DESIGN AND DEVELOPMENT OF THE LARGE SCALE IN-SITU PRACLAY HEATER TEST AND HORIZONTAL HLW DISPOSAL GALLERY SEAL TEST IN BELGIAN URL HADES
In Belgium, a tertiary clay formation, the Boom Clay, located under the Mol-Dessel nuclear site between 190 and 290 m, was selected as a potential host formation for the disposal of High Level and Long Lived Radioactive Waste (HLW). An underground research facility called HADES (High-Activity Disposal Experimental Site) excavated at 223 m depth close to the city of Mol was constructed to study the feasibility of HLW disposal in the Boom Clay layer. As a side effect of radioactive decay, the HLw releases significant amount of heat, even after several decades of cooling in surface facilities. The impact of the thermal load on the repository host rock is thus an important item for the long-terM safety of underground disposal system. The temperature rise should not affect the favourable properties of the host rock on which rest the fulfilment of key safety functions. In order to demonstrate at large scale the suitability of the Boom Clay host rock to undergo the thermal load induced by the vitrified HLW, a large scale in-situ heater test, called PRACLAY heater test is being designed and will be conducted in HADES. Owing to the limitations of the test (a short period of time compared with the time period considered in a real repository, different boundary conditions; etc.), the test is designed to simulate, in a conservative way, the most critical state and phenomena that could occur within the host rock. The Praclay gallery has been excavated at the end of 2007, the heating phase will begin in 2010 and will last at least 10 years. The Praclay gallery hosting the heater test leaves an opportunity to study the possibility to seal a disposal drift in Boom clay and to test the feasibility to cut-off hydraulically any preferential pathway to the main access gallery through the EDZ (Excavation Damage Zone) and the lining with a seal in a horizontal drift (horizontal seal) in Boom clay. Indeed, this is a generic problem for all deep geological disposal facilities for HLW. An annular seal made of compacted swelling bentonite will be installed at the head of heated part of the Praclay gallery for these objectives. Meanwhile, it will be shown that this bentonite seal is necessary for the Praclay heater test to provide the desired impermeable hydraulic boundary condition. This paper provides detailed consideration on the Thermal-HydroMechanical (THM) boundary conditions for the design of the Praclay heater and seal tests with the support of numerical scoping calculations. It is believed that these important items considered in the Praclay heater test design constitute also key issues for the repository design. The outcome of the Praclay heater test will be an important milestone for the Belgian repository design.
High Level Waste HLW geological disposal facility host formation Boom clay seal heater test EDZ hydraulic cut-off THM boundary conditions scoping calculation bentonite swelling
X.L. Li W. Bastiaens M.P. Van J. Verstricht G.J. Chen E. Weetjens X. Sillen
EURIDICE, European Underground Research Infrastructure for Disposal of nuclear waste In Clay Environ SCKCEN, Belgian Nuclear Research Center, Belgium Ondraf/Niras, Belgian Agency for Radioactive Waste and Enriched Fissile Materials, Belgium
国际会议
上海
英文
53-61
2009-08-24（万方平台首次上网日期，不代表论文的发表时间）