repository in the crystalline rock (granodiorite) of SKB-3V concept by developing a numerical model in the SIGMA/W, SEEP/W and TEMP/W software. For comparison, THME were also estimated in the same software for the Concept-4 (container placed axially in the tunnel). Simulations have shown that it is possible to construct an SNF repository in the crystalline rocks of Croatia or Slovenia, that the generic landfill project is well-designed and that a model of hydro-thermo-mechanical effects of spent nuclear fuel on the rock in Croatia/Slovenia can be produced which proves the suitability of the rock mass for this purpose. It has been shown that application of Concept-4 is also possible, if not more desirable. A qualitative model of potential rock behaviour and functionality of the chosen SNF disposal concept has been developed, and it has been demonstrated that there are capacities for designing and reviewing the functionality and safety of the future SNF repository in Croatia