A small-scale underground research laboratory, KAERI Underground Research Tunnel (KURT) at KAERI in Daejeon, was constructed to develop a Korean disposal system for the HLW repository, including spent fuels, between March 2005 and November 2006. The KURT, with an access tunnel and two research modules, as shown in Fig. 21.8 , is located in a mountainous area inside the KAERI territory. The KURT, has a total length of 255 m with a 180 m long access tunnel and two research tunnels 75 m long in total. The maximum depth of 90 m could be effectively achieved by select­ing the tunnel direction to the peak of a mountain. The horseshoe shaped tunnel, 6 m wide and 6 m high, is located in a granite rock body (Fig. 21.8). Regardless of limited applications of KURT, which only handles naturally occurring radionuclides, the KURT facility will be a major infrastructure for validating the safety and feasibility of the suggested disposal system by various in-situ experiments:

1. Single hole heater test in rock.

2. THM (thermal-hydraulic-mechanical) behavior of engineered barrier systems (EBS).

3. EDZ (excavation disturbed zone) characteristics and mechanical stabil­ity of rock.

4. Retardation of solute migration through fractured rock.

5. Site investigation techniques.

6. Hydrogeological and geochemical baseline data (Kwon et al., 2009 ).

The current 10-year plan for mid — and long-term nuclear R&D on HLW disposal was accepted by the AEC in 1997. This plan includes a program for development of a Korean repository for HLW disposal and for the associated system performance assessment. After completion of the

combined research output of this 10-year study, the Korean government will define the direction and prioritization of further R&D activities for HLW disposal. Since 1997, KAERI has been developing a permanent dis­posal facility for HLW and a total system performance assessment (TSPA). Its current R&D activities are focused on the preliminary conceptual design of the Korean Reference Disposal System (KRS), development of the key technologies, and geo-environmental studies to confirm the KRS’s safety, as shown in Fig. 21.9. Currently, the four major projects underway at KAERI are:

1. repository system development;

2. a TSPA;

3. geo-environmental science research; and

4. construction and operation of a KAERI underground research tunnel (KURT) to demonstrate the KRS ’s performance relevant to the func­tional criteria established in the disposal concept (Fig. 21.8).